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Reasonable selection, proper storage and correct use of manufacturing materials are the prerequisite and basis for ensuring the quality of pressure vessels. This article makes some meaningful discussions on the material quality management issues in pressure vessel manufacturing, hoping to serve as a reference and reference for colleagues in the industry. As a special pressure-bearing equipment, pressure vessel has been widely used in petrochemical, energy, scientific research and military industries. Its quality is directly related to the production safety of these industrial fields, so it must be given full attention. In order to ensure the manufacturing quality of pressure vessels, the first requirement is to manage and control the quality of vessel materials. If the pressure vessel manufacturing materials used have quality defects, no matter how the subsequent optimization and improvement of the process process, the final product quality is difficult to guarantee. Therefore, reasonable selection, proper storage and correct use of manufacturing materials are the prerequisite and basis for ensuring the quality of pressure vessel products. Based on this standpoint, this article makes some meaningful discussions on the material quality management issues in pressure vessel manufacturing, hoping to serve as a reference for colleagues in the industry. The pressure vessel parts are as follows: 1. Tube sheets 2. Baffles 3. Flanges 4. Heat Exchanger Bundle Tubes, etc Overview of pressure vessel manufacturing As a special pressure-bearing equipment, the pressure vessel’s manufacturing quality is very important for the safety application in the industrial field. At present, in order to ensure the production quality of pressure vessels, my country has issued corresponding standards and specifications, which must be designed and manufactured in strict accordance with the requirements of the national standard. In practical applications, the types of pressure vessels are different, and their functioning principles and application fields are also different. This requires that in the process of manufacturing them, the manufacturing quality must be ensured to meet the actual application requirements. In addition, as a special type of equipment, pressure vessels are more difficult to manufacture than general vessel products. The entire manufacturing process has very high quality and safety requirements, requiring close coordination and cooperation from multiple disciplines. In reality, there are many factors that affect the quality of pressure vessel manufacturing, and any error in any of them will affect the quality of the final product. Material selection is the first step of manufacturing, and strict quality control is also necessary. Considering that there are many types of materials available in practice, and the final material quality still depends on the control of storage and other links, it is of great significance to strengthen the control of factors related to material quality in the manufacturing process and must be given sufficient attention. Matters needing attention in material substitution In the manufacturing process, if a thick plate is used instead of a thin plate, the structure of the joint may be changed. For example, when the thickness increases more, the welding structure may change. When the overall thickness is replaced by thinness, even if the local stress at the joint between the head and the cylinder is not increased, it will affect the quality of the container product to a certain extent, and it will also cause the welding, flaw detection and heat treatment processes used in the original design to be changed. Land no longer applies. In addition, the substitution of materials for pressure vessels may also lead to changes in the weight of the container products, which in turn will affect the supporting support and foundation of the products. In short, in the manufacture of pressure vessels, in principle, it is not allowed to substitute materials randomly, because different materials will have different performances. Even if one performance has reached a higher level, it may be replaced by another. In terms of low-to-high, and these will make the process measures and schemes used in the entire production process must be modified accordingly, but this change often results in poor solderability and doubled manufacturing process difficulty. So we must be cautious about material substitution. Material quality management measures in pressure vessel manufacturing Material procurement measures For machinery manufacturing, the procurement of raw materials is a key basic link to control the quality of the final product, and the manufacturing of pressure vessels is naturally no exception. Taking into account the chaotic order of the current material supply market, even for materials of the same specification, quality differences caused by different manufacturers abound. Therefore, pressure vessel manufacturers must strengthen management of the procurement of raw materials. First of all, we must conduct credit checks on the production and suppliers of materials, and select those with good credit and long-term cooperative relations. Secondly, after each material purchase is completed, the company should evaluate the supplier’s supply speed, service quality and product quality, and record the evaluation results in the material supplier’s files for future material supplier selection Provide evidence. Finally, pressure vessel manufacturers should establish a sound and complete material procurement quality control system, strengthen supervision of whether the purchased materials comply with relevant national and industry standards, and strengthen inspections of the material quality certificates and other certification materials provided by suppliers. The responsibility for inspection is assigned to the inpidual, and strive to ensure that the selected materials meet the design performance index requirements. Measures in the acceptance link The quality management department shall strengthen the quality acceptance of the delivered materials, and the inspectors and engineers may conduct quality inspections on whether the materials meet the relevant standard requirements. Before the materials are put into storage, they must go through scientific acceptance and supervise whether the acceptance process meets the relevant process specifications. Make sure that the procedures are complete when materials are put into storage. Acceptance records of materials must be filled in accurately. All the above processes must form a clear process specification. Once there is an acceptance problem, the responsibility traceability mechanism can be activated immediately to find out the problems in the acceptance process and improve it. Material storage measures The purchased materials shall be classified and stored when they are put into the warehouse. They shall be kept scientifically according to the specifications, composition and physical and chemical properties of the materials, and shall be marked accordingly. The material storage warehouse should meet relevant requirements such as ventilation and drying, and different sensors should be set up in the storage area according to different materials to monitor whether the storage environment meets the storage requirements of the materials in real time to ensure that the materials will not appear in storage Degeneration and other issues. Finally, in the process of distributing materials, we must strictly abide by the “application-review” system, standardize the application and distribution process of materials, and ensure the scientific and reasonable use of materials. Material recycling measures Before using the material, the size and specification of the material should be checked according to relevant regulations and drawings. Only after the inspection is qualified can it be used for pressure vessel manufacturing. Mark the materials that have been received and still have surplus after manufacturing. After the materials pass the inspection and confirmation, the return procedures can be processed. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The intergranular corrosion tendency test of stainless steel is a common content in design documents, and the relevant content in standards such as HG/T 20581 is relatively clear. The water pressure test or the chloride ion content in the operating medium is also the basic content of the austenitic stainless steel equipment design. In addition to chloride ions, wet hydrogen sulfide, polythionine and other environments that may generate sulfides can also cause stress corrosion cracking of austenitic stainless steel. It is worth mentioning that although austenitic stainless steel is not mentioned in the chapter of HG/T 20581 wet hydrogen sulfide corrosion, the reference points out that although austenitic stainless steel has a much greater ability to dissolve atomic hydrogen than ferritic stainless steel, But hydrogen-induced wet hydrogen sulfide stress corrosion cracking will still occur, especially after cold work hardening appears deformed martensite structure transformation. Cold work hardening increases stress corrosion cracking sensitivity Austenitic stainless steel has excellent cold working properties, but its work hardening is very obvious. The greater the degree of cold working deformation, the higher the hardness rise. The increase in hardness caused by work hardening is also an important reason for the stress corrosion cracking of stainless steel, especially those where the base material is not welded. There are some cases: The first type of case is the cold spinning of austenitic stainless steel oval or dish-shaped head, the cold deformation of the transition zone is the largest, and the hardness also reaches the highest. After commissioning, chloride ion stress corrosion cracking occurred in the transition zone, resulting in equipment leakage. The second type of case is a U-shaped corrugated expansion joint made by hydroforming after the stainless steel sheet is rolled. The cold deformation is the largest at the wave crest, and the hardness is the highest. The stress corrosion cracking occurs along the wave crest the most, and even cracking along the wave crest occurs. Explosion accident with low stress and brittle fracture. The third case is the stress corrosion cracking of the corrugated heat exchange tube. The corrugated heat exchange tube is cold-extruded from a stainless steel seamless tube. The wave crests and troughs are subjected to different degrees of cold deformation and thinning. The crests and troughs may cause several stress corrosion cracks. The essence of cold work hardening of austenitic stainless steel is to produce deformed martensite. The greater the cold work deformation, the more deformed martensite and the higher its hardness. At the same time, the greater the internal stress within the material. In fact, if solution heat treatment is carried out after its processing and forming, the effect of reducing the hardness and greatly reducing the residual stress can be achieved, and the martensite structure can also be eliminated, thereby avoiding stress corrosion cracking. The embrittlement problem of long-term service under high temperature At present, the container and pipe materials at 400～500℃ are mainly Cr-Mo steel with higher high temperature strength, and at 500～600℃ or even 700℃, various austenitic stainless steels are mainly used. In the design, people often pay more attention to the high temperature strength of austenitic stainless steel, and require its carbon content not to be too low. The allowable stress at high temperature is basically obtained by the extrapolated high temperature endurance strength test, which can ensure that no creep rupture occurs under the design stress of 100,000 hours of service. However, the ageing embrittlement problem of austenitic stainless steel at high temperature cannot be ignored. After long-term service at high temperature, austenitic stainless steel will have a series of changes in the structure, which will seriously affect a series of mechanical properties of steel, especially the brittleness Significantly rise, resilience drops significantly. The embrittlement problem after long-term service at high temperature is generally caused by two factors, one is the formation of carbides, and the other is the formation of σ phase. The carbide phase and σ phase continue to precipitate along the crystal after long-term service of the material, and even form a continuous brittle phase on the grain boundary, which is very easy to form intergranular fracture. The formation temperature range of σ phase (Cr-Fe intermetallic compound) is about 600-980 ℃, but the specific temperature range is related to the alloy composition. As a result of the precipitation of σ phase, the strength of austenitic steel is greatly increased (the strength may be doubled), and it becomes hard and brittle. High chromium is the main reason for the formation of high-temperature σ phase, and Mo, V, Ti, Nb, etc. are alloy elements that strongly promote the formation of σ phase. The formation temperature of carbide (Cr23C6) is in the sensitization temperature range of austenitic stainless steel, which is 400～850 ℃. Cr23C6 will dissolve above the upper limit of the sensitization temperature, but the dissolved Cr will promote the further formation of σ phase. Therefore, when austenitic steel is used as a heat-resistant steel, the understanding and prevention of high-temperature aging embrittlement should be strengthened. Like the metal monitoring of thermal power plants, the metallographic structure and hardness changes can be checked regularly. If necessary, samples can be taken out for metallographic and hardness inspections, and even comprehensive mechanical properties and endurance strength tests can be performed. Source: China Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.steeljrv.com) (wilsonpipeline Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. wilsonpipeline products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.) If you want to have more information about the article or you want to share your opinion with us, contact us at sales@wilsonpipeline.com

In order to prevent the pipe sleeve forging from axial movement under axial load, the axial positioning device is applied to the bearing on the shaft and in the hole. How to design the size of axial positioning pipe sleeve forging? The following is mainly for you to talk about. The common pipe sleeve forging orientation positioning method is introduced as follows: The bearing inner ring is positioned on the shaft. When the bearing inner ring is installed, the bearing position is usually fixed by the shaft shoulder on one side, while the other side is fixed by nut, stop washer or spring retainer. The size of the contact part between the shoulder and the axial fixed parts and the inner ring of the bearing can be determined according to the installation dimensions of various bearings listed in the bearing size table. (1) When the pipe sleeve forging speed is high and bearing large axial load, the end face of nut contacting with bearing inner ring should be perpendicular to the rotation center line of shaft. Otherwise, even if the nut is tightened, the installation position of the pipe sleeve forging and the normal working state of the bearing will be damaged, and the rotation accuracy and service life of the bearing will be reduced. Especially when the fit between the inner hole of pipe sleeve forging and the shaft is loose, it needs to be strictly controlled. In order to prevent the nut from loosening in the process of rotation, appropriate technical measures should be taken to prevent the nut from loosening. Using the nut and the stop washer, place the key tooth of the lock washer into the keyway of the shaft, and then bend one of the teeth on the outer ring into the notch of the nut. (2) When the bearing bears little axial load, the rotating speed is not high, the shaft is short and it is difficult to process the thread on the journal, the elastic ring with rectangular cross section can be used. This method is convenient for loading and unloading, occupies a small position and is easy to manufacture. (3) When the thrust washer is positioned on the short journal, it is difficult to process the thread on the journal, and the bearing speed is high and the axial load is large, the washer can be used for positioning, that is, the washer is used for positioning on the shaft end face with more than two screws, and the locking washer or iron wire is screwed to prevent loosening. (4) The self-aligning roller bearing, which can bear steady radial load and small axial load, can be installed on the smooth shaft with the aid of tapered sleeve. The setting sleeve is positioned with nut and stop washer. The bearing is positioned by the friction force of the nut locking sleeve. (5) The bearing with taper in the inner hole is positioned. The bearing with taper in the inner hole is installed on the taper shaft. It is necessary to make the axial load check and tighten the shaft and bearing. Therefore, attention should be paid to the directionality of the taper of the inner hole during installation. If the bearing is located at the shaft end and is allowed to be processed into thread at the shaft end, the nut can be directly used for positioning. If the bearing is not mounted on the shaft end and the shaft is not allowed to be threaded. In this case, the two halves of the combined threaded ring can be clamped into the groove of the shaft, and then the nut is used to locate the pipe sleeve forging. (6) Special positioning in some special cases, when the shoulder and fillet dimensions of the shaft cannot be determined according to the installation dimensions listed in this catalog, the transition gasket can be used as the axial support. What are the application fields of large ring forgings? Large ring forgings are widely used, but what specific aspects can it be applied in? The following article is mainly about it. Ring forging of diesel engine: a kind of forging of diesel engine. Diesel engine is a kind of power machinery. It is often used as engine. Taking large diesel engine as an example, more than ten kinds of forgings are used, such as cylinder head, main journal, crankshaft end flange output shaft, connecting rod, piston rod, piston head, crosshead pin shaft, crankshaft transmission gear, gear ring, intermediate gear and oil pump body. Marine Ring Forgings: Marine forgings are pided into three categories: main engine forgings, shafting forgings and rudder forgings. The forging of main engine is the same as that of diesel engine. Shafting forgings include thrust shaft, intermediate shaft, stern shaft, etc. Rudder system forgings include rudder stock, rudder post, rudder pin, etc. Ring forgings of weapons: Forgings play an important role in the ordnance industry. By weight, 60% of tanks are forgings. The barrel, muzzle brake and tail of artillery, rifled barrel and three edged bayonet in infantry weapon, launching device and fixed base of rocket and submarine deep-water bomb, stainless steel valve body for high-pressure cooler of nuclear submarine, shell and bullet are all forged products. In addition to steel forgings, weapons are made of other materials. Petrochemical Ring Forgings: forgings are widely used in petrochemical equipment. For example, manhole and flange of spherical storage tank, various tubesheets required for heat exchanger, integral forged cylinder (pressure vessel) for catalytic cracking reactor, cylinder section for hydrogenation reactor, and top cover, bottom cover and head required by chemical fertilizer equipment are all forgings. Mining Ring Forgings: the proportion of forgings in mining equipment is 12-24% based on equipment weight. Mining equipment: mining equipment, hoisting equipment, crushing equipment, grinding equipment, washing equipment, sintering equipment. Source: China Pipe Sleeve Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In the fluid pipeline system, the valve is the control element, whose main functions are opening and closing, throttling, regulating flow, isolating equipment and pipeline system, preventing medium backflow, regulating and discharging pressure, etc. There are many kinds of valves with complex varieties. The commonly used valves include gate valve, globe valve, throttle valve, plug valve, butterfly valve, ball valve, check valve, diaphragm valve, etc., and special valves include drain valve, safety valve and pressure reducing valve. With the rapid development of petrochemical industry, most of the media in petrochemical production units are toxic, flammable, explosive and corrosive. The operating conditions are complex and harsh, the operating temperature and pressure are high, and the start-up cycle is long. Once the valve fails, the medium leakage will be caused, which not only pollutes the environment, but also causes economic losses, and even leads to shutdown of the plant, Even caused a vicious accident. It is very important to select the right valve, especially the special valve in the pipeline design. Safety valve and its selection method What is safety valve? Safety valve is an automatic valve for safety protection, which involves personal safety. It does not rely on any external force, but uses the force of the medium itself to discharge a certain amount of fluid to prevent the pressure in the system from exceeding the predetermined safety value. When the pressure is reduced to the specified value, the valve will be closed in time to protect the safe operation of equipment or pipeline. The safety valve is designed under the most unfavorable factors. In case of the following situations, explosion accidents may occur due to fire, operation failure or water and power failure, etc., and the equipment or pipeline shall be set with safety valve (or other safety measures shall be taken): Outlet pipeline of positive displacement pump and compressor; On liquefied hydrocarbon pipeline where both ends are likely to be closed, resulting in pressure rise; The pipeline with combustible gas and flammable liquid expansion that may exceed the design pressure when heated; The design pressure is less than the pressure source of the pressure vessel and pipeline; Steam outlet pipe of condensate turbine; All pressure vessels need to be equipped with pressure relief facilities. Classification of safety valves Safety valves are classified according to different methods as follows: ① According to the different overall structure and loading mechanism, it can be pided into lever heavy hammer type (usually used for lower pressure, generally installed on equipment), spring yellow type and control type; ② According to the ratio of disc opening height to valve flow diameter, it can be pided into micro open type, middle open type and full open type; ④ According to whether there is back pressure balance mechanism, it can be pided into back pressure balance type and conventional type; ⑤ According to the principle of action, it can be pided into direct acting type and indirect acting type (including pilot type and those with power auxiliary device). Description of safety valve selection There are many types and types of safety valves. For different occasions, the following types of safety valves should be selected: ① When discharging gas or steam, full open safety valve shall be selected; ② When discharging liquid, the micro open safety valve is generally selected; ③ When discharging steam or air, safety valve with wrench can be selected; ④ The safety valve with heat sink should be selected for the gas safety valve with set pressure greater than 3Mpa and temperature higher than 235 ℃ to prevent direct erosion of spring by relief medium; ⑤ General flammable, explosive or toxic media should be closed type, and steam or inert gas can be non closed type; ⑥ The bellows safety valve should be selected for the discharge of highly toxic, strong corrosive and extremely dangerous media; ⑦ High back pressure occasion, should choose back pressure balance type or pilot valve control type safety valve. Steam trap and its selection method What is a steam trap? The steam trap is a kind of automatic steam drainage device which does not drain the steam or steam from the condensation pipe at the same time. Because the trap has the function of blocking steam and draining water, it can make the steam heating equipment supply heat evenly and make full use of the latent heat of steam to prevent water hammer in the steam pipe. It is an energy-saving product which can ensure the temperature and heat required by various heating process equipment and can work normally. Classification of steam trap There are many kinds of traps with different performance. Steam trap should be able to “identify” the steam and condensate, in order to play the role of steam blocking and drainage. The identification of steam and condensate is based on three principles: density difference, temperature difference and phase change. According to the three principles, three types of traps are manufactured: mechanical type, thermal static type and thermal dynamic type. ① Mechanical type steam trap, also known as float type drain valve, is to use the density difference between condensate and steam, through the change of condensate level, float (spherical or barrel) lifting and driving the valve disc to open or close, so as to achieve the purpose of steam blocking and drainage. The mechanical type steam trap has small undercooling degree and is not affected by the working pressure and temperature changes. If there is water, it will be discharged. There is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency. Mechanical drain valve has free floating ball type, lever floating ball type, floating bucket type, inverted bucket type, etc; ② Thermal static type steam trap is to use the temperature difference between steam and condensate to cause the change or expansion of temperature sensing element to drive the valve core to open and close the valve. The super cooling degree of the thermal static type steam trap is large, which is generally 15 to 40 degrees. It can use part of the sensible heat in the condensate. There is always high-temperature condensate in front of the valve, no steam leakage, and remarkable energy-saving effect. There are bellows type, steam pressure type or balance pressure type, bimetallic plate type and liquid expansion type; ③ According to the phase change principle, the thermal power type steam trap is based on the different thermodynamic principles of the flow rate and volume change when steam and condensate pass through, which makes the valve plate produce different pressure difference and drives the valve plate to open and close the valve. Because the working power of thermal power steam trap comes from steam, the waste of steam is large. Thermal power type steam trap is pided into disc type, pulse type, labyrinth type or microporous type. Description of drain valve selection In the process of steam transportation, steam water separation, heating, drying, heat preservation, heat tracing, disinfection, distillation, concentration, cooking, heat exchange, heating, air conditioning and other heating processes, in order to ensure the temperature and heat required by various equipment processes, and timely discharge condensate to prevent steam leakage, steam trap must be installed. For the selection of drain valve, high sensitivity, accurate steam blocking and drainage, no leakage of steam, can improve steam utilization rate, reliable working performance, high back pressure, long service life, convenient maintenance and other conditions. Selection principle of steam trap: ① If the equipment is required to have the fastest heating speed, the heating temperature is strictly controlled, and condensate can not be accumulated in the heating equipment, the mechanical drain valve which can discharge saturated water should be selected; ② If the heating equipment has a large heating area, it is not required to heat as soon as possible, the heating temperature is not strict, and a certain amount of condensate can be required to accumulate, the thermal static type steam trap should be selected; ③ According to the drainage capacity of the equipment used, the safety factor must be considered when selecting the drain valve; ④ The drain valve is based on the pressure difference to determine the displacement. The specific selection instructions are as follows: ① The maximum back pressure of mechanical steam trap is 80% and the working quality is high. It is the most ideal drain valve for production process heating equipment. The sensitivity of valve with small gate diameter is higher than that of valve with gate diameter. In addition to the inverted bucket drain valve can remove a small amount of cold and hot air, this type of valve can not exclude air. The free floating ball type has the advantages of simple structure, high sensitivity, and can discharge saturated water. It has poor water hammer resistance and dirt resistance. It is suitable for large diameter and large displacement, but its manufacturing process is complex. ② The thermal static type steam trap can be installed on the upper part of steam consuming equipment and used as exhaust valve only. The liquid expansion type is suitable for the heat tracing pipeline with low heat tracing temperature and heating pipeline. The steam pressure type or balance pressure type has simple structure, sensitive action, can continuously drain and exhaust air, has good performance and small air leakage, but it has poor water hammer and dirt resistance, and has a wide application range. It can be used as the exhaust valve of steam system. Bellows type is widely used for heating system drainage, and can also be used as exhaust valve of steam system. The bimetallic chip has low sensitivity, continuous drainage, good drainage performance, large and adjustable undercooling. It can be applied from low pressure to high pressure, and the maximum service temperature can reach 550 ℃. It has strong resistance to dirt and water hammer. ③ The thermal power type steam trap has high sensitivity, small opening and closing parts, small inertia and fast switching speed. Disc type steam trap is suitable for high temperature and high pressure steam pipeline, dryer, heater and superheated steam equipment. The back pressure of pulse type steam trap is low, which is suitable for siphon drainage of rotary drying drum, and can remove a certain amount of cold and hot air. Labyrinth or microporous trap has simple structure and can continuously drain and exhaust air. Microporous type is suitable for small displacement, labyrinth type is suitable for extra large displacement. Installation requirements of steam trap The thermal power type steam trap should be installed in the horizontal pipeline; the floating ball type drain valve must be installed horizontally, and the necessary anti freezing measures should be taken for those arranged outdoors; the bimetallic trap can be installed horizontally or vertically; the pulse type steam trap is generally installed on the horizontal pipeline with the valve cover upward; the inverted bucket type steam trap should be installed horizontally and not inclined; when installing the steam trap, the main body should refer to The flow direction arrow indicated must be consistent with the direction of condensate flow in the pipeline, otherwise the trap will lose its function. Pressure reducing valve and its selection method What is pressure reducing valve? The pressure reducing valve is a kind of valve that can reduce the inlet pressure to a certain outlet pressure by throttling the opening and closing parts, and can use its own medium energy to keep the outlet pressure basically unchanged when the inlet pressure and flow rate change. Its function is to change the position of valve disc by means of sensitive elements, such as diaphragm and spring, so as to reduce the medium pressure and achieve the purpose of decompression. In general, the outlet pressure of the pressure reducing valve should be less than 0.5 times of the inlet pressure. The fluctuation of inlet pressure of the pressure reducing valve should be controlled at 80% ~ 105% of the given value of the inlet pressure. If the range is exceeded, the performance of the pressure reducing valve in the early stage will be affected. For the convenience of operation, adjustment and maintenance, the pressure reducing valve should be installed on the horizontal pipeline. Classification of pressure reducing valve Pressure reducing valve can be pided into bellows type (direct acting) pressure reducing valve, piston type pressure reducing valve and membrane type pressure reducing valve. ① Bellows type (direct acting) pressure reducing valve. Simplest pressure reducing valve, direct acting pressure reducing valve, with flat diaphragm or bellows. Independent structure, no need to install external sensing line downstream. It is the smallest and most economical one among the three pressure reducing valves, specially designed for medium and low flow. The accuracy of the direct acting pressure reducing valve is usually (+ 10% ~ – 10%) of the downstream set point; ② Piston type pressure reducing valve. This type of pressure reducing valve has two kinds of valves, pilot valve and main valve. The design of pilot valve is similar to that of direct acting pressure reducing valve. The exhaust pressure from the pilot valve acts on the piston to open the main valve. If the main valve is too large to be opened directly, this design will use the population pressure to open the main valve. As a result, this type of pressure relief valve has higher capacity and accuracy (+ 5% ~ – 5%) than direct acting pressure reducing valve at the same pipe size. Similar to the direct acting pressure reducing valve, the pressure reducing valve can sense the pressure inside without installing a sensing line outside; ③ Diaphragm pressure reducing valve. In this type of pressure reducing valve, the double diaphragm replaces the piston in the inner guide pressure reducing valve. This increased diaphragm area opens a larger main valve and, at the same pipe size, has a larger capacity than an internal guide piston pressure relief valve. In addition, the diaphragm is more sensitive to pressure changes, and the accuracy can reach (+ 1% ~ – 1%). The higher accuracy is due to the positioning of the downstream sensing line (outside the valve), where there is less gas or liquid turbulence. The pressure reducing valve is very flexible and can use different types of pilot valves, such as pressure valve, temperature valve and air loading valve. Selection of pressure reducing valve The pressure reducing valve is widely used in the equipment and pipeline of steam, compressed air, industrial gas, water, oil and other liquid media ① Bellows direct acting pressure reducing valve is suitable for low pressure, medium and small caliber steam, air and other media; ② Membrane direct acting pressure reducing valve is suitable for medium and low pressure, medium and small caliber steam or water; ③ The pilot piston type pressure reducing valve is suitable for steam, air and water media with various pressures, calibres and temperatures. If it is made of stainless acid resistant steel, it can be used in various corrosive media; ④ When the working temperature of medium is high, the piston type pressure reducing valve is generally selected; ⑤ When the sensitivity requirement is high, the spring diaphragm pressure reducing valve can be selected; ⑥ When the medium is air or water (liquid), direct acting membrane pressure reducing valve or pilot diaphragm pressure reducing valve is generally selected. Conclusion In the pipeline system of petroleum, chemical industry and other industries, there are more and more special valves such as safety valve, drain valve and pressure relief valve with energy saving function. Valve in operation has a very close relationship with the overall efficiency of the enterprise. Although the valve is small, it has a very important causal relationship with the survival and development of the enterprise. For the safety production and benefit of the enterprise, the designers and enterprises must use the valve in an all-round and scientific way. Reasonable selection of the valve can reduce the construction cost of the device and ensure the safe operation of the production. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Bolt pre-tightening force An important factor affecting sealing. The pre-tightening force must compress the gasket to achieve the initial seal. Properly increasing the bolt pre-tightening force can increase the sealing ability of the gasket, because increasing the pre-tightening force can make the gasket retain a larger contact surface pressure under normal working conditions. However, the pre-tightening force should not be too large, otherwise the gasket will yield as a whole and lose its resilience, or even extrude or crush the gasket. In addition, the preload should be applied to the gasket as evenly as possible. Measures are usually taken to reduce the bolt diameter, increase the number of bolts, and take appropriate pre-tightening methods to improve the sealing performance. Gasket performance The gasket is an important component of the seal. The function of the gasket is to seal the gap between the sealing surfaces of the two flanges and prevent fluid leakage. The types of gaskets include non-metal gaskets, non-metal and metal combination gaskets and metal gaskets. Appropriate gasket material requires that the gasket can produce the necessary elastic deformation under the action of appropriate pre-tightening force without being crushed or squeezed out; the distance between the flange sealing surface is increased during operation, and the gasket material should It has sufficient resilience to keep the gasket surface in close contact with the flange surface to continue to maintain good sealing performance; The working medium and working temperature should also be considered when selecting gasket materials. The width of the gasket is also an important factor affecting the seal. The wider the gasket, the greater the pre-tightening force required, and the larger the size of bolts and flanges is required. ① Non-metallic gaskets such as rubber, asbestos rubber, polytetrafluoroethylene, etc. are commonly used on medium and low pressure equipment and pipeline flanges. They have good corrosion resistance and flexibility, but their strength and temperature resistance are poor. They are usually cut from the entire gasket sheet. The shape of the entire gasket is a ring with a rectangular cross section. ② In order to improve the strength and heat resistance of the gasket, thin steel belts and asbestos belts (or PTFE belts or flexible graphite belts) are wound together to form spiral wound gaskets, or asbestos or other non-metallic materials are wrapped with metal sheets made of metal-clad gaskets have multiple sealing effects and good resilience. They are used in higher temperature and pressure ranges, and can maintain good sealing under pressure and temperature fluctuations, so they are widely used. Spiral wound gaskets are made by winding steel belts with asbestos, polytetrafluoroethylene or flexible graphite and other filling belts. To prevent looseness, weld the beginning and end of the metal strip. In order to increase the elasticity and resilience of the gasket, both the metal strip and the non-metal strip are rolled into a wave shape. There are two wave shapes: V-shaped and W-shaped. There are 4 types of V-shaped structures. Type A-also known as basic type, without reinforcement ring, used for tongue and groove sealing surface. Type B-with inner strengthening ring for concave and convex sealing surface. Type C-with outer reinforcement ring for flat sealing surface. Type D–there are reinforced rings inside and outside for flat sealing surfaces. ③ The metal cladding gasket is made of asbestos rubber sheet as the inner core, and the outer thickness is 0.2～0.5mm thick thin metal plate (as shown below). The material of the metal plate can be aluminum, steel and its alloys, stainless steel or high-quality carbon steel. Metal-clad gaskets are also only used on flanges of Type B flat welding and long-neck butt welding. ④ Metal gaskets are commonly used on flanges of high-pressure equipment and pipelines. The materials include soft aluminum, copper, mild steel and stainless steel. In addition to metal gaskets with rectangular cross-sections, there are also metal ring gaskets with elliptical or octagonal cross-sectional shapes and other special shapes. When the operating pressure is very high or the leakage rate is very strict, and the temperature is very high or the corrosiveness is very strong, metal gaskets can be used. The specific pressure value of the metal gasket is very large. In order to reduce the bolt force, the pressing surface must be very narrow, relying on the extremely narrow pressing surface to maintain a good seal, and must have a small surface roughness, Ra≤2.5μm to Ra ≤0.63μm. Types of sealing surface The contact surface where the gasket is inserted between the flanges and pressed to achieve a sealing effect is called the flange sealing surface or the pressing surface. The selection of the sealing surface type is related to the operating conditions, the consequences of leakage and the nature of the gasket. The common structure types are as follows. ① Flat sealing surface: Its structure is shown in the figure (a) below. The sealing surface is not a smooth plane. There are often 2 to 4 concentric triangular cross-section grooves (ie flange waterline) on the plane. The flat sealing surface has a simple structure, is convenient to manufacture, and is convenient for anti-corrosion lining. Secondly, the width of the sealing surface of this structure is large, so non-metal or metal soft gaskets are often used in use. But after the bolts are tightened, the gasket material is easy to stretch to both sides. Used in occasions where the required pressing force is not high and the medium is non-toxic. ② Concave-convex sealing surface: The structure of the sealing surface is shown in the figure (b) below. It is equivalent to a pair of flat sealing surface flanges, one of which is made as a pressing surface with a raised platform, and the flange is called a convex flange, and the other correspondingly made concave is called a concave flange. The gasket with the same size as the concave is embedded in it, and the gasket is easy to center. The height of the convex plane is slightly greater than the depth of the concave surface, and it is tightly pressed with bolts to play a sealing role. This structure can limit the radial deformation of the gasket, prevent the gasket from being extruded, and improve the sealing performance to a certain extent. Suitable for occasions with higher pressure. ③ Tongue and groove sealing surface: in the middle of a pair of flat sealing surfaces in the width direction, one is made into a cross-section like a tenon, and the other cross-section is like a groove. The pressing surface is paired, as shown in the following figure (c), the former is called a tenon surface flange, the latter is called groove flange. The groove-shaped pressing surface can limit the radial deformation of the embedded gasket, with good sealing performance, and the gasket can be less eroded and corroded by the medium. But the tenon part is easy to damage. It is often used in flammable, explosive, toxic media and higher pressure occasions. In addition, there are trapezoidal groove sealing surfaces and tapered sealing surfaces. The former uses an elliptical cross-section annular metal gasket, and the latter uses a lens-type annular metal gasket. The above two structures are forced sealing, which are commonly used on high-pressure pipelines. The form and surface properties of the flange sealing surface play a vital role in the influence of the sealing effect. The flatness of the flange sealing surface and the perpendicularity between the sealing surface and the flange centerline directly affect the uniformity of the gasket force and the good contact between the gasket and the flange. The roughness of the flange sealing surface should match the gasket requirements. Radial knife marks or scratches on the surface are not allowed, let alone surface cracks. Flange stiffness Excessive warpage due to insufficient flange rigidity (as shown in the figure below) is often one of the main reasons for the failure of the bolt flange connection seal in actual production. A flange with a large rigidity is small in deformation, and the bolt pre-tightening force can be evenly transmitted to the gasket, thereby improving the sealing performance of the flange. The rigidity of the flange is related to many factors. Appropriately increasing the thickness of the flange ring, reducing the diameter of the bolt center circle and increasing the outer diameter of the flange ring can increase the rigidity of the flange. Use a necked flange or increase the size of the tapered neck part. , Can significantly improve the bending resistance of the flange. However, if the rigidity of the flange is increased without principle, the flange will become bulky and the cost will increase. Operating conditions The influence of pressure, temperature and the physical and chemical properties of the medium on the sealing performance is very complicated. The influence of pure pressure and medium on the sealing is not significant, but under the combined action of temperature, especially under fluctuating high temperatures, it will seriously affect the sealing performance , and even make the seal completely fail due to fatigue. Because at high temperatures, the viscosity of the medium is small, the permeability is large, and it is easy to leak; the corrosive effect of the medium on gaskets and flanges is intensified, increasing the possibility of leakage; flanges, bolts and gaskets will all produce greater high temperatures creep and stress relaxation make the seal ineffective; certain non-metallic gaskets will also accelerate aging, deterioration, and even burn. Source: China China Gaskets Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

What is a breather valve? Breather valve is a kind of valve which can not only keep the tank space isolated from the atmosphere within a certain pressure range, but also connect with the atmosphere (breathing) when the pressure range is higher or lower. Its function is to prevent the tank from being damaged due to overpressure or vacuum, and to reduce the evaporation loss of the storage liquid. It is mainly composed of valve seat, valve cover, protective cover and two groups of opening and closing devices controlled by vacuum and pressure. The opening and closing device includes valve disc, guide rod, spring, spring seat and sealing ring. When the pressure in the tank reaches the rated exhaled positive pressure, the pressure valve flap opens and the steam in the tank is discharged; when the vacuum degree in the tank reaches the rated suction negative pressure, the vacuum valve flap opens and the air enters. Structure characteristics of breather valve The breather valve is made of cast iron, cast steel, aluminum alloy and stainless steel with good corrosion resistance. The valve disc and seal ring are made of stainless steel tetrafluoroethylene. The breather valve has good low temperature resistance and antifreeze performance. The breather valve is a ventilation device installed on the fixed roof tank to reduce the evaporation loss of oil and control the pressure of the tank. The breather valve has the advantages of large ventilation, small leakage, corrosion resistance and good antifreeze performance. It can automatically adjust the pressure inside and outside the oil tank. Function of breather valve The internal structure of the breather valve is essentially a combination of a pressure valve disc (that is, an exhalation valve) and a vacuum valve disc (that is, an inhalation valve). The pressure valve disc and the vacuum valve disc can be arranged side by side or overlapped. The working principle of the breather valve is that when the pressure in the tank reaches the rated positive exhalation pressure, the pressure valve flap opens and the vapor in the tank is discharged; when the vacuum in the tank reaches the rated suction negative pressure, the vacuum valve flap opens and air enters. 1. When the pressure of the medium in the tank is within the control operating pressure range of the breather valve, the breather valve does not work to maintain the tightness of the oil tank; 2. When the medium is added to the tank to increase the pressure in the upper gas space of the tank and reach the positive operating pressure of the breather valve, the pressure valve is opened and the gas escapes from the breather valve exhalation outlet, so that the pressure in the tank does not continue increase; as shown in the figure below: 3. The atmosphere outside the tank will open the negative pressure valve disc of the breather valve and suck in air; as shown in the figure below: The breather valve plays a sealing role under normal conditions. It can only work under the following conditions: (1) When the storage tank outputs materials, the breather valve begins to suck air or nitrogen into the tank. (2) When the material is filled into the tank, the breather valve starts to exhale the gas from the tank to the outside. (3) Due to climate change and other reasons, the vapor pressure of materials in the tank increases or decreases, and the breather valve exhales steam or inhales air or nitrogen (usually called thermal effect). (4) In case of fire, the evaporation of liquid in the tank increases sharply due to the heat of exhaled gas, and the breather valve begins to exhale out of the tank, so as to avoid the damage of the tank due to overpressure. (5) In other working conditions, such as the pressurized transportation of volatile liquid, chemical reaction of internal and external heat transfer devices, misoperation, etc., the breather valve will exhale or inhale accordingly, so as to avoid damage to the storage tank due to overpressure or ultra vacuum. Working principle of breather valve The internal structure of the breather valve is essentially composed of a pressure valve disc (i.e. exhalation valve) and a vacuum valve disc (i.e. suction valve). The pressure valve disc and vacuum valve disc can be arranged side by side or overlapped. Its working principle: when the pressure of the tank is equal to the atmospheric pressure, the disc and seat of the pressure valve and vacuum valve are closely matched, and the sealing structure on the side of the seat has “adsorption” effect, so that the seat is tight without leakage. When the pressure or vacuum degree increases, the valve disc starts to open, because there is still “adsorption” effect on the seat edge, so it can still maintain a good seal. When the pressure in the tank rises to the constant value, the pressure valve is opened, and the gas in the tank is discharged into the outside atmosphere through the exhalation valve (pressure valve). At this time, the vacuum valve is closed due to the positive pressure in the tank. On the contrary, when the pressure in the tank drops to a certain degree of vacuum, the vacuum valve opens due to the positive pressure of atmospheric pressure, and the external gas enters the tank through the suction valve (i.e. vacuum valve), and the pressure valve is closed. At any time, the pressure valve and vacuum valve cannot be opened at the same time. When the pressure or vacuum in the tank drops to the normal operating pressure, the pressure valve and vacuum valve are closed, and the process of exhalation or inhalation is stopped. Common standards for Breather valves Commonly used standards for Breather valves are: SY/T 0511.1-2010 “Petroleum Storage Tank Accessories Part 1: Breather valve” TB/T 3319-2013 “Breathing safety valve for railway tank car” QC/T 1064-2017 “Tank Vehicle Breather valve for Road Transport of Flammable Liquid and Dangerous Goods” DIN EN 14595-2016 “Dangerous Goods Transport Tank, Tank Operating Device Pressure and Vacuum Breather valve” Classification of breather valve Tight breather valve The tight breather valve is usually used in low-pressure straight-through pipelines. The sealing performance depends entirely on the goodness of the fit between the plug and the plug body. The compression of its sealing surface is achieved by tightening the lower nut. Generally used for PN≤0.6Mpa. Packed breather valve Packing type breather valve realizes the sealing of plug and plug body by pressing the packing. Due to the packing, the sealing performance is better. Usually, this kind of breather valve has a packing gland, and the plug does not need to extend out of the valve body, thus reducing a leakage path of the working medium. This kind of breather valve is widely used for the pressure of PN≤1Mpa. Self-sealing breather valve The self-sealing breather valve realizes the compression and sealing between the plug and the plug body through the pressure of the medium itself. The small head of the stopper extends upwards out of the body, and the medium enters the big head of the stopper through the small hole at the entrance to press the stopper upwards. This structure is generally used for air medium. Oil-sealed breather valve The scope of application of breather valves continues to expand, and oil-sealed breather valves with forced lubrication appear. Due to forced lubrication, an oil film is formed between the plug and the sealing surface of the plug body. In this way, the sealing performance is better, the opening and closing is labor-saving, and the sealing surface is prevented from being damaged. Classified by material Cast iron breather valve, carbon steel breather valve, cast steel breather valve, stainless steel (304, 304L, 316, 316L) breather valve, aluminum alloy breather valve, plastic (PVC, PP) breather valve; Classified by working principle The first is to exhale or inhale when a certain pressure is reached; the other is designed to only exhale but not inhale, which can be understood as replacing it with two check valves with appropriate pressure. The second type of breather valve is similar to a one-way check valve. It can only breathe out, not inhale. When the pressure in the system rises, the gas will pass through the breather valve to vent outwards to ensure a constant pressure in the system. For storage tanks that store toxic substances, there is no breather valve, and treatment devices such as activated carbon filters can be added. breather valves are generally used on normal pressure or low pressure storage tanks, that is, only normal pressure and low pressure storage tanks have breather discharge (the low pressure tank often has a steam recovery system), and the high pressure storage tank has no discharge, no breather loss and work loss . The main emissions of fixed roof tanks are pided into breather loss (small breather discharge) and work loss (large breather discharge). Installation of Breather valve 1. Remove the packaging, it is very important to read the product description. 2. When hoisting the breather valve, appropriate lifting tools should be used to avoid damage to the protective cap of the breather valve disc. 3. Check the coaxiality and verticality of the pipe flange on the tank or water tank, which is essential for the normal use of the pressure and vacuum relief valve (Breather valve). 4. Check the waterline surface of the pipe flange on the tank or water tank. It must be clean, free of scratches, corrosion, tool marks, and flat. 5. Remove the flange port protection cover and other packing materials. 6. Check the gasket; make sure the material is suitable for the application. 7. Use the bolt circle to center the washer. Installation points of Breather valve (1) The Breather valve should be installed at the highest point on the top of the tank. Theoretically speaking, from the viewpoint of reducing evaporation loss and other exhaust gas, the breather valve should be installed at the highest point of the gas phase space of the tank in order to smoothly provide the most direct and largest passage to the breather valve. (2) When the volume of the storage tank is large or the storage tank is more important, in order to prevent the risk of overpressure or negative pressure in the storage tank due to failure of a single Breather valve, two Breather valves can be installed at this time. In order to avoid two Breather valves operating at the same time and increasing the probability of failure, during process design, the suction and discharge pressure gradients of the two Breather valves are usually designed. Normally, the next one works and the other is standby. (3) If the breather volume is too large and the breather volume of a single Breather valve cannot meet the requirements, more than two Breather valves can be set. When installing two Breather valves, their distance from the center of the tank top should be equal, that is, they are arranged symmetrically on the tank top. (4) If the breather valve is installed on a nitrogen-sealed storage tank, the position of the nitrogen gas supply pipe must be far away from the breather valve interface and inserted into the storage tank from the top of the tank for about 200mm, so that the nitrogen is not directly discharged after entering the tank. Nitrogen sealing effect. (5) If there is a flame arrestor in the breather valve, the influence of the pressure drop of the flame arrestor on the discharge pressure of the breather valve must be considered to avoid overpressure in the storage tank. (6) When the average temperature of the coldest month in the tank building area is lower than or equal to 0, the breather valve must have anti-freezing measures to prevent freezing or blocking of the breather valve valve disc, resulting in poor exhaust or insufficient air supply of the storage tank , Which leads to overpressure drum or low pressure deflated tank. Breathing discharge calculation of breather valve The respiratory emissions of the fixed roof tank can be estimated by the following formula: LB=0.191×M(P/(100910-P))^0.68×D^1.73×H^0.51×△T^0.45×FP×C×KC In the formula: LB-respiratory discharge volume of fixed top tank (Kg/a); M-the molecular weight of the vapor in the tank; P-In a large amount of liquid state, the true vapor pressure (Pa); D-The diameter of the tank (m); H-average vapor space height (m); △T- the average temperature difference within a day (℃); FP-coating factor (dimensionless), the value is between 1 and 1.5 according to the paint condition; C-Adjustment factor for small diameter tanks (dimensionless); For tanks with a diameter between 0-9m, C=1-0.0123(D-9)^2; C=1 for tanks with a diameter greater than 9m; KC-product factor (Petroleum crude oil KC is 0.65, other organic liquids are 1.0). Working discharge calculation of Breather valve Work emissions are losses due to man-made loading and unloading. As a result of charging, when the pressure in the tank exceeds the release pressure, the vapor is forced out of the tank; while the discharge loss occurs when the liquid is discharged, and the air is drawn into the tank, and the air becomes a gas saturated with organic vapor and expands. Therefore, the capacity of the vapor space is exceeded. The working emissions of the fixed roof tank can be estimated by the following formula: LW=4.188×10^-7×M×P×KN×KC In the formula: LW-Work loss of fixed roof tank (Kg/m3 input); KN-Turnover factor (dimensionless), the value is determined by the number of annual turnover (K). Turnover times=annual input/tank capacity K<=36,KN=1 36 K>220, KN=0.26 Pressure test of Breather valve 1. Test preparation Install the fire-stop Breather valve on the test bench correctly, the device should not leak, and the inner wall of the test tube should be flat and smooth. 2. Detection medium The detection medium for the opening pressure, ventilation and leakage of the fire resistance Breather valve is air, the absolute pressure is 0.1Mpa, the temperature is 20℃, the relative humidity is 50%, and the density is 1.2kg/m3. If the air is not in this state, Should be converted to gas in this state. The detection medium for the pressure of the flame retardant Breather valve body is 5-35 ℃ clean water. 3. Air pressure detection First detect its leakage, and then detect its sensitivity and ventilation volume one by one. 4. Water pressure detection The water pressure test of the fire retardant Breather valve is 0.2Mpa, and the pressure holding time is 10min. 5. Pressure detection Install the fire-resistance Breather valve on the connecting flange of the gas storage tank, adjust the valve to gradually increase or decrease the pressure in the gas storage tank, adjust the valve disc to make it open, and read from the connected micromanometer Output the pressure value, read the value once every minute, and then rotate the valve disc by 90° and 180° respectively, repeat the above test, repeat each working condition three times, and take the average value. 6. Leakage detection The leak detection pressure is 0.75 times the operating pressure, and this value is read on the micromanometer. The value of the leakage is read from the flowmeter (the accuracy of the flowmeter is 0.5-1.0 level). Read each measurement value once per minute for a total of three readings, and take the average. 7. Low temperature detection fire resistance Breather valve. Install the fire resistance Breather valve on the test frame and put it in the low temperature box. The temperature in the low temperature box will drop to 4-15℃, and the continuous input relative temperature of the low temperature box should not be less than 70%. The air at room temperature reaches the end of the breather valve before the end of the valve disc is opened, and then the temperature in the low temperature box is reduced to -30 ℃, after 24 hours of constant temperature, connect one side of the test frame to the micromanometer, and the other side passes through A surge tank containing room temperature air is connected to the aerodynamic force. When the valve disc of the breather valve is in the open state, read the pressure value. repeat three times. Maintenance of Breather valve The Breather valve is maintained and maintained once a month and twice a month in winter. The method: first slightly open the valve cover, take out the vacuum valve disc and the pressure valve disc, check the valve disc and valve disc seal, valve disc guide rod and guide rod sleeve for oil and dirt, such as oil and dirt The objects should be cleaned up, then put back in place, and pull up and down a few times to check whether the opening is flexible and reliable. If everything is normal, then tighten the valve cover. In the maintenance and maintenance, if there is any abnormal phenomenon such as scratches or wear on the valve disc, it should be replaced immediately or contact the supplier company to solve it in time. How to choose the right breather valve Breather valve selection should first follow the four principles of safety, reliability, applicability, and economy in sequence, and then follow the six aspects of on-site working conditions (namely, pipeline parameters, fluid parameters, pressure parameters, action methods, and special requirements). select). The following factors are mainly considered when selecting the breather valve: 1. For the requirements of the installation location and temperature range, such as cold areas, all-weather Breather valves should be used, and pipeline breather valves should be used for installation in pipelines. 2. The control pressure of the mechanical Breather valve should be compatible with the relevant pressure bearing capacity. 3. The specifications (flange diameter) of the mechanical Breather valve should meet the requirements of the maximum flow rate of breather gas in and out of the oil tank. 4. Consider the exhalation volume caused by the increase in the evaporation of liquid in the tube caused by the heating of the tank during a fire. 5. Under the influence of climate, the increase of vapor pressure in the tank decreases, resulting in the thermal effect of breather. 6. Anti-freeze Breather valve should be selected for selection in northern cold regions. 7. The maximum amount of liquid in and out of the tank. First, determine the breather volume of the breather valve according to the working conditions of the specific occasions where the breather valve is set up and the prescribed calculation method or formula, and then select the breather valve according to the various specified performance curves of different constant pressure values ​​provided by the breather valve manufacturer size. It also determines the take-off pressure and ventilation pressure of the breather valve. When a single breather volume cannot meet the requirements, more than two Breather valves can be set. Confirm the minimum pressure of the vessel design and the maximum allowable pressure of the vessel, that is, the determination of negative pressure and positive pressure, and the operating pressure range. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Valve is the basic element used to control the flow direction, pressure and flow of fluid in pipeline. The valve is the control component in the pipeline fluid delivery system, which is used to change the section of the access and the medium flow direction, and has the functions of persion, cut-off, adjustment, throttling, check-back, persion or overflow pressure relief, etc. The valve used for fluid control, from the simplest stop valve to various valves used in extremely complex automatic control system, has many varieties and specifications, the nominal diameter of the valve is from the extremely tiny instrument valve to the industrial pipeline valve with a diameter of 10m. Classification of valves Classification by use and role (1) block valves are mainly used to cut off or connect medium flow. Including gate valve, stop valve, diaphragm valve, ball valve, plug valve, butterfly valve, plunger valve, ball plug valve, needle type instrument valve, etc. (2) control valve is mainly used to adjust medium flow, pressure, etc. Including regulating valve, throttle valve, pressure reducing valve, etc. (3) check valves are used to prevent dielectric from flowing backwards. Including check valves of various structures. (4) shunt valve type is used to separate, distribute or mix media. It includes the distribution valve and the trap valve of various structures. (5) safety valves are used for safety protection when medium overpressures. Including various types of safety valves. Classification by main parameters Classification by pressure (1) vacuum valve working pressure is lower than the standard atmospheric pressure of the valve. (2) the low pressure valve nominal pressure pn≤1. 6 mpa. (3) the valve whose nominal pressure PN of medium pressure valve is 2.5, 4.0 or 6.4 MPa. (4) high Pressure Valve nominal pressure PN is 10.0~80.0 MPa valve. (5) super High Pressure Valve nominal pressure pn≥100 MPa. Classification by medium temperature (1) high temperature valve is used for the valve with medium working temperature t> 450℃. (2) medium temperature valve is used for medium working temperature 120 ℃ valve. (3) normal temperature valve is used for valves with medium working temperature of-40℃ ≤t≤120℃. (4) low temperature valve is used for the valve of medium working temperature-100℃ ≤t≤40 ℃. (5) ultra low temperature valve is used for the valve with medium working temperature t <-100℃. Classification by valve body material (1) non-metallic material valves: such as ceramic valves, FRP valves, plastic valves. (2) metal material valves: such as copper alloy valve, aluminum alloy valve, lead alloy valve, hastelloy alloy valve, monel alloy valve, cast iron valve, carbon steel valve, stainless steel valve, low alloy steel valve, high alloy steel valve. (3) metal valve body lining valve: such as lead lining valve, plastic lining valve and enamel lining valve. General classification This kind of classification method is pided according to both the principle and function, which is currently the most commonly used classification method at home and abroad. It is generally pided into gate valve, stop valve, throttle valve, instrument valve, plunger valve, diaphragm valve, plug valve, ball valve, butterfly valve,globe valves,check valve, reducing valve, safety valve, trap valve, bottom valve, filter, drain valve, etc. Characteristics of valve Operating Characteristics It determines the main performance and scope of use of the valve. The use characteristics of valves include: Valve category (closed-circuit valve, regulating valve, safety valve, etc.); Product Type (gate valve, stop valve, butterfly valve, ball valve, etc.); Main parts of valve (valve body, material of bonnet, valve stem, disc and sealing surface); Valve transmission mode, etc. Structural characteristics It determines some structural characteristics of Valve installation, maintenance, maintenance and other methods. Belonging to the structural characteristics: the structural length and overall height of the valve, and the connection form with the pipeline (flange connection, threaded connection, clamp connection, external threaded connection, welding end connection, etc.); the form of sealing surface (insert ring, thread ring, overlaying, spray welding, valve body); Structure of valve stem rotating rod, lifting rod) and so on. Steps and basis of valve selection Steps for selecting valves (1) specify the use of the valve in the equipment or device, determine the working conditions of the valve: applicable medium, working pressure, working temperature, etc. (2) determine the nominal diameter and connection method of the pipe connected with the valve: flange, thread, welding, etc. (3) determine the mode of operating the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage, etc. (4) determine the materials of the shell and internals of the selected valve, gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc. (5) select the types of valves: Closed-circuit valves, regulating valve, safety valves, etc. (6) determine the form of the valve: gate valve, stop valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap valve, etc. (7) determine the parameters of the valve: for the automatic valve, according to different needs, first determine the allowable flow resistance, discharge capacity, back pressure, etc., and then determine the nominal diameter of the pipeline and the diameter of the valve seat hole. (8) determine the geometric parameter structure length of the selected valve, flange connection form and size, size of valve height direction after opening and closing, size and quantity of connected bolt holes, external dimensions of the whole valve, etc. (9) use the existing information, such as product catalog of valves and samples of valve products, to select appropriate valve products. Basis of valve selection (1) the purpose, working condition and control mode of the selected valve. For example, the choice of the pump house water pump outlet valve, first need to meet the water pump can close the valve start and stop to reduce the start current and stop the impact on the water pump; Second need to be equipped with a check valve, when the pump unit is accidentally shut down, the valve can be quickly closed to prevent the pump from being reversed for a long time; Thirdly, the valve to eliminate the water hammer should be equipped to ensure the operation safety of the pump unit. After understanding the purpose of the selected valve, it is necessary to understand the installation site and use conditions to correctly select the valve. If electric butterfly valve + micro stop check valve is selected, electric butterfly valve can meet the requirements of start-up and shutdown of the closed valve. Micro retarding closed check valve is used to prevent water pump reversal and water hammer. Due to its relatively simple structure, the failure rate is lower, but the installation length is longer and the water resistance is larger, so it is suitable for large installation space, the pump station which does not have high energy consumption requirements, such as the use of small pump station; The choice of the hydraulic slowly-closing type check valve can meet the three necessary functions of the pump outlet valve at the same time, and the installation length can be very small, and the water resistance is, however, due to the complicated structure, a set of high-pressure hydraulic system is needed, so the failure rate is high and the maintenance is difficult. Therefore, it is suitable to be installed in the large pumping station where there are many spare units; multi-function pump control valve is also available for pump outlet, and its installation length is shorter than that of electric butterfly valve + micro stop closed check valve, so there is no need for electric or hydraulic system vacancy, with the simplest structure and the lowest failure rate, and the water hammer has the best removal, however, the water resistance is the highest, which is suitable for the use of water hammer in severe or unattended pumping stations. (2) properties of working medium working pressure, working temperature, corrosion performance, whether it contains solid particle medium, whether it is toxic, whether it is the viscosity of flammable and explosive medium, etc. (3) requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc. (4) installation dimension and outer dimension requirements: nominal diameter, connection method and connection dimension of the pipe, outer dimension or weight limitation, etc. (5) additional requirements for the reliability, service life and explosion-proof performance of electric devices of valve products. Attention should be paid to when selecting parameters: if the valve is to be used for control purpose, the following additional parameters must be determined: Operation method, maximum and minimum flow requirements, normal flow pressure drop, pressure Drop when closed, maximum and minimum inlet pressure of valve. According to the above-mentioned basis and steps for selecting valves, the internal structure of various types of valves must also be understood in detail when selecting valves reasonably and correctly, so as to make the right choice for the preferred valves. The final control of the pipeline is the valve. The valve hoist controls the medium in the pipeline flow way the shape of the valve passage makes the valve have certain flow characteristics, which must be taken into account when choosing the most suitable valve for installation in the pipeline system. Principles that must be followed when choosing valves Valves for cut-off and open media The channel is a through-through valve, commonly used butterfly valve, gate valve, etc., whose flow resistance is relatively small, usually choose as the cut-off and open medium valve. The downward closed valve (stop valve, plunger valve) is seldom used because its channel is tortuous and its flow resistance is higher than other valves. In the occasion allowing a higher flow resistance, such as the transport medium is gas, you can choose to use the downward closed valve. When choosing butterfly valve, when there are more impurities in the transport medium, such as raw water or sewage, horizontal butterfly valve should be selected, because its valve shaft is horizontal, the bottom of the flow channel is not easy to accumulate debris and scale, which is conducive to the protection of the valve plate seal ring. Choose the type of gate valve that has no groove at the bottom of the valve runner to avoid valve leakage due to the accumulation of sundries in the groove. The valve used for flow control Generally, a valve that is easy to adjust the flow is selected to control the flow. A downward closed valve (such as a stop valve) is suitable for this purpose because its valve seat size is proportional to the stroke of the closing piece. Rotary Valve Rotary plug valve, butterfly valve, ball valve) and flexible valve body type 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 disc disc to make a cross-cutting movement of the circular valve seat. It can control the flow well only when it is close to the closed position, so it is usually not used for flow control. Reversing shunt valve According to the need of reversing shunt, this valve can have three or more channels. Plug valves and ball valves are more suitable for this purpose. Therefore, most of the valves used for reversing and shunt are one of these valves. However, in some cases, other types of valves, as long as two or more valves are properly connected to each other, can also be used for reversing persion. Valve for medium with suspended particles When the medium has suspended particles, it is most suitable to use its closing parts along the sealing surface to slide the valve with wiping effect. If the back and forth movement of the closing piece to the valve seat is vertical, it is possible to clamp the particles. Therefore, this valve is only suitable for basic clean media unless the sealing surface material can allow embedded particles. Ball valve and plug valve in the opening and closing process on the sealing surface are wiping effect, so it is suitable to be used in the medium with suspended particles. Valve installation The installation of the valve should be carried out in accordance with the valve instruction and relevant provisions. During the construction process, it should be carefully checked and carefully constructed. Before installing the valve, install it after the pressure is tested to be qualified, carefully check whether the specification and model of the valve are consistent with the drawings, check whether the parts of the valve are intact, and whether the opening and closing valve can rotate flexibly, whether the sealing surface is damaged or not can be installed after confirmation. When installing the valve, the operation mechanism of the valve should be at about 1.2m away from the operation ground and be in conformity with the chest. When the center of the valve and the hand wheel are more than 1.8m away from the operating ground, an operating platform should be set for valves and safety valves that are frequently operated. For pipelines with more valves, the valve should be concentrated on the platform as far as possible for easy operation. For a single valve exceeding 1.8m and not frequently operated, Sprocket, extension rod, movable platform, movable ladder and other equipment can be used. When the valve is installed under the operation surface, stretching rod should be set, and the ground valve should be set up in the ground well. For the sake of safety, the ground well should be covered. For the valve stem of the valve on the horizontal pipe, it is best to vertically up, and it is not suitable to install the valve stem down. The valve stem is installed downward, which is inconvenient to operate, inconvenient to repair, and easy to corrode the valve. The floor valve should not be installed in a crooked way to avoid inconvenience. Valves on the pipelines which are side by side should have vacancy for operation, maintenance and disassembling, and the net distance between the hand wheels should not be less than 100mm. If the distance between the pipes is narrow, the valves should be staggered. For those valves which have big opening force, low strength, high brittleness and heavy weight, the valve frame should be set to support the valve before installation to reduce starting stress. When installing the valve, the pipe near the valve uses the pipe wrench, while the valve itself uses a common wrench. At the same time, during installation, the valve should be semi-closed to prevent valve rotation and deformation. The correct installation of the valve should make the internal structure form conform to the flow direction of the medium, and the installation form conform to the special requirements and operation requirements of the valve structure. In particular, pay attention to the valve with medium flow requirements should be installed according to the requirements of the process pipeline. The arrangement of the valve should be convenient and reasonable, and it is easy for the operator to get access to the valve. For the lift stem type valve, the operating space should be reserved. Installation of valve connection surface When installing the valve connected with thread at the end, the thread should be screwed into the valve at a proper depth, and the thread should be screwed into a too deep and compressed valve seat, which will affect the good coordination between the valve seat and the Ram, and screwed into the shallow, it will affect the sealing reliability of the joint and easily introduce leakage. At the same time, the thread sealing material should use tetrafluoroethylene green tape or sealant. For the valve connected by the end of the flange, first find the connection surface of the positive flange, the cover is perpendicular to the pipeline, and the bolt holes should be aligned. The valve flange should be parallel to the pipe flange, the flange clearance is moderate, and the phenomena such as misopening and tilting should not occur. The center gasket between the flanges should be placed in the middle, without deflection, and the bolts should be tightened symmetrically and evenly. Prevent the tightening of the forced connection during the installation of the valve and produce an additional residual force. Before installation, it is necessary to thoroughly remove the dirt from the inner wall of the pipe and the external thread; Remove the burr and foreign matter that block the flow of the medium and may affect the operation of the equipment, and blow out the dirt in the pipe before connecting the pipe, slag and other sundries. To prevent damage to the sealing surface of the valve or blockage of the valve. When installing the welding end connection valve, the two ends of the valve should be opened after spot welding, and then the weld is welded according to the welding process card, and the appearance of the weld and the quality of the inner weld are inspected after welding, make sure that there are no pores, slag, cracks, etc., and the welding lines should be checked by ray or override when necessary. Heavy valve installation When installing heavier valve (DN>100), lifting tools or equipment should be used. The lifting rope should be tied to the flange or bracket of the valve, and should not be tied to the handle-type valve stem of the valve, to avoid damaging the valve. What are the general requirements for valve installation? The general requirements of valve installation, the most suitable installation height, the direction of the valve and the valve stem on the horizontal pipe are as follows: The valve should be set in a place that is easy to access, easy to operate and maintain. Valves on rows of pipes (such as pipes for receiving and discharging devices) should be arranged in a centralized manner, and the setting of operation platform and ladder should be considered. The central line of the valve on the pipe in parallel layout should be taken as close as possible. The net distance between the hand wheels should not be less than 100mm. In order to reduce the pipeline spacing, the valves can be staggered; The installation position of frequently operated valve should be easy to operate, and the most suitable installation height should be 1.2m or so away from the operation surface. When the height of the center of the valve hand wheel exceeds 2m of the operation surface, platform should be set for the central arrangement of the valves, the frequently operated inpidual valves and the safety valve, appropriate measures should also be taken for inpidual valves that are not frequently operated (e.g. sprocket, extension rod, movable platform and movable ladder, etc.). The chain of the sprocket should not hinder traffic. Pipelines of the dangerous media and valves of the equipment should not be installed within the height range of the head to avoid bumping and damaging the head or directly damaging people’s face due to valve leakage; The valve used for partition equipment should be directly connected with or close to the nozzle of equipment. The valve connecting the pipe with extremely harmful and highly harmful toxic medium should be directly connected with the equipment port, and the valve should not be operated by chain wheel; Accident handling valves such as fire water valve and fire steam valve should be arranged in separate places, and the safe operation in the accident should be considered. This kind of valve should be arranged in the control room. There are safety zones behind the safety wall, outside the factory gate, or within certain distance from the accident site; So that the operators can operate safely when there is a fire accident; Except for special requirements of craft, valves on the bottom pipelines of tower, reactor, vertical vessel and so on should not be arranged in skirt; The cut-off valve of the horizontal branch that leads out from the main pipe should be set on the horizontal pipe section near the root; Lifting check valves should be installed on the horizontal pipe, and vertical lifting check valves should be installed on the vertical pipe where media flows from bottom to top. Swing check valve should be preferentially installed on the horizontal pipe, or installed on the vertical pipe in which medium flows from bottom to top; Bottom valve should be installed on the installation height of centrifugal pump suction butterfly check valve can be selected; when the diameter of pump outlet is different from that of the connected pipe, reducing check valve can be used; The center distance between the hand wheel of the valve arranged around the operation platform and the edge of the operation platform should be no larger than 450mm. When the valve stem and the hand wheel stretch into the above of the platform with the height less than 2 meters, it should not affect the operation and transportation of the operator; The valve of underground pipeline should be set in the trench or valve well, and the extension rod of the valve should be set when necessary. Fire valve well should have obvious sign; For the valve on the horizontal pipe, the direction of the valve stem can be determined according to the following order: vertically up; Horizontally; Up to 45 °; Down to 45 °; Not vertically down; The stem is horizontally installed open-lever valve. When the valve is open, the stem shall not affect the passage. Technical requirements for valve installation Direction. On the valve body of general valve, the direction indicated by the arrow is the direction in which the gas flows forward. Special attention must be paid to the fact that it must not be reversed. Because there are various valves requiring one-way gas circulation, such as safety valve, pressure reducing valve, check valve, throttle valve, etc. For the stop valve, in order to facilitate opening and maintenance, gas is also required to pass through the valve seat from bottom to top, but the gate valve, when installing the cock, it is not limited by the flow direction. Installation location. The long-term operation and maintenance of the valve should be considered, making it as convenient as possible to operate and maintain, and at the same time, attention should be paid to the beautiful appearance when assembling. The valve handle can be turned vertically to the above direction, and can also be tilted to a certain angle or placed horizontally, but the hand wheel can not be downward to avoid the operation of looking up; The hand wheel of the landing valve should be best close to the chest to facilitate the opening and closing; the open bar gate valve cannot be used underground to prevent the valve stem from being corroded. The installation position of some valves has special requirements, such as the pressure reducing valve is required to be installed vertically on the horizontal pipe and cannot be tilted. The lift check valve requires that the valve clack is vertical swing check valve and the pin shaft is required to be horizontal. In short, the installation position should be determined according to the principle of the valve, otherwise the valve will not work effectively or even will not work. Installation of the cock. Check the specifications and models, identify whether there is any damage, clean the sealing cap of the threaded opening and excessive grease and sundries in the thread, and check the sealing performance of the cock. Proper strength must be applied when installing the gas cock. According to the size of the cock, different specifications of pipe tongs or spanners should be chosen to install. When installing the valve with screw thread, the valve company should ensure that the thread is intact and intact; When the wrench can be used, do not use the pipe wrench to avoid damage to the appearance of the valve body. The installation of flange valve must ensure that the two flange sections are parallel to each other and on the same axis. When tightening the bolt, it should be carried out in a cross way to make the valve end face evenly stressed. The valve connected by flange and thread should be installed in the closed state. When the butt welding valve is connected with the pipe, the bottom weld should be argon welded to ensure the internal clean welding, and the valve should not be closed to prevent heating deformation. Under normal circumstances, the valve is directly connected with the corrugated expansion joint, so the pipes on both sides of the valve and the corrugated expansion joint should be cut off according to the size of the valve and the corrugated expansion joint as well as the flange and the gasket to set aside the installation position. When the valve is hoisted, the rope should not be tied to the first wheel or valve stem to prevent damage. When placed on the pier, according to the requirements of the elevation pad is stable and balanced. There must be a solid pier or bracket under the valve to hold the valve, and the valve is not allowed to generate stress. Pipe valve installation 35 professional tips 1. Pay attention to the direction of medium flow during installation. 2. Check valve should be installed before condensate water enters the recycling main pipe after steam trap to prevent condensate water from returning. 3. The open bar valve cannot be buried to prevent the stem from rusting. In the trench with cover plate, the valve should be installed in a convenient place for maintenance, inspection and operation. 4. For pipelines that require to be closed with small water hammer impact or no water hammer, it is best to choose slow-closing butterfly check valve and slow-closing swing check valve. 5. When installing the threaded valve, it is necessary to ensure that the thread is intact, and the filler is coated according to the different media. When tightening, it is necessary to use even force to avoid damage to the valve and valve parts. 6. When installing the socket-welded valve, the socket-welded valve should have a gap of 1-2m to prevent the thermal stress from exceeding the ambassador during welding. 7. When installing on the horizontal pipe, the valve stem should be vertically upward, or inclined to a certain angle, and the valve stem is not allowed to be installed downward. 8. The bottom layer of welding seam connecting the docking valve and pipe should adopt argon arc welding, and the valve should be opened during welding to prevent overheating and deformation. 9. Before installing the steam trap, the pipeline must be blown with pressure steam to remove sundries in the pipeline. 10. Do not install the steam trap in series. 11. Diaphragm type check valve is often used in pipelines which are easy to generate water hammer, because the diaphragm can well eliminate the water hammer generated when the medium is countercurrent, but it is limited by the temperature and pressure, generally used on low pressure normal temperature pipes. 12. Filter should be installed before the steam trap to ensure that the steam trap is not blocked by pipeline sundries, and the filter should be cleaned regularly. 13. The valve connected with flange and thread should be closed during installation. 14. The direction of condensate water should be consistent with the sign of the arrow installed on the trap. 15. The steam trap should be installed at the lowest place of the equipment outlet, and the condensed water should be discharged in time to avoid steam resistance in the pipeline. 16. When installing flange valve, it should be ensured that the two flange end faces are parallel and concentric with each other. 17. The valve should be installed before and after the trap, so that the trap can be repaired at any time. 18. The mechanical trap should be installed horizontally. 19. If the drain valve is found to run steam, it should be discharged in time and the filter should be cleaned according to the actual use situation, and repaired at any time in case of failure. 20. Do not make the check valve bear the weight in the pipeline. Large check valve should be supported independently, so that it is not affected by the pressure generated by the pipeline system. 21. After the drain valve, the condensate recovery main pipe cannot climb, which will increase the back pressure of the drain valve. 22. If there is no trap installed at the lowest point of the equipment, a reverse water bend should be added at the lowest point of the water outlet to raise the condensation water level before installing a trap to avoid steam resistance. 23. The outlet pipe of the trap should not be soaked in water. 24. If condensate is recycled after the steam trap, the outlet pipe of the drain valve should be connected to the main pipe from above the recovery main pipe to reduce back pressure and prevent backflow. 25. Each equipment should be installed with traps. 30. Lift type level flap check valve should be installed on the level pipe. 31. Install a drain valve on the steam pipe. In the main pipe, a condensate water-collecting well which is close to the radius of the main pipe should be set, and then use a small tube to lead to the drain valve. 32. If there is condensate recovery after the trap, it needs to be recovered separately by pipelines with different levels of pressure. 33. Lift-type vertical flap check valve needs to be installed vertically. 34. When the mechanical trap is not in use for a long time, it is necessary to remove the sewage screw and let the water inside go to prevent freezing. 35. Before the thermostatic type steam trap, a subcooled pipe that does not keep warm is needed for more than one meter. Other types of steam trap should be as close as possible to the equipment. Conclusion At present, whether in municipal water supply, petrochemical, or in other industries, the application, operating frequency and service of pipeline system valves are ever-changing, it is most important to control or eliminate even low leakage, the most critical equipment is the valve. The final control of the pipeline is that the service and reliable performance of the valve in various fields are unique. Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Effect of forging on microstructure and properties of metal In forging production, in addition to ensuring the required shape and size of forged flanges, it must also meet the performance requirements of parts in the process of use, which mainly include: strength index, plasticity index, impact toughness, fatigue strength and initial fracture degree For parts working at high temperature, there are also high temperature instantaneous tensile property, endurance property, anti creep property and thermal fatigue property. The raw materials for forged flanges are ingot, rolling stock, extrusion stock and forging stock. Rolling stock, extrusion stock and forging stock are semi-finished products formed by rolling, extrusion and forging respectively. In forging production, the structure and properties of raw materials can be improved by adopting reasonable process and process parameters: 1. The results show that the columnar crystal is broken, the macrosegregation is improved, the as cast structure is changed into the forged structure, and the internal pores are welded under the appropriate temperature and stress conditions to improve the density of the material; 2. The fiber structure of ingot is formed by forging, and reasonable fiber direction distribution is obtained by rolling, extrusion and die forging; 3. Controlling the size and uniformity of grains; 4. Improve the distribution of the second phase (such as alloy carbide in ledeburite steel); 5. It can strengthen the structure by deformation. Because of the improvement of the above-mentioned structure, the plasticity, impact toughness, fatigue strength and endurance properties of the forging are also improved, and then through the final heat treatment of the parts, the good comprehensive properties such as hardness, strength and plasticity required by the parts can be obtained. However, if the quality of raw materials is poor or the forging process is unreasonable, the forging defects may occur, including surface defects, internal defects or unqualified performance. Influence of raw materials on forging quality Good quality of raw materials is a prerequisite to ensure the quality of forged flanges. If there are defects in raw materials, the forming process and final quality of forged flanges will be affected. If the chemical elements of raw materials exceed the specified range or the content of impurity elements is too high, it will have a great impact on the forming and quality of forged flanges, for example, s, B, Cu, Sn and other elements are easy to form low melting point phase, which makes forgings prone to hot embrittlement. In order to obtain essentially fine grain steel, the residual aluminum content in the steel should be controlled within a certain range, such as 0.02% – 0.04% (mass fraction) of A1 acid. If the aluminum content is too small, it can’t control the grain size, so it is easy to make the essential grain size of forged flanges unqualified; if the aluminum content is too high, it is easy to form wood grain fracture and tear mark fracture under the condition of forming fiber structure during pressure processing. For another example, in austenitic stainless steel, the more N, Si, Al and Mo are contained, the more ferrite phases are, the easier it is to form banded cracks during forging and make the parts magnetic. If there are some defects in the raw materials, such as residual shrinkage, blistering under the skin, serious carbide segregation, coarse non-metallic inclusions (slag) and so on, the forging is easy to produce cracks. The defects in raw materials, such as dendrite, serious porosity, non-metallic inclusion, white spot, oxide film, segregation band and mixture of different metals, are easy to cause the performance degradation of forgings. The surface cracks of forgings are easily caused by surface cracks, folds, scabs and coarse-grained rings of raw materials. Influence of forging process on forging quality The forging process generally consists of the following processes: blanking, heating, forming, cooling after forging, pickling and heat treatment after forging. If the forging process is improper, a series of forging defects may occur. The heating process includes charging temperature, heating temperature, heating speed, holding time, furnace gas composition, etc. Improper heating, such as too high heating temperature and too long heating time, will cause decarbonization, overheating, overburning and other defects. If the heating speed is too fast and the holding time is too short, the temperature distribution is often uneven, resulting in thermal stress and cracking of forging blank. Forging forming process includes deformation mode, deformation degree, deformation temperature, deformation speed, stress state, die condition and lubrication condition. If the forming process is not proper, coarse grains, uneven grains, various cracks, folding, flow through, eddy current and residual as cast structure may be caused. During the cooling process after forging, if the process is not proper, it may cause cooling cracks, white spots, network carbides and so on. Effect of forging microstructure on Microstructure and properties after final heat treatment Austenitic and ferritic heat-resistant stainless steel, superalloy, aluminum alloy, magnesium alloy and other materials without isomerism transformation during heating and cooling, as well as some copper alloy and titanium alloy, can not be improved by heat treatment. In the process of heating and cooling, some structural defects caused by improper forging process or some defects left by raw materials have great influence on the quality of forged flanges after heat treatment. Examples are as follows: 1. The microstructure defects of some forged flanges can be improved during post forging heat treatment, and satisfactory microstructure and properties can be obtained after final heat treatment. For example, coarse grain and widmanstatten structure in general overheated structural steel forgings, slight network carbide in hypereutectoid steel and bearing steel due to improper cooling, etc. 2. The structure defects of some forged flanges are difficult to be eliminated by normal heat treatment, which can be improved by high temperature normalizing, repeated normalizing, low temperature decomposition, high temperature diffusion annealing and other measures. 3. The structure defects of some forgings can’t be eliminated by general heat treatment process, resulting in the performance degradation or even disqualification of forgings after final heat treatment. For example, severe stone fracture and edge fracture, overburning, ferrite band in stainless steel, carbide net and band in ledeburite high alloy tool steel, etc. 4. The structure defects of some forgings will be further developed in the final heat treatment, and even cause cracking. For example, if the coarse-grained structure of alloy structural steel forgings is not improved during post forging heat treatment, the coarse martensite and unqualified properties are often caused after carbonitriding and quenching; the coarse banded carbide in high-speed steel often causes cracking after quenching. Different forming methods have different stress and strain characteristics, so the main defects may be different. For example, the main defects during upsetting are longitudinal or 45 ° cracks on the side surface, and only the upper and lower ends of the ingot usually have as cast structure; the main defects during drawing rectangular section billet are transverse cracks and corner cracks on the surface, diagonal cracks and transverse cracks inside; the main defects during open die forging are underfill, folding and dislocation. Different kinds of materials, due to their different composition and microstructure, have different microstructure changes and mechanical behaviors in the process of heating, forging and cooling. Therefore, when forging process is not appropriate, the possible defects also have their particularity. For example, the main defects of ledeburite high alloy tool steel forgings are coarse carbide particles, uneven distribution and cracks; the main defects of high temperature alloy forgings are coarse grains and cracks; the main defects of austenitic stainless steel forged flanges are poor intergranular chromium, reduced intergranular corrosion resistance, ferrite banded structure and cracks; the main defects of aluminum alloy forgings are coarse grains, folding, eddy current, etc And so on. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The differences of normalizing, tempering, annealing and quenching lie in different processes, different changes of material structure and different results of material properties. What is quenching? Quenching of Steel is to heat the steel to the critical temperature above Ac3 (hypoperformances steel) or Ac1 (hyperperformances steel), and keep it warm for a period of time to refine all or part of it, then conduct the heat treatment process of martensite (or baine) transformation with the cooling speed which is higher than the critical cooling speed to be cooled below Ms (or the isothermal around Ms). Generally, solid solution treatment of aluminum alloy, copper alloy, titanium alloy, steel glass and other materials or thermal treatment process with rapid cooling process are also called quenching. Purpose of quenching: 1) improve the mechanical properties of metal materials or parts. For example: improve the hardness and wear resistance of tools, bearings, etc., improve the elastic limit of the spring, improve the comprehensive mechanical properties of shaft parts, etc. 2) improve the material properties or chemical properties of some special steel. Such as improving the corrosion resistance of stainless steel, increasing the permanent magnetism of magnetic steel, etc. When quenching and cooling, in addition to reasonable selection of quenching medium, there must be correct quenching methods. The common quenching methods mainly include single-Liquid Quenching, double-Liquid Quenching, graded quenching and isothermal quenching, local quenching, etc. The steel workpiece has the following characteristics after quenching: ① unbalanced (I .e. unstable) structures such as martensite, bainitic and retained austenite are obtained. ② there is a large internal stress. ③ mechanical properties cannot meet the requirements. Therefore, steel workpieces generally have to be tempered after quenching. What is tempering? Tempering is a heat treatment process that heats the quenched metal materials or parts to a certain temperature and cools them down in a certain way after holding for a certain period of time, tempering is an operation that is followed after quenching. It is usually the last process for thermal treatment of the workpiece. Therefore, the combined process of quenching and tempering is called the final process. The main purpose of quenching and tempering is: 1) reduce internal stress and reduce brittleness. Quenching parts have great stress and brittleness. If they are not tempered in time, they will often deform or even crack. 2) adjust the mechanical properties of the workpiece, after the workpiece is quenched, the hardness is high and the brittleness is large, in order to meet the different performance requirements of various workpieces, it can be adjusted by tempering, hardness, strength, plasticity and toughness. 3) stabilize the size of the workpiece. Tempering can stabilize the metallographic structure to ensure that no deformation will occur in the future use process. 4) improve the cutting performance of some alloy steel. The role of tempering is: ① improve the stability of the tissue, so that the workpiece will not be changed in the process of use, so that the geometric size and performance of the workpiece remain stable. ② eliminate internal stress in order to improve the performance of the workpiece and stabilize the geometric size of the workpiece. ③ adjust the mechanical properties of steel to meet the use requirements. The reason why tempering has these effects is that with the temperature rising, the atomic mobility will be enhanced, and the atoms of iron, carbon and other alloying elements in steel can be diffused faster, thus realizing the rearrangement and combination of atoms, so as to gradually transform the unstable and unbalanced organization into a stable and balanced organization. The elimination of internal stress is also related to the decrease of metal strength when the temperature rises. Generally, when steel is tempered, the hardness and strength decrease and the plasticity increases. The higher the tempering temperature, the greater the change of these mechanical properties. For the alloy steel with high alloying elements, when tempering at a certain temperature range, some metallic compounds with fine particles will be precipitated out to increase the strength and hardness. This phenomenon is called secondary hardening. Tempering requirements: workpieces with different uses should be tempered at different temperatures to meet the requirements in use. ① tools, bearings, carburizing and quenching parts, surface quenching parts are usually tempered at a low temperature below 250℃. After tempering at low temperature, the hardness changes little, the internal stress decreases, and the toughness increases slightly. ② the spring can obtain higher elasticity and necessary toughness by tempering at medium temperature of 350 ~ 500℃. ③ parts made of medium carbon structural steel are usually tempered at 500 ~ 600℃ to obtain a good coordination of appropriate strength and toughness. When steel is tempered at about 300℃, its brittleness is often increased. This phenomenon is called the first class of tempering brittleness. Generally should not temper in this temperature range. Some medium carbon alloy structural steel after high temperature tempering, if slowly cooled to room temperature, also easy to become brittle. This phenomenon is called the second class of tempering brittleness. Adding molybdenum to steel, or cooling in oil or water when tempering, can prevent the second class of tempering brittleness. Reheating the steel of the second type of tempering brittleness to the original tempering temperature can eliminate this brittleness. In production, it is often based on the requirements of workpiece performance. According to different heating temperatures, tempering is pided into low temperature tempering, medium temperature tempering and high temperature tempering. The heat treatment process combined with quenching and subsequent high temperature tempering is called quenching and tempering, that is, it has high strength and good plastic toughness. 1. Low temperature tempering: 150-250 ℃ ,M loop, reduce internal stress and brittleness, improve plastic toughness, and have higher hardness and wear resistance. It is used to make measuring tools, cutting tools and rolling bearings. 2. Medium temperature tempering: 350-500 ℃ ,T back, with high elasticity and certain plasticity and hardness. Used to make springs, forging dies, etc. 3. High temperature tempering: 500-650℃ ,S back, with good comprehensive mechanical properties. Used to make gears, crankshaft, etc. What is normal fire? Normalizing is a heat treatment that improves the toughness of steel. After heating the steel members to the temperature of Ac3 above 30~50 ℃, heat the temperature for a period of time to cool the air. The main feature is that the cooling rate is faster than annealing but lower than quenching. When normalizing can refine the crystalline grains of the steel in the faster cooling, not only can obtain satisfactory strength, moreover, the toughness (AKV value) can be obviously improved and the cracking tendency of components can be reduced. The comprehensive mechanical properties of materials can be greatly improved, and the cutting properties can also be improved after normalized treatment for low alloy hot rolled steel plates, low alloy steel forgings and castings. Normalizing has the following purposes and uses: ① for hypoeutectic steel, normalizing is used to eliminate the over-heated coarse crystal structure and widthhouse structure of casting, forging and welding parts, and the band structure in rolled material; Refine the crystal grain; and can be used as pre-heat treatment before quenching. ② as for hyperdialysis steel, normalizing can eliminate remullated carbonized body and refine pearlite, which not only improves mechanical property, but also is beneficial to later spheroidization annealing. ③ for low carbon deep drawing thin steel plates, normalizing can eliminate free cementite at grain boundary to improve their deep drawing performance. ④ for low carbon steel and low carbon and low alloy steel, using normalizing can get more fine flake pearlite structure, increasing the hardness to HB140-190, and avoiding the “sticking” phenomenon during cutting, improve machinability. For medium carbon steel, it is more economical and convenient to use normalizing in the situation where normalizing and annealing are available. ⑤ for ordinary medium carbon structural steel, under the occasion of low requirement of mechanical property, use normalizing instead of quenching and tempering high temperature, which is not only easy to operate, but also stablize the structure and size of the steel. ⑥ high temperature normalizing (150 ~ 200℃ above Ac3) due to the high diffusion velocity at high temperature, composition segregation of castings and forgings can be reduced. Coarse and large grains after high temperature normalizing can be refined by the following second lower temperature normalizing. ⑦ as for some low-carbon and middle-carbon alloy steels used for steam turbine and boiler, normalizing is usually used to obtain bainitic structure, and then after tempering at high temperature, they have good creep resistance when temperature is between 400℃ and 550℃. ⑧ in addition to steel and steel, normalizing is also widely used in the heat treatment of ductile iron to obtain pearlite matrix and improve the strength of ductile iron. Because the characteristic of normalizing is air cooling, the environment temperature, stacking mode, air flow and workpiece size have influence on the organization and performance after normalizing. Normalizing structure can also be used as a classification method for alloy steel. Usually, the microstructure obtained by air cooling after heating the sample with a diameter of 25mm is pided into pearlite steel, balanced steel, martensite steel and austenitic steel. What is annealing? Annealing is a metal heat treatment process that slowly heats the metal to a certain temperature, maintains enough time, and then cools at an appropriate rate. Annealing heat treatment is pided into complete annealing, incomplete annealing and stress relief annealing. The mechanical properties of annealed materials can be tested by tensile test or hardness test. Many steels are supplied in the state of annealing heat treatment. For steel hardness test, Rockwell hardness meter can be used to test HRB hardness. For thinner steel plate, steel strip and thin steel tube, surface Rockwell hardness meter can be used, HRT hardness was detected. The purpose of annealing is: ① improve or eliminate all kinds of microstructure defects and residual stress caused by steel in the process of casting, forging, rolling and welding, and prevent deformation and cracking of workpieces. ② soften the workpiece for cutting. ③ refine the grain and improve the structure to improve the mechanical properties of the workpiece. ④ prepare for the final heat treatment (quenching and tempering). Commonly used annealing processes are: ① complete annealing. Used to refine medium and low carbon steel with poor mechanical properties after casting, forging and welding. The workpiece is heated to a temperature above 30 ~ 50℃ that ferrite will all transform into austenite, kept warm for a period of time, and then cooled slowly with the furnace. During the cooling process, austenite changes again, the structure of the steel can be thinned. ② spheroidization annealing. Used to reduce the hardness of tool steel and bearing steel after forging. The workpiece is heated to a temperature of 20 ~ 40℃ When austenite begins to form in steel, and then cooled slowly after heat preservation. During the cooling process, the lamellar cementite in pearlite becomes spherical, thus reducing the hardness. ③ isothermal annealing. It is used to reduce the high hardness of some alloy structural steel with high content of nickel and chromium to be cut. Generally, it is cooled to the most unstable temperature of austenite at a relatively fast speed first, and when it is kept at a suitable time, austenite is converted into torchian or Sorbite, and the hardness can be reduced. ④ recrystallization annealing. It is used to eliminate the hardening phenomenon (increase in hardness and decrease in plasticity) of metal wire and sheet in the process of cold drawing and cold rolling. The heating temperature is generally the steel began to form austenite temperature below 50~150 ℃, only in this way can eliminate work hardening effect to soften the metal. ⑤ graphitization annealing. It is used to turn cast iron containing a large amount of cementite into malleable cast iron with good plasticity. The process operation is to heat the casting to about 950℃ and cool down after holding for a certain period of time, so that the cementite can decompose into bulk graphite. ⑥ diffusion annealing. It is used to homogenize the chemical composition of alloy castings and improve their performance. The method is, on the premise of no melting, to heat the casting to the highest temperature as much as possible, and keep the heat for a long time, and then after the various elements in the alloy diffusion tend to uniform distribution, slow cooling. ⑦ stress relief annealing. It is used to eliminate internal stress of steel castings and welding parts. For steel products after heating began to form austenite temperature below 100~200 ℃, after the heat insulation in the air cooling, can eliminate internal stress. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Flange is a common part in piping system. They are mainly used to connect shafts and shafts or to connect two devices. In general, flanges are used with gaskets and bolts. The purpose is to fix two pipes, pipe fittings or equipment on the flange, then add flange gasket between the two flanges, and then use bolts to tighten the two flanges to make it tight connection. Therefore, it is also a common connection method in pipeline system. However, we will find that the flange connection will still fail in the actual production process. This may be caused by three factors of flange, gasket and bolt, such as insufficient flange stiffness, bolt stiffness and bolt pre tightening stiffness, form and surface characteristics of flange sealing surface and selection of gasket (and sealing performance), or incorrect flange installation and use. It may also be affected by operating temperature, pressure and the chemical and physical properties of the medium. Therefore, we need to select the flange, gasket and bolt first, and then install them. This is to make better use of the sealing performance of flange connection. So, can we touch the flange directly during the flange installation? What are the precautions for flange installation? Ensure that the sealing surface is clean and free from defects Before installing the flange, we need to make sure that the sealing surface of the flange is clean and free from defects. The sealing surface of flange should be cleaned. This is because the sealing surface of flange should be closely connected with washer and bolt. If the flange sealing surface is not cleaned, flange leakage is likely to occur in the future use process, and the proper sealing performance of the flange will be invalid. As for the defect free flange sealing surface, it means that the flange sealing surface has no defects such as radial scratch, serious corrosion and deformation. When cleaning the flange sealing surface, use latex gloves, alcohol, dust-free cloth and other tools. We need to wear latex gloves, moisten the dust-free cloth with alcohol, and then wipe the whole flange. It is worth noting that when cleaning the flange sealing surface, do not use a screwdriver to clean it, so as not to damage the flange sealing surface. Flange installation Connection between flange and pipe The connection of flange and piping system requires high connection skills, because not only the strength of the connection part, but also the tightness should be considered during installation. If one of the two points fails to meet the standard, the pipeline may be damaged. Therefore, flange and pipe installation should meet the following requirements: (1) The center of the flange must be in line with the center of the pipe. (2) The flange sealing surface must be perpendicular to the piping center. (3) The position of flange threaded hole on the pipeline shall be consistent with that on the opposite equipment or pipeline, and the position of flange threaded hole on both ends of the same pipeline shall be consistent. Installation of flat welding flange The installation process of flat welding flange is relatively simple. When installing, the flange should be put into the pipe end first, and then a certain distance should be left between the pipe orifice and the flange sealing surface, which is determined by the pipe wall thickness. Then you can start spot welding on both sides of the pipe. Installation of weld neck flange Weld neck flange this kind of pipe fittings refers to the flange with neck and round pipe transition and butt welding connection with the pipe. Different from flat welding flange, weld neck flange is not easy to deform and has good sealing performance. In addition, they are relatively cheap, so they are widely used. Weld neck flange is suitable for pipes with large fluctuation of pressure or temperature or high temperature, high pressure and low temperature pipes. It is used to transport precious, flammable and explosive media. So, do you know how to install and use weld neck flange? When installing and using weld neck flange, we should know the precautions? 1. Before installing the weld neck flange, pay attention to check whether the nominal pressure of the flange meets the design requirements; check whether the sealing surface of the flange is smooth and clean, whether there are burrs and radial grooves, and whether the threaded part of the flange is complete and intact. Whether the concave and convex flange can fit in naturally, especially the nondestructive testing of the welding flange must be done well, so as to avoid damaging the inside of the welding flange and affecting the performance and service life of the flange. 2. Please pay attention to cleaning before installing weld neck flange. After all, the sealing surface of the flange should be tightly connected with washer and bolt. Flange sealing surface shall be cleaned with special cleaning tools and methods to prevent damage of weld neck flange. The installation and use of weld neck flange must pay attention to the method and sequence. After all, if the installation method and installation sequence is wrong, it will affect the flange installation, so that the flange can not be installed. In the process of use, due to the influence of transportation medium and operating conditions, loosening and sliding may also occur, which will lead to pipeline leakage. Therefore, in order to use the weld neck flange better and longer in the future, we need to master the correct installation method and installation sequence of the welding flange. There are two installation methods for welding flange: 1. Before connecting the weld neck flange, first arrange the inside and outside of the stainless steel pipe fittings, and then install the flange with slotted ring on the pipe to be connected. Above, the end of the pipe needs 90 degree flanging. After treatment, the end surface of the pipe needs to be polished. After grinding, it should be free of burr, concave convex and deformation, vertical and flat, and need to use special tools to round it. 2. The finished flanging short pipe is welded on the pipe, and the O-shaped rubber seal ring and stainless steel seal ring installed on both sides are inserted into the flange with groove ring for sealing. The inner diameter of the inner hole of the sealing ring is the same as that of the pipe, and then the flange hole is connected with bolts. The bolt assembly needs to be tightened symmetrically. When tightening the weld neck flange, please pay attention to the sealing of each joint and meet the required specifications. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

With the development and progress of medium thick steel plate technology, people pay more attention to the product quality, and the production enterprises pay more attention to the requirements of product quality and energy saving. From the current development situation in the world, the heat treatment thick plate products in the treatment, Japan’s technology is the most advanced. Compared with the advanced technology in China and the world, there are many quality defects in production, which have a serious negative impact on the quality of medium thick steel plates, which leads to the repair and treatment in a large range in the operation, which greatly affects the whole production order, and also causes the steel plate to be scrapped due to the repair and grinding, resulting in a certain amount of economic loss of the enterprise and adverse impact on the development of the enterprise. 1. heat treatment process of medium thick steel plate With the improvement of social productivity, people have gradually improved the quality of steel. The mechanical properties of steel can be improved by adding a certain amount of alloy elements to the steel production process and then heat treatment. The heat treatment of medium thick steel plates is mainly in four aspects: normalizing, high temperature, tempering, spheroidization. 1.1 normalizing treatment Normalizing treatment is also called normalization treatment. The strength of medium thick steel plates is usually large, but the toughness is very low. Therefore, normalizing treatment should be carried out, and then placed in air for cooling. Thus, fine gold particles will exist after cooling, and high-tech plate materials can be obtained after normalization treatment. 1.2 high temperature treatment High temperature treatment is also called tempering treatment, the main function of this treatment is to remove the stress existing inside the steel plate. There is a significant difference between the treatment and the normalizing treatment, which requires that the temperature control is within AC3. 1.3 conditioning and quality control The quenching and tempering process is a combination of quenching and tempering. The requirements of this process for heat treatment are relatively high. Heat treatment furnace, low temperature tempering furnace and pressure quenching machine are the necessary equipment. Martensite structure can be formed in the production of medium thick steel plates. It can be heated and tempered at low temperature, which is the whole process of tempering treatment. 1.4 spheroidization treatment Spheroidization is to form spheroidized structure after heating treatment of medium thick steel plates. After the treatment, the plate can be used as tool steel plate, and its comprehensive performance is relatively high. In addition to the above mentioned heat treatment processes, in the specific production practice, technicians can optimize and integrate many aspects, and then form new heat treatment processes, such as the new normalizing cooling control process and the normalizing tempering new process. The former is to avoid the insufficient strength of steel plate after normalizing treatment. After the heat treatment of steel plate, the treatment with water-cooled equipment can realize cold control treatment, and can prevent the steel plate strength from falling. The heat treatment of boiler pressure vessel steel plate is the best by normalizing tempering heat treatment. While the normalizing tempering treatment technology can be used for CrMo steel plate. 2. defect analysis 2.1 shot press in When the roller brush of shot blasting machine enters the end of a cycle, it will lead to the existence of wear. In the treatment of smaller steel plate, the shot material will follow the steel plate directly out of the shot blasting machine body. If there is no effective cleaning treatment, the shot material of the sheet material will be pressed after the stacking of the steel plate. In addition, due to the lack of shot blasting machine design, shot material is easy to appear in the position between steel plate and roller table in the process of processing. Because of the effect of self weight, the steel plate presses the shot material into the lower part, and enters into the steel plate after several times of rolling. 2.2 indentation of bottom roller The formation of the defects of the bottom roller indentation is that the bottom rolling surface is nodular, and the larger thickness of the steel plate appears indentation due to the high temperature on the lower surface. Causes of the surface nodulation of the bottom roller: there is a certain amount of oxide iron on some positions of the roller surface, and the increasing of the charging quantity causes the increase of the oxide scale, and then the accumulation in this position. At the same time, there is high temperature oxidation reaction under the soft condition of hot melt, and the roll surface nodule will increase. Under quenching or normalizing conditions, the layer oxide skin bonded on the roller surface is rolled by steel plate, and the layer by layer increases, and the density increases. In this case, the surface of the steel plate with larger thickness appears indentation under the influence of high temperature. In addition, the defects of drum and deformation at the bottom of the furnace will also have the problem of nodule. Source of iron oxide: one is outside the production link, the other is the abnormal situation in the furnace. The oxide skin outside the production link is the unclean shot blasting and the residual of shot material, because the design of shot blasting machine is unreasonable, the mechanical cleaning is not complete, the surface of steel plate has shot material, and there is oxide skin on the steel plate itself. The reason for the formation of iron oxide sheet in furnace is that the internal environment of heat treatment is abnormal and the residual oxygen is too large. The reason for the abnormal environment in the furnace is the quality problem of radiation tube. It can be checked by shutdown to determine whether it is caused by this reason. The furnace heating is carried out after mixing gas and combustion supporting air. The combustion in the radiation tube is realized by radiation. The sealing effect of the whole furnace is good. Therefore, the existence of internal oxygen is that air enters the inside when the furnace door is open. Because the furnace is designed as positive pressure and the furnace door is opened, nitrogen is used for automatic cleaning, so the probability of air entering into the furnace door is low; after the radiation pipe is treated for a long time with high temperature, the quality problems of the ceramic inner pipe, or the problems such as breakage and fracture due to the long service time, are caused, The reason for the metal appearance to be broken due to the lack of uniformity of heating may be due to the quality problems of the metal appearance itself. The burning through situation occurs in the work, which leads to the combustion air entering the inside from the damaged part. 2.3 extrusion deformation of side The deformation of the side extrusion is mainly due to the defects of the drum deformation in the roller table at the bottom of the heat treatment furnace. In the high temperature production process, the lower part of the steel plate contacts the drum at the bottom of the furnace and its gravity action will produce extrusion deformation under the movement in the furnace. The reason for the formation of drum drum is that the temperature difference between bottom roller and steel plate exceeds the standard, and the thickness of bottom roller wall is very small and the strength is relatively low. It is deformed when it contacts the steel plate due to the high temperature. 3. control measures 3.1 control of shot material pressing In order to effectively prevent the residual shot material on the surface of steel plate after shot blasting and prevent the shot material entering the furnace, generally, the scraper structure should be set at the outlet position of the shot blasting machine. At this time, the blowing device can be added at the outlet position to better clean the surface shot material; The following two points should be taken for pressing the shot material on the lower surface. One is that adding scraper in the cleaning room can prevent the existence of shot material on the lower surface of the steel plate; the second is to set up a supporting ring device on the surface of the conveying roller in the cleaning room of the shot blasting machine, which can effectively reduce the contact area between the steel plate and the roller, and prevent the pellet from entering the furnace. The above-mentioned shot blasting machine transformation can effectively prevent the pressing of shot material, eliminate these problems, and realize that the steel plate with thickness less than 50mm will not have any problem of shot pressing; the pressing of steel plate with thickness of more than 50mm generally appears on both sides of the steel plate. After treatment, the probability of shot pressing is reduced to less than 1%, which can improve the quality of steel plate, The productivity of shot blasting is promoted and the economic benefit is obviously improved. 3.2 control of the indentation of furnace bottom roller Strengthen the quality management of shot blasting to ensure that there is no residual and pressing of shot material on the surface of steel plate. The shot blasting effect reaches Sa2.5. According to the requirements of production process, the furnace cleaning can be carried out. According to the influence of the surface weight and friction force of the steel plate, the oxide skin can be crushed, and then the oxide skin will be removed before entering the furnace, so as to ensure the steel plate quality is qualified, and the service life of the bottom roller can be prolonged, and the indentation of the bottom roller can be eliminated from the root. After the above treatment, the treatment practice analysis of the indentation of the bottom roller is carried out for a long time. Under the condition that the temperature in the production environment is controlled below 900 ℃, there is no bottom roller indentation. When the production temperature is above 900 ℃, and the thickness is more than 30mm, the indentation of the bottom roller will be found, and the depth has been reduced from 0.3 to 1.0mm to 0.1-0.3mm, and the decrease is obvious. After the above treatment, the workload of manual grinding can be effectively reduced, the work efficiency is improved, and the surface nodular defects of bottom roller can be eliminated completely, which has high quality requirements. 3.3 control of extrusion deformation at the side To make the temperature of furnace bottom roll reach the uniformity standard, one is to raise the roller speed properly. The longer the steel plate contacts the roller surface, the lower the temperature will be, the temperature difference will increase, which will lead to the appearance of drum. If the low speed operation time is longer, the problem of roller table bending deformation will appear, and the speed can be improved to lower the temperature better, thus avoiding the problem of drum drum. Second, increase the swing amplitude appropriately. When the bottom roller rotates for one week, it can be determined as the best swing amplitude. At this time, the contact between the roller and the steel plate can be more uniform, and the heating of the roller table will become more uniform. Through installing the furnace offset control device, in the production of high temperature steel plate, it should be classified according to the thickness and time: the plate with thickness no more than 100mm is normally installed in the furnace; the quenched (positive) fire plate with thickness greater than 100m shall be padded on one side of wood block when aligning, so that the steel plate will be offset 200-300mm to the side. Through the implementation of the control measures of offset charging, the working surface of the bottom roller can be used alternately, and the temperature difference on the bottom roller position can be reduced better, and the heating is more uniform, and then the problem of drum drum of bottom roller can be prevented and the whole production level can be promoted. After the above treatment measures, the quenching furnace produces 145 pieces of 2725t steel plates with thickness of 150 mm, and has been put into the furnace 335 times. After the production of steel plates in the enterprise, the quality level of the side is relatively high, and there is no defect of side extrusion deformation. 4. conclusion In conclusion, the causes of surface quality defects of medium thick steel plate heat treatment are analyzed, and necessary treatment measures are taken. After some time of test, it is found that the quality improvement of steel plate is obvious, such as the pressing rate of shot material is controlled below 1% for a long time, the depth of the bottom roller indentation is kept at 0.1-0.3mm, the manual grinding quantity is small, and the edge of steel plate has no extrusion deformation defects, The overall quality level is very high, which brings high economic benefits to the enterprise. Author: Yugang China Stainless Steel Plates Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com) Reference [1] Xujianxiang, wuyuwan. Analysis and solution of surface quality problems of shot blasting steel plate in heat treatment line of medium thick steel plate [j]. Internal combustion engine and accessories, 2019, (12): 45-47 [2] Dong Zhanbin, Wang Xuesong, Liu Xiaohui, et al. Simulation and application of heat treatment furnace washing test of medium thick steel plate based on BP neural network [j]. Rolling steel, 2015, (2): 65-68

Let’s discuss the installation position of the check valve today. So how to determine the installation position of check valve? What is the difference between the installation before the pump and the check valve after the pump, and where is the pre pump installation applicable? Check valve is usually used with other valves. Where should check valve be installed when used with other valves? Let’s discuss it together. Check valve is an automatic valve. It relies on the pressure of the flowing medium in the pipeline to push the valve disc to close and open the valve. When the medium stops flowing, the check valve disc will close. It can effectively prevent the medium in the pipeline from backflow, which plays a great role in ensuring the safety of the pipeline. According to the structure, check valve can be pided into lift check valve, swing check valve and butterfly check valve. Lift check valve can be pided into vertical and straight through type. Swing check valve is pided into three types: single valve, double valve and multi valve. Butterfly check valve is pided into butterfly double valve and butterfly single valve. The above check valves can be pided into threaded connection, flange connection, welding and clamp connection. The installation of check valve is to ensure the flow direction of water inside the pump, so as to ensure the normal operation of the pump. Therefore, the installation position of the check valve can be pided into two situations: before the water pump or after the water pump One is installed at the end of the vertical suction pipe in front of the water pump, also known as the bottom valve. The purpose is not to pump a water to the pump to fill a water, because the pump and the pump in front of the suction pipe when there is no water, the pump can only idle pumping water, so the pump must be filled with water to pump water. The installation of this pump is a method higher than the liquid level, also known as negative pressure method. The other is installed behind the pump. This installation method is that when the liquid level is higher than the water pump, it is convenient to shut down the water outlet valve of the pump when starting and stopping the water pump, especially for the main control water pump system to prevent the backflow. The check valve must be installed at the outlet of the pump and in front of the outlet control valve to facilitate the maintenance of the check valve. Generally, the first outlet of the pump is the soft connection (shock absorber), followed by the check valve, and then the block valve (such as butterfly valve, gate valve, stop valve, etc.). 1. First install check valve, then install gate valve or butterfly valve Advantages: it can protect the check valve, especially in the parallel pump. When one pump is not started, its outlet valve is closed, and the other pump is started, the impact force is borne by the gate valve or butterfly valve. When the check valve fails, the inlet and outlet valve isolation system can be closed for repair. Disadvantages: who will protect gate valve or butterfly valve? There was a case where the valve plate of butterfly valve was broken. 2. Install gate valve or butterfly valve before check valve Advantages: it can protect butterfly valve or gate valve, and the impact force is borne by check valve. Disadvantages: who will protect the check valve? The check valve is opened and closed by the pressure difference. If the main pipe pressure is high, it will be closed and the pump pressure is high, it will be opened. If the flow is unstable, the check valve will be opened and closed repeatedly, which will affect the service life of the check valve. Moreover, the check valve is broken, especially the main control system, which needs to be shut down before repair. Generally speaking, due to the frequent opening and closing actions of check valves, the internal connection parts and sealing parts are easy to be damaged. In order to facilitate repair and prevent the shutdown of the whole system due to the failure of check valves, from this point of view, check valves will be installed in front of outlet gate valves or butterfly valves. Is that basically what you see? Source: China Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)