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1. The introduction of seamless steel pipe The seamless steel pipe is a circular, square, rectangular steel with a hollow section and no seams around it. The seamless steel pipe is formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn. The seamless steel pipe has a hollow section and is used as a pipe for conveying fluid. Compared with a solid steel such as round steel, the steel pipe has a lighter weight when it has the same bending and torsional strength, and is an economical section steel which is widely used for manufacturing structures. Parts and mechanical parts, such as steel scaffolding for oil drills. 2. The history of seamless steel pipe development Seamless steel pipe production has a history of nearly 100 years. In 1885, the German Mannesmann brothers first invented the two-roller cross-rolling punching machine. In 1891, the cycle rolling mill was invented. In 1903, the Swiss Ritteriefel invented the automatic rolling mill (also called the head rolling). Pipe machine), and various extension machines such as continuous tube rolling mills and pipe jacking machines appeared in the future, and the modern seamless steel pipe industry began to form. In the 1930s, the quality of the steel pipe was improved due to the use of a three-roll mill, an extruder, and a periodic cold-rolled pipe mill. In the 1960s, due to the improvement of continuous rolling mills, the emergence of three-roller punching machines, especially the application of tension reducing machines and continuous casting blanks, increased production efficiency and enhanced the ability of seamless pipes to compete with welded pipes. In the 1970s, seamless pipes and welded pipes were moving in parallel, and the world’s steel pipe production increased at a rate of more than 5% per year. After 1953, China attached great importance to the development of seamless steel pipe industry, and has initially formed a production system for rolling various large, medium and small pipes. Copper pipes are generally also used in the ingot blank rolling piercing, rolling mill rolling, coil stretching process. 3. The use and classification of seamless steel pipe Uses: Seamless steel pipe is an economical section steel, which has a very important position in the national economy. It is widely used in petroleum, chemical, boiler, power station, shipbuilding, machinery manufacturing, automobile, aviation, aerospace, energy, geology, construction and Military and other departments. Seamless tube classification: According to the shape of the section: circular section tube, profiled section tube According to the material: carbon steel pipe, alloy steel pipe, stainless steel pipe, composite pipe According to the connection method: threaded connecting pipe, welded pipe According to the production mode: hot rolling (squeeze, top, expand) pipe, cold rolling (pull) pipe According to the purpose: boiler tube, oil well tube, line tube, structural tube, fertilizer tube, etc. 4. The production process of seamless steel pipe 1 Main production process of hot-rolled seamless steel pipe (main inspection process): Tube blank preparation and inspection → tube billet heating → perforation → rolling tube → waste tube reheating → fixed (reduced) diameter → heat treatment → finished product Tube straightening → finishing → inspection (non-destructive, physical and chemical, Taiwan inspection) → storage 2 cold rolling (drawing) seamless steel pipe main production process Blank preparation → pickling lubrication → cold rolling (pull) → heat treatment → straightening → finishing → inspection Hot rolling seamless steel pipe production process flow chart

The sudden emergence of duplex stainless steel pipe has become one of the major breakthroughs in the stainless steel pipe industry in the past few decades. Duplex stainless steel has good corrosion resistance and high strength, and is the best substitute for traditional stainless steel and structural steel. As the prices of important alloys such as nickel and molybdenum continue to rise, the price-stable duplex stainless steel is gradually favored by users. However, from a technical point of view, a stable price can be considered as an additional incidental advantage given by duplex stainless steel. Low nickel duplex stainless steel LDX2101® (Outokumpu commercial grade, EN1.4162, UNS S32101) has become a rookie in the duplex stainless steel family. LDX2101®’s technical characteristics such as corrosion resistance, weldability and strength are unique, saving resources and low nickel content making it more economically competitive. Duplex stainless steel was born in the late 1920s. The test records kept by the Outokumpu Avista Research Center date back to December 23, 1930. The first generation of duplex stainless steel developed by Avista Iron Works in 1930 is a typical 25Cr-5Ni, without molybdenum or 1.5% Mo. Among them, 453S (25%Cr-5%Ni-1.5%Mo) is the pioneer of AISI 329. The early duplex stainless steel has a high content of sulphur, which is about 60% to 70% in the solid solution state. And the carbon content is as high as 0.1% at the time. Compared with austenitic stainless steel, the main advantage of duplex stainless steel is its high strength and better resistance to intergranular corrosion. Duplex stainless steel can be used in environments where normal austenitic stainless steels are inevitably subjected to stress corrosion cracking. After the invention of the AOD process in the 1970s, the decarburization rate of stainless steel increased and the addition of nitrogen was more precise. This resulted in a modern low-carbon nitrogen-rich duplex duplex stainless steel. Compared to their predecessors, modern duplex stainless steels have improved pitting resistance and weldability. The first steel grade of modern duplex stainless steel is 2205, and its mechanical strength and corrosion resistance are significantly higher than 316L and 317L. In many application fields, it fully reflects the better cost performance of 2205, and has built many battles for a long time. Known as Super Duplex Stainless Steel, the 2507 was introduced in the 1980s for the more demanding environments that the 2205 could not meet. Also available in the same period is the 2304 with lower alloy content, but its use is limited. In 2007, the rapid rise in nickel prices caused interest in 2304, and the 2304 with high strength characteristics could replace 316L to meet the requirements of most application environments. Duplex stainless steel is suitable for pressure vessels, scouring and abrading equipment for the paper industry, cargo tanks for chemical tankers, industrial tanks and bridges. At present, the apparent consumption of global duplex stainless steel has doubled in the level of 70,000 tons in 1997. This paper introduces the basic characteristics and research cases of modern duplex stainless steel to illustrate their characteristics in welded pipes, pipe fittings and Application in accessories. Basic characteristics of modern duplex stainless steel 1.1 Mechanical properties High strength is the commonality of duplex steels, which is twice as high as that of ordinary austenitic stainless steels and is significantly higher than that of ferritic stainless steels. The high strength is advantageous for thinning the thickness, thereby reducing the structural weight. The mechanical properties of modern duplex stainless steels are shown in Table 2 in the solution annealed state. The hardness of duplex steels exceeds that of austenitic and ferritic stainless steels. This is what most scouring and wear applications require. In terms of stretch forming. Duplex steel is found between high-form austenitic and ferritic steels. Due to poor plasticity, the geometry of ordinary austenitic steels is generally not achieved, and its high yield strength requires an increase in the strength of the forming. 1.2 Corrosion characteristics Existing dual phase steels are resistant to chloride pitting and stress corrosion between 304 and 6 Mo austenitic stainless steels. The PRE value is a simple measure of the local corrosion resistance of steel grades. However, this is basically the same as the alignment of the laboratory CPT (Critical Pitting Temperature) test according to ASTM G150. Duplex stainless steel is much better resistant to chloride stress corrosion than austenitic stainless steel 304 and 316. Laboratory erosion test: The erosion test is carried out in three different liquids, pided into immersion and no immersion, and finally subjected to wear tests. The samples used were identical. In the 24-hour erosion test (test 1) of the double sample, the test materials were all in passivated and the weight defects were completely polished. However, if the test material is first immersed in a high chloride solution (1000 mg/l) for one week and then polished for 5 hours (Test 2 Environment 2), the passivation film may be partially broken, causing pitting and abrasion. In the 1NH2SO4 solution, the test materials were all melted and corroded, and the wear rate was extremely fast during the 5-hour grinding period (Test 3 Environment 3), and the erosion rate was about 1 mm/year (see Figure 2). In a mildly corrosive environment with a chloride content of 200 mg/l (environment 1), the erosion rate of 316L is higher than that of LDX2101® by 24% to 30%. In the environment with a chloride content of 1000 mg/l (environment 2), the erosion rates of the two steel grades differ by 16% to 18%. At the most corrosive (environment 3), the 316L erosion rate is only 6% higher than the LDX 2101®. Laboratory erosion tests have shown that the mechanical strength of the material has a large impact on overall performance because LDX 2101® has the least weight loss in all test environments. Duplex stainless steel is gradually replacing 304 and 316L in the paper industry. The alloy additive nitrogen enhances the pitting resistance while increasing the strength of the duplex stainless steel. In addition, higher temperature components made of duplex stainless steel, such as steam boxes, are also resistant to stress corrosion. 1.3 Physical properties The physical properties of duplex stainless steel and austenitic stainless steel are basically the same, the important difference is the coefficient of thermal expansion (linear expansion), and the duplex stainless steel is lower. In general, a low coefficient of linear expansion is an advantage, especially in a mixture of stainless steel and carbon steel, which reduces the risk of thermal fatigue. Case study 2.1 Process tube design Some chemical plants have high requirements for pipes that transport chemicals and fluids. This is because corrosive substances go from one process to the next. Pipes and components are designed to use standard parts as much as possible. Specifications and inspection standards are based on the European standard (EN-standard, such as: 13480-3) or American standard (ASME/ANSI-standard). The chemical plant design is mainly pided into the following parts: Factory layout Flow chart, including chemical, mechanical and physical processes Pipeline assembly drawing The selection of steel pipes and fittings is often limited by the total purchase price, which is generally determined by the weight and length of the required pipe. Therefore, designers and purchasing managers are keen on new steel grades that are expected to reduce pipeline costs. To reduce the weight, it is necessary to use a thin steel pipe wall, and the benefits are as follows: transportation and installation costs are reduced, and the amount of welding on site is significantly reduced. Lightweight brackets can also save some money. Whether the wall thickness of the pressure tube can be thinned depends on several factors. The ASME standard is more conservative than the EN standard in wall thickness design. However, in both standards, the economical duplex stainless steel LDX2101® has a wall thickness that is 40% thinner than 304L. The actual design thickness should refer to the ASME comparison table. Also consider the design pressure. For pipes with lower pressure, the reduction in wall thickness is smaller. If the wall thickness of the original design is already thin, it cannot be reduced. There are other factors to consider when designing the pipeline. Internal pressure is not the only load to be considered in the piping design. The support spacing should also be appropriate. The support spacing depends on: Bracket type Pipe diameter and wall thickness Medium in the tube Whether insulation is required Whether to absorb shock Taking into account the above factors, changes in the temperature of the surrounding or in-tube medium will create additional loads, which should be considered in material selection or piping design. 2.2 Hollow steel design Stainless steel has been used as a decorative material for buildings. Hollow sections for construction, construction and transportation are often carbon steel. Carbon steel structural design is moving in the direction of high strength steel. This is because the design is more economical when the material strength is fully utilized. Carbon steel is prone to corrosion in many applications and requires thorough corrosion inspection and corrosion protection, including planned and unplanned shutdowns or power outages (water, gas) – for maintenance, maintenance and painting. The related costs required for the maintenance of painted carbon steel are expected to increase in the future. The application of duplex stainless steel in building components has attracted a lot of attention. Duplex stainless steel is the most cost effective in corrosive environments. Compared with 300 series stainless steel, the cost has decreased to varying degrees. Duplex stainless steels have twice the yield strength than 300 series stainless steels. For the same load, thinner duplex stainless steels can be used. Duplex stainless steel is also cheaper to make than other materials because it is easy to machine and weld. The ferrite phase improves the weldability of duplex stainless steels compared to high nickel alloys. This alone saves a lot of soldering time. Using high-speed steel cutting tools, the economical duplex stainless steel LDX 2101® is machined similarly to 316 stainless steel or easier. Moreover, the labor required for duplex stainless steel machining is also less than that of high nickel alloys. The structural parts can be designed according to the European standard EN1993-1-4:2006. The basis for structural design in EN 1993-1-4 is the limit state analysis. The limit values used are the maximum limit state and the usability limit state. The maximum limit state means that once this limit is exceeded, the component or the entire structure collapses. The usability limit state indicates that if the limit is exceeded, the specified use criteria cannot be achieved. The design specifications specified in the EN 1993-1-4 standard apply to solution annealed materials with yield strength fy = 480 N/mm2 and cold worked materials with strength classes C700 and CP350. According to the Euro-InoxDesign Manual, after cold working, the austenitic stainless steel has improved yield strength and tensile strength and can be used as the basic material for the strength class CP500. According to the European-Stainless Steel Design Manual, the design strength of the members subjected to the axial force and the members subjected to the axial force + bending force is equal to 0.2% proof strength, and the material temperature is also considered. When the ignition temperature is reached, stainless steel performs differently than other metals, and it can maintain its mechanical properties (mainly elastic modulus and yield strength) at a temperature of 30 minutes in a standard fire. The stability of the yield strength of stainless steel depends on the alloy composition of the material, ie the stainless steel grade selected. The structural design of stainless steel is not more complicated than carbon steel. The thermal expansion coefficient of duplex stainless steel is the same as that of carbon steel, which is much lower than that of austenitic stainless steel. The fatigue strength of welded joints is as good as that of carbon steel joints. Their structural strength is better than standard austenite, and the bearing capacity of the members is greater. Cold working can increase the strength value of stainless steel hollow profiles. Cold working refers to the flattening of strips for the production of hollow sections, such as hardened cold rolling, which can be carried out in a pipe mill or in a steel mill. The mechanical properties of the entire batch of hollow tubes are to be recorded in the inspection report. In the vertical load support, the use of high-strength hollow profiles serves as a load-bearing function and can beautify the building. It is an economical and practical solution. 2.3 Water heater This is an aluminum heat exchanger with an external stainless steel tube. The principle is to let the heated gas flow through the aluminum heat exchanger, and the gas is added to the water around the heat exchanger. In order to prevent corrosion of the aluminum heat exchanger, the outer surface of the aluminum core is sealed with a cold drawn stainless steel tube. Users have been using 316 titanium stainless steel early on, and the weight has been reduced by 30% with LDX2101®. Duplex stainless steel with low nickel and molybdenum content allows users to save a large amount of alloy and the material price is relatively stable. Duplex steel is generally better at stress corrosion cracking than 316 stainless steel. The performance of stainless steel varies from series to series, and changes from austenitic or ferritic series to duplex steels place new demands on production equipment and processes. Duplex steel has a high yield strength and requires more force during forming. When the thickness of the pipe wall is thinned by the high strength characteristic, the influence of the increased forming force is not sufficiently taken care of. The resilience of duplex steel is significantly higher than that of other stainless steel series. When the duplex stainless steel is welded by the automatic TIG method, the traveling speed of the torch is slower than that of the welded austenitic stainless steel, but the duplex stainless steel is easier to weld than the ferritic stainless steel. 2205 and other duplex steels are commonly used in heat exchanger tubes and enclosures. In heat exchanger applications, the coefficient of thermal expansion of duplex steels is generally lower than that of austenitic stainless steels. 2.4 Mine An example of this application is the drain pipe at the Boliden mine in northern Sweden. The water in the mine is taken from the underground 450 meters. Pipe diameter DN600, pressure between 45 and 200 meters underground 45 bar, 200 meters to ground 32 bar. The pipeline is 1200 meters long. However, the applicable temperature range of duplex steel is -40 to 300 °C, which cannot completely replace austenitic stainless steel. If the most commonly used 304L is compared with the LDX 2101®, the welding factor is 0.7 according to the EN standard. For a pressure of 45 bar, the wall thickness of the 304L tube is 13.4 mm, and the wall thickness of the LDX 2101® tube should be 7.2 mm. The section with a pressure of 32 bar has wall thicknesses of 9.6 mm and 5.1 mm, respectively. When the design pressure is 45 bar, the closest standard specifications are 14 mm and 10 mm, and the design pressure is 32 bar. The standard specifications are 8 mm and 6 mm, respectively. With 304L, the pipe weighs 196 tons and the LDX 2101® weighs 113 tons. This can reduce the use of 83 tons of stainless steel, saving 42.5%. In addition to the direct benefits of saving tubing, there are many aspects that are indirectly beneficial. The length of the weld of 230 ring seams is 437 meters, the welding of 304L steel pipes takes about 2100 hours, and the welding of LDX 2101® takes only 1325 hours because of its The tube wall is thin. Save 775 hours and shorten on-site work time. The weight reduction of the steel pipe can save energy required during the hoisting process, thereby reducing CO2 emissions. The freight rate from the production plant to the site is also reduced. The distance between the two places in the project is 1500km, electric train transportation, CO2 emission reduction 125kg. If transported by truck, CO2 emissions will be 75 times higher. Due to the low amount of LDX2101®, steelmaking emits less CO2 than 304L. Cut costs Pipe weight reduction Reduce welding labor costs Saving welding consumables Steel pipe lifting energy saving Transportation energy saving Reduce CO2 emissions (smelting, lifting, etc.) Considering raw material costs and exchange rates, the total savings are between $300,000 and $500,000. Duplex stainless steel welded pipes not only replace austenitic and ferritic stainless steels, but also other metals such as anti-corrosive carbon steel and aluminum, and even polymers. Application examples cover a wide range of areas: construction, mine drainage and domestic water heaters. Global economic development places higher demands on energy and transportation. More families need modern home facilities, such as home hot water centers, and this demand will continue to rise in the future. 2205 is one of the grades of duplex stainless steel series. The corrosion resistance of this series of steels is strong and weak. Duplex stainless steel is gradually being accepted. In applications where the 316L is unsatisfactory, more and more users are choosing duplex stainless steel because it is suitable for a wider range of corrosive environments. Due to the light weight, high strength and good corrosion resistance of duplex stainless steel, the application items are increasing. It cannot be ignored that the high nickel price in 2006-2007 has increased the status of duplex stainless steel, and the increase in sales of duplex stainless steel includes the replacement of austenitic stainless steel for purely price reasons. The comprehensive performance of duplex stainless steel is perfectly suited for many existing and newly developed applications. In terms of corrosion resistance, the grade of duplex stainless steel is more complete than a decade ago. It is certain that duplex stainless steel will continue to grow in the past decade. Source: China Duplex Stainless Steel Pipe Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The stamping reducer is a reducer produced by a stamping process. The reducer has the advantages of stable structure, fast forming, high hardness, high pressure resistance, corrosion resistance, abrasion resistance and high temperature resistance. The size of the reducer is classified into: stainless steel reducer, alloy steel reducer, carbon steel reducer. Reducer, 10# reducer, 20G carbon steel reducer, Control caliber: DIN standard (DN10-DN150), 3A/IDF standard (1/2″-6″), ISO standard (Ф12.7-Ф152.4). International industry standards: DIN, ISO, SMS, 3A, IDF and so on. Product materials: stainless steel 304, 316, 316L. Quality and use: the inside and outside of the reducer with a polishing equipment to achieve surface precision requirements, this product is suitable for dairy, food, beer, beverage, pharmaceutical, cosmetics and other industrial fields. External processing: can be based on user requirements to map, sample processing non-standard products. Connection: clamp (quick) type, welded, thread (live) type. Stamping reducer classification Stamping eccentric reducer: Refers to the size of the reducer produced by the stamping process that is not on the same straight line. The function of the stamping eccentric reducer is to connect two pipes with different nominal diameters and allow the pipe to be docked at different angles. Because the stamping eccentric reducer is formed by stamping process, it has the advantages of high production efficiency, stable product structure, high product quality, low production cost, and mass production. This process can be used to produce various pipe fittings, such as Elbows, tees, flanges, etc. Materials that can be used to produce stamping eccentric reducers include carbon steel, stainless steel, alloy steel, cast iron, aluminum alloy, pure aluminum, etc. Different materials have different characteristics and can be used in different piping systems. Stamping eccentric reducers can be pided into national standard, electric standard, ship standard, chemical standard, water standard, American standard, German standard, Japanese standard, Russian standard and so on. Stamping eccentric reducers are widely used in oil, natural gas, tap water, machinery manufacturing, shipbuilding, chemical, paper and other industries. Stamping concentric reducers: The reducer of the center on the same line is called the concentric reducer. Basic process of stamping size forming technology The reducer is a type of pipe used for pipe diameter reduction. The forming process usually adopted is a reduction press, a diameter expansion press, or a reduction and diameter expansion press. For some sizes of the reducer, press forming can also be used. The size of the reducer is characterized by a carbon steel having a strength significantly higher than that of the same carbon, which has good toughness and plasticity as well as good weldability and corrosion resistance. The reduction forming process of the large and small reducers is to put a tube blank having the same diameter as the large end of the large and small reducers into a forming mold, and to move the metal along the cavity and shrink and form by pressing in the axial direction of the tube blank. According to the size of the size reduction reducer, it is pided into one press forming or multiple press forming. The expanded diameter forming adopts a tube blank smaller than the diameter of the large end of the different diameter tube, and is formed by expanding the inner diameter of the tube blank by the inner die. The diameter expansion process mainly solves the problem that the large and small diameter reducers are not easily formed by the diameter reduction, and sometimes the method of expanding the diameter and reducing the diameter is combined according to the material and product forming requirements. In the process of reducing or expanding the deformation and deformation, it is determined that cold pressing or hot pressing is adopted according to different materials and the diameter reduction conditions. Cold pressing is used as much as possible, but in the case of severe work hardening caused by multiple reductions, thick wall thickness or alloy steel material, hot pressing is recommended. In addition to the use of steel pipes as raw materials for the production of different diameter pipes, the partial diameter of the different diameter pipes can also be produced by the stamping forming process. Need to pay attention when stamping the size of the reducer There are many places to pay attention to when stamping the reducer, because some places can directly affect the quality of the welding. If the welding is not good, not only the size of the reducer but also the damage to the pipeline, so the scientific and reasonable welding is the top. The choice. After the stamping reducer is welded, the hardening property is large, and cracks are easily generated. If the same type of stamping reducer welding is used, it is necessary to perform preheating at 300 °C or more and slow cooling at around 700 °C after welding. If the weldment cannot be post-weld heat treated. A stamping reducer electrode should be used. In order to prevent the stamping reducer from being attacked by the eye due to heating, the welding current should not be too large, about 20% less than the carbon steel electrode, the arc should not be too long, and the layer is fast cold, and the narrow bead is suitable. Source: China Stamping Reducer Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1. What are the specific requirements for the design of the side pipe of the tower? The tower side piping design has these requirements: (1) The pipe on the side of the tower body generally has reflux, feed, side line extraction, stripping steam, reboiler inlet and return pipe, etc. In order to make the valve closed without liquid accumulation, the valve on the pipe should be directly connected with the tower pipe. The ports are directly connected, and when the inlet (outlet) material pipe has more than two inlets (outlet) openings at the same angle, the pipe should consider a certain flexibility; (2) If there is a regulating valve on the pipeline from the side line of the fractionation tower to the stripper, the installation position should be close to the stripper. In order to ensure that there is a period of liquid in the same adjustment. The height of the liquid column should meet the requirements of the process. 2. What are the characteristics of the tower bottom piping design? Features of the tower bottom piping design: (1) The operating temperature of the bottom of the tower is generally high, so the flexibility of the bottom piping should meet the requirements of relevant standards or specifications when arranging the bottom piping. In particular, when the bottom draw pipe is connected to the pump, the pipe should be short and less curved, and sufficient flexibility is required to reduce the force on the pump nozzle. The bottom drawing line should be led to the outside of the tower skirt or the base. It is strictly forbidden to set the flange into the pipe fittings and other fittings. The extraction pipe from the bottom of the tower to the bottom of the pump shall not have a “pocket shape” on the horizontal pipe section, and it shall be “low step” to avoid cavitation of the bottom pump. The partition valve on the extraction pipe should be closest to the tower body. And easy to operate. (2) Unless it is an auxiliary reboiler, or two or more parallel reboilers are operated at the same time, and it is required to adjust the heat load over a wide range, the bottom of the tower to the reboiler is generally not suitable for a valve. When the bottom tank type heavy Buddha is equipped with a centrifugal pump, the elevation of the reboiler should meet the effective NPSH required by the centrifugal pump, and at the same time, the static difference between the liquid level of the bottom of the tower and the liquid level of the reboiler The indenter is sufficient to overcome the pressure loss of the downcomer, reboiler and riser. Therefore, the piping should be arranged to meet the flexibility requirements, the piping should be short, and the elbow should be small. 3. What requirements should be placed in the arrangement of manholes on the tower? The arrangement of manholes on the tower should meet these requirements: (1) The manhole of the tower should be located in the operating area of the tower. It is convenient, safe and reasonable to enter and exit the tower, and should be located in the same orientation. (2) The location of the manhole must be noted that the internal components of the tower should generally be located in the bubbling area above the tray and should not be placed in the downcomer or receiver tank area of the tower; (3) Manholes (or hand holes) on the tower body, generally one for every 3-8 layers of trays; (4) The height of the manhole center from the platform surface is generally between 600mm and 1000mm, and the most suitable height is 750mm; (5) The holes on a tower should be arranged on the same vertical line to make it neat and beautiful. 4. What are the requirements for the nozzle orientation of the tower? The nozzle orientation requirements of the tower are as follows: (1) The nozzle orientation of the tower should meet the working principle and structure requirements of the inner part of the tower. The overall structure of the inner part of the equipment and the relative orientation of the nozzle should be paid attention to during design; the gas phase opening at the top of the tower is arranged in the middle of the top cover of the tower; The opening is generally arranged on the side of the pipe above the tray; the gas feed inlet is above the tray, parallel to the downcomer; the gas-liquid mixed phase feed opening is above the tray, and a distribution pipe is provided; the stripping steam opening is stripped Below the tray, add a gas distribution tube. The side line product extraction outlet should be provided with an extraction hopper in the arc range below the downcomer. For the double overflow tray of the intermediate downcomer, the extraction outlet can be arranged at any angle there, and the extraction hopper is provided; The mouth is located in the middle of the bottom cover of the tower, and is provided with a vortex prevention plate, and the suction outlet should extend outside the skirt of the tower; (2) For towers with trays, the manholes should be arranged on the diameter of the tower parallel to the overflow weir of the tray. If the conditions are not allowed, the gaps may not be parallel, but the clearance between the manhole and the weir in the horizontal direction should not be Greater than 50mm; (3) The orientation of the manhole lifting and the setting of the ladder should be arranged uniformly. In the event of an accident, the direction in which the human cover is smoothly closed should be consistent with the direction of evacuation; (4) The level gauge interface can be directly connected to the level gauge through the root valve, or can be connected to the level gauge through the root valve. The level gauge interface must not be placed within the 60° angle of the opposite side of the inlet, unless the inlet is protected by an internal baffle. The outer float type liquid level control nozzle directly connected to the tower shall be provided with a baffle. Level gauges, liquid level control buoys, alarms and other devices are often located in the tower platform or at the end of the local platform to facilitate maintenance; (5) The pressure gauge interface should be placed in the gas phase zone of the tower so that the pressure gauge reading is not affected by the liquid level head; (6) Arrangement of sampling port and temperature measuring port, gas phase sampling port and temperature measuring port should avoid the gas phase zone of the tray downtake tank, liquid phase sampling port and temperature measuring port should be set in the tray holding area of the downcomer area In the layer; for the liquid phase sampling tube which is easy to crystallize, it should be directed to the tray; (7) The top of the tower shall be positioned so that it can reach above the lifting point outside the platform and the position of all the holes in the platform. 5. What is the orientation of the device nozzle orientation map in addition to the nozzle? In addition to the process and common media nozzles, it should also indicate: (1) The orientation of the instrument takeover, including temperature, pressure, and liquid level; (2) the orientation of the manhole, the hand hole and the hanging column, and the orientation of the venting hole of the skirt; (3) the orientation of the anchor bolt holes of the equipment or the orientation of the lugs; (4) the orientation of the lifting lugs, the grounding plate and the nameplate; (5) The orientation of the internal ladder and the bottom of the skirt to strengthen the support. 6. How to determine the fixed side of the horizontal container support? Find the most important (difficult or most demanding) pipe for the flexible calculation from the pipe to which the container is to be connected, such as a pipe with a large amount of compensation and a large pipe diameter, as the basis for determining the type of support. The position of the fixed side support should facilitate the flexible calculation of the pipe. 7. What are the requirements for the orientation of the horizontal container? What are the requirements for the orientation of the horizontal container? (1) The liquid inlet and outlet spacing on the equipment housing should be as far as possible. The liquid inlet pipe should be as far as possible from the container level gauge interface; (2) The level gauge interface should be placed in a position that is easy for the operator to observe and convenient. Sometimes, in order to reduce the nozzle on the device, a measuring device such as a liquid level gauge, a liquid level controller, and a liquid level alarm can be installed on the header. The orientation of the wave gauge nozzle shall be arranged on the same side as the liquid level regulating valve group; (3) Manhole covers connected by hinges (or hanging columns) shall not affect other nozzles or pipes when opened; (4) The safety valve nozzle shall be located at the top of the vessel. 8. What are the general requirements for piping arrangements for horizontal containers? The piping of the vessel (tank) is relatively simple; the piping arrangement of the vertical vessel is generally similar to that of the tower, and is also designed along the tank wall. The valve on the pipeline is also required to be directly connected to the opening; this avoids fluid accumulation. When the horizontal container equipment is arranged, the tank is generally perpendicular to the longitudinal direction of the pipe gallery, so that the pipes such as the gas outlet pipe, the safety valve outlet pipe, the liquid outlet pipe, etc. are all oriented toward the pipe gallery and related to the pipe gallery; connection. The pipe that is open at the top of the vessel should have an elevation higher than the main pipe that meets the pipe gallery to facilitate access to the top of the main pipe. When the liquid outlet pipe at the bottom of the vessel is connected to the pump under the pipe, the bottom elevation of the pipe should not affect the passage of people. (1) For the pipe connecting the liquid outlet of the horizontal container to the pump suction port, the minimum clearance height is 2200mrn if the pipe is overhead on the channel; (2) The pipe connected to the bottom nozzle of the horizontal container, the low discharge point of the low point is 150mm from the floor; (3) When the outlet of the safety valve is discharged into the closed pipe system, the liquid should be avoided, and the outlet pipe of the safety valve should be connected to the top of the closed main pipe at a 45° downward flow direction, and there is no “pocket shape”. If the safety valve is installed away from the container, check the pressure drop from the container to the safety valve inlet pipe; (4) The regulating valve group of the tank top pipe is arranged on the platform; (5) The platform should be set according to the equipment and piping layout. 9. What are the general requirements for the layout design of the heating furnace piping? The general requirements for the design of the furnace piping layout are: (1) The arrangement of the heating furnace piping varies with the furnace type of the heating furnace. When the heating furnace piping is arranged, the inlet and outlet piping, fuel system piping, ash blowing gas pipeline, fire extinguishing steam pipeline, etc. should be considered uniformly; (2) The cylindrical furnace inlet and outlet manifolds are usually arranged in a ring shape around the furnace body and can be supported on the ground or the furnace body. The annular main pipe shall be arranged above the fire door to facilitate the normal operation and maintenance of the fire door; (3) If necessary, bend the pipe at the exit of the furnace. An anti-vibration bracket is provided in addition to the tee or the larger diameter, or from the bottom of the furnace top vertically downward; (4) If a rupture disc is placed in the pipe, its direction shall not be directed towards the operation or equipment; (5) The main regulating valve group is usually arranged between the pipe gallery and the furnace body and pay attention to the passage requirements; (6) The valves on the steam, fuel oil or fuel gas pipelines should be placed on vertical pipes near the fire door and meet the requirements for regulation and overhaul; (7) In cold areas, steam heating shall be applied to the fuel oil pipeline according to regulations; (8) Pipes close to the nozzle shall be connected in a convenient structure for easy cleaning and maintenance; (9) Platforms and ladders shall be provided at frequently operated valves and observation points at higher positions; (10) The discharge point of the fuel pipeline shall be at least 15m away from the furnace and shall be discharged into the collection system and shall not be discharged directly into the sewer; (11) Pipes connected to the furnace should be arranged as concentrated as possible to facilitate support and achieve coordination. Aesthetic purpose (12) For the feed pipe of the heating furnace, the flow rate of each pipe should be kept uniform; for the whole liquid phase feed pipe, generally, each channel is provided with a flow regulating valve to adjust the flow of each road, otherwise the pipe should be symmetrically arranged, and the gas-liquid two phase The inlet and outlet pipes must be arranged symmetrically to ensure the same pressure drop across the roads; (l3) The annular oil line should calculate the thermal compensation amount at the highest temperature and absorb the thermal expansion amount by natural compensation of the pipeline. 10. What are the general requirements for the fuel gas piping arrangement of the furnace? The general requirements for the fuel gas piping arrangement of the furnace are: (1) The fuel gas should be provided with a distribution main pipe so that the fuel gas of each nozzle can be evenly distributed; the fuel gas branch pipe is led out from the upper part of the distribution main pipe to ensure that the fuel gas entering the nozzle does not carry water or condensed oil. At the end of the fuel gas distribution main control, a drain valve of DN20 is installed to facilitate the trial flushing and draining after the line is cleaned, and the oxygen content in the pipeline is sampled and analyzed at the time of starting. Two drain valves should be provided on the drain pipe to avoid leakage. The valve can be operated on the ground or on the platform. The fuel gas shut-off master valve should be placed 15m away from the furnace. (2) The flame arrester can be prevented by providing a flame arrester on the fuel gas pipeline. The flame arrester can be pided into a dry flame arrester and a safe water seal according to the principle of action. A dry flame arrester of a multi-layer copper mesh is generally used on a fuel gas pipe of a heating furnace in an industrial production plant. The flame arrester should be placed close to the nozzle. The distance between the pipeline flame arrester and the burner should not be greater than 12m. In this way, the flame arrester is not subject to severe explosion conditions and the service life can be extended. 11. How to consider the piping arrangement of shell-and-tube type heat exchanger equipment? Pipe arrangements for shell and tube and heat exchangers should consider the following: (l) The process piping arrangement should pay attention to the flow direction of the cold and hot streams, generally the cold flow is from bottom to top, and the heat flow is from top to bottom; (2) The piping arrangement should be easy to operate and does not hinder the maintenance of the equipment; (3) The basic elevation of the heat exchange equipment shall be such that the lower drain pipe is not less than 150 mm from the ground or platform surface; (4) Pipes of heat exchange equipment can only have one high point and one low point, avoiding “air bag” or “liquid bag” in the middle, and set high point to vacate and low point to clean; in the area of heat exchange equipment Try to avoid pipe crossing and bypass; try to reduce the number of layers of pipe overhead, usually 2-3 layers; (5) Two or more parallel heat exchange equipment inlet pipes are arranged in a straight symmetrical manner, and the gas-liquid two-phase flow heat exchange equipment must be symmetrically arranged to achieve a good heat transfer effect; (6) The measuring instrument on the inlet and outlet pipes of the heat exchange equipment shall be installed close to the operation channel and the place where it is easy to observe and overhaul; (7) Pipes of easy-to-condensate medium or pipelines containing solid particles connected to the heat exchange equipment, the shut-off valves shall be provided on the horizontal pipes, and the formation of dead angle effusion shall be prevented; (8) In the cold area, the upper and upper water pipes of the outdoor heat exchange equipment shall be provided with a drain valve and an antifreeze connecting pipe. 12. How should the piping arrangement of the heat exchangers arranged in groups be designed? The piping layout design of heat exchangers arranged in groups should pay attention to the following points: (1) In the area of heat exchange equipment arranged in groups, pipes may be laid on the ground or platform surface, but shall not impede access and operation; (2) When there is no regulating valve or draining pipe on the pipeline, the clearance from the bottom of the pipe should be greater than or equal to 150mm; (3) The regulating valve group shall be arranged parallel to the cold changing equipment; (4) The clearance between the heat exchangers arranged in groups shall be greater than or equal to 650 mm; (5) Pipe layout should consider the disassembly space of the pipe box and head cover of each heat exchange equipment; (6) The inlet and outlet pipes of multiple sets of heat exchange equipment in parallel should be arranged symmetrically. 13. What are the requirements for the piping arrangement of the vertical reboiler? The piping arrangement of the vertical reboiler has these requirements: (1) Pipes must be flexible enough to compensate for thermal expansion of equipment and piping under various operating conditions; (2) When the mouth of the reboiler is docked with the nozzle of the tower, if the load conditions permit, it is better to provide a bracket to support the reboiler on the tower body, and the position and form of the bracket should be able to meet the expansion of the tower body and the pipeline. The resulting displacement and load requirements; (3) The piping should be left with the space required for the reboiler bundle to be removed in situ; (4) For the one-way fixed tube-plate heat exchanger with expansion joint on the casing, the influence of the expansion joint should be considered when piping, flexibility analysis and equipment support design; (5) When the ratio of length to diameter (L/D) of the reboiler is greater than 6.0, a guide bracket should be provided; (6) When the valve and blind plate of the reboiler are more than 3m away from the ground, the platform should be set on the tower. 14. What are the requirements for the piping arrangement of the shell-and-shell horizontal horizontal reboiler? The piping layout requirements for the shell-and-tube horizontal horizontal reboiler are as follows: (1) Within the allowable stress range of thermal expansion, the downcomer and the riser pipe of the reboiler should be as short as possible to reduce the number of bends to reduce the pressure drop; (2) When the reboiler has two rising ports, in order to make the flow green in the tube equal, the steam moving department should be arranged symmetrically. If the diameters of the riser pipes are different and the arrangement is asymmetrical, the resistance of the two pipe sections should be made equal. Otherwise, the flow rate of the pipe with a large resistance will cause uneven heat distribution; (3) The liquid drawn from the reboiler is a saturated liquid. If the piping system produces a pressure drop, the liquid will begin to flash, resulting in a gas-liquid two-phase fluid flow, affecting the operation and accuracy of the control and measuring instruments. Therefore, when arranging a saturated liquid pipe, the basic principle is to minimize the pressure drop and not to have a vertical rise pipe section before measuring or controlling the meter; (4) Reboiler tube The inlet pipe of the heating medium is usually equipped with a temperature regulating valve and a valve block thereof, and these valves are generally arranged on the ground or platform surface near the inlet of the reboiler tube. 15. What are the specific requirements for the design of the air cooler? The piping design of the air cooler has these specific requirements: (1) The “liquid bag” is generally not suitable for the top of the fractionation tower to the oil and gas pipeline of the air cooler. When there is no valve or two-phase flow in the inlet and outlet of the air cooler, the pipes must be symmetrically arranged to make the flow of each air cooler uniform; (2) The inlet manifold of the air cooler should be connected to the nozzle of the air cooler. If the stress or installation needs, the outlet manifold may not be connected to the nozzle, and the cross-sectional area of the manifold shall be greater than the sum of the cross-sectional areas of the branch pipe; (3) When the air-cooler population is a gas-liquid two-phase flow, each branch pipe should be inserted into the population collecting pipe from below; so that the fluid distribution at the bottom of the collecting pipe is evenly distributed; at the same time, a shutdown liquid discharging pipe is arranged below the collecting pipe, and is connected to the air cooler outlet. On the pipeline; (4) The air cooler has a high population pipeline; if the distance is long, a special pipe rack is required in the middle to support the pipeline; (5) The softened water returning system of the wet air cooler is a self-flowing pipe. Therefore, attention should be paid to the arrangement of the piping system, and the turning should not be excessive. The return water main pipe should have a slope along the flow direction of the medium; (6) The operating platform of the air cooler is provided with a semi-fixed steam purging joint. The valve should be located at an easy access point, and the direction of the steam joint should be paid attention to ensure safe operation. 16. What are the general requirements for pump design for pumps? The general requirements for pump piping are as follows: (l) The inlet and outlet pipes of the pump shall be provided with a cutting net. The pipe must have sufficient flexibility to reduce the stress and moment of the pipe acting on the pump nozzle; (2) The suction pipe of the pump should meet the requirements of the “cavitation allowance” of the pump. The pipe should be as short as possible and less curved. If it is difficult to avoid, the vent valve should be installed at the high point; (3) When the pump suction pipe is long, it should be designed to have a certain slope (i=5‰); when the pump is lower than the container, it should be inclined to the pump. When the pump is higher than the container, it should be inclined to the container; (4) In the downstream of the pump population pipeline shut-off valve, a filter or temporary filter shall be provided. In order to prevent the pump’s impeller from being reversed due to the backflow of the pump, the pump outlet shall be equipped with a check valve; (5) The pipeline of the pump under the premise of meeting the process requirements. The valve handwheel shall not affect the space required for normal operation of the pump and maintenance inspection; (6) The design of the inlet and outlet pipes of the reciprocating pump should consider the influence of fluid pulsation. 17. What kinds of protection lines are there for the pump? what is the function? There are 6 kinds of protection lines for the pump, which are used to protect the pump body from damage and normal operation, and set the protection pipeline of the pump according to the conditions of use. (1) Warm pump line——When the temperature of the medium is higher than 200 °C, when there is a spare pump, the DN20～25 warm pump line should be set; (2) Small flow line——When the working flow of the pump is lower than 30% of the rated flow of the pump, the small flow line of the pump running normally at the lowest flow rate should be set; (3) Balance line—for conveying a liquid with a saturated vapor pressure higher than atmospheric pressure at normal temperature or a liquid in a bubble state, in order to prevent steam from entering the pump liquid or air bubbles entering the pump, the cavitation should be balanced; (4) Bypass line – When the pump is used for trial operation or when the outlet main valve is closed under abnormal operating conditions, the pump can still be operated. Generally, a bypass valve with a limited flow hole is provided in a case where the pressure difference between the valve and the front is very high; (5) Anti-coagulation line – When conveying liquid with high pour point or high freezing point solidified at normal temperature, the backup pump and pipeline should be equipped with anti-condensation line to avoid plugging of spare pump and pipeline; (6) Safety valve line——For the volumetric pumps such as electric reciprocating pump, gear pump and screw cylinder, the safety valve line is set on the outlet side. When the outlet pressure exceeds the constant pressure value, the safety valve takes off and the fluid returns to the pump population tube. 18. What are the general requirements for the arrangement of centrifugal compressor piping? The general requirements for piping arrangements for centrifugal compressors are: (l) Centrifugal compressor housings come in two forms: vertical split type for high pressure, no pipes and other obstacles in front of the machine; horizontal split type for medium and low pressure, no upper part of the machine Other obstacles; (2) Arrangement of import and export pipelines Under the condition of satisfying thermal compensation and allowable stress, the number of elbows should be reduced as much as possible to reduce the pressure drop; (3) The inlet and outlet nozzles are generally facing downwards, and the casing is centrally supported. During operation, the amount of thermal expansion should be absorbed by the pipeline; (4) When the compressor nozzle provided in the factory is up and up, a detachable short section shall be provided on the pipe of the inlet and outlet nozzles for the compressor to be repaired. 19. What are the general points of piping design for reciprocating compressors? The general points of piping design for reciprocating compressors are: (1) The piping of the inlet and outlet of the compressor should be short and straight, and the number of elbows should be reduced as much as possible. However, when the outlet pipe is inflated, the pipe should be flexible; (2) The piping arrangement should consider the liquid flowing from the liquid to the liquid separation tank. When the pipeline has a “liquid bag”, it should be set at a low point; (3) When multiple units are arranged side by side, the valves and instruments on the inlet and outlet pipes shall be arranged in a place that is easy to operate and accessible; (4) In order to prevent the vibration of the compressor inlet and outlet pipes, the necessary vibration analysis should be carried out. The pipe arrangement should be as low as possible, and the brackets should be laid on the ground and be an independent foundation to increase the rigidity of the brackets and pipes; (5) When the medium of the compressor is flammable, the pipe will be condensed at a low point, and the high-point venting valve shall be provided with a wire plug, cap or flange cover to prevent leakage, and the pipe around the unit shall be filled with sand to avoid combustible gas. Accumulation (6) When arranging the inlet and outlet pipes of the compressor, it shall not affect the walking of the maintenance crane; (7) The pipeline of the compressor should be arranged under the operating platform, so that there is more spacious operation and maintenance space around the unit. Source: China Stainless Steel Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are more and more kinds of stainless steel flanges in the production process, for different kinds of flanges, installation methods are also different, then for everyone to introduce the correct installation sequence of stainless steel flanges. The stainless steel pipe or stainless steel pipe fittings contaminated before the stainless steel flange connection should be cleaned up. Stainless steel flanges are connected with a flange with grooved rings respectively. Flanging the ends of two pipes at 90 degrees. The flanged ends should be grinded in a flat and vertical manner without burrs, concave-convex or deformation, and the nozzles should be rounded with special tools. It can also be welded on the pipe with finished flanging short pipe. Insert the stainless steel sealing ring with O-ring on both sides into the flange with groove ring. The inner hole diameter of the stainless steel sealing ring is the same as the inner diameter of the pipe, and both are concentric circles. Connect the flange hole with bolts and connect the bolt assembly symmetrically. During the tightening process, the flanging planes of the two tubes are pushed along the axial direction, and the O-rings on both sides are uniformly compressed in a rigid contact and flexible sealing state, so that the joint is sealed. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1 Industrial pipeline on-line inspection, what parts should be focused on inspection? (1) the outlet of the compressor and pump; (2) compensator, tee, elbow (elbow), size head, branch pipe connection and dead angle of medium flow, etc. (3) pipe components and welded joints near the damaged parts of the hanger. (4) there have been problems affecting the safe operation of pipelines. (5) the pipe section in the key part of the production process and the pipe section connected with the important device or equipment; (6) pipe sections with harsh working conditions or subjected to alternating loads. 2 Why piping stress analysis? What does it contain? What are the purposes of various analyses? Ensure the safety of the pipeline itself. Ensure the safety of connected equipment; Ensure the safety of civil structures. It mainly includes static analysis and dynamic analysis. Static analysis includes: The first stress calculation of pipes under pressure, gravity and other loads – to prevent plastic deformation and failure; Secondary stress calculation under thermal expansion, cold contraction and additional displacement at the end point to prevent fatigue failure. The calculation of the force acting on the machine and equipment by the pipeline – preventing the excessive force and ensuring the normal operation of the machine and equipment; The force calculation of pipe supports and hangers provides the basis for the design of supports and hangers. The force calculation of flange on pipeline to prevent flange leakage; Piping displacement calculation to prevent pipeline collision and excessive displacement of supporting points. The dynamic analysis includes: Natural frequency analysis of gas (liquid) column in reciprocating compressor (pump) pipeline – preventing gas (liquid) column resonance; Pressure pulsation analysis of reciprocating compressor (pump) piping – control pressure fluctuation value; Analysis of natural frequencies of pipelines to prevent piping system resonance; Pipeline seismic analysis to prevent excessive seismic stress of pipelines. Stress analysis of pipelines under impact loading – to prevent pipe vibration and stress. 3 What is a primary stress? The two stress? What loads are generated by them? What are the characteristics of these two stresses? The primary stress is the stress generated by the interaction of pressure and gravity with other external loads. It is the stress required to balance external loads and increases with the increase of external loads. Characteristics: there is no self limiting nature. Secondary stress is caused by the constraints of pipeline deformation. It is caused by the thermal expansion, cold contraction and end displacement of pipeline. It is necessary to meet the continuous requirements of constraints or the deformation of the pipeline itself. Characteristics: self limiting. 4 What is pipeline flexibility? How to design flexible pipes? It is a concept that reflects the degree of difficulty of pipeline deformation, indicating the ability of pipeline to absorb heat account, cold shrinkage and other displacement deformation through its own deformation. In design, it is necessary to ensure that the pipeline is flexible enough to absorb displacement and strain, so that the length of the pipeline is as short as possible or the investment is as small as possible. Generally, the following methods are used to increase the flexibility of pipes: Change the direction of the pipeline; Waveform compensator; Choose spring hangers. 5 What is the purpose of flexible piping design? Ensure that the pipeline is flexible enough under the design conditions to prevent the following problems caused by cold shrinkage of heat account, additional displacement of end point, improper installation of pipeline support, etc. Pipeline failure caused by excessive stress or metal fatigue. Leakage occurs at piping connections. Excessive pipe thrust or torque will cause excessive stress and deformation of the equipment connected with the pipeline and affect the normal operation of the equipment. Piping failure is caused by excessive pipe thrust or moment. 6 Generally speaking, which point of stress on the pipe is larger? Why? Generally speaking, the stress on the three way and elbow pipe is larger. Because, compared with straight pipe, the stress increasing coefficient of the three way and elbow pipe is larger. 7 What displacement can the fixed bracket, the guide bracket and the supporting bracket limit? There are three functions of pipe hangers. The weight load of the pipeline (including self weight, medium weight, etc.); Limit the displacement of the pipeline to prevent unexpected displacement of the pipeline. Control vibration to control swing, vibration or impact. Fixed frame: limiting the linear displacement in three directions and the angular displacement in three directions; Guide frame: the displacement in two directions is limited. The bracket (or one-way thrust frame) restricts the linear displacement in one direction. 8 What problems should we pay attention to when designing vibrating pipe supports? The bracket should use anti vibration pipe card, not simply supported. The distance between supports should be determined by vibration analysis. The structure of scaffolds and the rooting parts of scaffolds should have enough stiffness. It is advisable to set up an independent foundation so as to avoid rooting in the beams and columns of the workshop. When the temperature of the medium is high and the thermal expansion occurs, the flexibility requirement should be satisfied. Support should be set along the ground.

Stainless steel pipe fittings are one kind of pipe fittings. They are made of stainless steel, so they are called stainless steel pipe fittings. They include: stainless steel elbows, stainless steel tees, stainless steel crosses, stainless steel reducers, stainless steel caps, etc., according to the coupling method. It is pided into four types: socket type stainless steel pipe fittings, threaded stainless steel pipe fittings, flanged stainless steel pipe fittings and welded stainless steel pipe fittings. The stainless steel elbow is used for the turning of the pipe; the flange is used to connect the pipe to the pipe, the pipe is connected to the pipe end, the stainless steel tee is used for the collection of the three pipes; the stainless steel pipe is used for the collection of the four pipes. Place; stainless steel reducer for the connection of two pipes of different pipe diameters. Main stainless steel: 304, 304L, 316|, 316L. Stainless steel pipe fittings offer 1. At present, there are mainly stainless steel pipes of 304, 201, and 301 materials on the market. Different materials have different performances. The difference between different materials is mainly reflected in the amount of nickel and chromium. The 304 stainless steel tube contains 18 chrome and 8-9 nickel. The other two materials, 201 and 301, have a chromium and nickel content of 14, 16 and 1, respectively. The higher the nickel and chromium content, the better the performance. 2. 316 stainless steel plate surface is smooth, with high plasticity, toughness and mechanical strength, acid, alkaline gas, solution and other media corrosion. It is an alloy steel that does not rust easily, but it does not rust. The corrosion resistance of stainless steel mainly depends on its alloy composition (chromium, nickel, titanium, silicon, aluminum, etc.) and the internal structure, and the main role is chromium. Chromium has high chemical stability and can form a passivation film on the steel surface to isolate the metal from the outside, protect the steel plate from oxidation, and increase the corrosion resistance of the steel plate. After the passivation film is destroyed, the corrosion resistance is lowered. The price is 100-120 yuan, 3. 200 stainless steel pipe price quotes, also need to look at the specifications and wall thickness. So not the same requirements, not the same price quote. Wenzhou Rongrui stainless steel price is reasonable. 4. In terms of price, stainless steel pipes are generally determined by weight. In the market, they are generally more than ten yuan a kilogram. However, for some industrial purposes, large quantities of pipes are required, usually in tons. unit of measurement. Stainless steel pipe fittings 1 Corrosion resistance Most stainless steel products require good corrosion resistance. Some foreign merchants also carry out corrosion resistance test on products: use NACL aqueous solution to warm to boiling, after a period of time, pour off the solution, wash and dry, weigh the weight loss, to determine the Degree of corrosion (Note: When the product is polished, the content of Fe in the abrasive cloth or sandpaper will cause rust on the surface during the test) 2. Weldability The requirements for welding performance vary from product to product. A type of tableware generally does not require welding performance, and even includes some pot enterprises. However, most products require good welding performance of raw materials, such as second-class tableware, thermos cups, steel pipes, water heaters, water dispensers, etc. 3, polishing performance (BQ) At present, stainless steel products are generally polished during the production process, and only a few products such as water heaters, water dispenser liners, etc. do not need to be polished. Therefore, this requires a good polishing performance of the raw material. Summary of standards, quotations, characteristics, etc. of stainless steel pipe fittings Stainless steel pipe welding technology and requirements For manual arc welding, the welding machine adopts DC reverse connection, and the argon arc welding adopts DC positive connection; Before welding, the wire should be brushed off with stainless steel wire brush and washed with acetone; the electrode should be dried at 200-250 °C for 1 h, with the use; Clean the oil stains within 25 mm on both sides of the groove of the workpiece before welding, and wash the sides of the groove with acetone for 25 mm; When argon arc welding, the nozzle diameter is Φ2 mm, tungsten is extremely 钵 tungsten, the specification is Φ2.5 mm; 5 argon arc welding stainless steel, the back must be filled with argon gas protection to ensure the back forming. The method of partially filling argon in the pipeline has a flow rate of 5-14 L/min and a front argon flow rate of 12-13 L/min. Welding precautions for stainless steel pipe fittings In order to prevent the erosion between the eyes due to heating, the welding current should not be too large, 20% less than the carbon steel electrode, the arc should not be too long, the layer is fast cold, and the narrow weld bead is suitable. The hardening property of stainless steel pipe fittings is relatively good after welding, which is convenient for cracks. If it is welded with a typical stainless steel pipe fitting, it is necessary to perform preheating above 300 °C and slow cooling at 700 °C after welding. If the weldment cannot be subjected to post-weld heat treatment, a stainless steel pipe electrode should be used. Stainless steel pipe fittings, in order to improve the corrosion resistance and weldability, appropriately add the appropriate amount of invariable elements Ti, Nb, Mo, etc., the weldability is better than the stainless steel pipe fittings. When accepting the same chrome stainless steel electrode, it should be preheated above 200 °C and tempered at 800 °C after welding. If the weldment cannot be heat treated, a chrome-nickel stainless steel electrode should be used. Stainless steel pipe electrode has fine corrosion resistance and oxidation resistance, commonly used in chemical, fertilizer, petroleum, medical machinery manufacturing. Stainless steel pipe fittings have titanium calcium type and low hydrogen type. Titanium-calcium type can be used for AC and DC, but the AC penetration is shallower and the redness is convenient. Therefore, the DC power supply is accepted as a whole. Stainless steel pipe fittings have certain corrosion resistance (oxidizing acid, organic acid, cavitation), heat resistance and wear resistance. All used in power stations, chemicals, oil and other equipment and equipment. Stainless steel pipe fittings have poor weldability. Care should be taken to select the appropriate welding electrode before welding and heat treatment. The electrode should be dry when it is operated. The titanium calcium type should be dried at 150 °C for 1 hour. The low hydrogen type should be dried at 200-250 °C for 1 hour (can not be dried repeatedly, otherwise the coating is easy to crack and peel off), and the electrode is protected. The viscous oil and other dirt are not allowed to cause the weld to increase the carbon content and affect the quality of the weldment. When welding stainless steel pipe fittings, it is repeatedly heated to precipitate carbides, which reduces corrosion resistance and mechanical performance. Formula for calculating the weight of stainless steel pipe fittings 1. Stainless steel round tube: (outer diameter – thickness) * thickness * tube length * 0.02491, the theoretical weight of the example 6 m 51 round tube 0.9 solid thickness is (51-0.9) * 0.9 * 6 * 0.02491 = 6.74; 2. Stainless steel square tube: (outer diameter * 4 / 3.14 – thickness) * thickness * tube length * 0.02491, the theoretical weight of the example 6 m 25 square tube 0.9 real thickness is (25 * 4 / 3.14 – 0.9) * 0.9 * 6 *0.02491=4.16; 3. Stainless steel rectangular tube: [(length + width) * 2 / 3.14 – thickness] * thickness * tube length * 0.02491, the theoretical weight of the example 6 m 30 * 10 square tube 0.9 solid thickness is [(30 + 10) * 2 /3.14-0.9]*0.9*6*0.02491=3.31; 4. In the formula, the unit of outer diameter and wall thickness is millimeter (mm), the unit of tube length is meter (m), and the calculated weight unit is kilogram (kg). Common problems with stainless steel fittings There are mainly the following, specifically: 1. Uneven wall thickness of sanitary stainless steel pipe fittings The uneven wall thickness of sanitary stainless steel pipe fittings mainly occurs in the most deformed parts of stainless steel pipe fittings, such as the wall thickness of the back of the elbow is thinner than other parts; the wall thickness of the pipe mouth and the stainless steel pipe body are not equal. In order to check these problems, the commonly used measuring tools such as calipers are not easy to detect, and only the ultrasonic thickness gauge can be used. 2. The hardness exceeds the standard The problem of excessive hardness is mainly due to the heat treatment process after forming, and the solution is to perform a heat treatment again with the correct heat treatment process. 3. Inspection of stainless steel pipe fittings before delivery and after arrival Inspection plays an important role as the last step in ensuring the quality of sanitary stainless steel fittings, especially for stainless steel fittings subjected to high temperature and pressure and flammable and highly toxic media. Stainless steel pipe fittings, used as pipes for conveying fluids, such as petroleum, natural gas, water, gas, steam, etc., steel pipes subjected to fluid pressure must be hydraulically tested to test their pressure resistance and quality, and do not occur under the specified pressure. Leakage, wetting or expansion is qualified. In addition, when the bending and torsional strength are the same, the weight is light, so it is also widely used in the manufacture of mechanical parts and engineering structures. Source: China Stainless Steel Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

DN DN refers to the nominal diameter of the pipe. Note: This is neither the outer diameter nor the inner diameter; it should be related to the imperial unit in the initial development of the pipeline engineering; it is usually used to describe the galvanized steel pipe. Its correspondence with the imperial units is as follows: 1 1/4 inch tube: 1 1/4 inch: DN32; 1/2 Inch tube: 1 1/2 inch: DN40; 2 inch tube: 2 inches: DN50; 3 inch tube: 3 inches: DN80 (also marked DN75 in many places); 4 inch tube: 4 inches: DN100; De De mainly refers to the outer diameter of the pipe, generally marked with De, and needs to be marked as the outer diameter X wall thickness; mainly used for description: seamless steel pipe, PVC and other plastic pipes, and other pipes requiring a clear wall thickness. Take galvanized welded steel pipe as an example. The two methods of marking with DN and De are as follows: DN20 De25×2.5mm DN25 De32×3mm DN32 De40×4mm DN40 De50×4mm We are accustomed to using DN to label welded steel pipes. It is rarely used to mark pipes without involving wall thickness; however, labeling plastic pipes is another matter; it is related to industry habits, during actual construction. The pipes we call 20, 25, and 32, etc., refer to De, not to DN. There is a difference between them. It is easy to cause losses in the procurement and construction process without knowing it. The connection of the two pipe materials is nothing more than: threaded connection and flange connection. Other connections are used sparingly. Both the galvanized steel pipe and the PPR pipe can be connected by the above two types, but the pipe thread of less than 50 is more convenient, and the flange of more than 50 is relatively reliable. Note: If the metal pipes of two different materials are connected, it is necessary to consider whether the primary battery reaction will occur, otherwise the corrosion speed of the active metal material pipe will be accelerated. It is best to use flange connection and use rubber gasket type insulation material to The metal is separated, including the bolts are separated by a gasket to avoid contact. The respective ranges of De, DN, d, and ф! De– PPR, PE pipe, polypropylene pipe Outer diameter DN– Polyethylene (PVC) pipe, cast iron pipe, steel-plastic composite pipe, galvanized steel pipe nominal diameter a D– Nominal diameter of concrete pipe ф– Nominal diameter of seamless steel pipe, its specification is, for example, ф100:108 × 4 DN15-ф22mm, DN20-ф27mm, DN25-ф34mm, DN32-ф42mm, DN40-ф48mm, DN50-ф60mm, DN65-ф76 (73) mm, DN80-ф89mm, DN100-ф114mm, DN125-ф140mm, DN150-ф168mm, DN200-ф219mm, DN250-ф273mm, DN300-ф324mm, DN350-ф360mm, DN400-ф406mm, DN450-ф457mm, DN500-ф508mm, DN600-ф610mm, DN15-ф18mm, DN20-ф25mm, DN25-ф32mm, DN32-ф38mm, DN40-ф45mm, DN50-ф57mm, DN65-ф73mm, DN80-ф89mm, DN100-ф108mm, DN125-ф133mm, DN150-ф159mm, DN200-ф219mm, DN250-ф273mm, DN300-ф325mm, DN350-ф377mm, DN400-ф426mm, DN450-ф480mm, DN500-ф530mm, DN600-ф630mm. Source: China Stainless Steel Pipelines Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

In engineering design, the pressure level of the nozzle flange of the container is usually given by the professional of the process system. The following factors should be considered when selecting the pressure rating of the takeover flange. 1 Design pressure and design temperature of the container; 2 Connection standards of valves directly connected to them, valves, fittings, temperature, pressure and liquid level. 3 The influence of thermal stress of process piping (especially high temperature and heat pipe) on the flange of nozzle. 4 Characteristics of process and operation medium: For vessels operated in vacuum, the pressure level of nozzle flange should not be less than 0.6 MPa when the vacuum degree is less than 79.980 kPa (600 mmHg), and for vessels operated in vacuum from 9.980 kPa to 101.175 kPa (600-759 mmHg), the pressure level of nozzle flange should not be less than 1.0 MPa. For explosive or toxic medium, the pressure level of pipe flange should not be less than 1.0 MPa; for toxic medium of high and extreme harm or strong permeability, the pressure level of nozzle flange should not be less than 1.6 MPa. 5 The flange with neck butt welded pipe should be used as far as height, extreme hazardous medium and three types of containers should be adopted. Source: China Stainless Steel Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Factors affecting gasket and packing seal (1) Surface condition of sealing surface: the shape and surface roughness of sealing surface have certain influence on sealing performance, and smooth surface is beneficial to sealing. The soft gasket is insensitive to the surface condition because of its easy deformation, while the hard gasket is greatly affected by the surface condition. (2) Contact width of sealing surface: the larger the contact width between sealing surface and gasket or filler, the longer the path of fluid leakage, the greater the loss of flow resistance, thus conducive to sealing. But under the same compression force, the larger the contact width, the lower the sealing pressure. Therefore, the appropriate contact width should be sought according to the material quality of the seals. (3) Properties of the fluid: The viscosity of the liquid has a great influence on the sealing of the packing and gasket. The fluid with high viscosity is easy to seal because of its poor fluidity. The viscosity of the liquid is much larger than that of the gas, so the liquid is easier to seal than the gas. Saturated vapor is easier to seal than superheated vapor because it will condensate droplets and block the passage between the sealing surfaces. The larger the molecular volume of the fluid is, the easier it is to be blocked by a narrow sealing gap, which is easy to seal. The wettability of liquid to seal material also has a certain effect on sealing. The liquid which is easy to soak is easy to produce leakage due to the capillary action of the micro-pores in the gasket and filler. (4) the temperature of the fluid: the temperature affects the viscosity of the liquid, thereby affecting the sealing performance. When the temperature increases, the viscosity of the liquid decreases and the viscosity of the gas increases. On the other hand, temperature changes often deform the seal assembly and cause leakage easily. Material of gaskets and fillers: Soft materials are prone to elastic or plastic deformation under preloading force, thus blocking the passage of fluid leakage, thus conducive to sealing; but soft materials generally can not withstand the role of high-pressure fluid. The corrosion resistance, heat resistance, compactness and hydrophilicity of sealing materials have certain effects on sealing. Specific pressure of sealing surface: The normal force acting on the unit contact surface between sealing surface is called the sealing specific pressure. The sealing surface specific pressure is an important factor affecting the sealing performance of gaskets or packing. Usually, by applying pre-tightening force on the sealing surface to produce a certain specific pressure, so that the deformation of the seal to reduce or eliminate the gap between the sealing contact surfaces, to prevent the flow through, to achieve the purpose of sealing. It should be pointed out that the effect of fluid pressure will change the relative pressure of the sealing surface. Although the increase of specific pressure of sealing surface is beneficial to sealing, it is limited by the extrusion strength of sealing material. For dynamic sealing, the increase of specific pressure of sealing surface will also cause the corresponding increase of friction resistance. Influence of external conditions: vibration of pipeline system, deformation of connecting components, offset of installation position and other reasons will produce additional force on the seal, thus causing adverse effects on the seal. Especially, vibration will cause periodic changes in the pressure between the sealing surfaces, so that the connection bolt relaxation, resulting in seal failure. The cause of vibration may be external or possibly caused by fluid flow inside the system. In order to make the seal reliable, the above factors must be carefully considered, and the manufacture and selection of gaskets and fillers are very important. Source: China Stainless Steel Gaskets Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Screw is the most common type of fixing device in daily life. Usually it is used for fastening. Of course, it is hoped that it will be tightened, but it also adds some trouble to the subsequent maintenance technicians. When the screw is severely rusted, it is difficult to use a wrench to screw it down. For this reason, the workers will use various methods such as knocking, dripping, burning, punching, welding, foaming, and the like. First of all, let’s talk to you about several commonly used methods: Method one: knock Severely rusted screws should not be hardened with a wrench to prevent them from slipping and cornering, twisting the screws or screwing the wrench. At this point, you can tap the handle of the wrench with a hammer, and the rusted screws will often loosen to unscrew. Method two: drop If the screw is not severely rusted, you can try to drip first. If you can’t open it, you can drop a little oil or vegetable oil along the gap between the screw and the nut. With wire cutters and wrenches, you can easily unscrew it. (The oil does not work for rusted screws and will affect disassembly) Method three: burn Some screws are severely rusted and can be fire attacked. step: (1) Fully grill the screws and nuts with a gas welding flame. (2) Then apply oil or sewing machine oil to the red-hot screw. (3) The screw is heated and expanded, and the rust between the screw and the nut is squeezed to increase the gap. After the oil drops, the screw shrinks rapidly and cools, and the gap between the screw and the nut is further increased. After the oil flows in, the screw can be unscrewed. Note that this method should be used with caution for screws with plastic parts nearby, and the screws that have been burned should not be reused. Method four: rush Some of the tops of the screws are deformed by a word or cross, which cannot be removed with a screwdriver, a wrench or a wire cutter. The impact method can be used. step: (1) First, use a hammer and a flat-blade screwdriver to impact a V-shaped groove on the vertical surface of the top of the screw; (2) Then adjust the angle of the flat-blade screwdriver to impact in the direction in which the thread is unscrewed; (3) After the screw is loosened, the screw can be screwed out with a wire cutter. Recommended for everyone is a very practical method – induction heating This method is simple to operate and is suitable for the disassembly or installation of various metal parts, such as drive parts, bearings, housings, gears, bolts, nuts, pipe fittings and small parts. It is versatile and suitable for use in confined spaces. Moreover, the local heating can be accurately performed, so that the area outside the heated workpiece still retains the original temperature; and the heated workpiece is expanded and loosened, which is convenient for disassembly or installation. Especially for bolts and nuts, this is the most ideal solution. When bolts and nuts are stuck, the traditional method is nothing more than cutting or gun heating. However, whether it is cutting or gun heating, the resulting open flame or spark is likely to cause greater danger or damage to other parts, or local area pollution, and this inductive heating is not only faster, but also safer. And it will not cause any pollution. Source: China Stainless Steel Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

1 The second-generation duplex stainless steel is generally called standard duplex stainless steel. Its composition is ultra-low carbon and nitrogen. Its typical composition is 22% cr + 5% ni + 0.17% n, compared with the first generation duplex stainless steel. 2205 further increases the nitrogen content and enhances the stress corrosion resistance and pitting resistance in an acidic medium with a high chloride ion concentration. Nitrogen is a strong austenite forming element and is added to the duplex stainless steel to improve the strength of the steel without significantly impairing the plastic toughness of the steel, and inhibiting the precipitation and retardation of the carbide. 2 Tissue characteristics: Duplex stainless steel accounts for about half of the austenite and ferrite in the solid solution in the greenhouse, and has two-phase structure characteristics. It retains the characteristics of small ferritic stainless steel guide, small pitting resistance, crack and chloride stress corrosion, austenitic stainless steel with good toughness, low brittle transition temperature, resistance to intergranular corrosion, mechanical properties and welding. Good performance. 3 The performance is outstanding in yield strength and stress corrosion resistance. Duplex stainless steel is nearly twice as high as the austenitic stainless steel. Under the same pressure rating conditions, materials can be saved. The austenitic stainless steel has a low coefficient of linear thermal expansion and is close to that of low carbon steel. It makes the connection of duplex stainless steel and carbon steel suitable, which has great engineering significance. Forging and cold forming are not as good as austenitic stainless steel. 4 Weldability: Duplex stainless steel 2205 has good weldability and is less sensitive to weld cold cracks and hot cracks. Usually no preheating before welding, no heat treatment after welding. Due to the high nitrogen content, the single-phase ferrite tendency of the heat-affected zone is small. When the welding material is selected reasonably, the welding line energy control, the welding head has good comprehensive performance. 5 Thermal cracking: The sensitivity of hot cracks is much smaller than that of austenitic stainless steels. This is because the amount of nickel is not high, and impurities which easily form a low-melting eutectic are extremely small, and it is difficult to produce a low-melting liquid film. In addition, the crystal grains do not have a sharp increase in temperature at high temperatures. 6 Heat-affected zone embrittlement: The main problem of duplex stainless steel welding is not in the weld, but in the heat affected zone. Because the heat-affected zone is in a fast-cooling non-equilibrium state under the thermal cycle of welding, more ferrite is always retained after cooling, thereby increasing the corrosion tendency and hydrogen-induced crack (brittle) sensitivity. 7 Welding metallurgy: During the welding process of duplex stainless steel, a series of changes occur in the microstructure of the weld metal and heat affected zone under the action of thermal cycling. At high temperatures, the metallurgical structure of all duplex stainless steels is entirely composed of ferrite, which is precipitated during cooling. The amount of austenite precipitation is affected by many factors. 8 Comparative requirements: The mechanical properties and corrosion resistance of duplex stainless steel welded joints depend on whether the welded joints can maintain proper proportions. Therefore, the welding is based on how to ensure the two-phase structure. When the amount of ferrite and austenite is close to 50%, the performance is better, close to the performance of the base metal. Changing this relationship will reduce the corrosion resistance and mechanical properties of duplex stainless steel welded joints. Duplex stainless steel 2205 ferrite content of the best 45%, too low ferrite content of less than 25% will lead to a decrease in strength and resistance to stress corrosion cracking; excessive ferrite content greater than 75% will also be detrimental to Corrosion resistance and reduced impact toughness. 9 Influencing factors: The equilibrium relationship between ferrite and austenite in welded joints is affected by the content of alloying elements in steel and by the filling metal, welding thermal cycle and shielding gas. 10 The influence of alloying elements: According to research and a large number of experiments, it is found that the nitrogen content of the base metal is very important. Nitrogen plays an important role in ensuring a sufficient amount of austenite in the weld metal and in the post-weld heat affected zone. Like nickel, nitrogen forms austenite and enlarges austenite. However, nitrogen has a greater capacity than nickel to prevent single-phase ferrite from occurring after welding and to prevent the precipitation of harmful metal phases. Due to the effect of the welding heat cycle, when the self-welding or filler metal composition is the same as that of the base material, the amount of ferrite of the weld metal increases sharply, and even pure ferrite structure appears. In order to suppress the excessive increase of ferrite in the weld, the weld metal which is dominated by austenite is the welding tendency of duplex stainless steel. Generally, it is adopted to increase nickel or nitrogen in the welding material. Usually, the content of nickel is 2%-4% higher than that of the base material. For example, the nickel content of the 2205 filler metal is as high as 8%-10%. The filler material containing nitrogen is more stable than the filler material which only improves nickel, but nitrogen is added. It not only delays the precipitation between metals, but also improves the strength and corrosion resistance of the weld metal. At present, the filler material is generally based on the increase of nickel, and then the nitrogen content of the base material is equivalent. 11 For duplex stainless steel 2205, sandvik 22.8.3L (ER2209) welding wire is used for tungsten argon arc welding, and Avesta 2205AC/DC welding rod is used for electrode arc welding to meet the requirements of welding materials. These characteristics of duplex stainless steel 2205 and welding materials on alloying elements provide a certain range for the selection of welding process parameters, ie welding line energy, which is very advantageous for welding. 12 Thermal cycling: The most important feature of duplex stainless steel welding is that the welding thermal cycle has an effect on the microstructure inside the welded joint. There is a phase change in both the weld and the thermal star zone, which has a great influence on the performance of the welded joint. Therefore, multi-layer multi-pass welding is beneficial, the subsequent bead has a heat treatment effect on the front bead, and the ferrite in the weld metal is further transformed into austenite, which becomes a two-phase structure dominated by austenite; The austenite phase in the heat-affected zone adjacent to the weld is correspondingly increased, and the ferrite grains can be refined to reduce the precipitation of carbides and nitrides from the grains and grain boundaries, thereby making the microstructure of the entire welded joint. Significant improvement. It is also because of the influence of the welding heat cycle that the weld bead which is required to contact the medium during the welding of the duplex stainless steel should be welded, which is exactly the opposite of the welding sequence requirement of the austenitic stainless steel. 13 Effect of process parameters: The number of welding processes, ie the welding line energy, also plays a key role in the balance of the two-phase structure. Since the duplex stainless steel is 100% ferrite at high temperature, if the line energy is too small, the heat affected zone cools quickly, and the austenite does not have enough precipitation of ferrite to be kept cold in the greenhouse. If the line energy is too large, the cooling rate is too slow. Although a sufficient amount of austenite can be obtained, it also causes the ferrite grain growth in the heat-affected zone and the precipitation of the harmful metal phase with the same σ, resulting in brittleness of the joint. In order to avoid this, the best measure is to control the weld line energy and the interlayer temperature and use a filler metal. 14 Effect of protective gas: In tungsten argon arc welding, 2% nitrogen can be added to argon to prevent the surface of the weld from losing nitrogen due to diffusion, which helps the balance between ferrite and austenite. Source: China 2205 Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)