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For micro internal pressure or low pressure vessels, the wall thickness obtained by rounding is generally smaller after considering corrosion allowance and negative deviation according to the internal pressure pitch diameter formula. If the thickness is directly used as the nominal thickness, it will lead to a series of problems in manufacturing, transportation and installation. It includes: a. In the manufacturing process of thin-walled cylinder, in order to ensure the roundness and stiffness, a lot of auxiliary measures are needed, which costs manpower and material resources. For example, it is necessary to use internal strengthening tooling to round the tube section, especially at the butt edge of two tube sections. b. Thin walled cylinder wall, especially when the diameter of cylinder is small, usually adopts the welding method of single side welding and double side forming. However, the single side welding of thin-walled vessels is prone to defects such as incomplete penetration, burn through and poor back forming. Even if the backing plate is added at the back, it is easy to produce welding defects at the root because the backing plate is not easy to stick tightly. At the same time, the influence of misalignment and angular deformation on the welding quality of thin-walled cylinder is much greater than that of thick-walled cylinder. c. Due to the poor rigidity and easy deformation of thin-walled vessels, it is usually necessary to temporarily support or reinforce the shell during transportation and hoisting. If the cost of manufacturing, transportation and installation is too high, it is better to increase the thickness of the cylinder to ensure the quality. Therefore, the minimum thickness of pressure vessel cylinder is also specified in GB 150 and other standards. GB 150-1989 has strict requirements on the minimum wall thickness of carbon steel and low alloy steel pressure vessels. The minimum wall thickness of carbon steel and low alloy steel specified in GB 150-98 is: when DN < 3800, 2DI / 1000, not less than 3mm, without corrosion allowance. Dn3800 above, beyond the railway transportation limit, on-site production, no regulations. For high alloy steel, due to the material price, the minimum thickness requirement is low, so the strengthening in transportation and hoisting needs special consideration. GB / T 150-2011 only requires the minimum wall thickness of 3 mm for carbon steel and low alloy steel. The minimum wall thickness of high alloy steel cylinder in each version is 2 mm. The minimum wall thickness requirements of GB 150-1989 refer to the formula previously recommended by American Society of mechanical engineers δ min=0.001D+2.54 mm And the former Soviet Union “oil production machinery and equipment” in the formula: When DN ≤ 1 200 mm, δ min=0.001D +2.54 mm； When DN > 1 200 mm, δ min=0.001D +4 mm. GB 150-1989 comprehensively considers the minimum wall thickness requirements of carbon steel and low alloy steel pressure vessels in transportation, manufacture and hoisting. The requirements for minimum wall thickness of carbon steel in GB 150-1998 and GB / T 150-2011, as well as the requirements for minimum wall thickness of high alloy steel in various versions, are more from the perspective of welding. As for transportation, installation and other aspects, designers need to consider according to the actual situation. On the whole, GB 150-1989 has strong operability, which should be liked by designers. However, such detailed and rigid standards will hinder technological progress. However, the later version of GB 150 only stipulates in general terms that considering the force during transportation or hoisting, it is obviously not easy to operate under the background of current design and manufacturing pision in China. Of course, there are also successful examples, such as the hoisting of large towers. The hoisting scheme (including the required reinforcement measures) is proposed by the hoisting unit and confirmed by the design. Some things should not be specified too carefully in national standards and industry standards, but enterprise standards and group standards can. For example, a wealthy and prudent owner made the following provisions on the minimum thickness of the equipment: DN<900, tmin=6； DN: 900~1500, tmin=8; DN: 1500~2100, tmin=8; DN: 2100~3600, tmin=10; DN>900, tmin=11. The above thickness includes a corrosion allowance of 3 mm. Of course, the owner also stipulates that if the quality can be guaranteed, the minimum thickness can be discussed.

In the pipeline system, the valve is the control element, just like the human hand, so whether in life or in all walks of life, its importance is self-evident. What are its functions? How to install pipeline valve? Next, let’s get to know the four most important aspects. Four functions of valve Cut off and open media The flow channel is straight through valve, and its flow resistance is small. It is usually selected as the valve for cut-off and open medium. Downward closing valve (stop valve, plunger valve) is less used because of its tortuous flow channel and higher flow resistance than other valves. Closed type valve can be selected when higher flow resistance is allowed. Control flow Usually choose easy to adjust the flow of the valve as control flow. A downward closing valve, such as a globe valve, is suitable for this purpose because its seat size is proportional to the stroke of the closing element. Rotary valve (plug valve, butterfly valve, ball valve) and flex body valve (clamp valve, diaphragm valve) can also be used for throttling control, but usually only in a limited range of valve diameter. Gate valve is a disc-shaped gate to cross cut the round valve seat. It can control the flow only when it is close to the closed position, so it is not usually used for flow control. Commutation shunt The valve can have three or more channels according to the need of directional persion. Plug valve and ball valve are more suitable for this purpose, therefore, most of the valves used for directional persion are selected as one of these valves. But in some cases, other types of valves, as long as two or more valves are properly connected with each other, can also be used for persion. Medium with suspended particles When there are suspended particles in the medium, it is most suitable to use the valve whose closing part slides along the sealing surface and has the function of wiping. If the back and forth movement of the closing part to the seat is vertical, particles may be trapped. Therefore, this kind of valve is only suitable for basically clean medium unless the sealing surface material can allow particles to be embedded. Ball valve and plug valve can wipe the sealing surface in the process of opening and closing, so they are suitable for medium with suspended particles. Three installation problems of valves Inspection before installation 1. Carefully check whether the valve model and specification meet the drawing requirements. 2. Check whether the valve stem and disc are opened flexibly, and whether they are stuck or skewed. 3. Check whether the valve is damaged and whether the thread of threaded valve is correct and complete. 4. Check whether the combination of valve seat and valve body is firm, the connection between valve disc and valve seat, valve cover and valve body, and the connection between valve stem and valve disc. 5. Check whether the valve gasket, packing and fasteners (bolts) are suitable for the requirements of working medium properties. 6. The old or long-standing pressure relief valve should be removed, and the dust, sand and other debris should be cleaned with water. 7. Remove the port cover and check the sealing degree. The valve disc must be closed tightly. General provisions for installation 1. The installation position of the valve shall not hinder the operation, disassembly and overhaul of the equipment, pipeline and valve body, and the appearance of the assembly shall be considered. 2. The valve on the horizontal pipeline should be installed with the valve stem upward or inclined at a certain angle, but not with the hand wheel downward. The valve, stem and hand wheel on the high-altitude pipeline can be installed horizontally, and the valve can be opened and closed remotely by the chain at the lower part. 3. The arrangement is symmetrical, neat and beautiful; for the valves on the riser, if the process permits, the valve handwheel should be at the breast height, generally 1.0-1.2m above the ground, and the valve stem must be installed along the direction of the operator. 4. For valves on parallel risers, the elevation of the center line should be the same, and the clear distance between the hand wheels should not be less than 100 mm; for valves on parallel horizontal pipelines, they should be staggered to reduce the pipe spacing. 5. When heavy valves are installed on water pumps, heat exchangers and other equipment, valve supports shall be set; when valves are frequently operated and installed more than 1.8m away from the operating surface, a fixed operating platform shall be set. 6. If there is an arrow mark on the valve body, the direction of the arrow is the flow direction of the medium. When installing the valve, the arrow should point to the same direction as the medium in the pipeline. 7. When installing the flange valve, ensure that the two flange end faces are parallel and concentric with each other, and do not use double gaskets. 8. When installing threaded valve, a threaded valve shall be equipped with a union joint for easy disassembly. The setting of the movable joint should consider the convenience of maintenance, usually the water flows through the valve first and then through the movable joint. Installation precautions 1. The valve body material is mostly made of cast iron, which is brittle, so it shall not be impacted by heavy objects. 2. When handling the valve, it is not allowed to throw it at will; when lifting the valve, the rope should be tied to the valve body, and it is strictly forbidden to be tied to the hand wheel, valve stem and flange bolt hole. 3. The valve shall be installed in the most convenient place for operation, maintenance and overhaul, and it is strictly prohibited to be buried underground. Inspection chamber shall be set for valves on directly buried pipelines and pipelines in trench to facilitate opening, closing and adjustment of valves. 4. Ensure that the thread is intact, and wrap hemp, lead oil or polytetrafluoroethylene raw material belt on the thread. When screwing, use a wrench to screw into the hexagonal valve body at one end of the pipe. 5. When installing the flange valve, pay attention to tighten the connecting bolts along the diagonal direction, and the force should be even when screwing, so as to prevent the gasket from deviation or causing the deformation and damage of the valve body. 6. The valve shall be kept closed during installation. For the threaded valve close to the wall, it is often necessary to remove the stem disc and hand wheel before turning. When disassembling, the valve should be disassembled after turning the hand wheel to keep the valve open. Installation of six common pipeline valves 1、 Gate valve Also known as gate valve, is the use of gate to control the opening and closing of the valve, by changing the cross section to adjust the pipeline flow and opening and closing of the pipeline. Gate valves are mostly used for pipelines with full open or full close operation for fluid medium. Gate valve installation generally has no directional requirements, but can not be inverted. 2、 Stop valve Is the use of disc to control the opening and closing of the valve. By changing the clearance between the disc and the seat, that is, changing the size of the channel section to adjust the medium flow or cut off the medium channel. Pay attention to the flow direction when installing the stop valve. The principle that must be observed when installing the stop valve is that the fluid in the pipeline passes through the valve hole from bottom to top, commonly known as “low in and high out”, and reverse installation is not allowed. 3、 Check valve Check valve, also known as check valve and one-way valve, is a kind of valve that opens and closes automatically under the pressure difference between the front and back of the valve. Its function is to make the medium flow in only one direction and prevent the medium from flowing backward. Check valve according to its different structure, there are lift type, swing type and butterfly clamp type. Lift check valve is pided into horizontal and vertical. When installing the check valve, also pay attention to the flow direction of the medium, can not be installed reversely. 4、 Pressure reducing valve The pressure reducing valve is a kind of valve that reduces the inlet pressure to a certain required outlet pressure by regulation and keeps the outlet pressure stable automatically by relying on the energy of the medium itself. From the point of view of fluid mechanics, the pressure reducing valve is a throttling element whose local resistance can be changed, that is, by changing the throttling area, the flow velocity and the kinetic energy of the fluid can be changed, resulting in different pressure loss, so as to achieve the purpose of reducing pressure. Then, the fluctuation of the pressure behind the valve is balanced with the spring force by the regulation of the control and regulation system, so that the pressure behind the valve remains constant within a certain error range. Installation 1. The pressure reducing valve group installed vertically is generally set at a suitable height from the ground along the wall; the pressure reducing valve group installed horizontally is generally installed on the permanent operation platform. 2. Profile steel shall be respectively loaded into the wall outside two control valves (commonly used for stop valve) to form a bracket, and the bypass pipe shall also be stuck on the bracket for leveling and alignment. 3. The pressure reducing valve shall be vertically installed on the horizontal pipeline, and shall not be inclined. The arrow on the valve body shall point to the medium flow direction, and shall not be installed reversely. 4. Stop valves and high and low pressure gauges should be installed on both sides to observe the pressure changes before and after the valve. The diameter of the pipe behind the pressure reducing valve shall be 2 # – 3 #, larger than that of the inlet in front of the valve, and the bypass pipe shall be installed for maintenance. 5. The equalizing pipe of membrane pressure reducing valve should be connected to the low pressure pipe. Safety valve shall be set for low pressure pipeline to ensure safe operation of the system. 6. When it is used for steam decompression, a drain pipe shall be set. For the pipeline system with high purification requirements, a filter should be set in front of the pressure reducing valve. 7. After the installation of pressure reducing valve group, the pressure reducing valve and safety valve shall be tested, washed and adjusted according to the design requirements, and the adjusted marks shall be made. 8. When flushing the pressure reducing valve, close the inlet valve of the pressure reducer and open the flushing valve for flushing. 5、 Steam trap The basic function of the steam trap is to discharge the condensate, air and carbon dioxide gas in the steam system as soon as possible, and at the same time, to prevent the leakage of steam automatically to the maximum extent. There are many kinds of traps with different performances. According to the different working principle of the trap, it can be pided into the following three types: ❶ mechanical type: depending on the change of condensate water level in steam trap. Include: Floating ball type: the float is a closed hollow ball. Open up float type: the float is bucket type with open up. Open down float type: the float is a bucket type with open down. ❷ thermostatic type: depending on the change of liquid temperature. Include: Bimetallic sheet: the sensitive element is bimetallic sheet. Vapor pressure type: the sensitive element is bellows or ink cartridge filled with volatile liquid. ❸ thermodynamic type: it depends on the change of thermodynamic properties of liquid. Include: Disc type: due to the same pressure, liquid and gas flow rate is different, resulting in different dynamic and static pressure, drive disc valve action. Pulse type: when condensate with different temperatures passes through two throttling orifices in series, different pressures will be formed between two throttling orifices to drive the valve disc to act. Installation 1. Block valve (stop valve) should be set before and after the steam trap, and a filter should be set between the steam trap and the front block valve to prevent the dirt in the condensate from blocking the steam trap. 2. A check pipe should be set between the drain valve and the rear block valve to check whether the drain valve works normally. If the check pipe is opened and a large amount of steam is emitted, the drain valve is broken and needs to be repaired. 3. The bypass pipe is set to discharge a large amount of condensate during start-up and reduce the drainage load of the steam trap. 4. When the steam trap is used to drain the condensate from the hot equipment, it should be installed at the lower part of the hot equipment, so that the condensate pipe can be connected to the steam trap vertically to prevent the hot equipment from storing water. 5. The installation position should be close to the drainage point as far as possible. If the distance is too far, air or steam will accumulate in the slender pipe in front of the trap. 6. When the horizontal pipeline of steam main is too long, the problem of drainage should be considered. 6、 Safety valve The safety valve is a special valve which is normally closed under the action of external force. When the medium pressure in the equipment or pipeline rises beyond the specified value, the medium pressure in the pipeline or equipment can be prevented from exceeding the specified value by discharging the medium to the outside of the system. Safety valve is an automatic valve, which is mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. Injection safety valve can only be used after pressure test. Install 1. Before installation, the product must be carefully inspected to check whether there is a certificate and product instructions, so as to clarify the constant pressure situation when leaving the factory. 2. The safety valve should be arranged near the platform as far as possible for inspection and maintenance. 3. The safety valve should be installed vertically, the medium should flow from the bottom to the top, and the verticality of the valve stem should be checked. 4. In general, the front and back of the safety valve can not be set with block valve to ensure safety and reliability. 5. Pressure relief of safety valve: when the medium is liquid, it is generally discharged into the pipeline or closed system; when the medium is gas, it is generally discharged to the outdoor atmosphere. 6. The oil and gas medium can be discharged into the atmosphere generally. The outlet of the relief pipe of the safety valve should be 3M higher than the highest structure around, but the following situations should be discharged into the closed system to ensure safety. 7. The minimum diameter of the pipeline shall be equal to the inlet diameter of the valve; the diameter of the discharge pipe shall not be less than the outlet diameter of the valve, and the discharge pipe shall be led to the outside and installed with elbow, so that the outlet of the pipe faces the safety zone. 8. When the safety valve is installed, when the connection between the safety valve and equipment and pipeline is open hole welding, the opening diameter shall be the same as the nominal diameter of the safety valve. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Valve is an important component in the piping system of petrochemical plant. It is one of the main leakage sources in the plant with many kinds and large quantity. Therefore, the leakage requirement of valve is very important. Valve sealing performance refers to the ability of each sealing part of the valve to prevent medium leakage. The main sealing parts of the valve are: the matching surface between the opening and closing parts and the valve seat, the matching of the packing and the valve stem and the stuffing box, and the connection between the valve body and the valve cover. The first leakage is called internal leakage, which directly affects the ability of the valve to cut off the medium and the normal operation of the equipment. The leakage of the last two places is called external leakage, that is, the medium leaks from the inside of the valve to the outside of the valve, which directly affects the safe production, causes the loss of working medium and enterprise economic loss, environmental pollution, and even causes production accidents in serious cases. Especially for high temperature and high pressure, flammable and explosive, toxic or corrosive media, the leakage of the valve is not allowed, because the consequences are more serious than the internal leakage, so the valve must have reliable sealing performance, to meet the requirements of its use conditions on the leakage. 1. Classification standard of valve sealing grade in China At present, there are two common classification standards of valve sealing grade in China. 1.1 Classification of valve sealing grade in Chinese national standard GB / T 13927 pressure test for industrial valves. 1.2 Classification of valve sealing grade in China mechanical industry standard JB / T 9092 inspection and test of valves. 2. International valve seal classification standard At present, there are five commonly used classification standards of valve sealing grade. 2.1 Classification of valve sealing grade in former Soviet Union In order to select the products according to the sealing degree and the specified use of the valves, the valves are classified according to the sealing degree. 2.2 ISO classification of valve sealing grade ISO 5208 pressure testing of industrial valves and metal valves. 2.3 American Petroleum Institute (APL) classification of valve sealing grade American Petroleum Institute standard API 598-2004 inspection and testing of valves. 2.4 Classification of valve sealing class by MSS the allowable valve leakage requirements of MSS SP61 are as follows: (1) If one sealing surface of the valve sealing pair is made of plastic or rubber, there shall be no visible leakage during the duration of the sealing test. (2) The maximum allowable leakage on each side when closing shall be: the liquid is 0.4ml/mm and 0.4ml/h of nominal size (DN); The gas is nominal size (DN) 120 ml per millimeter per hour. (3) The allowable leakage of check valve can be increased by 4 times. 2.5 Classification of control valve sealing class in ANSI / FCI ANSI / FCI 70-2 (ASME b16.104) control valve seat leakage. 2.6 Classification of valve sealing grade in European standard European standard EN 12266-1 testing of industrial valves Part 1. Pressure tests, test methods and acceptance criteria – mandatory requirements. 3. Selection of valve sealing grade 3.1 Selection of domestic valve sealing grade (1) The national standard GB / T 13927 (pressure test for industrial valves) implemented on July 1, 2009 is formulated with reference to the European standard ISO 5208. It is suitable for inspection and pressure test of industrial metal valves, including gate valve, globe valve, check valve, plug valve, ball valve and butterfly valve. The classification and maximum allowable leakage of sealing test are the same as those specified in ISO 5208. This standard is a revision of GB / T 13927 (pressure test for general purpose valves). Compared with GB / t13927, it adds AA, CC, e, EE, F and G grades. The new version of the standard stipulates that “the selection of leakage grade shall be one of the strict requirements in the relevant valve product standard or order contract. If there is no special provision in the product standard or order contract, the non-metallic elastic sealing valve shall meet the requirements of class A, and the metal sealing auxiliary valve shall meet the requirements of class D. ” Generally, class D is suitable for general valves, and the leakage class above class D should be selected for key valves. (2) Mechanical industry standard JB / t9092 “inspection and test of valves” is a revision of zbj16006. The maximum allowable leakage of sealing test is made according to API 598-1996. It is suitable for inspection and pressure test of gate valve, globe valve, plug valve, ball valve, check valve and butterfly valve used in petroleum industry, including metal sealing pair, elastic sealing pair and non-metal sealing pair (such as ceramic). At present, GB / T 9092 is being revised. (3) It should be noted in engineering design that the national standard GB / T 19672 (technical specifications for pipeline valves) is formulated with reference to European standard ISO 14313 and American Petroleum Institute standard API 6D. The national standard GB / T 20173 “pipeline valves for petroleum and natural gas industries” is formulated with reference to the European standard ISO 14313. Both GB / T 19672 and GB / T 20173 have the same acceptance criteria for valve leakage as ISO 5208 class A and D. Therefore, the leakage requirement higher than the standard in the engineering design should be given in the order contract. 3.2 Selection of foreign valve sealing grade (1) The former Soviet Union mainly used the classification of valve sealing grade in the 1950s. With the disintegration of the former Soviet Union, most countries do not use this classification of valve sealing grade, but use European and American standards seal grade classification. European standard EN 12266-1 seal grade classification conforms to ISO 5208, but lacks AA, CC and EE. Compared with the 1999 edition, the ISO 5208 has added AA, CC, e, EE, F and G grades. ISO 5208 standard gives the comparison of several seal grades with API 598 and EN 12266 standards. The comparison of other nominal size seal grades can be obtained by calculating the leakage according to the diameter. (2) API 598 is the most commonly used inspection and pressure test standard for American Standard valves. The manufacturer’s standard msssp61 is often used for the inspection of “fully open” and “fully closed” steel valves, but it is not applicable Not suitable for control valves. Msssp61 is not usually used for American Standard valves. API598 is applicable to the sealing performance test of valves manufactured according to the following API standards: Flange type, lug type, clip type and butt welded check valve API 594; Flange, thread and butt welding metal plug valve API 599; DN l00 and below steel gate valve, globe valve and check valve API 602 for petroleum and natural gas industry; Flange and butt welded corrosion-resistant bolted bonnet gate valve API 603; Flange, thread and butt welding metal ball valve API 608; Double flange, lug and wafer butterfly valve API 609. Attention should be paid in engineering design: API 598-2004 cancels the inspection and pressure test of API 600 (bolted bonnet steel gate valve for petroleum and natural gas industry) compared with 1996 edition. API 600-2001 (ISO 10434-1998) stipulates that the sealing performance test of valves shall refer to ISO 5208, but the leakage in Table 17 and table 18 of the standard is the same as that of API 598-1996, instead of ISO 5208. API 600 standard implemented in September, 2009 corrected this contradiction in 2001 edition, which stipulated that the sealing performance test of valves should be carried out in accordance with API 598, but there was no specified edition, which was in contradiction with API 598-2004. Therefore, when selecting API 600 and API 598 standard for sealing performance test in engineering design, the version of the standard must be clear to ensure the consistency of the content of the standard. (3) American Petroleum Institute standard API 6D (ISO 14313) Petroleum and natural gas industries – pipeline transportation systems – pipeline valves: the acceptance criteria for valve leakage are as follows: “the leakage of soft seal valve and oil seal plug valve shall not exceed ISO 5208A (no visible leakage), and the leakage of metal seat valve shall not exceed ISO 5208 (1993) d, but according to the sealing test described in b.4, The leakage shall not be more than twice of ISO 5208 (1993) class D unless otherwise specified. ” Note in the standard: “special applications may require leakage less than ISO 5208 (1993) class D ¨ J.” Therefore, the leakage requirement higher than the standard in engineering design should be given in the order contract. API 6D-2008 Appendix B additional test requirements specifies the additional test requirements of valve FJ to be conducted by the manufacturer when specified by the buyer. Seal test includes low pressure and high pressure gas seal test. High pressure seal test with inert gas as test medium will replace liquid seal test and liquid seal test. According to the type, diameter and pressure level of the valve, the selection of sealing test can refer to the provisions of ISO 5208 standard. It is suggested that low pressure sealing test should be used for valves on gal and GCL of long distance pipeline to improve the qualified rate of valves. When selecting high pressure sealing test, it should be noted that the sealing performance of elastic sealing valve under low pressure condition may be reduced after high pressure sealing test. The production cost of valve can be effectively reduced by reasonably selecting the valve sealing test requirements according to the actual working conditions of medium. (4) American national standard ANSI / FCI 70-2 (ASME B16.104) is applicable to control valve sealing class. In engineering design, metal elastic seal or metal seal should be selected according to the characteristics of medium and the opening frequency of valve. The sealing grade of metal sealing control valve shall be specified in the order contract. According to experience, for metal seal control valve, the requirements of grade I, II and III are relatively low, and the selection in engineering design is relatively small. Generally, grade IV is the lowest for metal seal control valve, and grade V or VI is the most critical control valve. The control valve of the flare system of an ethylene plant is designed to meet the requirements of grade IV metal seal, which runs well. (5) In addition, attention should be paid in engineering design: API 6D stipulates that the chloride ion content of water used in austenitic stainless steel valve sealing test shall not exceed 30ug/g, and ISO 5208 and API 598 both stipulate that the chloride ion content of water used in austenitic stainless steel valve sealing test shall not exceed 100ug/g. Due to the different requirements of each standard, it is suggested that the chloride ion content of water used in sealing test should be specified in the valve order contract. 4. Classification standard for sealing grade of low leakage valve Low leakage valve refers to the valve actual leakage is very small, rely on conventional water pressure, air pressure seal test has been unable to determine, need to use more advanced means and instruments to detect the small leakage. The tiny leakage of the valve to the external environment is called low leakage. At present, there are three standards commonly used to detect low leakage of valves in the world (1) EPA method 21, leakage detection of volatile organic components. (2) ISO 15848 (industrial valves: low leakage measurement, testing and qualification procedures). (3) Shell MESC SPE 77 / 312 “industrial valves: low leakage measurement, classification system, qualification procedures and type approval and product testing of on-off and control valves”. EPA method 21 standard of the United States Environmental Protection Agency only specifies the detection method, but does not pide the leakage level. It belongs to the local standard regulations, and is rarely used. According to ISO 15848 and shell MESC SPE 77 / 312, the performance of valves is evaluated from three aspects: tightness grade, durability grade and temperature grade. According to the leakage of valve stem and valve body seal, the tightness grade is pided into a, B and C. for iso15848 standard, the leakage requirement of valve body seal is ≤ 50 em3/m3, while the leakage of valve stem is calculated according to the diameter of valve stem. The sealing grade of ISO 15848A is the highest, and that of B and C is the same as shell MESC SPE 77/312. Generally, the sealing grade of low leakage valve is lower than grade B, while the sealing grade of bellows seal valve is lower than grade a due to the metal bellows seal used in the sealing part of valve stem. 5. Selection of low leakage valve Bellows seal valve is one of the low leakage valves. In the past, bellows sealing valve was generally used in the working conditions with special requirements for valve leakage grade. However, due to the great difficulty and high technical requirements of bellows sealing valve f-jjm, its bellows material can not be completely localized and the cost is too high, which restricts its extensive application in petrochemical industry. At present, with the continuous enhancement of people’s awareness of safety and environmental protection, the increase of technical cooperation with foreign countries, and the continuous strengthening of domestic valve manufacturers’ own technical strength, domestic technical personnel’s understanding of low leakage valves is also constantly improving, so that its application scope is constantly expanding. If the valves selected for inflammable, explosive and toxic media in petrochemical enterprises can meet the low leakage standard, it will undoubtedly greatly reduce the emission of toxic, combustible and explosive media in the device, and avoid fire, explosion, poisoning and other accidents endangering life safety caused by valve leakage. Compared with bellows valves, low leakage valves meeting ISO 15848 and shell MESC SPE 77/31 standards have simple structure and easy manufacturing, and their cost is about 10% – 20% higher than that of general valves. According to the previous analysis and comparison of the two standard sealing grades, the leakage of tight grade B valve can generally meet the low leakage requirements of some special working conditions, the machining accuracy requirements are relatively easy to achieve, and the manufacturing cost is not much increased. It can replace part of the bellows valve. At present, low leakage valve has more practical significance for purification system of oil and gas field with high content of hydrogen sulfide. Because hydrogen sulfide is a highly toxic and combustible gas, heavier than air, and can gather in low-lying areas. Inhaling a certain concentration of hydrogen sulfide will harm the body and even lead to death. Therefore, the requirements for leakage of such natural gas purification facilities are more stringent. 6. Conclusion When selecting the sealing grade and the specified allowable leakage, it should be noted that the leakage of medium between the sealing surfaces of high-pressure valves will cause surface erosion. If there is leakage of corrosive medium, the metal at the leakage place will be corroded. With the increase of leakage gap, the leakage volume will also increase rapidly, so that the valve will be scrapped. Therefore, for the high pressure or corrosive medium working condition of the valve, in ensuring the sealing should put forward higher requirements. In the pipeline conveying flammable, explosive and toxic media, the leakage of media between valve sealing surfaces may cause personal harm, economic loss and even accidents. Therefore, for the valves conveying flammable, explosive and toxic media, the requirements for sealing should be reasonably put forward according to the dangerous level of the media. Any seal sometimes allows a small amount of leakage, if the leakage does not play a practical role, it can be considered as sealed. The technical standard of valve manufacturing usually stipulates that metal to metal seal is allowed to have a certain amount of leakage when sealing performance test is carried out under closed state. In order to ensure the high sealing performance of the valve, it is necessary to grind the sealing surface carefully, increase the specific pressure on the sealing surface, but it should be less than the allowable specific pressure of the sealing surface material, and improve the structural stiffness. The application experience of valves shows that in many cases, it is unnecessary to put forward too high requirements on the sealing performance of valves, because some working conditions completely allow a small amount of medium leakage, because the leakage is not enough to affect the use of valves. On the contrary, improving the sealing performance of these valves will complicate the manufacturing process, increase the cost and cause unnecessary waste. The structural design and manufacturing process of the valve itself have the most obvious impact on its external leakage. For low leakage valves, the design, manufacturing and processing requirements of key components such as valve body, stem and stuffing box are more stringent, such as: (1) The quality of valve body and cover, especially in forging or casting, should avoid folding, slag inclusion, porosity, microstructure evacuation, hidden cracks and other defects and uneven composition. (2) The processing quality of the parts at the connection of valve stem and valve body, especially the roughness of valve stem and stuffing box, the straightness of valve stem, the verticality of valve cover stuffing box hole and the processing accuracy. (3) The structure selection of the valve stuffing box, because the seal at the valve stem is dynamic seal, the packing is easy to wear during the rotation or sliding of the valve stem. It is necessary to select a special low leakage packing seal and packing seal combination, and strictly control the gap between the packing and the valve stem, and between the packing and the packing box. To sum up, the selection of valve type should not only meet the process conditions and standards, but also fully consider various working conditions. In the engineering design, the valve sealing grade should meet the principles of safety, rationality and economy. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Selection of heat exchanger type and scaling treatment method 1. When the temperature difference is large, floating head heat exchanger, U-shaped tube heat exchanger, stuffing box heat exchanger and sliding tube sheet heat exchanger can be selected. When the shell side is often mechanically cleaned, the structure with withdrawable tube bundle can be selected. Under high temperature and high pressure, U-tube heat exchanger can be selected. When the shell side medium is flammable, explosive, toxic or volatile, and the service pressure and temperature are high, the stuffing box heat exchanger should not be used. When the tube side medium and shell side medium are not allowed to be mixed, the heat exchanger with double tubesheet structure can be used. 2. Types and selection principles of tubular heat exchangers (1) Tubular heat exchangers can be pided into the following main types: ① The tubesheets at both ends of the tube bundle of the tubular heat exchanger are connected with the shell as a whole, with simple structure, but it is only applicable to the heat exchange operation when the temperature difference between cold and hot fluids is small and the shell side does not need mechanical cleaning. When the temperature difference is slightly large and the shell side pressure is not too high, an elastic compensation ring can be installed on the shell to reduce the thermal stress. ② The tube sheet at one end of the floating head heat exchanger tube bundle can float freely, which completely eliminates the thermal stress, and the whole tube bundle can be extracted from the shell, which is convenient for mechanical cleaning and maintenance. Floating head heat exchanger is widely used, but its structure is complex and its cost is high. ③ Each heat exchange tube of the tubular heat exchanger is bent into a U shape, and both ends are respectively fixed in the upper and lower areas of the same tube plate, which is pided into inlet and outlet chambers with the help of the diaphragm in the tube box. The heat exchanger completely eliminates the thermal stress and has a simpler structure than the floating head sheet type, but the tube side is not easy to clean. For the heat exchange of highly corrosive fluids in chemical production, non-metallic materials such as ceramics, glass, polytetrafluoroethylene and graphite need to be used to make shell and tube heat exchangers. This kind of heat exchanger has poor heat exchange performance and is only used in occasions with low pressure, low vibration and low temperature. (2) For the cold and hot fluids for heat exchange, the flow channel shall be selected according to the following principles: ① Unclean and easy to scale fluids should go through the pipe side, because it is more convenient to clean in the pipe. ② Corrosive fluid should go through the tube side to avoid corrosion of tube bundle and shell at the same time. ③ The fluid with high pressure should go through the pipe side to avoid pressure on the shell. ④ The saturated steam should go through the shell side, because the heat transfer coefficient of steam condensation has nothing to do with the flow rate, and the condensate is easy to discharge. 3. Precautions and working principle of fixed tubesheet heat exchanger Precautions for fixed tubesheet heat exchanger during operation include: (1) The heat exchanger can only be used after pressure test after new installation or maintenance. (2) When starting the heat exchanger, the cold flow shall be followed by the heat flow, and when stopping the work, the heat flow shall be stopped first and then the cold flow. To prevent leakage or damage caused by uneven thermal expansion and cold contraction. (3) The fixed tubesheet heat exchanger is not allowed to be heated in one direction, and the temperature difference on both sides of the tube and shell of the floating heat exchanger is not allowed to be too large. (4) During startup, the exhaust valve shall be kept open to discharge all air, and shall be closed after startup. (5) If hydrocarbons are used, the air in the heat exchanger shall be removed with inert gas before loading hydrocarbons to avoid explosion. (6) During shutdown and purging, the condensate must be drained before steam introduction, and the air shall be ventilated slowly to prevent water hammer. When one side of the heat exchanger is ventilated, the vent valve on the other side must be opened to avoid damage to the pressure. When the heat exchanger is closed, the exhaust valve and drain valve shall be opened to prevent the equipment from being damaged by vacuum caused by cooling. (7) When using the air cooler, pay attention to the uniform flow of some parts to ensure the cooling effect. (8) Always pay attention to monitoring to prevent leakage. Working principle of fixed tubesheet heat exchanger: It is the structure of fixed tubesheet heat exchanger. A fluid flows into the housing from the connecting pipe 1 and flows out from the connecting pipe 2 through the pipe. B fluid flows in from the connecting pipe 3 and out of the connecting pipe 4 through the pipe. If the temperature of fluid a is higher than that of fluid B, heat is transferred from fluid a to fluid B through the pipe wall; On the contrary, it is transferred from fluid B to fluid a through the pipe wall. The area inside the shell and outside the pipe and pipe box is called the shell side, and the fluid passing through the shell side is called the shell side fluid (a fluid). The area inside the pipe and the pipe box is called the pipe pass, and the fluid passing through the pipe pass is called the pipe pass fluid (B fluid). Shell and tube heat exchanger is mainly composed of tube box, tube plate, tube, shell and baffle. Generally, the shell is cylindrical and the pipe is straight or U-shaped. In order to improve the heat transfer efficiency of the heat exchanger, threaded tubes and finned tubes can also be used. The arrangement of pipes has many forms, such as equilateral triangle, square, square skew 45 ° and concentric circle. The first three are the most common. When arranged in a triangle, more tubes can be arranged in the shell with the same diameter to increase the heat transfer area, but it is difficult to clean the tubes mechanically and the fluid resistance is large. The overall of tubesheet and tube is called tube bundle. There are two types of connection between the end of the pipe and the tubesheet: welding and expansion. Some baffles are set transversely in the tube bundle to guide the shell side fluid to change the flow direction for many times and effectively scour the tube, so as to improve the heat transfer efficiency and support the tube at the same time. The shapes of baffles include bow, circle and rectangle. In order to reduce the flow cross section of shell side and tube side fluid, speed up the flow rate and improve the heat transfer efficiency, split partition plates can be set longitudinally in the tube box and shell, pide the shell side into 2 passes and the tube side into 2 passes, 4 passes, 6 passes and 8 passes. 4. Type and connection mode of floating head heat exchanger One end of the tubesheet at both ends of the floating head heat exchanger is not connected with the shell, and this end is called floating head. When the tube is heated, the tube bundle and the floating head can expand and contract freely along the axial direction, completely eliminating the temperature difference stress. The floating head heat exchanger has a tubesheet at one end fixed with the shell, while the tubesheet at the other end can float freely in the shell. The shell and tube bundle are free from thermal expansion, so when the temperature difference between the two media is large, there will be no temperature difference stress between the tube bundle and the shell. The floating head end is designed into a detachable structure, so that the tube bundle can be easily inserted or pulled out, which provides convenience for maintenance and cleaning. This type of heat exchanger is especially suitable for working conditions where the temperature difference stress between the shell and the heat exchange tube is large and both the shell side and the tube side are required to be cleaned. (1) Advantages of floating head heat exchanger: A the tube bundle can be pulled out to facilitate the cleaning of the tube and shell side. B. the temperature difference between media is not limited. C. It can work under high temperature and high pressure. Generally, the temperature is less than or equal to 450 degrees and the pressure is less than or equal to MPa. D. It can be used in occasions with serious scaling. E. it can be used in places where the pipe side is easy to corrode. (2) Disadvantages of floating head heat exchanger: A small floating head is prone to internal leakage. B the consumption of metal materials is large and the cost is 20%. C complex structure. (3) Selection requirements for parts and materials of floating head heat exchanger. (4) Connection mode of heat exchange tube and tubesheet: the connection mode of heat exchange tube and tubesheet includes expansion, welding, expansion and welding, etc. A. Expansion joint Expansion joint formation can be pided into sticking expansion and strength expansion according to expansion tightness. Sticking expansion refers to the slight expansion to eliminate the gap between heat exchange tube and tubesheet. Strength expansion refers to the expansion joint to ensure the sealing performance and tensile strength of the connection between heat exchange tube and tubesheet. B. Welding The welding connection between heat exchange tube and tubesheet is pided into strength welding and sealing welding. Strength welding refers to the welding to ensure the sealing performance and tensile strength of the connection between heat exchange tube and tubesheet. Seal welding refers to the welding to ensure the sealing performance of the connection between heat exchange tube and tubesheet. The welding of heat exchange tube and tube sheet generally adopts manual arc welding, manual sub arc welding and automatic rotating argon arc welding. C. Expansion and welding In terms of expansion welding connection process, it can be pided into expansion before welding and welding before expansion. Expansion and welding are suitable for occasions with high sealing performance requirements; Occasions bearing vibration or fatigue load; Occasions with interstitial corrosion; Where composite tubesheet is used. (5) Selection of connection type between heat pipe and tubesheet The application scope of strength expansion specified in GB150 pressure vessels is: the design pressure is less than or equal to 4MPa; Design temperature is less than or equal to 300 ° C; There is no violent vibration, excessive temperature change and obvious stress corrosion during operation. The application scope of strength welding is: it can be used for the design pressure specified in this standard, but it is not suitable for occasions with large vibration and interstitial corrosion. Expansion and welding are suitable for occasions with high sealing performance requirements; Occasions bearing vibration or fatigue load; Occasions with interstitial corrosion; Where composite tubesheet is used. 5. Reasonable selection of heat exchange medium and preliminary treatment method Generally, scale inhibitor and algicide are added. If necessary, sulfuric acid is added to adjust the pH value. Pay attention to the hardness and pH value of circulating water, and timely adjust the dosage of scale inhibitor and sulfuric acid. Algicide is generally added by impact method. Pay attention to sewage discharge 1-2 days after algicide is added. If possible, the soft water treatment system can be used, but algicide must be added. Even so, some biological slime will adhere to the heat exchanger, and high-pressure water can be considered for cleaning. The agents added in the circulating water system are mainly bactericidal algicide and corrosion and scale inhibitor, which aims to improve the circulating water quality, slow down the corrosion of equipment and pipelines and prevent scaling in the heat exchanger, To increase the fouling thermal resistance, we should strictly control the relevant process parameters in the actual production process, hang hanging pieces at different points in the circulating water system, and properly adjust the agent according to the hanging piece corrosion. 6. Reduce and eliminate scale formation from the process control of heat exchanger operation The process conditions of heat exchanger include heat transfer, thermodynamic parameters of fluid (temperature, pressure, flow, phase state, etc.) and physicochemical properties (density, viscosity, corrosivity, etc.). While ensuring heat transfer efficiency, minimize the conditions for scaling formation; The operation shall be carried out in strict accordance with the specifications. The general practice is: (1) Increase the heat transfer coefficient. On the premise of comprehensively considering the fluid resistance and no fluid induced vibration, the high flow rate shall be selected as far as possible. (2) Increase the average temperature difference. For the fluid without phase change, the heat transfer mode close to countercurrent shall be adopted as far as possible. Because this can not only improve the average temperature difference, but also help to reduce the temperature difference stress in the structure. Under allowable conditions, the inlet temperature of hot fluid can be increased or the inlet temperature of cold fluid can be reduced. (3) Properly arrange the heat transfer surface. For example, heat exchangers, cold disks, etc. adopting appropriate tube spacing or arrangement can not only increase the heat transfer area in unit space, but also improve the fluid flow characteristics. The heat transfer mode of staggered tube bundle is better than that of parallel tube bundle. (4) Cleaning method of formed scale ① Chemical method The chemical method is to remove the scale by chemical reaction or loosen the scale by chemical reaction, and then remove it by external force. Of course, for chemical cleaning, it is best to ask an experienced professional company for cleaning. The cleaning cost is low. Before cleaning, analyze the scaling composition and formulate a detailed construction scheme. During cleaning, ensure that the chemical solution will not erode the heat exchange pipe and process pipeline. ② Mechanical method (a) High pressure water jet cleaning: generally, 1-5mpa pressure is used to form a strong jet through the spray gun nozzle, and the water volume reaches 80-120l / min to break and scour the scale layer to achieve the purpose of cleaning. At present, the manual hand-held flexible or rigid spray gun is basically used to flush the inner side of the heat transfer tube one by one, and the outer side of the tube bundle is rotated section by section to flush from multiple directions. In order to improve efficiency and reduce labor intensity, different spraying instruments shall be used according to the scale conditions, such as improving the nozzle (nozzle size, shape, quantity and angle). For some insoluble scale and blockage, special cleaning methods shall be adopted, such as high-pressure water jet drill bit or ultra-high-pressure water jet > 70MPa. Combined cleaning can also be carried out by reagent or heating. (b) Manual cleaning or pipeline mechanical cleaning brush: manual cleaning or pipeline mechanical cleaning brush is used to clean the inner wall of the pipe. This method has good adaptability and can be cleaned for many times, but attention must be paid not to damage the pipe wall. ③ Regular cleaning In order to eliminate the scaling during the operation of the heat exchanger, the flow can be increased periodically and temporarily or countercurrent operation can be carried out, which can effectively eliminate the light attachments on the inner wall of the pipe, but the backwash pipeline shall be preset on the equipment. It can also be cleaned with rubber balls. Appropriate chemicals can also be injected according to the type of fluid to remove the dirt. Timely cleaning shall be carried out during each shutdown and maintenance, and the effect is the best. ④ Cleaning during parking The shutdown cleaning of heat exchanger shall adopt different methods for different types of heat exchangers and scaling conditions, mainly including high-pressure water jet cleaning, chemical cleaning and mechanical cleaning. Mechanical cleaning is to manually pull through the strip or rotate the heat transfer pipe one by one with an electric drill bit. If the compressed oil cooler is overhauled, it shall be cleaned in time. It is not easy to clean for a long time, with high labor intensity and easy to damage the inner wall of the steel pipe. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Strainer is an indispensable device in the medium pipeline. It is usually installed at the inlet of pressure reducing valve, pressure relief valve, constant water level valve, square strainer and other equipment. The strainer is composed of cylinder, stainless steel strainer screen, blowdown part, transmission device and electrical control part. After the water to be treated passes through the strainer cartridge of the strainer screen, its impurities are blocked. When it needs to be cleaned, as long as the detachable strainer cartridge is taken out and re loaded after treatment, it is very convenient to use and maintain. Selection principle and requirement of strainer The strainer is a small equipment to remove a small amount of solid particles in the liquid, which can protect the normal operation of the equipment. When the fluid enters the strainer cartridge with a certain size strainer screen, its impurities are blocked, and the clean filtrate is discharged from the outlet of the strainer. When cleaning is needed, just take out the detachable strainer cartridge and reload it after treatment. 1. Inlet and outlet diameter of strainer: In principle, the inlet and outlet diameter of the strainer should not be less than the inlet diameter of the matching pump, which is generally consistent with the inlet pipe diameter. 2. Nominal pressure selection: The pressure level of the strainer is determined according to the highest possible pressure in the strainer pipeline. 3. Selection of hole number: The selection of the number of strainer holes mainly considers the particle size of impurities to be intercepted, which is determined according to the process requirements of medium flow. For the interceptable particle size of various specifications of screen, please refer to the table “screen specifications”. 4. Strainer material: The material of the strainer is generally the same as that of the connecting process pipe. For different service conditions, the strainer made of cast iron, carbon steel, low alloy steel or stainless steel can be selected. 5. Calculation of strainer resistance loss The pressure loss of water strainer is 0.52-1.2kpa at the rated flow rate. Application of strainer 1. Stainless steel strainer Stainless steel strainer is widely used in steam, air, water, oil, and other media pipelines; Protect all kinds of equipment, pumps and valves in pipeline system; It is free from blockage and damage caused by rust, welding slag and other impurities in the pipeline. The stainless steel strainer has the advantages of strong pollution resistance, convenient pollution discharge, large circulation area, small pressure loss, simple structure, small volume and light weight. The strainer screen is made of stainless steel with strong corrosion resistance and long service life. 2. Y-type strainer Y-type strainer is an indispensable strainering device in the pipeline system of conveying medium. Y-type strainer is usually installed at the inlet end of pressure reducing valve, pressure relief valve, constant water level valve or other equipment to remove impurities in medium and protect the normal use of valve and equipment. The Y-type strainer has the advantages of advanced structure, small resistance and convenient discharge. 3. Y-type pull rod telescopic strainer The Y-type telescopic strainer adopts a new design, which combines the Y-type strainer with the expansion joint. The structure is simple and easy to use. It solves the problem of inconvenient installation on the fixed pipeline caused by different flange lengths of different standard products. The telescopic strainer is mainly used for water supply and drainage piping in high-rise buildings, multi-storey buildings or factories, and is usually installed on the pressure reducing valve, the pressure reducing valve and the pipe The inlet end of pressure relief valve, constant water level valve or other main equipment is installed with pull rod telescopic strainer, which is convenient for removing pipe debris or installation and disassembly, so as to ensure the normal use of valves or equipment. 4. Basket strainer Basket type strainer can remove small equipment with a small amount of solids in liquid, which can protect compressor, pump and other equipment and instruments; It is also a small equipment to improve product purity and purify gas. Therefore, basket strainer is widely used in petroleum, chemical, chemical fiber, medicine, food and other industries. Basket strainer is composed of shell, drain cover, strainer element, strainer screen, bolt, etc. 5. T-type strainer T-type strainer is widely used in the pipeline of steam, air, water, oil and other media to protect all kinds of equipment in the pipeline system, such as water pumps, valves, etc., from the blockage and damage of the pipeline caused by rust, welding slag and other debris in the pipeline. The T-type strainer produced by Shanghai rimei Valve Manufacturing Co., Ltd. has the characteristics of strong anti fouling performance, convenient discharge, large circulation area, small pressure loss, simple structure and small volume; The strainer screen of T-type strainer is made of stainless steel with strong corrosion resistance and long service life; T-type strainer is also pided into direct current type and baffled type. The density of the strainer screen is 10-120 mesh, and the temperature is 0-450 ℃. It can be selected according to the needs of users. Source: China Strainers Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

What is shot blasting? Shot blasting is a process that uses compressed air as power to spray shot onto the workpiece surface and clean or strengthen the workpiece surface. The medium used for shot blasting is round particles without edges and corners, such as steel shot, iron shot, glass shot and ceramic shot. Shot blasting relies on the strong impact force of shot particles to make the workpiece surface closer, so as to make the workpiece more wear-resistant, ductile and corrosion-resistant. Shot blasting, also known as shot blasting strengthening, is one of the effective methods to reduce fatigue and improve service life of parts. Shot blasting is to spray high-speed projectile flow onto the surface of parts, resulting in plastic deformation on the surface of parts, forming a strengthening layer with a certain thickness. High residual stress is formed in the strengthening layer. Due to the existence of compressive stress on the surface of parts, When the parts bear load, it can offset part of the stress, so as to improve the fatigue strength of the parts. Shot blasting is a surface strengthening process widely used in factories, that is, the cold working process of bombarding the workpiece surface with shot particles and implanting residual compressive stress to improve the fatigue strength of the workpiece. It is widely used to improve the mechanical strength, wear resistance, fatigue resistance and corrosion resistance of parts. The advantages of shot blasting are simple equipment, low cost, not limited by workpiece shape and position, and convenient operation. The disadvantages are poor working environment, low unit output and lower efficiency than shot blasting. The types of shot blasting include steel shot, cast iron shot, glass shot, ceramic shot, etc. Types of pills Pills are generally spherical particles without edges and corners, such as steel wire cut pills. Cast steel shot Its hardness is generally 40 ~ 50HRC. When processing hard metals, the hardness can be increased to 57 ~ 62HRC. Cast steel shot has good toughness and is widely used. Its service life is several times that of cast iron shot Cast iron shot Its hardness is 58 ~ 65HRC, brittle and easy to break. Short service life and not widely used. It is mainly used for occasions requiring high shot blasting strength Glass pellet The hardness is lower than the first two. It is mainly used for stainless steel, titanium, aluminum, magnesium and other materials that do not allow iron pollution. It can also be used for secondary processing after steel shot blasting to remove iron pollution and reduce the surface roughness of parts. Ceramic pill The chemical composition of ceramic pellets is approximately 67% ZrO2, 31% SiO2 and 2% Al2O3 inclusions, which are made by melting, atomizing, drying, rounding and screening, and the hardness is equivalent to HRC57 ~ 63. Its outstanding properties are higher density and hardness than glass. It was first used for aircraft parts strengthening in the early 1980s. Ceramic pellets have higher strength, longer service life and lower price than glass pellets. Now they have been extended to the surface strengthening of non-ferrous metals such as titanium alloy and aluminum alloy. Therefore, there are four categories of shot: cast steel shot, cast iron shot, glass shot and ceramic shot Special note: Glass shot for shot blasting and glass shot for other purposes are two different concepts. The biggest feature of shot peened glass shot is that its minimum hardness is not less than 6-7 Mohs, and it has certain toughness, and the minimum rounding rate is not less than 90%. The road reflective glass shot has no requirements for hardness. Generally, ordinary glass can be used as raw material, and the rounding rate is required to be at least 75%. The two prices are very different, but the appearance is almost the same. If ordinary glass shot is used for shot blasting, it seems that the cost is low. When shot blasting, the crushing rate is high and the workpiece with high strength is almost broken at one time. In contrast, the total cost is much higher. Characteristics of shot blasting 1) Metallic or non-metallic projectiles can be used arbitrarily to meet the different requirements of cleaning the workpiece surface; 2) The cleaning is flexible, easy to clean the inner and outer surfaces of complex workpieces and the inner wall of pipe fittings, and is not limited by the site. The equipment can be placed near super large workpieces; 3) The equipment has simple structure, less investment, less vulnerable parts and low maintenance cost; 4) A high-power air compressor station must be equipped, which consumes more energy under the condition of the same cleaning effect; 5) The cleaned surface is prone to moisture and rust regeneration; 6) Low cleaning efficiency, many operators and high labor intensity. ▲ strong shot blasting machine The advantages of shot blasting are simple equipment, low cost, not limited by workpiece shape and position, and convenient operation. The disadvantages are poor working environment, low unit output and lower efficiency than shot blasting. The types of shot blasting include steel shot, cast iron shot, glass shot, ceramic shot, etc. Gear shot blasting strengthening: it is mainly to impact the surface of parts with the help of high-speed bullets to make them undergo elastic-plastic deformation, resulting in favorable changes such as residual compressive stress, work hardening and microstructure refinement, so as to improve the bending fatigue strength and contact fatigue strength of gears. It is an important way to improve the anti bite ability of gears and improve the service life of gears. During shot blasting, the small-size spherical steel shot strikes the surface of the workpiece to form a compressive stress. The impact of each shot will produce a certain plastic deformation of the metal, and the final surface can not completely recover to form a permanent compressive stress state. As a surface strengthening process, shot blasting can form residual compressive stress on the surface, which is equivalent to 55% ~ 60% of the tensile strength limit of the material, and the workpiece surface is the place where cracks are easy to initiate. For carburized and quenched gears, the compressive stress can reach 1177 ~ 1725mpa, which can greatly improve the fatigue performance. Improving surface hardness of carburized gear by gear shot blasting For example, the shot blasting equipment of FAW heat treatment branch adopts German tr5svr-1 stress shot blasting equipment. Shot blasting process: use steel shot with diameter of ￠ 0.8mm, shot blasting time of 9min and shot blasting speed of 2800r / min. The gear material is 22CrMoH steel, which is carburized, Quenched and tempered. After shot blasting, the surface structure of the gear is refined. The residual austenite content of the surface is about 10% lower than that of the workpiece without shot blasting, and the change is obvious within 0.15mm from the surface; The surface hardness of the gear after enhanced shot blasting is increased by 0.5 ~ 2hrc. Shot blasting improves the fatigue life of gears For example, FAW carried out the fatigue life test on the first gear of “Jiefang” automobile transmission by using the enhanced shot blasting process, which significantly improved the fatigue life of the gear. In order to improve the fatigue life of the “Jiefang” brand driving helical gear, the large arc hob is used to cut the teeth. Increasing the gear fillet can increase the service life of the driving helical gear from 208300 times to 695400 times. If enhanced shot blasting is used, the fatigue life can be increased to 2109000 times. Classification of shot blasting Shot blasting is pided into shot blasting and sand blasting. The surface treatment with shot blasting has great striking force and obvious cleaning effect. However, the treatment of thin plate workpiece by shot blasting is easy to deform the workpiece, and the steel shot strikes the workpiece surface (whether shot blasting or shot blasting) to deform the metal substrate. Because Fe3O4 and Fe2O3 are not plastic, they are stripped after crushing, and the oil film is deformed together with the substrate, shot blasting and shot blasting cannot completely remove the oil stain on the workpiece with oil stain. Among the existing workpiece surface treatment methods, sand blasting has a good cleaning effect. Sand blasting is suitable for cleaning the workpiece surface with high requirements. However, the general sand blasting equipment in China is mostly composed of original heavy sand conveying machinery such as hinged dragon, scraper and bucket elevator. Users need to build a deep pit and make a waterproof layer to install machinery. The construction cost is high, the maintenance workload and maintenance cost are great, and a large amount of silicon dust generated in the sand blasting process cannot be removed, which seriously affects the health of operators and pollutes the environment. Shot blasting is pided into general shot blasting and stress shot blasting. During general treatment, when the steel plate is in a free state, the inside of the steel plate is hit with high-speed steel shot to produce preloading stress on its surface. To reduce the tensile stress on the steel plate surface and increase the service life. Stress shot blasting is the pre bending of the steel plate under a certain force, and then shot blasting. Application of shot blasting Shot blasting is used to remove oxide scale, rust, molding sand and old paint film on medium and large metal products with a thickness of not less than 2mm or not required to maintain accurate size and contour, as well as castings and forgings. It is a cleaning method before surface coating (plating). It is widely used in large shipyards, heavy machinery factories, automobile factories, etc. Shot blasting is a cold treatment process, which is widely used to improve the fatigue resistance of metal parts in long-term service under high stress conditions, such as aircraft engine compressor blades, fuselage structural parts, automobile transmission system parts and so on. Shot blasting strengthening is to spray the medium called steel shot at a high speed and continuously in a fully controlled state and hammer it to the surface of the part, so as to produce a residual compressive stress layer on the surface. Because when each steel shot hits the metal part, it is like a miniature rod hammering the surface, hammering out small indentation or depression. In order to form a depression, the metal surface must be stretched. Under the surface layer, the compressed grains try to restore the surface to its original shape, resulting in a hemisphere under the action of high compressive force. Numerous depressions overlap to form a uniform residual compressive stress layer. Finally, under the protection of compressive stress layer, the fatigue strength of parts is greatly improved and the safe working life is prolonged. Difference from shot blasting and sand blasting Difference between shot peening and shot blasting Shot peening uses high-pressure air or compressed air as power, and shot blasting is generally a high-speed rotating flywheel to shoot out the steel sand at high speed. Shot blasting has high efficiency, but there will be dead corners, while shot blasting is more flexible, but the power consumption is large. Although the two processes have different spraying power and methods, they both aim at high-speed impact on workpieces, and their effects are basically the same. In comparison, shot peening is relatively fine and easy to control accuracy, but the efficiency is not as high as shot blasting. It is suitable for small workpieces with complex shapes. Shot blasting is more economical and practical, easy to control efficiency and cost, and can control the particle size of shot to control the spraying effect, However, there will be dead corners, which is suitable for batch processing of workpieces with single shape and surface. The selection of the two processes mainly depends on the shape of the workpiece and the machining efficiency. Difference from sand blasting Both shot blasting and sand blasting use high-pressure air or compressed air as power to blow it out at high speed and impact the workpiece surface to achieve cleaning effect, but the effect is also different due to different media. After sand blasting, the dirt on the workpiece surface is removed and the surface area is greatly increased, thus increasing the bonding strength between the workpiece and the coating. The surface of the workpiece after sand blasting is of the natural color of metal, but because the surface is rough and the light is refracted, it has no metal luster and is a darkened surface. After shot blasting, the dirt on the workpiece surface is removed, and the workpiece surface is slightly damaged, which is not easy to be damaged. The surface area has increased. Because the workpiece surface is not damaged in the machining process, the excess energy generated during machining will lead to the surface strengthening of the workpiece matrix. The surface of the workpiece after shot blasting is also the natural color of metal, but because the surface is spherical and the light is partially refracted, the workpiece is processed into matte effect. Quality evaluation of shot blasting Cleaning quality level a. Most thorough cleaning level (SA3) The cleaned steel surface is completely silver gray, with a certain surface roughness to improve the adhesion of the coating. b. Very thorough cleaning level (SA2.5) The cleaned steel surface shall be free of grease, dirt, scale, rust, corrosion products, oxides and other impurities. Shadows and color differences due to incomplete cleaning are allowed, but at least 95% of the surface per square inch shall reach the level of the most thorough cleaning, and only slight shadows and color differences shall appear in the rest. c. More thorough cleaning level The cleaned steel surface shall be free of grease, dirt, rust scale and other impurities. The oxide scale, rust and old paint shall be removed. Light shadows and color differences due to incomplete removal of rust and oxide scale are allowed, and the area shall not exceed 33% per square inch; If pitting corrosion has occurred on the steel surface, a small amount of rust and old paint are allowed at the depth of the corrosion point. d. Non thorough cleaning level After the surface is completely cleaned, grease, dirt, loose oxide skin and loose paint skin are removed. Oxide skin, rust, paint and coating that are firmly bonded to the substrate and cannot be removed with a very sharp blade are allowed to remain on the surface after cleaning. A large number of evenly distributed metal spots appear on the surface. Surface roughness Surface roughness and surface cleanliness are produced at the same time. Determining the appropriate surface roughness is as important as determining the correct cleanliness requirements. Effect of surface roughness 1) The actual bonding area between the coating and the workpiece surface is increased, which is conducive to improving the bonding force of the coating; 2) The coating will produce great internal stress during curing. The existence of roughness can effectively eliminate the stress concentration in the coating and prevent the coating from cracking; 3) The existence of surface roughness can support the quality of some coatings and help to eliminate sagging, especially for vertically coated surfaces. The factors affecting roughness are as follows: 1) Abrasive particle size, hardness and particle shape; 2) Hardness of workpiece material; 3) Pressure and stability of compressed air; 4) The distance between the nozzle and the workpiece surface and the included angle between the nozzle and the workpiece surface. Several problems related to surface roughness: 1) The cleaning time is almost independent of the surface roughness; 2) The angle between the nozzle and the surface will affect the surface roughness, but the change is not obvious between 45 degrees and 90 degrees; 3) Cleaning the difficult surface with large particle abrasive can improve the work efficiency, but the surface roughness will be high. The research shows that the roughness value caused by abrasive with particle size greater than 1.2mm is high. The surface with high roughness can be cleaned again with small grain abrasive to reduce the roughness to the specified requirements. Shot blasting produces greater compressive stress on the surface than sand blasting. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

What is shot peening? Shot peening uses the high-speed rotating impeller to throw out small steel shot or small iron shot and impact the part surface at high speed, so the oxide layer on the part surface can be removed. At the same time, steel shot or iron shot impacts the part surface at high speed, resulting in lattice distortion and deformation on the part surface and increasing the surface hardness. Shot peening is a method to clean the part surface. Shot peening is often used to clean the casting surface or strengthen the part surface. Generally, shot peening is used for regular shapes. Several throwing heads are up, down, left and right together, with high efficiency and little pollution. In the shipbuilding industry, shot peening and sand blasting are widely used. Shot peening uses the high-speed rotating impeller to throw out the abrasive; Sand blasting is the use of compressed air to blow out the abrasive at high speed. Of course, shot peening does not have to use a high-speed rotating impeller. In the repair and shipbuilding industry, generally speaking, shot peening (small steel shot) is mostly used in steel plate pretreatment (rust removal before coating); Sand blasting (mineral sand is used in repair and shipbuilding) is mostly used in formed ships or sections to remove the old paint and rust on the steel plate and repaint it. In the repair and shipbuilding industry, the main function of shot peening and sand blasting is to increase the adhesion of steel plate coating paint. The research shows that in terms of damage, when there is tensile stress on the surface of metal materials, it is much easier than compressive stress. When there is compressive stress on the surface, the fatigue life of materials is greatly improved. Therefore, shot blasting is usually used to form surface compressive stress for parts prone to fatigue fracture such as shafts, so as to improve the product life. In addition, metal materials are very sensitive to tension, This is the reason why the tensile strength of materials is much lower than the compressive strength. This is also the reason why metal materials generally use tensile strength (yield, tensile) to represent material properties. The steel plate working face of our daily car is strengthened with shot blasting, which can significantly improve the fatigue strength of the material. Shot peening uses the motor to drive the impeller body to rotate, and by the action of centrifugal force, throws the balls (including cast shot, cut shot, stainless steel shot, etc.) with a diameter of 0.2 – 3.0 to the surface of the workpiece, so as to make the workpiece beautiful, or change the welding tensile stress of the workpiece to compressive stress, so as to improve the service life of the workpiece. Almost used in most fields of machinery, such as repair, shipbuilding, auto parts, aircraft parts, gun and tank surfaces, bridges, steel structures, glass, steel plates, pipelines, etc. Sand blasting (shot) uses compressed air as power to spray sand with a diameter of 40 – 120 mesh or shot with a diameter of about 0.1 – 2.0 to the surface of the workpiece, so that the workpiece can achieve the same effect. The treatment effect will be different if the size of the shot is different. It is emphasized that shot blasting can also play a role in strengthening. Now the domestic equipment has entered a misunderstanding that only shot peening can achieve the purpose of strengthening. Enterprises in the United States and Japan use shot blasting for strengthening, and each has its own advantages. For example, for a workpiece such as a gear, the shot angle of shot peening cannot be changed, and the initial speed can only be changed by frequency conversion. However, it has large processing capacity and fast speed, while shot blasting is just the opposite. The effect of shot peening is not as good as that of shot blasting. What is sand blasting? Sand blasting is a method that uses compressed air to blow out quartz sand at high speed to clean the surface of parts. It is also called sand blowing in the factory. It can not only remove rust, but also remove oil. It is very useful for coating. Commonly used for rust removal on the surface of parts; Surface modification of parts (this is the purpose of small wet sand blasting machine sold in the market. The sand is usually corundum and the medium is water); In the steel structure, the application of high-strength bolts for connection is a more advanced method. Because the high-strength connection uses the friction between the joint surfaces to transfer the force, the quality requirements of the joint surface are very high. At this time, the joint surface must be treated by sand blasting. Sand blasting is used for complex shape, easy to remove rust by hand, low efficiency, poor site environment and uneven rust removal. General sandblasting machines have sandblasting guns of various specifications. As long as they are not a particularly small box, they can put the gun in and clean it. The supporting product of pressure vessel – head adopts sand blasting to remove the oxide scale on the workpiece surface. One kind of processing is to use water as a carrier to drive emery to process parts, which is a kind of sand blasting. Both shot peening and sand blasting can clean and decontaminate the workpiece. The purpose is to prepare for the next process, that is, to ensure the roughness requirements of the next process. In addition, in order to ensure the consistency of the surface, shot blasting can strengthen the workpiece, so sand blasting is not obvious. Generally, shot blasting is a small steel ball and sand blasting is quartz sand. According to different requirements, the mesh number. Sand blasting and shot peening are used in precision casting almost every day. Supplement: 1. Both shot peening and sand blasting are surface treatment, but it does not mean that only castings are shot peening. 2. The main function of sand blasting is to remove rust and oxide scale on the surface, such as parts after heat treatment, while shot peening has many functions and functions. It not only removes rust and surface oxide scale, but also improves surface roughness, removes machining burrs of parts, eliminates internal stress of parts, reduces deformation of parts after heat treatment, and improves wear resistance and pressure resistance of parts. 3. There are many processes for shot blasting, such as castings, forgings, parts surface after machining, parts surface after heat treatment, etc. 4. Sand blasting is mainly manual operation, while shot peening is more automatic and semi-automatic. Add again (some repetition, some conflict): 1. Shot and sand Shot is generally spherical particles without edges and corners, such as cast steel shot, steel wire grinding shot, etc; Sand refers to angular sand particles, such as cast steel sand, brown corundum, white corundum, river sand, etc. 2. Spraying and throwing Spraying is to use compressed air as power to spray sand or shot onto the material surface to achieve removal and certain roughness. Polishing is a method of impacting the material surface with centrifugal force generated when the shot rotates at high speed to achieve removal and certain roughness. Comparison of sandblasting, shot blasting and shot peening Difference between shot blasting and shot peening The sandblasting process shot blasting uses high-pressure air or compressed air as power, while shot peening generally uses a high-speed rotating flywheel to eject the steel sand at high speed. Shot peening has high efficiency, but there will be dead corners, while shot blasting is more flexible, but the power consumption is large. Although the two processes have different injection power and methods, they both aim at high-speed impact on workpieces, and their effects are basically the same. In comparison, shot blasting is relatively fine and easy to control accuracy, but its efficiency is not as high as shot peening. Shot peening is suitable for small workpieces with complex shapes. Shot peening is more economical and practical, easy to control efficiency and cost, and can control the particle size of pellets to control the injection effect, However, there will be dead corners, which is suitable for batch processing of workpieces with single shape and surface. The selection of the two processes mainly depends on the shape of the workpiece and the machining efficiency. Difference between shot blasting and sand blasting Both shot blasting and sand blasting use high-pressure air or compressed air as power to blow it out at high speed and impact the workpiece surface to achieve cleaning effect, but the effect is also different due to different media. Difference between sand blasting and shot blasting After sand blasting, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged, and the surface area is greatly increased, thus increasing the bonding strength between the workpiece and the coating/coating. The surface of the workpiece after sand blasting is of the natural color of metal, but because the surface is rough and the light is refracted, it has no metal luster and is a darkened surface. After shot blasting treatment, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged without damage, and the surface area is increased. Because the workpiece surface is not damaged in the machining process, the excess energy generated during machining will lead to the surface strengthening of the workpiece matrix. After sandblasting, the surface of the workpiece is also the natural color of metal. However, because the surface is a spherical surface, part of the light is refracted, so the workpiece is processed into matte effect. Difference between sand blasting and shot peening 1. The two are different in meaning: shot peening uses the high-speed rotating impeller to throw out small steel shot or small iron shot and impact the part surface at high speed, so the oxide layer on the part surface can be removed. Sand blasting is the process of cleaning and roughening the substrate surface by using the impact of high-speed sand flow. 2. Different in nature: shot peening uses the high-speed rotating impeller to throw out the abrasive; Sand blasting is the use of compressed air to blow out the abrasive at high speed. 3. The two are suitable: shot peening is often used to clean the casting surface or strengthen the part surface; After sand blasting, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged, and the surface area is greatly increased, thus increasing the bonding strength between the workpiece and the coating/coating. The steel plate working face of our daily car is strengthened with shot blasting, which can significantly improve the fatigue strength of the material. Shot peening uses a motor to drive the impeller body to rotate, relying on the action of centrifugal force; Shot peening is usually a high-speed rotating flywheel that ejects steel sand at high speed. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

What is shot peening? Shot peening is a process that uses a high-speed rotating impeller to shoot the shot out at high speed, hit the workpiece surface, and clean or strengthen the workpiece surface. The materials used for shot peening include steel shot, aluminum shot, glass ball and ceramic shot. Characteristics of shot peening 1) High cleaning efficiency, low cost, few operators, easy to realize mechanization, suitable for mass production; 2) No compressed air is used to accelerate the projectile, so there is no need to set up a high-power air compression station, and the cleaned surface is free of moisture; 3) Poor flexibility, limited by the site, some blindness when cleaning the workpiece, and it is easy to produce dead corners on the workpiece surface that cannot be cleaned; 4) The equipment structure is complex, there are many vulnerable parts, especially the blades and other parts wear fast, there are many maintenance hours and high costs; 5) Generally, light and small projectiles cannot be used. Shot peening process Shot peening is also the name of a mechanical surface treatment process, similar to sand peening and shot peening. Shot peening is a cold treatment process, which is pided into shot peening cleaning and shot peening strengthening. Shot peening cleaning, as the name implies, is to remove surface oxide and other impurities to improve the appearance quality. Shot peening strengthening is to use high-speed motion of the projectile (60-110m/s) flow to continuously impact the surface of the strengthened workpiece. The target surface and surface layer (0.10-0.85mm) are forced to undergo the following changes during cyclic deformation: 1. Modification of microstructure; 2. Non-uniform plasticized outer surface introduces residual compressive stress and inner surface produces residual tensile stress; 3. The outer surface roughness changes (Ra Rz). Impact: it can improve the fatigue fracture resistance of materials/parts, prevent fatigue failure, plastic deformation and brittle fracture, and improve the fatigue life. Structure principle The two disks in the shot peening device are riveted together to form an impeller body. The impeller body is provided with eight blades, and the impeller body and the shot splitting wheel located in the center of the shot peening wheel are mounted on the main shaft driven by an electric motor. The cover is lined with a guard plate, and the cover shell is provided with a directional sleeve and a shot tube. When working, the shot from the shot tube into the shot peening device. The projectile wheel, which rotates synchronously with the blades, gives the projectile its initial velocity. The projectile flies out of the window of the directional sleeve and is thrown to the high-speed rotating blade outside the directional sleeve. After being further accelerated by the blade, it is thrown onto the surface of the cleaned workpiece. Because the synchronous rotation of the shot wheel and the blade ensures the non-vibration transmission of the projectile to the blade, thus reducing the wear of the blade. Peening principle is the body of the motor to drive the impeller rotation (direct drive or use the “V” belt drive), by the effect of centrifugal force, the diameter is about 0.2 ~ 3.0 of the projectile (have pills for cast steel, steel cut wire shot, stainless steel, such as different types) to the surface of the workpiece, the workpiece surface reaches a certain roughness, makes the artifacts become beautiful, Or change the welding tensile stress of the workpiece to compressive stress, improve the service life of the workpiece. By improving the surface finish of the workpiece, the film adhesion of the subsequent painting of the workpiece is also improved. Shot peening is almost used in most fields of machinery, such as shipbuilding, automobile parts, aircraft parts, surface of guns and tanks, Bridges, steel structures, glass, steel plate profiles, pipe internal and external wall corrosion and even road surface and so on. Bring about shot peening machine Shot peening machine is a kind of processing technology which impacts steel sand and steel shot on the surface of material object at high speed by shot peening device. It is faster and more efficient than other surface treatment techniques, and allows for partial retention or stamping after the casting process. Shot peening machine can also be used to remove burrs, diaphragms and rust, shot peening machine can also be directed at a partially coated surface to remove surface contaminants and provide an increase in coating adhesion surface profile, to achieve the purpose of strengthening the workpiece. Shot peening equipment is first applied to the surface of cast steel, cast iron sand and oxide cleaning. Almost all steel castings, gray castings, ductile iron and so on should be shot peening. This is not only to remove the oxide scale and sand on the surface of the casting, but also an indispensable preparation process before the quality inspection of the casting. For example, before the non-destructive inspection of the large gas turbine casing, strict shot peening cleaning must be carried out to ensure the reliability of the inspection results. Casting shot peening In general casting production, shot peening is an essential technological means to find surface defects of castings such as subcutaneous pores, slag holes, sand sticking, cold insulation, peeling, etc. The surface cleaning of non-ferrous metal castings, such as aluminum alloy and copper alloy, in addition to removing the oxide scale and finding the surface defects of the castings, the main purpose is to remove the burr of the die-casting parts by shot peening and obtain the surface quality with decoration significance, so as to achieve comprehensive results. Mechanical adjustment The new shot peening device must correctly adjust the position of the directional sleeve window before use, so that the projectile thrown as much as possible to be cleaned on the surface of the workpiece, in order to ensure the cleaning effect, reduce the wear of the indoor wall wear parts. The position of the directional sleeve window can be adjusted by referring to the manual. Shot peening material Common shot peening materials are steel shot, aluminum shot, ceramic powder, steel sand, walnut sand, corn cob, glass beads, resin sand, plastic sand and so on. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

For the skilled copper pipe installer, there are a variety of copper pipe connection options available. Not only are there the normal brazed joints, but there are also the excellent performance sleeve joints. We can make joints directly on the pipe and then weld them using hard brazing or bronze welding techniques, or we can use copper and copper alloy brazed sleeves. We can also use a variety of extruded joints. All of these copper pipe connections have been continuously developed and perfected, and they are completely reliable for qualified professional installers. In addition, the combination of copper and casing characteristics allows for long-term, reliable, safe and economical operation of gas, water supply, sewerage, and heating facilities. Mechanical connection Non-processing compression type connection The use of non-processing compression fittings to implement the mechanical connection of copper pipes, is a relatively simple construction method, simple operation, easy to grasp, the construction personnel only need a little training, you can master the operating skills. It is a common connection method in the current project. When connecting, as long as the end face of the pipe cutout can be kept vertical with the axis of the pipe, and the cutout burr and other clean, pipe assembly is the correct position of the card ring placement, and tighten the nut, you can achieve a tight connection of copper pipe. But this connection, is to rely on the thread on the compression force of the ring to keep the joint tight, so the joint should not be directly buried in the wall, it is advisable to lay the joint in the location can be serviced, so that once the compression force is slack and leakage, by further tightening the nut to maintain the necessary pressure. Processing compression type connection The use of processing compression fittings to implement the mechanical connection of copper pipe, is also one of the common construction methods of copper pipe connection, which is different from the construction method of non-processing compression connection, is that the end of the copper pipe must be shaped and processed before construction, that is, the construction of copper pipe, the end of the tube after cutting correction, but also need to use special forming tools, the end of the pipe processing bracket into a cup or cone, and the shape of the cup or cone, the size needs to be Standardized and unified. Because the connection of processing compression copper pipe fittings, is to rely on the cup or conical end of the pipe directly with the copper pipe fittings corresponding to the sealing surface to the tightness of the pipe joint, copper pipe end forming norms or not, directly affect the quality of the joint connection, therefore, engaged in copper pipe processing compression mechanical connection construction personnel, should be the necessary technical training, mastering the processing skills of forming before engaging in construction, in order to ensure that the processing of compression type connection construction quality. Flange and groove type connection The connection between the larger diameter copper pipe, copper pipe and valve fittings, as well as copper pipe and equipment, containers, the connection between the general use of flange connection, that is, copper pipe by brazing brass flange, or processing into the form of flanged plus steel flange, the formation of flange type joint, there are bolts and nuts to implement the flange connection. The connection between the larger diameter copper pipe, can also be used groove type connection, that is, the use of special groove forming machinery, the end of the copper pipe tied a depth and width in line with the standard groove connection ring groove, and then use the groove connection fittings, the two copper pipe connected into one. Using this connection, the wall thickness of the copper pipe must comply with the relevant standards. Copper and non-copper groove connection fittings contact surface, should be taken to isolate measures to prevent galvanic corrosion. Plug-in connection The use of plug-in copper fittings to implement the mechanical connection of copper pipes, is currently one of the simple construction methods, simple and convenient operation, the construction personnel only need to be familiar with its operational requirements, a little practice can be mastered. When connected, the end face of the pipe incision should be perpendicular to the axis of the pipe, the burr inside and outside the incision should be cleaned up, and marked with a marker on the outside of the front of the copper pipe to insert the depth, and then force the copper pipe into the pipe fittings to the end to stop the pipe. This bell connection method is to rely on special fittings in the stainless steel clamping ring to fasten the copper pipe in the fittings, the use of fittings and the outer wall of the copper pipe closely with the “O” rubber ring to implement the seal to complete the tight connection of the copper pipe. When using the plug-in connection method, the copper pipe can not be inserted once the exit, such as installation errors need to be changed, you must check the fittings to be sure there is no damage to use again. Crimp connection Using crimped copper fittings to implement the crimp connection of copper pipes, is one of the newer construction methods, operation is also simple, but need to be equipped with special and complete specifications of crimping machinery. Connection, the pipe notch end face should be perpendicular to the axis of the pipe, the burr inside and outside the notch should be cleaned, and then insert the pipe into the pipe fittings in the end, and gently turn the pipe, so that the pipe and pipe fittings with concentric segments, and then crimping machinery with special copper pipe and pipe fittings crimped into one. This bell connection method, is the use of cold crimping technology to make the copper pipe and pipe fittings into one, the use of rubber seals within the flange of the pipe to implement the seal, complete the tight connection of copper pipe. The use of crimping connection method, pipe laying is very convenient, before crimping, copper pipe and pipe fittings can be freely disassembled, as long as the time of crimping is properly selected, it can make the installation in one step. Brazing connection The principle and characteristics of brazing A. Definition of brazing Brazing is the use of brazing material with a lower melting point than the base material and the base material together with the heating, in the case of the base material does not melt, the brazing material melted wetting and filling into the gap between the two base material connections, forming a brazing seam, in the gap, the brazing material and the base material dissolve and diffuse each other, so as to get a solid bond. Brazing can be pided into two categories according to the melting point of the brazing material used, generally 450°C as the boundary, brazing material melting point <450°C brazing for soft brazing, brazing material melting point >450°C brazing for hard brazing. Soft brazing is simple to operate and easy to master, but its joints. B. Characteristics of brazing Firstly, the base material does not melt when brazing, but only the brazing material melts. Secondly, in brazed joints, the brazing material composition and properties are significantly different from the base material, and the melted brazing material needs to fill the gap of the pro-joint by capillary action and improve its load-bearing capacity by the lap area of the joint. The main features of brazing are lower heating temperature, smaller changes in the organization and mechanical properties of the welded parts, flat and smooth joints, little deformation, and the possibility of connecting different materials, high productivity. Therefore, brazing is widely used in the construction of copper pipes. However, the strength of brazed joints is directly affected by the size of the joint assembly gap. Some test data prove that the strength of brazed joints decreases with the increase of the device gap, and the size of the gap also affects the capillary action and brazing area, so the brazed joint assembly should be maintained with a uniform and strict gap to ensure the quality of the brazed joint. C. The formation process of brazed joints The formation process of brazed joints is that the base material and brazing material are heated to the brazing temperature, the brazing material melts and flows into the gap of the joint while interacting with the base material to form a new alloy, and then cools and crystallizes in the brazing gap to form a brazed joint. Therefore, the key to a solid joint is that the melted brazing material flows well into the gap to fill the brazing joint and interacts with the base material and cools and crystallizes. In brazing, the gap of the brazing seam is small, and the brazing material needs to flow in the brazing seam under capillary action, which is only formed when the liquid brazing material can wet the surface of the base material, so the wetting of the base material by the liquid brazing material is the key to whether the brazing material can flow into the brazing seam and fill the brazing seam. Only when the liquid brazing material can dissolve or form a compound with the base material, the brazing material can wet the base material better. Therefore, it is necessary to choose a suitable brazing material so that the liquid brazing material can have sufficient wetting to the base material. The tin brazing material, silver brazing material and copper phosphorus brazing material selected for copper tube brazing have quite good wettability for copper. Secondly, the influence of the oxide on the surface of the base material, the oxide on the surface of the metal prevents the atoms of the brazing material from coming into direct contact with the base material, so that the liquid brazing material is agglomerated into spheres under the action of surface tension, forming a non-wetting phenomenon. Therefore, the oxides on the surface of the base material should be removed during brazing, including those generated during the brazing process, so that the brazing material maintains wettability to the base material. A common method is to choose a suitable brazing flux to effectively remove the oxide. Type and selection of brazing material and brazing flux A. The type and selection of brazing material Brazing material, also known as solder, is a metal or alloy that melts and fills into the brazed joint at a temperature lower than the melting temperature of the base material when brazing. The brazing materials used for brazing copper pipes are as follows. (1) Tin brazing solder tin brazing solder is mainly composed of tin-lead, tin-antimony, tin-silver and other alloys, which are soft brazing solder with low brazing temperature, good wettability and easy operation, but the joint strength is low and the temperature resistance is poor, mainly used for brazing of small diameter copper water pipes below 2″. (a) Tin-lead solder, commonly used is tin-lead solder with 50% of tin-lead each, its melting temperature is 210°C, solidification temperature is 183°C. Because the excessive lead in the solder will affect the water quality in the pipe, it is not suitable for use in domestic water supply pipes, and can be used in drainage pipes. (b) Pure tin brazing material, generally the tin brazing solder containing more than 90% tin is called pure tin brazing material. But high-purity tin can not be used as brazing material, because pure tin is white at room temperature, once the temperature drops low enough, it will change to gray, the volume increases by about 25%, which will turn white tin into gray powder, commonly known as “tin epidemic”. Therefore, pure tin solder must be added to 3-5% antimony, or the right amount of lead to prevent tin plague. Its melting temperature is 222°C, solidification temperature is 183°C, is the current tin brazing solder for copper water pipes. (c) Tin-silver brazing material, an alloy composed of 96% tin and 4% silver, with a melting temperature of 225°C and a solidification temperature of 221°C. If the silver improves the heat resistance of the brazing material and the strength of the brazing joint, it is a more ideal tin brazing material for brazing copper water pipes. Don’t market the increase in solidification temperature, in the adjacent joints need to successively braze to bring convenience, can be used in the first welding head in the tin-silver brazing material, after welding head in the use of pure tin brazing material, to avoid after welding head heating temperature on the first welding head to produce adverse effects. (2) Silver brazing material silver brazing material is mainly composed of silver-copper, silver-copper-tin, silver-copper-zinc and other alloys, is a hard brazing material, with high strength brazing joints, good wettability and other characteristics, but the brazing temperature is high, the operation is difficult, mainly for more than 2 “large diameter copper tubes and brazing joints with high quality requirements and brazing rate requirements. (3) Copper phosphorus brazing material copper phosphorus brazing material is composed of copper phosphorus binary alloy, is a hard brazing material, because phosphorus can reduce copper oxide, so the use of copper phosphorus brazing material brazing copper without additional brazing flux, brazing process performance, and cheap, so inappropriate to use tin brazing solder brazing copper tube is widely used. B. Types and selection of brazing flux Brazing flux is also called brazing solvent, whose main function is to remove the oxide film on the surface of the base material and brazing material, inhibit the re-oxidation of the base material and brazing material in the brazing process, so as to improve the wetting effect of brazing material on the brazed material. Therefore, the brazing flux should have sufficient ability to remove the oxide film on the surface of the base material and brazing material, and the melting point and active temperature of the brazing flux should be lower than the melting point of the brazing material and have sufficient stability in the brazing temperature range. The brazing fluxes used for brazing copper tubes are as follows. (1) Tin brazing with brazing flux Tin brazing can use organic brazing fluxes such as rosin. However, its activity is poor, and it is difficult to adapt to the requirements of copper brazing. Therefore, inorganic brazing fluxes consisting of inorganic salts such as zinc chloride are mostly used for tin brazing of copper pipes. Commonly used are solder paste and liquid brazing flux supplied by the market, and can also be configured by themselves. (2) Silver brazing with brazing flux copper tube silver brazing, must use the market supply of powdered silver brazing special brazing flux. It can be used directly, or can be made into a paste and then used. (3) Copper brazing with brazing flux using copper phosphorus brazing material welding purple copper, generally can be used without brazing flux. However, when brazing copper tubes and brass and other copper alloys, copper brazing flux is also required, and the main component of copper brazing flux is borax, which can be used in bottles of copper soldering powder supplied by the market, and can also be configured by itself, and should be modulated into a paste when used. The types and applications of copper brazing connection A. Tin brazing connection of copper pipes tin brazing connection of copper pipes is soft brazing, although the brazing temperature is low and the operation is simple, but the strength of the joint is low and the temperature resistance is poor, so it is mainly used in pipes with medium of water below 2″, such as hot and cold water supply and drainage pipes and air-conditioning water pipes, etc. (1) Ordinary welding type brazing requires the operator to add solder from the outside of the pipe and dissolve it into the gap, and form a brazed joint after cooling and crystallization. The quality of the brazed joint needs to be determined by the operating skills. (2) Built-in tin ring type built-in tin ring type pipe is in the production, the casing of the pipe at the inside of the pressed a ring-shaped groove, and cast in the groove with the inner wall of the pipe flush with the tin brazing solder, brazing, no need to add solder, only the implementation of heating at the joint, heating can be conventional flame heating method, can also use the electric heating method, that is, the use of special electric heating clamp held at the joint, and then energized Heating, so that the tin brazing material ring in the groove of the tube dissolves and fills the gap at the joint, and then brazes the joint after cooling and crystallization. The quality of brazed joints is easy and the operating skills required are low, but the cost is high. B. Phosphor bronze brazing connection of copper tube Phosphor bronze brazing connection of copper pipe is hard brazing, the joint strength is higher, temperature resistance is better, suitable for brazing connection of small and large diameter copper pipes of various media, but its brazing temperature is higher, and the requirement of operation skills is higher. Because when brazing, the temperature of the joint directly affects the phosphorus copper brazing material on the wettability of the copper tube, as well as the brazing material in the brazing seam mobility, especially in the brazing of large-diameter copper tubes, to make phosphorus copper brazing material can be better dissolved into the brazing seam, must control the heating temperature of the joint, and can maintain a good joint in the circumferential and length direction temperature uniformity, if there is a local temperature of overheating or too low, will affect the joint in the brazing material If the local temperature is too hot or too low, it will affect the flow of brazing material in the joint, thus affecting the quality of the brazed joint. C. Silver brazing connection of copper tubes Although the brazing temperature is high and the operation is difficult, the silver brazing material has better wettability and fluidity compared with the phosphor bronze brazing connection under the same brazing conditions, which makes it easier to melt into and fill the brazing seam, thus making it easier to get the quality of the brazed joint. This makes it easier to guarantee the quality of brazed joints. Processing methods of copper tubes There are many methods of processing copper tubes, but they can be pided into two categories: hot processing and cold processing. Such as extrusion manufacturing billet, oblique rolling perforation and other methods are heated to much higher than the recrystallization temperature of copper billet for deformation processing, so as to get the billet. The billet is then made into a tube at room temperature by cold rolling and cold drawing methods. This traditional process has been used for many years and is still in use today. The production process is to melt and cast electrolytic copper into solid ingots, and then heated to more than 850°C in the heating furnace, one by one into the extrusion machine extrusion into billets, and then through cold rolling or multiple linear stretching to disc stretching required billets. Extrusion is pided into two kinds of high extrusion ratio and low extrusion ratio, both of which have refined grain organization and good surface quality. High extrusion ratio extrusion billet specifications are small, thin wall thickness, can be directly in the continuous direct machine or disc stretching machine for processing; low extrusion ratio extrusion can be used for large ingot extrusion large specifications billet, and then extended processing with cold rolling mill. For the same size and specifications of the ingot, high extrusion ratio requires a larger extrusion tonnage, and extrusion of the tube wall thickness tolerance is large. At present in China is very popular is the continuous casting and rolling supply method, this is a new supply method in the 1990s, its production process is the horizontal continuous casting of hollow tube billet cut off the milling surface directly into the three-roller planetary rolling mill to roll out smaller diameter thin-walled copper pipe. As the three-roller mill can make the rolled copper tube without rotation, so it is easy to reel online into a tray. It is characterized by a short production process, eliminating the reheating and extrusion process, whether in saving energy, reducing equipment investment, reducing costs in all methods have the advantage.

Installation process and complete construction operation process of natural gas pipeline The installation and construction of natural gas pipeline includes three steps: pipeline welding, pipeline anti-corrosion and pipeline pressure test. Survey site According to the design and construction technical disclosure, the site survey shall be carried out jointly with the owner, supervision engineer and other relevant personnel. Preparation before construction 1. Organize all construction personnel to conduct detailed investigation on other pipelines within the site and draw detailed construction sketches to ensure construction safety. 2. Check the performance indexes of the pipes used. 3. Cooperate with the on-site construction team, including pipe welding, pressurization and air tightness test. 4. The placement of equipment shall be considered from many aspects, that is, to facilitate construction and minimize the impact on the surrounding environment. Surveying and setting out According to the comparison between the design drawings and the site, accurately measure, point and mark the design pipeline position, and find and eliminate the obstacles that may affect the construction as early as possible. Steel pipe derusting, anti-corrosion and painting 1. Before steel pipe welding, the oxide layer and dirt on the inner and outer pipe walls shall be removed. The derusting shall be carried out by electric polishing machine. The derusted pipes shall be painted with primer in time to prevent secondary oxidation. 2. The steel pipe adopts ordinary anti-corrosion, primer → finish coat → finish coat. Before anti-corrosion and painting of the steel pipe, the dirt such as rust, welding slag, burr, oil and water on the coated surface shall be removed. The coating shall be complete and uniform, the color shall be consistent, and there shall be no damage and flow; The coating film shall be firmly attached and the color shall be consistent. Pipe welding Steel pipe welding process requirements 1. The steel pipe should be cut by mechanical method. If it is cut by oxygen or acetylene flame, the size must be correct, the surface must be flat, and the notch shall be free of crack, double skin, burr, oxide, etc. Mechanical method should be adopted for groove processing to polish the uneven parts. 2. For pipe connection, it is not allowed to eliminate the gap, deviation, staggered joint and non concentricity of the pipe section by means of strong matching or heating the pipe. During alignment, the balance shall be measured 200mm away from the grounding center, and the allowable deviation is 2mm. 3. The inclination deviation of the cut end face shall not be greater than 1% of the outer diameter of the pipe and shall not exceed 3mm. 4. Pipe welding process: (1) Material requirements: the material and specification must meet the design requirements, with factory certificate and retest report. (2) Welding rod requirements: the coating shall be free of cracks, pores and other defects. During welding, the arc shall burn stably, melt evenly, and there shall be no blocking and falling off. It shall be dried for use. (3) Preparation before welding: the pipe orifice shall be cleaned, the inner wall shall be flush, the misalignment shall not be greater than 1mm, the welded junction device shall be firm, and necessary measures shall be taken to prevent stress deformation during welding. (4) Welding equipment: AC welding machine, DC welding machine, angle grinder, drying box and insulation barrel. (5) Welder requirements: Welders must hold welding certificates and undergo pre job training and assessment. Safety protection shall be provided at the operation site to prevent burns, electric shock and collapse. (6) Welding process: rust shall be removed before welding, and antirust paint shall be applied after exposing the natural color of the metal. During pipeline welding, reasonable welding methods and sequences shall be adopted to ensure the quality of arc starting and arc ending. Multi layer welded joints shall be staggered, and slag and spatter shall be removed after each layer is welded. If there is any defect, angular grinder shall be used to eliminate and re weld. Single side manual arc welding shall be used for welding, and after each welding is completed The first layer shall be polished with hand grinding wheel before welding the next layer. In order to reduce welding deformation and welding stress, symmetrical or segmented welding methods can be adopted. The welds shall be visually inspected. The weld reinforcement height shall be 1mm and the weld width shall cover the groove by 2mm. The weld surface shall be free of cracks: seams, pores and slag inclusion. The welds shall meet the 100% qualification of grade II films. (7) Welding parameters:Pipe wall thickness (mm)Number of welding layersDiameter of electrodeWelding current (A)3.5-823.2105-120Name of the connectorPipe wall thickness (mm)Blunt edgeGroove angleHi-LoV-groove3-3.50-330º1 (8) Welding inspection: The surface quality of welds for visual inspection shall comply with class II I weld standard (GB50236-98), and the internal quality shall comply with class III weld standard (GB50236-98). The number of NDT for welds in general sections shall not be less than 20% of the total number of welds. (9) For manual arc welding, the wind speed shall not exceed 8m / s, and the number of times of repairing the same part of the unqualified weld shall not exceed 2. During welding, a reasonable welding sequence shall be adopted, and the interlayer joints of multi-layer welding shall be staggered. Pipeline excavation 1. The line shall be clearly marked on the road according to the drawing size and relevant regulations, and all sign lines must be double lines. 2. Mechanical trenching and manual trenching shall be used for earth excavation. Manual and careful operation shall be carried out at the location where the site is narrow or there are underground pipelines. 3. The earthwork is located in the south of the trench, and the operation site is located in the north of the trench. 4. The straight pipe trench shall be straight and smooth, and the curved pipe trench shall be smooth and excessive without concave convex and broken lines. The ditch wall and bottom shall be flat, and there shall be no collapse and sundries in the ditch. 5. When excavating the pipe trench, it is necessary to prevent rainwater from scouring the pipe trench. The excavation of each section of pipe trench shall be closely combined with pipeline assembly and welding and trench backfilling, and one section of excavation shall be completed in combination with medium and short-term weather forecast. 6. In the process of slotting, humus and residue need to be discarded, and the excess earthwork should be temporarily stored in a temporary storage yard near the site. Electrofusion connection 1. Cut off the pipe with special tools, keep the end face of the pipe perpendicular to the pipe axis, scrape off its skin, scrape off half the length of the electric melting sleeve, and wipe the dirt on the connecting surface of the pipe and pipe fittings with clean cotton cloth 2. Draw a positioning line according to the insertion depth of the pipe, so as to ensure that the pipe can be equally inserted into the electric melting sleeve during assembly 3. Insert the pipe into the socket at one end of the electric melting sleeve to the positioning line, and check whether the inlet and outlet parts meet the requirements. 4. Install the sleeved pipe and electrofusion sleeve on the interface fixture and fix it with the fixture; 5. Fix the pipe at the other end on the fixture, push the fixture along the sliding shaft to insert it into the socket at the other end of the electric melting sleeve, and keep the two connecting pipes on the same axis. 6. Connect the wire plug of the controller with the electric fusion sleeve socket, correctly set the welding voltage, current, welding time and other parameters, open the electric fusion button of the controller, conduct electric fusion, and the welding time enters the countdown. 7. After the dissolution is completed, cool it to the ambient temperature according to the specified cooling time, and remove the fixture and electrofusion wire. Pipe laying 1. Before the pipeline is laid into the trench, the trench bottom shall be measured to remove sundries, large soil blocks and ponding in the trench. 2. Special slings must be used for lowering the pipeline into the trench. It is strictly prohibited to damage the external anti-corrosion coating of the pipeline. It is strictly prohibited to lift the pipeline sharply or tighten the pipeline, resulting in bending or permanent bending. The spacing between lifting pipes is less than 20m. 3. After the pipeline is lowered to the groove bottom, it shall be close to the groove bottom and properly placed without external force. If there is any suspended part, it must be filled up. Pipe backfilling 1. After the installation inspection of the main body of the pipeline is qualified, the trench shall be backfilled in time, but the installation interface that has not been inspected shall be reserved. Before backfilling, the sundries left at the bottom of the trench must be removed. 2. Garbage, wood and soft materials shall not be used for backfilling. The backfill on both sides of the pipeline and within 0.5m above the pipe top shall not contain debris such as gravel and bricks, and shall not be backfilled with lime soil. The stones in the backfill soil above 0.5m from the pipe top shall not be more than 10%, the diameter shall not be more than 0.1M, and shall be evenly distributed. 3. During trench backfilling, the partially suspended part of the pipe bottom shall be backfilled first, and then both sides of the pipe shall be backfilled. 4. The backfill soil shall be compacted in layers. The virtual paving thickness of each layer is 0.2-0.3m. The backfill soil on both sides of the pipeline and within 0.5m above the pipe top must be compacted manually. The backfill soil above 0.5m above the pipe top can be compacted by small machinery. The virtual paving thickness of each layer should be 0.25-0.4m. 5. After backfilling and compaction on both sides of the pipe and 0.5m above the pipe top, the support of the trench shall be removed under the condition of ensuring safety, and the gap shall be filled with fine sand. 6. After the backfill is compacted, the compactness shall be checked in layers, and the backfill records shall be made. Pipe installation 1. Before the installation of pipes, pipe fittings and valves, the model, specification and material shall be checked in detail to see whether they meet the design requirements, and the manufacturer’s product factory certificate and other quality assurance data shall be provided. 2. Before the installation of valves, the shell strength and tightness test shall be carried out one by one. The strength test pressure shall be the nominal pressure of the valve [1.5 times of the nominal pressure of the valve, the test medium shall be water, the pressure shall be maintained for 5 minutes, the test J shall be water, the pressure shall be maintained for 10 minutes, and the valve disc sealing surface shall be qualified if there is no leakage. 3. During pipe alignment, the flatness shall be checked and measured 200mm away from the interface center, and the allowable deviation shall not be greater than 1mm. Pay attention to the radian in the overall layout of the pipe group. 4. The pipe assembly clearance shall not be greater than 2mm, and the misalignment of the outer wall shall not be greater than 3mm, otherwise it shall be thinned and corrected. 5. During pipe connection, it is not allowed to use strong butt joint, or heat the pipe, add offset pad and other methods to eliminate the defects such as gap, deviation, staggered joint or non concentricity at the end face of the interface. 6. The flange connection shall be coaxial, the center deviation of the bolt hole shall not exceed 5% of the outer diameter of the hole, and the bolt shall penetrate freely, and the flange end face shall be parallel, the deviation shall not be greater than 1.5 ‰ of the outer diameter of the flange, and shall not be greater than 2mm, and the skew shall not be eliminated by tightening the bolt. All bolts shall be grade 8.8 strength bolts. 7. During installation, the safety distance between the gas pipeline and other adjacent pipelines and structures shall be strictly controlled, and the operation shall be carried out according to relevant operating procedures. The buried slope and depth must meet the design requirements. 8. For construction every other day, cast iron pipe shall be used to block the pipe orifice temporarily to prevent sewage, sundries and animals from entering the pipe. 9. The pipeline installation shall be inspected every 6-10m according to the inspection contents, and the next process can be carried out only after it is qualified. Install the retaining bracket 1. During pipeline installation, the support shall be fixed and adjusted in time, the position of the support shall be accurate, the installation shall be flat and firm, and the contact with the pipeline shall be close. 2. The specification, type and installation position of the adopted support shall meet the design requirements, and the deviation of elevation and coordinate shall not exceed 10mm (there shall be no positive deviation of elevation). 3. The sliding surface of the guide support or sliding support shall be smooth and flat without jamming. The guide plate shall not affect the sliding of the pipe support. The fixed support shall be fixed firmly. The height of the vertical plate of the pipe support shall meet the requirements of the insulation thickness. 4. The support weld shall be fully welded. When welding with the pipe, the pipe wall shall be free of defects such as biting and burning through, and the welding shall be completed before the pipe system test. 5. After the installation of pipe support, check whether the specification, type, installation position, weld and bolt fastening meet the requirements of drawing design and construction specifications one by one, whether there is missing installation and whether they are in close contact with the pipe. 6. The overhead of low-pressure gas pipeline can be laid along the outer wall of buildings with fire resistance rating not lower than grade II. 7. The clear distance between the gas pipeline along the outer wall of the building and the door and window openings of the building: the low-pressure pipeline shall not be less than 0.3m. Installation of valves and accessories 1. Check the packing before valve installation, and the gland bolt must have sufficient adjustment allowance. 2. Valves with flange or threaded connection shall be installed in the closed state. 3. Before installing the valve, the model shall be checked according to the design, and the installation direction shall be determined according to the gas flow direction. 4. The valve stem of the valve on the horizontal pipeline shall generally be installed within the upper half circumference. 5. When installing cast iron valves, avoid damage caused by strong connection or uneven stress. 6. The installation position of the valve shall not hinder the disassembly and maintenance of the equipment, pipeline and valve itself. The installation height of the valve shall be convenient for operation and maintenance. Generally, it is appropriate to be 1.2m away from the ground. When the valve is more than 1.8m away from the floor, it shall be centrally arranged and a fixed platform shall be set. 7. For valves on side-by-side pipelines, the clear distance between hand wheels shall not be less than 100mm. In order to reduce the pipeline spacing, valves arranged side-by-side shall be staggered. 8. The operating mechanism and transmission device of the valve shall be adjusted as necessary to make the action flexible and accurate. Indoor pipeline installation 1. First install the pipe support according to the drawing and the actual situation, then install the processed pipe, and fix it after appropriate adjustment. If the floor has reserved the casing, install it according to the reserved position. If not reserved, the casing shall be added. 2. In order to ensure the installation quality, the riser installation shall be measured and installed with pendant and level. 3. The installation of buried pipeline at the entrance shall be constructed according to the slope requirements of the drawing of 0.02%, and polyethylene shall be strengthened for anti-corrosion treatment according to the requirements of the drawing. 4. There shall be no welded junction in the pipe passing through the floor casing. 5. The finished pipe orifice shall be bound with plastic cloth to prevent foreign matters from entering. 6. The straightness of horizontal pipeline for pipeline installation shall be 2L / 1000 and 3L / 1000 of riser. 7. The horizontal clear distance from indoor water supply, drainage and heating pipes shall not be less than 100mm, and the cross clear distance shall not be less than 10mm. Gas meter installation 1. The gas meter must meet the following conditions before installation. 2. The gas meter has factory certificate, the manufacturer has production license, and the meter has been tested by legal testing unit; 3. It shall not exceed 4 months from the date of delivery. If it exceeds, it shall be tested by the legal testing unit; 4. No obvious damage. During the installation of gas meter, collision, inversion and knocking are not allowed, and rust, sundries and oil stain are not allowed to fall into the instrument. 5. The diaphragm meter must be installed flatly, and the lower part shall be supported. The horizontal clear distance between the gas meter and the surrounding facilities is listed in the following table. Installation of surge tank 1. It shall be stated on the certificate of the pressure regulating box that it meets the requirements of the quality standard through the air pressure test, strength and tightness, as well as the adjustment of inlet and outlet pressure. Do not install without the above instructions. 2. When installing the surge tank, it shall meet the following requirements: 3. Before installation, check that the outer surface of the surge tank is free of defects such as sand sticking, sand holes and cracks; 4. The installation of the surge tank shall be flat and stable, and the inlet and outlet directions shall not be wrong; 5. The connecting pipe of the membrane of the surge tank and the connecting pipe of the commander shall be connected above the outlet pipe of the surge tank, and the length of the connecting pipe shall meet the actual requirements. Overhead pipeline installation 1. The construction personnel shall be skilled and have high-altitude operation experience. 2. The lifting machinery used by the personnel shall be an electric basket (the disassembly and assembly of the basket must be operated by licensed professionals), and the lifting of pipes shall be a 2-ton electric crane. Walkie talkies shall be equipped on site to ensure clear signals and close cooperation among the commanders, overhead construction personnel, lifting machinery operators and ground assistance personnel. 3. Safety rope shall be set along the overhead construction pipeline. The safety rope shall be bound firmly and independently, and shall not be bound on the lifting machinery and basket support. A falling self-locking device is set on the safety rope. Overhead construction personnel shall wear safety helmets and safety belts. The connection between the safety belt and the self-locking device shall be reliable and firm. 4. Before the installation of the pipe support, the measurement shall be carried out to ensure the correct position of the support. The support installation must be flat and firm and in good contact with the pipe. 5. The overhead pipeline shall be prefabricated and derusted on the ground, and the first layer of yellow marking ready mixed paint shall be painted. 6. The prefabricated pipeline shall be hoisted to the installation position with hoisting machinery, fixed by personnel in a basket, and painted with the second layer of yellow marking ready mixed paint. Construction of supporting facilities 1. Valve installation When installing indoor steel valves, select corresponding connecting accessories according to the material of the pipeline, and be equipped with steel flanges, gaskets, bolts and other accessories of the same diameter. The flange surface and the valve flange shall be concentric and parallel, and the parallel deviation shall be 1.5% of the outer diameter of the flange and ≯ 2mm. 2. The specifications, dimensions and accuracy of bolts and nuts used in the project shall meet the requirements of drawings and GB97-81. The threads shall be complete, free of scars, thorns and other defects, and the bolts and nuts shall be well matched without looseness, jamming and other phenomena. 3. The installation position of the valve shall avoid the areas with dense and complex underground pipe network or heavy traffic as far as possible, and choose the place convenient for daily maintenance. Pipeline purging Pipeline purging is the same as general pipeline purging. Blasting purging can be carried out in sections. The medium is compressed air, and the pressure shall not exceed the working pressure of the pipeline. Strength test After removing the air in the pipeline, start the strength pressure test. The medium pressure gauge pressure is 0.6MPa and the low pressure is 0.2MPa. There is no pressure drop after stabilizing for 1h, and the inspection result is qualified. Air tightness test In the air tightness test, the medium pressure is 0.46mpa and the low pressure is 0.1MPa. It shall be maintained for a certain time to make the temperature of the test medium in the pipeline consistent with the ambient temperature of the pipeline. After the temperature and pressure are stable, the timing shall be started. The air tightness test shall be stabilized for 24 hours. If there is no obvious leakage or pressure drop, it will be qualified. Handover acceptance 1. After the completion of all construction of the project, the handover acceptance shall be carried out, and the owner, the supervision unit and other relevant departments shall be notified to attend the handover. 2. The acceptance items mainly include strength, air tightness test, valve well and other aboveground facilities, which can be passed only after confirmation and signature. 3. The project acceptance shall be formally completed after the owner’s acceptance team and other departments issue the acceptance certificate. 4. For the delivery of completion data, the completion data shall include all contents in the completion data specified by the owner, and the owner shall issue the handover certificate of completion data.

Flange is the main connecting equipment of process pipeline in petrochemical enterprises. It has a large number and plays a very important role in production and operation. Most of Fujian coastal petrochemical enterprises are located in coastal areas. The high salt and high humidity marine corrosive atmosphere accelerates the corrosion rate of station flanges, resulting in a wide range of flange corrosion, especially flange clearance and flange gasket corrosion, which will not only cause equipment damage and shorten service life, but also cause management medium leakage, and bring great potential safety hazards to production safety. Flange corrosion mechanism By analyzing the mechanism of flange corrosion, there are mainly the following: The flange clearance space is narrow (the common flange clearance size is about 2 ~ 20mm, which is easy to accumulate dust and salt in the air, which are the inducing factors of corrosion and will lead to rapid corrosion; The flange has a gap structure, which is a typical structure of crevice corrosion and a prerequisite for the formation of crevice corrosion. A narrow flange gap will cause different oxygen concentrations inside and outside the gap, forming an oxygen concentration difference battery, greatly accelerating the occurrence of corrosion; Some petrochemical enterprises are located in coastal areas. The coastal air is high in humidity and salt. The water, gas and salt rich in the air are very easy to damage the flange coating and cause local corrosion; In the design stage, attention is not paid to the anti-corrosion part or anti-corrosion structure design, resulting in the connection of flange surfaces of different materials and the selection of metal gaskets with different materials from the flange surface during construction, resulting in galvanic corrosion. Flange anti-corrosion method The most appropriate anti-corrosion process shall be selected according to the corrosion environment and corrosion severity of the flange. The details are as follows: The anti-corrosion design avoids the design of narrow gap structure, resulting in gap corrosion and impurity accumulation, and the same metal is designed for the same flange surface to avoid galvanic corrosion; Strengthen the construction quality control during construction and strictly control the substrate bottom; Treatment and coating construction quality; Consider using non-metallic gaskets to reduce the probability of galvanic corrosion of gaskets. If sacrificial anode protection is provided, consider flange bridging; The new coating anti-corrosion process is adopted, and the coating material with excellent anti-corrosion performance is selected to completely fill and cover the flange gap, isolate the corrosion sources such as water, air and impurities, and contact the inner surface and gasket of the flange gap, so as to realize long-term anti-corrosion. The flange is coated with anti-corrosion materials In the case that the traditional coating anti-corrosion can not effectively prevent the flange from corrosion, through investigation, a variety of new coating materials are selected and tested on the flange, and their anti-corrosion processes are tested and improved. Some flange coating anti-corrosion processes have achieved good anti-corrosion effects. Wax magnetic anti-corrosion material is an excellent anti-corrosion protection material. Wax Tape anti-corrosion material mainly includes wax tape and wax magnetic primer, which can well isolate water and air. It can be applied to the anti-corrosion of various irregular pipelines, valves, flanges, bolts and other equipment in various corrosive environments. In 2006, NACE formulated the standards related to wax magnetic anti-corrosion materials. Viscoelastic anti-corrosion material is a new type of high molecular polymer anti-corrosion material originated in the Netherlands. Its state is between liquid and solid. At room temperature, it can remain in a state of no flow and no solidification for a long time. In addition, viscoelastic has very good bonding performance, waterproof and air isolation performance. According to the experience of equipment anti-corrosion maintenance in many petrochemical enterprises along the coast of Fujian, the traditional coating anti-corrosion can not meet the increasingly severe demand for station flange anti-corrosion. According to the characteristics of coastal and long-term marine corrosive atmosphere with high humidity and high salt, the disadvantages of the traditional coating anti-corrosion method are analyzed, and two coating anti-corrosion materials with excellent anti-corrosion performance are selected to be used in Fujian After several years of experience accumulation, it is considered that the wax magnetic anti-corrosion material and viscoelastic anti-corrosion material have good applicability and good anti-corrosion effect on the process flange equipment of petrochemical enterprises. Several solutions to flange corrosion The integrity of the flange connection is very important for the fluid piping system. Since the sealing surface of the flange connection can only be visually inspected when the whole system is closed, the inspection process should be as simple as possible. First, external corrosion should be eliminated. If it cannot be stopped, only ultrasonic technology can be used for detection. If external corrosion cannot be controlled, the process will be more complex and cannot be controlled Therefore, in order to monitor the whole system and provide effective and feasible quality control and maintenance procedures, the external corrosion protection of flanges and fasteners is very important. The ideal solution should take into account excellent corrosion resistance and simple construction procedures. It is suitable for flanges of various sizes and shapes. It is easy to operate bolts during maintenance. At present, the following solutions are commonly used in the market. 1. Maintenance paint solution Maintenance paint is a hard film that can be directly bonded to the substrate, usually epoxy or polyurethane paint. The flange has many corners and edges. Due to the effect of edge thinning, it is difficult for the traditional coating system to effectively cover the edge. Although the thickened coating can solve the problem of edge protection, it will seal the fasteners and cannot be removed for future maintenance. 2. Mechanical solutions The gap between flange and flange surface is mainly sealed by protective cover, usually made of stainless steel or plastic clamp, and equipped with rubber sealing strip. This protection method is not flexible, and it is necessary to store covers or fixing devices that fully match flanges of various sizes. 3. Tape or semi-solid anti-corrosion tape solution Roll packaged tape (such as Vaseline tape, wax tape or elastic polymer bandage) is protected by winding on the surface of the substrate. Since the semi-solid polymer is waterproof, this protection method can provide reliable protection. However, if the flange shape is complex, this material is not only time-consuming, but also difficult to construct. 4. Hot melt plastic solutions Hot melt plastic is essentially a waxy fusible polymer heated at high temperature, which can be sprayed on the substrate surface through professional hot melt equipment. The advantage of this protection method is that it can be remelted and reused, saving cost. However, although it can be reused, it still needs hot work, professional equipment and construction services, but it is not easy to open and close during maintenance Seal. 5. Polymer sealed bag solution The sealing bag can completely cover the flange. Its composition is composed of low permeability polymer, corrosion inhibitor steam and desiccant. It is easy to install, but the two ends of the bag are only sealed with tape instead of long-term effective mechanical bonding. The steam space has a large area, it is easy to accumulate a large amount of water, and the corrosion inhibitor will be consumed over a period of time. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Pipeline pressure test is the last process of pipeline construction engineering. It is not only a comprehensive inspection of pipeline construction quality, material performance and pipeline integrity, but also an inspection and guarantee of whether the pipeline system can operate safely without fault under the design operating pressure. Therefore, great attention should be paid to the pressure test. The purpose of the pressure test of the main pipeline is to eliminate the hidden dangers and defects of the pipeline, obtain a greater degree of safety and ensure the safety of the pipeline in operation. There are generally two types of pressure test methods for long-distance pipeline: air pressure and water pressure. Water pressure can be pided into fresh water pressure test and sea water pressure test due to different pressure test media. Using water as pressure test medium has the following advantages: low cost; Although water is compressible in theory, the effect of compression on hydrostatic test can be ignored; Water is not toxic; Water is not flammable; The emission problem is also small; The pressure of water on the pipe wall is uniform; When the pipeline breaks, the water pressure will be released quickly, which can reduce the damage to the environment; For most areas, water intake is also more convenient, and has been increasingly used as a main means of pressure test of long-distance pipeline. Pressure test process of pipeline The pipeline pressure test process mainly includes: water injection in the pipe, strength pressure test, tightness pressure test, pressure relief and drainage. The above processes are introduced below. Pressure test steps: fill water and check whether the air in the exhaust pipe is drained; Conduct strength test after boosting; Conduct tightness test for pressure stabilization; Pressure relief for a period of time; Drain water after passing the hydrostatic test; If the natural gas pipeline is subject to hydrostatic test, it shall be dried after drainage. Before water supply for pipeline hydrostatic test, the water quality of water source shall be tested and analyzed to confirm that the water for pressure test is clean and the PH value is neutral, which has no harmful impact on the pipeline. The cleanliness of the pipeline has a great impact on the pre commissioning, construction and operation of the pipeline. If there is a large amount of sediment deposition after the pressure test of the pipeline, it will increase the water pushing pressure, and seriously cause the phenomenon of ball passing and pipe blocking. It is very difficult and dangerous to deal with, especially if there are a large number of dust particles during the operation of the gas pipeline, it will cause damage to pipe fittings and valves, And different substances in the water will affect the corrosion of the pipeline: After the pipeline is filled with water, start the pressure test pump to boost the pressure and conduct the strength pressure test of the pipeline. As long as the pressure at one end of the pipe section reaches the predetermined pressure, the pressure rise will be stopped. The strength test pressure in China is 1.25 times of the operating pressure, and the operating pressure shall be implemented in accordance with the relevant provisions in China’s specifications. If the strength is stabilized for 4 hours and the pressure drop is not greater than 1%, it is qualified. The tightness pressure test shall be conducted after the strength stabilization is qualified. During the tightness test, slowly open the relief valve to reduce the pressure to the test pressure value. The same as the strength pressure test, the pressure relief shall be stopped as long as the pressure at one end of the pipe section reaches the predetermined pressure. The tightness test is qualified if the pressure is stabilized for 24 hours and the pressure drop is less than 1%. After the pressure test is completed, the pressure of the pipeline shall be removed through the pressure relief valve, and the water in the pipeline shall be discharged by using the original water feeding pig in the pipeline and the air compressor. During drainage, the water can be discharged outside the pipeline, or the water can be discharged to the next pipeline as the water supply source of the next pipeline. This not only saves time and labor, but also saves limited water resources. Source: China Chemical Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)