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At present, China’s valve industry has not only become the world’s number one in six: the world’s production area, the world’s first equipment level, the world’s largest production capacity, the world’s first valve production, the world’s first market demand, and the world’s largest overcapacity. Moreover, it is more than four and three fast: the largest number of enterprises, the largest number of employees, the largest number of valve orders, the largest variety of production; the fastest delivery, the fastest valve development, the industry’s fastest progress. ” The number of valve enterprises in China ranks first in the world, and there are more than 6,000 valve companies of various sizes. There are several types of valve products available, more than 3,500 varieties and more than 40,000 specifications. Widely used in various fields of social life, industrial production and manufacturing. From the perspective of application distribution, how many types of valves are there in China? (1) Valves for urban construction: The urban construction department generally adopts low-pressure valves and is currently developing in the direction of environmental protection and energy conservation. Environmentally friendly rubber plate valves, balancing valves, and mid-line butterfly valves and metal-sealed butterfly valves are gradually replacing low-pressure iron gate valves. Most of the valves used in urban construction in the country are balance valves, soft seal gate valves, butterfly valves, etc. (2) Valves for urban heating: In the urban heat generation system, a large number of metal sealing butterfly valves, horizontal balance valves and direct-buried ball valves are needed. Because of such valves, the longitudinal and lateral hydraulic imbalance problems of the pipeline are solved, and the purpose of energy saving and heat balance is achieved. (3) Valves for environmental protection: In the domestic environmental protection system, the water supply system mainly needs the middle line butterfly valve, the soft seal gate valve, the ball valve, and the exhaust valve (used to remove the air in the pipeline). Sewage treatment systems mainly require soft sealing gate valves and butterfly valves. (4) Valves for city gas: City gas accounts for 22% of the entire natural market, and the valve usage is large, and there are many types. Ball valves, plug valves, pressure reducing valves, and safety valves are mainly required. (5) Valves for long-distance pipelines: Long-distance pipelines are mainly crude oil, finished products and natural pipelines. The valves that require a large amount of such pipelines are forged steel three-piece full-bore ball valves, sulfur-resistant slab gate valves, safety valves, and check valves. (6) Valves for petrochemical plants: a, oil refining device. Most of the valves required for this device are pipeline valves, mainly gate valves, globe valves, check valves, safety valves, ball valves, butterfly valves, steam traps, among which the gate valve accounts for about 80% of the total number of valves. 3 to 5% of investment). b. Chemical fiber device. Chemical fiber products mainly include polyester, acrylic and vinylon. Ball valve and jacketed valve (jacketed ball valve, jacketed gate valve, jacketed shut-off valve) for the valve to be used. c, acrylonitrile device. The device generally needs to use the valve produced by the api scale, mainly for the gate valve, the stop valve, the check valve, the ball valve, the trap, the needle valve, the plug valve, wherein the gate valve accounts for about 75% of the total valve. d, ammonia plant. Because the synthesis of ammonia and purification methods are different, the process flow is different, and the technical functions of the required valves are also different. At present, domestic ammonia plants mainly need gate valves, globe valves, check valves, traps, butterfly valves, ball valves, diaphragm valves, regulating valves, needle valves, safety valves, and high temperature cryogenic valves. e, polyethylene device. Gate valves, globe valves, check valves, and lift-rod ball valves account for the majority, with gate valves needing to take the lead. In the “10th Five-Year Plan”, there are still 6 sets of ethylene plants with an annual output of 660,000 tons, and the demand for valves is considerable. In addition, large-scale ethylene and high-pressure polyethylene devices require ultra-high temperature, lower temperature and ultra-high pressure valve series. f, air separation device. “Air separation” means air separation. The device mainly requires a shut-off valve, a safety valve, a check valve, a regulating valve, a ball valve, a butterfly valve, and a cryogenic valve. g, polypropylene device. Polypropylene is a polymer compound which is polymerized by using propylene as a raw material. The device mainly requires a gate valve, a shut-off valve, a check valve, a needle valve, a ball valve, and a steam trap. Among them, the shut-off valve accounts for 53.4% of the total valve data of the device, the gate valve accounts for 25.1%, the trap accounts for 7.7%, the safety valve accounts for 2.4%, the regulating valve and the cryogenic valve and other 11.4%.e, ethylene device, ethylene device It is a leading device for petrochemical industry, which requires a wide variety of valves. (7) Valves for power stations: The construction of power stations in China is developing in the direction of large-scale, so it is necessary to use large-diameter and high-pressure safety valves, pressure reducing valves, globe valves, gate valves, butterfly valves, emergency blocking valves and flow control valves, and spherical sealing instrument shut-off valves. In the “10th Five-Year Plan”, except for the provinces of Inner Mongolia and Guizhou, which can build more than 200,000 kilowatts, other provinces and cities can only build units of more than 300,000 kilowatts. (8) Metallurgical valves: In the metallurgical industry, the behavior of alumina mainly requires the use of wear-resistant slurry valves (in the flow-type shut-off valve) and the adjustment of the trap. The steelmaking industry mainly needs metal sealed ball valves, butterfly valves and oxidized ball valves, cut-off flash and four-way reversing valves. (9) Marine flat applicable valve: With the development of offshore oilfield exploitation, the amount of valves required for ocean flat hair has also gradually increased. Offshore valves, check valves, and multi-way valves are required for offshore platforms. Source: China Stainless Steel Valves Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Stainless steel pipe is a kind of hollow long steel. which is used as a pipeline for conveying fluids. such as oil. natural gas. water. gas. steam. etc. In addition. when the bending and torsional strength are the same. the weight is light. so Widely used in the manufacture of mechanical parts and engineering structures. Also used to produce a variety of conventional weapons. barrels. shells and so on. Because many pipes are exposed to the outdoors for a long time or buried in the ground. they are easily corroded and rusted and corroded. Therefore. the choice of stainless steel pipe is a good way to avoid these drawbacks and improve the service life of stainless steel pipe. Common stainless steel pipe model 304 stainless steel pipe full name SUS304 stainless steel pipe; SUS304 stainless steel tube is a stainless steel tube of the US grade material. the domestic grade is equivalent to 0Cr19Ni9 stainless steel tube. usually replaced by 0Cr18Ni9; 201 series – chromium-nickel-manganese austenitic stainless steel; 300 series – chromium-nickel austenitic stainless steel; 301 – good ductility. used for molding products. it can also be quickly hardened by mechanical processing. good weldability. abrasion resistance and fatigue strength better than 304 stainless steel; 302 – corrosion resistance is the same as 304. because the carbon content is relatively high and the strength is better; 303—by adding a small amount of sulfur and phosphorus to make it easier to cut than 304; 304 – general model; that is 18/8 stainless steel. GB grade is 0Cr18Ni9; 309 – better temperature resistance than 304; 316—After 304. the second most widely used steel grade. mainly used in the food industry and surgical equipment. adding molybdenum to obtain a special structure resistant to corrosion; since it has more than 304 Good resistance to chloride corrosion is therefore also used as “ship steel”; SS316 is usually used in nuclear fuel recovery units; 18/10 grade stainless steels are usually also suitable for this application level; Model 321 – except for the addition of titanium to reduce the risk of corrosion of the material welds. other performance similar to 304; 400 series – ferritic and martensitic stainless steel; 408 – good heat resistance. weak corrosion resistance. 11% Cr. 8% Ni; 409 – the cheapest model (British and American). usually used as a car exhaust pipe. is a ferritic stainless steel (chrome steel); 410—Martensite (high-strength chrome steel). good wear resistance and poor corrosion resistance; 416—The addition of sulfur improves the processing properties of the material; 420—“cutting grade” martensitic steel. similar to Brinell high-chromium steel. the earliest stainless steel. also used for surgical knives. can be very bright; 430—ferritic stainless steel. used for decoration. for example. for automotive accessories. good formability. but poor temperature resistance and corrosion resistance; 440—high-strength cutting tool steel with slightly higher carbon content. After proper heat treatment. it can obtain higher yield strength and hardness can reach 58HRC. It belongs to the hardest stainless steel. The most common application example is “shaving blade”. “. there are three commonly used models: 440A. 440B. 440C. in addition to 440F (easy processing type); 500 series – heat-resistant chrome alloy steel; 600 series – martensitic precipitation hardening stainless steel; 630 – the most commonly used type of precipitation hardened stainless steel. usually also called 17-4; 17% Cr. 4% Ni. Classification of stainless steel pipes 1. Classification by production mode Stainless steel pipes are pided into two types according to production methods: seamless pipes and welded pipes. Seamless steel pipes can be pided into hot rolled pipes. cold rolled pipes. cold drawn pipes and extruded pipes. Cold drawing and cold rolling are secondary to steel pipes. Processing; welded pipes are pided into straight welded pipes and spiral welded pipes. 2. According to the shape of the section Stainless steel tubes can be pided into round tubes and shaped tubes according to the cross-sectional shape. The special-shaped tube has a rectangular tube. a rhombic tube. an elliptical tube. a hexagonal tube. an eight-sided tube. and various cross-section asymmetric tubes. Shaped tubes are widely used in a variety of structural parts. tools and mechanical parts. Compared with the round pipe. the special-shaped pipe generally has a large moment of inertia and a section modulus. and has a large bending and torsion resistance. which can greatly reduce the structural weight and save steel. Stainless steel pipes can be pided into equal-section pipes and variable-section pipes according to the longitudinal section shape. The variable section pipe has a conical pipe. a stepped pipe and a periodic section pipe. 3. By material classification Stainless steel pipes are pided into ordinary carbon steel pipes. high-quality carbon structural steel pipes. alloy structural pipes. alloy steel pipes. bearing steel pipes. stainless steel pipes. and bimetallic composite pipes. coatings and coated pipes for saving precious metals and meeting special requirements. . 4. According to the shape of the tube end The stainless steel tube can be pided into a light pipe and a wire tube (threaded steel pipe) according to the state of the pipe end. The wire tube can be pided into ordinary car wire tube (transfer water. gas and other low pressure pipes. using ordinary cylindrical or conical pipe thread connection) and special threaded pipe (oil. geological drilling pipe. for important wire pipe. use Special thread connection). for some special tubes. in order to compensate for the influence of the thread on the strength of the tube end. the tube end is usually thickened (inner thickening. outer thickening or inner and outer thickening) before the wire. 5. Classification by purpose According to the application. it can be pided into oil well pipe (casing. oil pipe and drill pipe. etc.). pipeline pipe. boiler pipe. mechanical structural pipe. hydraulic pillar pipe. gas cylinder pipe. geological pipe. chemical pipe (high pressure fertilizer pipe. petroleum cracking pipe). ) and ships and other pipes. 6. Classification by production method Seamless pipe – hot rolled pipe. cold rolled pipe. cold drawn pipe. extruded pipe. top pipe; Welded pipe According to the process points – arc welded pipe. electric resistance welded pipe (high frequency. low frequency). gas welded pipe. furnace welded pipe; According to the weld seam – straight seam welded pipe. spiral welded pipe; 7. Classification by section shape Simple section steel pipe – round steel pipe. square steel pipe. elliptical steel pipe. triangular steel pipe. hexagonal steel pipe. diamond steel pipe. octagonal steel pipe. semicircular steel circle. others; Complex section steel pipe – unequal hexagonal steel pipe. five-petal plum-shaped steel pipe. double convex steel pipe. double concave steel pipe. melon-shaped steel pipe. conical steel pipe. corrugated steel pipe. case steel pipe. and others. 8. According to wall thickness classification Thin-walled steel pipes and thick-walled steel pipes. (1) Welded pipe classification 1. Classified by purpose It is also pided into general welded pipe. galvanized welded pipe. blown oxygen welded pipe. wire casing. metric welded pipe. idler pipe. deep well pump pipe. automobile pipe. transformer pipe. electric welding thin wall pipe. electric welding shaped pipe and spiral welded pipe. General welded pipe: The general welded pipe is used to transport low pressure fluid. Made of Q195A. Q215A. Q235A steel. It can also be made of other mild steel that is easy to weld. The steel pipe is subjected to experiments such as water pressure. bending and flattening. and has certain requirements on the surface quality. Usually. the delivery length is 4-10 m. and the fixed length (or double rule) is often required for delivery. The specification of the welded pipe is expressed by the nominal diameter (mm or inch). The nominal diameter of the welded pipe is different from the actual one. The welded pipe has two kinds of ordinary steel pipe and thick steel pipe according to the specified wall thickness. The steel pipe is pided into two types according to the pipe end form with and without thread. Galvanized steel pipe: In order to improve the corrosion resistance of the steel pipe. the general steel pipe (black pipe) is galvanized. Galvanized steel pipes are pided into hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing galvanized layer is thick and the cost of electro-galvanizing is low. Blown oxygen welded pipe: used as a steel pipe for oxygen blowing. generally with small diameter welded steel pipe. the specifications are from 8/8 inch to 2 inch. Made of 08. 10. 15. 20 or Q195-Q235 steel strip. For corrosion protection. some are aluminized. Wire casing: that is. ordinary carbon steel electric welded steel pipe. used in concrete and various structural power distribution projects. commonly used nominal diameter from 13-76mm. The sleeve of the wire sleeve is thin. and most of it is coated or galvanized. and a cold bend test is required. Metric welded pipe: Specification for seamless pipe form. welded steel pipe with outer diameter * wall thickness mm. tropical or cold band welding with ordinary carbon steel. high quality carbon steel or ordinary low alloy steel. or tropical After welding. it is made by cold dialing method. Metric welded pipes are pided into general and thin walls. which are commonly used as structural members. such as transmission shafts. or for conveying fluids. Thin walls are used to produce furniture. lamps. etc.. to ensure the strength and bending test of steel pipes. Roller tube: used for belt conveyor roller welded steel pipe. generally made of Q215. Q235A. B steel and 20 steel. diameter 63.5-219.0mm. The pipe bending degree. the end surface should be perpendicular to the center line. and the ellipticity is required. Generally. the water pressure and the flattening test are performed. Transformer tube: used to manufacture transformer heat pipe and other heat exchangers. It is made of ordinary carbon steel and requires flattening. flare. bending and hydraulic test. Steel pipes are delivered in fixed lengths or multiples. which have certain requirements for the bending of steel pipes. Shaped tube: square tube. rectangular tube. hat tube. empty steel door and window steel tube welded by ordinary carbon knot structural steel and 16Mn steel. mainly used as agricultural machinery components. steel window doors. etc. Electric welding thin wall tube: mainly used for making furniture. toys. lamps and so on. In recent years. thin-walled tubes made of stainless steel strips have been widely used. such as high-grade furniture. decoration. and fences. Spiral welded pipe: It is made by rolling a low carbon carbon structural steel or a low alloy structural steel strip into a tube blank at a certain angle of a helix (called a forming angle). and then welding the pipe joint to make it narrower. The strip produces large diameter steel tubes. Spiral welded pipe is mainly used for oil and natural gas transmission pipelines. and its specifications are expressed by outer diameter * wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipe shall ensure that the hydraulic test and the tensile strength and cold bending performance of the weld are in compliance with the regulations. (2) Classification of spiral tubes Spiral submerged arc welded pipe for pressure fluid transportation is mainly used for conveying oil and natural gas pipelines. The steel pipe has strong pressure bearing capacity and good plasticity. which is convenient for welding and processing. Generally. spiral submerged arc welded steel pipe for low pressure fluid transportation adopts double-sided automatic Submerged arc welded steel pipe for general low-pressure fluid transportation such as water. gas. air and steam made by submerged arc welding or single-sided welding. (3) Classification of bearing steel At present. there are five main types of bearing steels used in countries around the world. namely high carbon chromium bearing steel. carburized bearing steel. stainless bearing steel. high temperature bearing steel. and medium carbon bearing steel. Stainless steel pipe quote 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. 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. 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. 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 tube characteristics 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 composition 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 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. Quality control method for stainless steel pipe construction Stainless steel pipes must be cleaned before installation. When the pipeline is long or the temperature of the conveying medium is high. the compensator should be set at the appropriate position. The compensator usually has a square shape and a waveform. When selecting. it should be selected according to the working pressure and temperature. The stainless steel pipe is not allowed to be in contact with the carbon steel bracket. A stainless steel piece or a plastic or rubber gasket containing no chloride ions should be placed between the bracket and the pipe. When using the pressure connection. it should be connected by special pipe fittings. and the insulation between the pipe fittings and the stainless steel pipe can be made of plastic. rubber or asbestos rubber plates without chloride ions. When the stainless steel pipe passes through the wall or the floor. the casing should be installed. The gap between the casing and the stainless steel pipe should not be less than 10mm. and the insulation should be filled in the gap. The asbestos rope can be used. and the iron and rust should not be used. Miscellaneous stuffing. The quality of the sub-projects shall meet the following requirements: The inspection batch included in the 1 sub-project shall meet the requirements for qualified quality. In general. 201 stainless steel welded pipe is resistant to high temperature 315 degrees. and the ultimate temperature of 304 stainless steel welded pipe is 650 degrees. When the temperature exceeds this temperature. the heavy metal will precipitate. When the stainless steel welded pipe is heated more than this degree. the stainless steel pipe creep material will start to deform. . Therefore. the environment in which the stainless steel pipe is used should be below the corresponding temperature. If the temperature exceeds this temperature. the stainless steel pipe will definitely be broken. Due to the increase in nickel content. the high temperature resistance of the stainless steel tube can be improved. so the 304 stainless steel tube has a slightly higher temperature resistance than the 201 stainless steel tube. Source: China Stainless Steel Pipes Manufacturer – wilsonpipeline Pipe Industry Co.. Limited (www.wilsonpipeline.com)

The stainless steel bellow is installed as a flexible pressure-resistant pipe in a liquid (gas) conveying system to compensate for the connection of pipes or machines and equipment. So what are the advantages of this stainless steel bellows to replace the rubber tube? The following is a brief introduction to the advantages and disadvantages of stainless steel bellows and the installation and application of gas stainless steel bellows. Natural gas stainless steel hose adopts integrated manufacturing technology. The surface of the pipe body is covered with transparent flame-retardant PVC protective cover. It is specially used for the connection of indoor air source terminal and gas appliance. The joint is made of all metal, which effectively eliminates rubber. The hose is accidentally detached, aged and cracked, leaked by the mouse, leaking, poisoning, explosion and other safety hazards, with corrosion resistance, long service life, good bending performance, convenient connection, beautiful appearance, safer use, relative price more economics. The name of the specification should be called “stainless steel corrugated hose for gas transmission” and “stainless steel bellows for gas appliance connection”. Gas stainless steel bellows standard As early as 2010, China issued the relevant Chinese standard “GB/T 26002-2010 “stainless steel corrugated hose and fittings for gas transmission””. This standard applies to the nominal size DN10-DN50, the nominal pressure PN is less than or equal to 0.2 Pa. Hose and fittings. The industry standard is CJ/T197-2010 “stainless steel corrugated hose for gas appliance connection”. This standard is applicable to gas stoves, gas water heaters and gas meters with a nominal size DN of less than or equal to N32 and a nominal pressure PN of less than or equal to 0.01 Pa. Hose for pipe connection. Stainless steel corrugated hose advantages and disadvantages Good construction: stainless steel corrugated hose is a thin-walled hose, the overall weight is reduced, greatly reducing the load of construction work and construction time. Corrosion resistance: The main body of the bellows is made of 304 or 316L stainless steel. Both ends are made of stainless steel joints or carbon steel joints, which have good corrosion resistance. Sealing is ensured. High pressure resistance: Considering the actual working pressure of the bellows, the use environment and the use condition, all the parameters have been carefully calculated and tested repeatedly to ensure the pressure safety in the work. Many types: existing bellows diameter range: DN8-DN4000, other customized according to customer requirements. Anti-vibration and anti-dislocation: Stainless steel corrugated hose has good flexibility and compensation displacement. Beautiful appearance: the appearance is clear, and the permanent light is as new. Shock resistance and high speed It can transmit torque itself. In the normal mechanical seal operation, the structure must be added to transmit the seal. Less leakage points. Stainless steel bellows instead of galvanized pipe High safety and reliability The stainless steel bellows changes the threaded connection process into a plug-in connection, and the connecting part adopts a side seal, which can effectively prevent the burr of the bellows from cutting the sealing gasket and causing leakage, and has a refractory material, a water sealing gasket and a fall-proof design. Due to the superior bending performance, the length is optional. A large number of elbows, wires, pipe clamps, etc. are omitted. The leakage point is reduced compared with the galvanized pipe. After installation, the pipe can be rotated 360° without leakage, and the pressure rating is fully applicable. Indoors (pressure 16kg). The stainless steel bellows is made of sus304 stainless steel and is non-aging. It has corrosion resistance and melting point of up to 1500-1600 °C. It is higher than the melting point of copper (950 °C) and the melting point of galvanized pipe (1 200 °C), even in the event of fire. At high temperatures (500 ° C), there is no port dropout and “fire on the fire”. Due to the waveform of the pipe wall, the stainless steel bellows has strong compensability and can resist deformation caused by thermal expansion and contraction and building displacement. (40% of the length of the tube itself does not break) Stainless steel corrugated hose installation The bellows of the stainless steel hose is made of chrome-nickel austenitic stainless steel. When using it, pay attention to prevent pitting corrosion of nitrogen ions and corrosive damage of dilute sulfuric acid and dilute sulfuric acid. After the user conducts the water pressure test on the equipment and piping with stainless steel hoses, it should prevent the impact of rust block and chloride ion sediment, causing corrosion and mechanical damage. The metal hose should be protected from splashing and mechanical damage during welding, otherwise it will cause leakage. The sealing pipe system should strictly abide by the safe operating procedures to prevent the hose from being pulled off or blasted due to overpressure caused by improper operation or other factors. Please carefully digest the stainless steel hose installation method and install it in strict accordance with the correct sketch. Stainless steel bellows connection methods are pided into: flange connection, welding, threaded connection, quick joint connection, small-diameter metal hose is generally connected by thread and quick joint, and the larger diameter is generally flanged and welded. Easy to install and beautiful The stainless steel bellows is easy to install and easy to carry. The tools required for installation are simple and the control is more convenient. It is suitable for the new user to preset the gas pipeline, and is also suitable for the transformation of the old user pipeline. Can meet the various installation needs of users, can be buried in the wall, concealed, surface mounted and other installation methods. The installation efficiency is now three times the quota of 3.5 households/person. The ductility and flexibility of the stainless steel bellows determine its special bending properties, which can be done manually by bending. The corrosion resistance and oxidation resistance of stainless steel bellows determine its service life of more than 50 years, which is in line with the life of the building. The galvanized pipe has a service life of about 20 years in a good installation environment. Stainless steel bellows make your kitchen more tidy and more beautiful while ensuring safer and more economical. At the same time, you can save expensive pipeline renovation costs. Reduce accident leakage points Now the galvanized pipe behind the table, about 10-15 pieces of various fittings used by each household, leaving a hidden trouble of 20 to 30 threaded interfaces. It is connected by stainless steel bellows. There are only 2 interfaces from the back of the watch to the front of the stove. The accident leakage rate is reduced by 90%. The fixed-length stainless steel bellows is a new product that replaces the existing gas hose. It can be screwed at both ends, or it can be rubber-clamped at the valve end of the stove and screwed at the end of the stove. It can be directly connected with the stove on the table, the set stove and the water heater, thus fundamentally overcoming the unsafe factors such as the aging crack of the hose, oil corrosion, no fire, easy to fall off. Shortcomings of stainless steel bellows Of course, the use of stainless steel hose is not foolproof, can not be paralyzed. Wrapping back and forth may cause metal fatigue or air leakage at the threaded interface, so stainless steel corrugated hoses may not be twisted back and forth. If it exceeds 2m, it needs to be fixed. After a mechanical injury has been caused by an external force, we cannot judge whether there is a crack or stress concentration by the naked eye, and it must be replaced. Why should we vigorously promote the application of gas stainless steel bellows? According to statistics, more than 80% of indoor gas accidents are caused by pipe materials, gas cookers, gas valves, hoses connected to stoves or private modifications. The hose problem is particularly serious, mainly in the following cases: The hose is detached. This is mainly due to the fact that the hose is not tightened when it is installed, or it is rusted or loosened after a long period of use, which may cause the hose to fall off and run. Therefore, it is necessary to check whether the connection at both ends of the hose is tight and prevent the hose from being tight. The occurrence of shedding. The hose is aged. The hose is used for a long time and is not replaced in time. It is prone to aging and cracking, which leads to leaking of the hose. Under normal circumstances, the hose needs to be replaced after two years of use. The hose passes through the wall. Some users move the gas cooker to the balcony, the construction is not standardized, and the hose passes through the wall. This will not only make the rubber tube in the wall easily break, break and run due to friction, and it is not convenient for daily operation. Inspection brings great security risks to the home. If the gas facilities in your home need to be changed, you must find a professional. The hose is too long. The hose is too long to be easily mopped. Once it is stepped on by the pedal or pierced by the cutting tool, and the deformation and rupture caused by the pressing, it is easy to cause a gas leakage accident. Gas hoses generally cannot exceed two meters. Use a non-dedicated hose. When conducting safety inspections in the gas department, the technicians found that some users did not use gas-specific hoses in their homes and replaced them with other materials. The gas department hereby reminds us that it is necessary to use a special gas hose, but not other hoses, and it is forbidden to have a joint in the middle of the hose. The embedded cooker hose is generally hidden in the cabinet, easy to scratch off, and difficult to find, so it should be checked frequently. Faced with various problems caused by hoses, the promotion and application of gas stainless steel bellows in recent years can greatly reduce the probability of safety accidents of the above common hoses. How to prevent security products from entering the households to prevent gas accidents, how to enhance residents’ safety awareness, only the gas company’s human and material resources are limited, and it is necessary to mobilize various social forces more widely and actively participate in gas safety management. Expand the points, lines and surfaces of safety management to eliminate hidden dangers in a timely manner. In the gas industry, the property management offices and neighborhood committees are jointly launched to publicize the common sense of gas safety. Make full use of all kinds of media and do security promotion. As long as everyone is committed to gas safety management, as long as everyone has safety knowledge, and has the determination to maintain safety, there are actions to ensure safety; the gas safety work of the community and residents will be able to create a brand new situation. In order to build a socialist harmonious society, for the safety and health of the people, and in order to have a safe family environment, it is recommended that new materials and technologies complying with relevant national standards should be adopted in the design and construction of gas engineering. Mature experience with the necessary safety protection. The gas management department shall increase publicity efforts to support and encourage users to select gas appliance products, supplies, materials and alarm devices with strong safety protection performance from regular manufacturers to eliminate hidden dangers of gas leakage, stay away from danger, and live safely. . The above is about the defects of stainless steel bellows and the introduction of stainless steel corrugated hoses for gas. In addition, the gas stainless steel bellows is expensive but has a long service life. The service life of rubber hoses is 18 months, that is, one and a half years. The service life of stainless steel corrugated hose is more than 10 years, and the comprehensive calculation cost is more economical and safe. Source: China Stainless Steel Bellows Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Types of flanges (1) flange of pressure vessel is pided into general flange and reverse flange according to overall structure. (2) according to the layout of gaskets, it can be pided into two categories: narrow flange and wide flange. A) Narrow flange refers to the gasket contact surface located in the flange bolt hole around the circumference of the flange, is the most widely used flange. B) wide flange is the flange on the two sides of the center of the flange. Generally only for low pressure occasions. (3) According to the integrity of each part of the flange, it can be pided into loose flange, integral flange and arbitrary flange. Its characteristics are: A) loose flange: flange that fails to effectively connect the container or nozzle. In the calculation, it is considered that the cylinder does not bear the action of flange moment with the flange ring, and the flange moment is completely borne by the flange ring itself. B) integral flange: finger ring, neck and cylinder three can be effectively connected into a whole flange. The three part bears the role of flange torque. C) arbitrary flange: flange with the overall degree between them. Although the cylinder and the flange ring can not form a whole structure, but as a structural element, they can bear the effect of flange torque together. Flat welding flange belongs to such flange. (4) According to the connection between flange and cylinder, it is pided into looper flange, thread connection flange, socket welding flange, flat welding flange and butt welding flange. (5) The pressure vessel flange standard pides the flange into three kinds: A-type flat welding flange, B-type flat welding flange and long neck butt welding flange. Flange connection design Flange design refers to the design of flange connection, including three parts: gasket design, bolt (stud) design and flange body design. The most important method of flange design is the famous Waters method, GB 150. The design points are as follows: (1) Gasket design This is the basis of flange connection design, according to the design conditions and the use of media, should select the appropriate gasket type, material, determine the size of gasket (inner diameter, outer diameter, thickness), and then calculate the gasket in the pre-tightening state and operating state of the pressure. (2) Bolt / stud design According to the design conditions, the bolt area needed to meet the pre-tightening and operating conditions of the gasket is calculated. The actual bolt area should not be less than the calculated area. The principle of bolt design is to determine the smaller central diameter of bolts. It is possible to meet the requirements by selecting the appropriate bolt specifications and quantities. (3) Flange design Flange design is pided into two parts: internal pressure and external pressure. Flanges subjected to external pressure can be designed according to the calculation method of flanges subjected to internal pressure, but the calculation of flange operating torque is slightly different. The calculation method of narrow flange is pided into two types: loose flange calculation and integral flange calculation. Arbitrary flange is usually calculated by integral flange, which can be simplified to loose flange under certain conditions. Loose flange calculation is relatively simple, flange thickness can be calculated at one time. The design of the whole flange should be completed by assuming that the structural size of each part is calculated repeatedly. For the whole flange, first, according to the structural conditions of the equipment, suppose the dimensions of the flange cone neck and the flange ring. The torque and stress generated by the flange are calculated. When the difference between each stress and the corresponding allowable stress is large, the original size of the flange should be adjusted, and the above calculation should be repeated until all the stresses are less than their allowable stress and the difference is not too big. The calculation of wide flange is irrespective of form, and is calculated according to the simplified model of “simply supported beam”. Source: China Flanges Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

What is the meaning of “steel” and “iron”, what are the characteristics, and what is the relationship between us, 304, 304L, 316, 316L, which we usually say, and what is the difference between them? Steel: A material containing iron as the main element and having a carbon content of generally less than 2% and containing other elements. ——GB/T 13304-91 “Steel Classification” Iron: A metal element, atomic number 26. Iron materials have strong ferromagnetism and good plasticity and thermal conductivity. Stainless steel: resistant to weak corrosive media such as air, steam, water or stainless steel. The commonly used steel grades are 304, 304L, 316, and 316L, which are 300 series steels of austenitic stainless steel. 304 stainless steel Performance introduction 304 stainless steel is the most common steel grade. As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties. It has good hot workability such as stamping and bending, and has no heat treatment hardening phenomenon (non-magnetic , the temperature is -196 ° C ~ 800 ° C). Scope of application Household items (1, 2 types of tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs) Auto parts (windshield wipers, mufflers, molded products) Medical equipment, building materials, chemicals, food industry, agriculture, ship parts 304L stainless steel – (L is low carbon) Performance introduction As a low-carbon 304 steel, its corrosion resistance is similar to that of 304 under normal conditions, but it has excellent resistance to intergranular corrosion after welding or after stress relief; it can also be maintained well without heat treatment. Corrosion resistance, the use temperature -196 ° C ~ 800 ° C. Scope of application It is used in field open-air machines for chemical, coal, and petroleum industries with high resistance to intergranular corrosion, heat-resistant parts for building materials, and parts with difficult heat treatment. 316 stainless steel Performance introduction Due to the addition of molybdenum, 316 stainless steel has excellent corrosion resistance, atmospheric corrosion resistance and high temperature strength, and can be used under severe conditions; it has excellent work hardening property (non-magnetic). Scope of application Equipment for the use of equipment, chemicals, dyes, paper, oxalic acid, fertilizers, etc. in seawater; photo, food industry, coastal facilities, ropes, CD rods, bolts, nuts. 316L stainless steel – (L is low carbon) Performance introduction As a low carbon series of 316 steel, it has excellent resistance to intergranular corrosion in addition to the same characteristics as 316 steel. Scope of application A product that has special requirements for resistance to grain boundary corrosion. Performance comparison Chemical component 316 and 316L stainless steels are molybdenum-containing stainless steels. The molybdenum content in 316L stainless steel is slightly higher than that of 316 stainless steel. Due to the molybdenum in steel, the total performance of this steel is better than that of 310 and 304 stainless steel. Under high temperature conditions, when the concentration of sulfuric acid is lower than 15% and higher than 85%, 316 Stainless steel has a wide range of uses. 316 stainless steel also has good chloride attack properties and is therefore commonly used in marine environments. 316L stainless steel has a maximum carbon content of 0.03 and can be used in applications where annealing is not possible and maximum corrosion resistance is required. Corrosion resistance 316 stainless steel has better corrosion resistance than 304 stainless steel and has good corrosion resistance in the production of pulp and paper. Moreover, 316 stainless steel is also resistant to erosion by marine and aggressive industrial atmospheres. In general, 304 stainless steel and 316 stainless steel have little difference in chemical resistance, but they differ in some specific media. The stainless steel originally developed was 304. In certain cases, this material is sensitive to pitting Corrosion. An additional 2-3% increase in molybdenum can reduce this sensitivity, thus giving birth to 316. In addition, these additional molybdenum can also reduce the corrosion of certain hot organic acids. 316 stainless steel has almost become the standard material in the food and beverage industry. Due to the shortage of molybdenum in the world and the high nickel content in 316 stainless steel, the price of 316 stainless steel is more expensive than 304 stainless steel. Pitting corrosion is a phenomenon mainly caused by deposition corrosion of stainless steel surfaces because oxygen deficiency does not form a chromium oxide protective layer. Especially in small valves, the possibility of deposits on the valve plate is small, so pitting corrosion is rare. In all types of water media (distilled water, drinking water, river water, boiler water, sea water, etc.), 304 stainless steel and 316 stainless steel have almost the same corrosion resistance, unless the chloride ion content in the medium is very high, then 316 stainless steel more suitable. In most cases, the corrosion resistance of 304 stainless steel and 316 stainless steel is not much different, but in some cases it may vary greatly, and specific analysis is required. In general, valve users should be aware of the fact that they will select the material of the container and the pipe according to the condition of the medium. It is not recommended to recommend the material to the user. Heat resistance 316 stainless steel has good oxidation resistance in intermittent use below 1600 °C and continuous use below 1700 °C. In the range of 800-1575 degrees, it is preferable not to continuously apply 316 stainless steel, but when 316 stainless steel is continuously used outside this temperature range, the stainless steel has good heat resistance. 316L stainless steel has better carbide precipitation resistance than 316 stainless steel and can be used in the above temperature range. Heat treatment Annealing is carried out at a temperature ranging from 1850 to 2050 degrees, followed by rapid annealing and rapid cooling. 316 stainless steel cannot be hardened by heat treatment. Welding 316 stainless steel has good welding properties. All standard welding methods can be used for welding. When welding, 316Cb, 316L or 309Cb stainless steel filler rods or welding rods can be used for welding according to the application. For best corrosion resistance, the welded section of 316 stainless steel requires post-weld annealing. If 316L stainless steel is used, post-weld annealing is not required. Mechanical behavior Among all steels, austenitic stainless steel has the lowest yield point. Therefore, from the viewpoint of mechanical properties, austenitic stainless steel is not the best material for the valve stem, because the diameter of the valve stem is increased to ensure a certain strength. The yield point cannot be increased by heat treatment, but can be improved by cold forming. magnetic Due to the wide application of austenitic stainless steel, it gives people the wrong impression that all stainless steels are not magnetic. For austenitic stainless steels, it can be basically understood as non-magnetic, as is the case with quenched forged steel. However, the 304 processed by cold forming will be somewhat magnetic. For cast steel, if it is 100% austenitic stainless steel, it is not magnetic. Low carbon type stainless steel The corrosion resistance of austenitic stainless steel comes from the chromium oxide protective layer formed on the metal surface. If the material is heated to a temperature between 450 ° C and 900 ° C, the structure of the material changes and chromium carbide forms along the edges of the crystal. Thus, a chromium oxide protective layer cannot be formed at the edge of the crystal, resulting in a decrease in corrosion resistance. This type of corrosion is called “intergranular corrosion.” This resulted in the development of 304L stainless steel and 316L stainless steel to combat this corrosion. Both 304L stainless steel and 316L stainless steel have a lower carbon content. Because of the reduced carbon content, chromium carbide is not produced and no intergranular corrosion occurs. It should be noted that higher intergranular corrosion sensitivity does not mean that non-low carbon materials are more susceptible to corrosion. This sensitivity is also higher in high chlorine environments. Please note that this phenomenon is due to high temperatures (450 ° C – 900 ° C). Usually soldering is the direct cause of reaching this temperature. For soft seat conventional butterfly valves, the use of low carbon stainless steel does not make much sense since we do not weld on the valve plate, but most specifications require 304L stainless steel or 316L stainless steel. Source: China Pipe Fittings Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Shell-and-tube heat exchangers are widely used in industrial plants. Different structures can be selected according to different operating conditions such as temperature, pressure and medium, such as fixed tubesheet heat exchangers (or fixed heat exchangers), floating-head heat exchangers, filled-tube heat exchangers, U-tube heat exchangers and so on. Tube sheet is one of the main parts of shell and tube heat exchangers. The reasonable design of tubesheet is of great significance to the correct selection and saving of materials, the reduction of difficulties in manufacturing process, the reduction of cost and the guarantee of safety in use. Therefore, the tube plate strength must be correctly analyzed to determine the thickness of tube sheet reasonably. GB 151 “Heat Exchanger” provides a complete set of technical requirements for the design, manufacture, inspection and acceptance of shell-and-tube heat exchangers. As a whole, the parameters of the heat exchanger which are applicable to the standard are specified. The calculation method of tube sheet given in the standard (see Chapter 7) can be applied to all pressure and diameter parameters of shell-and-tube heat exchangers with PN < 35 MPa. GB 151 gives the design and calculation methods of U-tube heat exchanger, floating head heat exchanger and fixed tube-plate heat exchanger. The strength calculation methods of heat exchanger tube sheets with different structure types are different because of different load conditions, support conditions and boundary constraints. The U-tube heat exchanger has only one tubesheet. Six different connection structures are given in the standard. The calculation model of U-tube heat exchanger is that the tubesheet is a common circular plate which bears uniform load and is weakened uniformly by the holes in the tube. The influence of the non-distributed area around the tubesheet on the tubesheet stress is considered in the calculation method. For floating head heat exchangers and filled-in heat exchangers, most of the fixed end of a tube plate is clamped between shell flange and tube box flange with bolts and gaskets. The calculation model regards the pipe distribution area of the tube sheet as a circular plate on the elastic foundation and weakened uniformly by the hole, and the non-pipe distribution area around the tube sheet as an annular plate. The whole tube sheet is simply supported and bears uniformly distributed load. For other connection forms, the tube plate is designed according to JB 4732 standard. In a fixed tubesheet heat exchanger, two tubesheets are fixedly connected with a shell-side cylinder, and the periphery of the fixed tubesheet can be extended as a flange, forming a “tube plate with an extended part as a flange” or directly connected with the shell-side and the tubesheet cylinder to form a “tube plate without flange”. According to the requirement of poor thermal expansion of shell-side cylinder and tube bundle, expansion joint may be set in fixed tube-sheet heat exchanger. Regardless of the specific structure of the fixed heat exchanger, the size and material properties of almost all the structural elements of the heat exchanger directly or indirectly affect the strength of the tube sheet. Because the strength analysis and calculation of tubesheet are very complicated, so far, most of the national codes have simplified and hypothesized the actual tubesheet to varying degrees. The tubesheet is regarded as an equivalent circular plate which bears uniformly distributed loads, is placed on an elastic foundation and is weakened uniformly by the hole. On the basis of the above simplification, the standard method GB 151 proposed by Professor Huang Keming of Tsinghua University, which considers quantitatively the effects of the following factors on the stress of tubesheet, has been put forward in China. (1) the influence of the pipe area (ring plate) on the stress of tube sheet. (2) The restraint effect of shell side cylinder (flange), tube box cylinder (flange), bolt and gasket system on the edge corner of tube sheet; 3. When the extension part of the tube plate is used as flange, the influence of flange torque on the stress of tube sheet is also discussed. (4) When calculating the elastic stress of tube sheet, the primary bending stress caused by pressure load and flange moment and the secondary stress caused by thermal expansion difference between tube and shell side are distinguished, and the allowable values are determined. Source: China Stainless Steel Tube Sheets Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

The bellows compensator expansion joint is widely used in many industries. In addition to considering good compensation capacity, reliability is the key to the bellows compensator expansion joint. However, reliability is ensured through multiple links such as design and manufacturing. Any negligence of any link will lead to the reduction or even failure of the life of the compensator. Most bellows compensator expansion joints manufacturers have analyzed the failure reasons of the bellows compensator expansion joints. It is found that the failures during operation are mainly manifested by corrosion leakage and instability deformation, among which corrosion failure is mostly. Anatomical analysis of corrosion-infected bellows found that corrosion failure is usually characterized by point corrosion perforation and stress corrosion cracking, in which chloride stress corrosion cracking accounts for about 95% of the total corrosion failure. Therefore, the correct selection of corrugated pipe fabrication materials and structures, reasonable design of waveform parameters and fatigue life, and assurance of installation quality can greatly improve the safety and reliability of the bellows compensator expansion joint. In design, the stability of the bellows should be considered to prevent the instability of the bellows. The data show that the compensation amount of the bellows depends on its fatigue life, and the higher the fatigue life, the smaller the single wave compensation amount of the bellows. In order to reduce the cost and increase the single-wave compensation amount, the lower the allowable fatigue life, the greater the bending stress of the corrugated pipe caused by the displacement, and the higher the comprehensive stress, the stability of the bellows is greatly reduced. When the permissible life of the bellows design is low, not only the meridional comprehensive stress is high, but also the hoop stress is relatively high, so that the bellows partially enters the plastic deformation quickly, resulting in failure of the bellows instability. In addition to design, the choice of material for the bellows is also critical. For the selection of corrugated pipes, in addition to the working medium, working temperature and external environment, the possibility of stress corrosion, the effect of water treatment agent and pipe cleaning agent on the material should be considered, and the corrugation should be combined on this basis. The welding material of the pipe material, the molding and the cost performance of the material are preferably made of a corrugated pipe material which satisfies working conditions and is practical. Experts suggest that the material selected for the bellows should meet the following conditions: (1) Good plasticity, facilitating the forming of the bellows, and obtaining sufficient hardness and strength by a subsequent treatment process (cold work hardening, heat treatment, etc.). (2) High elastic limit, tensile strength and fatigue strength to ensure the normal operation of the bellows. (3) Good welding performance, meeting the welding process requirements of the bellows in the manufacturing process. (4) Good corrosion resistance, meeting the requirements of bellows working in different environments. At present, most manufacturers use austenitic stainless steel (such as 304, 304L, 316, 316), 254SMO, 904L, AL6XN and other super austenitic stainless steels have become important materials. For the heat pipe network laid in the trench, when the pipeline at the expansion section of the bellows compensator is low, the rainwater or accidental sewage will be immersed, and materials with stronger corrosion resistance, such as high-nickel alloy and iron-nickel alloy, should be considered. Etc., such as INCOLOY800, INCOLOY825, INCONEL625 and Hastelloy C-276. The special materials for the bellows compensator expansion joints and expansion joints are as follows: 1. Super austenitic special stainless steel: 254SMO, 904L, AL6XN 2, duplex stainless steel: 2205 duplex steel (S31803) 3. Nickel-based alloy steel: INCOLOY800/800H/800HT/840/825, INCONEL600/601/690/625/X-750 Hastelloy C-276/C-22/X, MONEL400/K500 4. Pure nickel: N4 N6 (Ni200, Ni201) 5. Titanium plate for press: GR1, GR2, TA1, TA2 6, austenitic stainless steel: SUS304, SUS304L, SUS316, SUS316L, SUS310S, SUS321, SUS316Ti. Source: China Stainless Steel Bellows Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are many types of pressure vessel heads, and the commonly used forms include a hemispherical head, an elliptical head, a dish head, a spherical cap, a conical head, a flat cover, a flanged convex head, and the like. There are two types of internal pressure and external pressure from the load condition. Hemispherical head The calculation formula is derived from the film theory, and the wall thickness can be calculated based on the inner or outer diameter of the container. See the contents of the spherical shell in Section 3.4 of GB150.3 for details. The medium diameter formula of the cylinder is based on the equivalent strength and failure criteria: Oval head The calculation formula is based on the cylinder formula, and the boundary effect of the joint between the head and the cylinder is reflected by the shape factor K. The larger the ratio of the long and short axes α/b, the larger the K value; when the ratio of the long and short axes is greater than 2.5, the head is prone to circumferential instability, so α/b is controlled at 2.6. The standard elliptical head has a ratio of length to length of 2, which is most commonly used, with K=1. The head can be calculated based on the inner or outer diameter of the container. In addition to meeting the strength, the thickness calculation of the head should also meet the stability requirements. For an elliptical head with α/b less than or equal to 2, the effective thickness shall not be less than 0.15% Di, and the effective thickness of the elliptical head with α/b>2 shall not be less than 0.30% Di. Dish head The calculation formula is calculated by multiplying the spherical shell calculation formula of the spherical portion by the shape factor M. The larger Ri/r is, the more prominent the local stress is at the discontinuity of the surface of the head, and the larger the shape factor M is. Therefore, the inner diameter of the transition section should be limited to the range of r >= 10% Di. Heads can be used to calculate the wall thickness based on the inner or outer diameter of the container. In addition to meeting the strength, the thickness calculation of the 3 heads should also meet the stability requirements. For a dish-shaped head with M<=1.34, the effective thickness shall not be less than 0.15% di, and for a dish-shaped head with m> 1.34, the effective thickness shall not be less than 0.30% Di. Ball crown The calculation formula is based on the cylinder formula. For the joint between the spherical crown and the barrel, the influence of local film stress and bending stress caused by the boundary effect is corrected by the coefficient Q. For different pressure conditions, the Q values are taken from different maps. For the large-diameter spherical crown head, it can be considered that the middle spherical area of the head and the reinforcing section of the end take different thicknesses, wherein the length of the head reinforcing section should not be less than Conical head Due to the discontinuity of the structure, large local stresses are generated at the joint. When the half angle apex α of the cone shell is less than or equal to 30 degrees, the bending stress is small. At this time, a non-folded cone head can be used. When α > 30 degrees, the large end of the cone shell should adopt a hemmed structure, when α> At 45 degrees, the small end of the cone shell should also adopt a transition structure with a hem. The formula for calculating the thickness of the cone shell is calculated by the equivalent cylinder. For the large and small end reinforcement section, the cylinder calculation formula is also adopted, and the stress increase coefficient Q is corrected. For the tapered head with the hemming, the big end can be calculated by the equivalent disc shape head. Eccentric cone The eccentric cone shell can be treated as a cone shell. When the cone apex angle α is less than or equal to 30 degrees under internal pressure, the thickness of the eccentric cone shell is calculated according to the plated head. The half apex angle α of the cone shell is larger than the angle between the eccentric cone shell and the simplified body. Value selection. Under the action of external pressure, when the half apex angle α of the cone shell is less than or equal to 60 degrees, the thickness of the cone shell is stably checked according to the outer pressure cone shell, and the check should be carried out according to the two half angles. Flat cover The coefficient K is used to represent the support around the flat cover. The smaller the K value, the closer the periphery of the flat cover is to the solid support, and the closer it is to the simple support. Flanged head with flange There are four forms of calculation of the thickness of the seal head and the calculation of the flange thickness. Among them, a flanged crown head is often used for a floating head heat exchanger. Source: China Stainless Steel Heads Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

There are many types of gaskets, and gaskets of different materials and shapes have different functions. If you choose the wrong gasket, not only can it not be sealed well, it may also become a safety hazard, and there is a possibility of danger at any time. Do you know what are the gaskets and what are their characteristics? Industrial rubber sheet Natural rubber is suitable for mediums such as water, sea water, air, inert gases, alkalis, salt aqueous solutions, but not resistant to mineral oils and non-polar solvents. The long-term use temperature does not exceed 90 ° C, and the low temperature performance is excellent, and can be used at -60 ° C. Used above. Nitrile rubber is suitable for petroleum products such as petroleum, lubricating oil, fuel oil, etc. The long-term use temperature is 120 ° C, such as 150 ° C in hot oil and -10 ~ -20 ° C in low temperature. Neoprene is suitable for seawater, weak acid, weak alkali, salt solution, excellent in oxygen and ozone aging resistance, oil resistance is inferior to nitrile rubber and superior to other general rubber. Long-term use temperature is lower than 90 °C, and the maximum use temperature is not more than 130 ° C, low temperature -30 ~ -50 ° C. There are many varieties of fluororubbers, which have good acid and oxidation resistance, oil and solvent resistance. It can be used in almost all acid media as well as some oils and solvents. The long-term use temperature is below 200 °C. As a flange gasket, the rubber sheet is mostly used for pipes or hand holes that are frequently disassembled, and the pressure does not exceed 1.568 MPa. Because in all kinds of gaskets, the rubber gasket is the softest, the fitting performance is good, and the sealing effect can be exerted under a small pre-tightening force. For this reason, when the internal pressure is applied, it is easily extruded because the gasket is thick or the hardness is low. The rubber sheet is used in organic solvents such as benzene, ketone and ether, and is prone to swelling, weight gain, softening and stickiness, resulting in seal failure. Generally, the degree of swelling exceeds 30% and cannot be used. In the case of low pressure (especially 0.6 MPa or less) and vacuum, it is suitable to use a rubber mat. The rubber material has good compactness and low air permeability. For example, fluororubber is the most suitable gasket for vacuum containers, and the vacuum can be up to 1.3×10-7Pa. When the rubber mat is used in the vacuum range of 10-1~10-7Pa, it needs to be baked and pumped. Asbestos Rubber Sheet The price is lower than other gaskets and it is easy to use. The biggest problem is that although the gasket material is added with rubber and some fillers, it is still impossible to completely fill the micropores that are colluded, and there is a slight infiltration. Therefore, in a highly polluting medium, even if the pressure and temperature are not high, it cannot be used. When used in some high-temperature oil-based media, usually in the later stage of use, due to the carbonization of rubber and filler, the strength is reduced, the material becomes loose, and penetration occurs inside the interface and the gasket, and coking and smoking occur. In addition, the asbestos rubber sheet is easily bonded to the flange sealing surface at a high temperature, which causes a lot of trouble for replacing the gasket. The pressure at which the gasket is used in various media in a heated state depends on the strength retention of the gasket material. Crystallized water and adsorbed water are present in the asbestos fiber material. At 110 ° C, the adsorption water between the fibers has been precipitated by 2/3, and the tensile strength of the fiber is reduced by about 10%; At 368 ° C, the adsorbed water is completely precipitated, and the tensile strength of the fiber is reduced by about 20%; When the temperature exceeds 500 ° C, the crystal water starts to precipitate and the strength is lower. The influence of the medium on the strength of the asbestos rubber sheet is also great. For example, in aviation lubricants and aviation fuels, the transverse tensile strength of No. 400 oil-resistant asbestos rubber sheets differs by 80%, which is due to the fact that aviation fuels swell the rubber in the sheet more than aviation lubricants. Taking into account the above factors, the recommended safe use range of domestic asbestos rubber sheet XB450: temperature 250 ° C ~ 300 ° C, pressure 3 ~ 3.5MPa; 400 oil-resistant asbestos rubber sheet use temperature should not exceed 350 ° C. Asbestos rubber sheet contains chloride ions and sulfides. It is easy to form a corrosion original battery with water metal after water absorption. Especially the oil-resistant asbestos rubber sheet has several times higher sulfur content than ordinary asbestos rubber sheet, so it should not be used in non-oily medium. The gasket will swell in oil and solvent-based media, but within a certain range, it has little effect on the sealing performance. For example, the No. 400 oil-resistant asbestos rubber sheet is subjected to a 24-hour immersion test in a normal-temperature aviation fuel, and the required increase in suction weight must not exceed 15%. There is still a certain gap between domestic asbestos rubber sheets and foreign famous brand products. Statistics from a certain unit indicate that in oil media exceeding 350 °C, most of the asbestos rubber sheets are not leaking. Japanese Petroleum Industry Standard JPI-7S-71 “Asbestos Rubber Sheet Standards for Petroleum Industry”, the use period is about one year. PTFE PTFE is easy to cold flow and creep under pressure and high temperature, so it is generally used for low pressure, medium temperature, strong corrosion and media that do not allow pollution, such as strong acid, strong alkali, halogen, medicine and so on. The safe use temperature is 150 ° C and the pressure is 1 MPa or less. Although the strength of the filled polytetrafluoroethylene is higher, the use temperature does not exceed 200 ° C, and the corrosion resistance is lowered. The maximum use pressure of the Teflon pad is generally not more than 2 MPa. As the temperature rises, the material creeps, causing the seal pressure to drop significantly. Even if it does not heat up, the compressive stress of the sealing surface will decrease with the extension of time, resulting in “stress relaxation phenomenon. This phenomenon will occur in various gaskets, but the stress relaxation phenomenon of the Teflon pad is more serious. It should be noted. The friction coefficient of PTFE is small (the compaction stress is more than 4 MPa, the friction coefficient is 0.035~0.04), and the gasket is easy to slide outward when pre-tightening, so it is better to use the concave-convex flange surface. When using a flat flange, the outer diameter of the gasket can be contacted with the bolt, and the bolt can be used to prevent the gasket from slipping out. Since the glass-lined equipment is sintered after spraying a layer of enamel on the metal surface, the glaze layer is very brittle, coupled with uneven spraying and glaze flow, the flatness of the flange surface is poor. The use of metal composite gaskets is easy to damage the glaze layer, so it is recommended to use a PTFE sheet with a core material and a rubber wool board. The pad is easy to adhere to the flange surface and corrosion resistant, and the effect is good. There are many factories in the strong corrosive medium with low temperature and pressure. The asbestos rubber sheet is wrapped with polytetrafluoroethylene raw material tape for manholes and pipes that are frequently disassembled. Because it is easy to make and use, it is very popular. Asbestos resin sheet and impregnated asbestos sheet gasket Pipes, pumps, valves, inlet and outlet flanges, which are mostly used in various acidic media, have a temperature of 80 ° C and a pressure of 0.6 MPa or less. Asbestos-made gaskets are suitable for low-pressure and high-temperature conditions with a pressure below 0.1 MPa and a temperature not exceeding 800 °C. According to the specific requirements of the equipment, we can weave the gasket with the width, thickness and diameter. Or cut the asbestos tape directly onto the flange surface. It is used in large sulfuric acid, nitric acid oxidation furnaces and some unprocessed equipment interfaces, far more effective than the original asbestos rope. Metal asbestos pad The asbestos sheet or the asbestos rubber sheet is covered by the metal sheet so as not to be in direct contact with the medium, the strength of the asbestos fiber is prevented from being lowered, and the leakage phenomenon is overcome, thereby expanding the use range of the asbestos rubber sheet. Generally, the metal asbestos pad is used at a temperature of 450 ° C (inpidually, it can reach 600 to 700 ° C, such as in a flue gas of atmospheric pressure ~ 0.16 MPa), and the use pressure is 4 MPa, and the maximum is 6 MPa. If the pressure is increased again, the gasket is prone to cross flow and the core material is extruded from the lap joint. Since the metal asbestos pad requires a large bolt tightening force, even when the operating pressure is lower than 2.45 MPa, a flange of pg 25 kg or less cannot be used. Otherwise, the rigidity of the flange and the bolt is insufficient, resulting in deformation and failure of the seal. Some people think that if the core material is changed to a synthetic rubber with better elasticity, the fastening force will decrease. In fact, because the core material is softened, the fastening force is absorbed by the core material, and the fastening force required for the metal plate to be attached to the flange surface cannot be provided, and the pad is easily damaged. In addition, in the medium containing more chlorine ions and the acidic medium, the lap joint of the stainless steel pad and the iron pad is prone to crevice corrosion. The temperature is higher than 450 ° C, and the core material can use ceramic fiber or carbon fiber. A steel plant uses metal-clad ceramic fiber gaskets for high temperature of 1100 ° C, and has not been damaged for two years. Flexible graphite is the most suitable core material. At present, metal-coated flexible graphite mats have been mass-produced in China. Its use is better than metal asbestos pads. The metal pad can be made into various shapes, and is widely used for various heat exchangers, large covers of the reactor, loading and unloading holes, manhole flanges, and the like. The iron pad with a diameter of 2m has been produced in China and is in good condition. A layer of flexible graphite sheet is applied on the surface of the metal pad. Compared with the uncoated metal pad on the surface, the pre-tightening pressure is smaller and the sealing performance is better. At present, there is no such product in China, so some units have attached the existing flexible graphite wrinkle tape to the metal pad and metal flat pad, toothed pad and even asbestos rubber pad surface, solving many leakage problems. For example, a heat exchanger of a plant has a pressure of 5.88 MPa and a temperature of 450 ° C, and the medium is hydrogen/oil and gas. I have used metal flat pads and toothed pads, all of which have leaks. After the flexible graphite wrinkle tape was attached to the flat pad, the problem was solved. It should be pointed out that this gasket form is a simple measure to solve the leakage of the flange gasket. The work quality of the flexible graphite tape directly affects the normal operation of the equipment. If a layer of glue is applied to the back of the strip, the quality of the overlay can be improved. Metal winding mat The metal wound mat skillfully utilizes the heat resistance, resilience and strength of the metal and the softness of the non-metallic material, so that the sealing performance is good, and the performance of winding the flexible graphite mat with the stainless steel strip is optimal. The pre-tightening pressure is smaller than that of the asbestos winding mat, and there is no disadvantage of leakage of asbestos fiber capillary pores. In oil media, 0Cr13 is used for metal strips, while 1Cr18Ni9Ti is recommended for other media. The stainless steel belt with flexible graphite winding mat is used in a gas medium with a pressure of 14.7 MPa (up to 19.6 MPa in China) and 30 MPa in liquid. Temperature -190~+600 °C (available to 1000 °C in the absence of oxygen and low pressure). Teflon has good low-temperature resistance, and its yield strength at low temperatures is much higher than that at normal temperature. Therefore, the Teflon winding mat can be used for low temperature media such as liquid hydrocarbons. At the same time, the thermal conductivity is improved by the addition of the metal strip, and the temperature of the Teflon winding mat can reach 250 ° C, and can be used up to 9 MPa and 200 ° C in an acidic medium. The winding pad is suitable for heat exchangers, reactors, pipes, valves, and pump inlet and outlet flanges with large pressure and temperature fluctuations. For medium to medium pressures and temperatures above 300 °C, the inner ring, outer ring or inner and outer rings should be considered. If a concave-convex flange is used, the winding mat with the inner ring is better. A good sealing effect can also be obtained by attaching a flexible graphite sheet to both sides of the flexible graphite winding mat. A large-scale chemical fertilizer plant waste heat boiler is a key equipment for high temperature and high pressure. It uses a flexible graphite winding mat with an outer ring, which does not leak at full load and leaks when the load is reduced. A 0.5 mm thick flexible graphite plate was added to both sides of the gasket, which was cut into an arc shape, and the joint portion was overlapped by a slanting opening, and the use condition was good. Metal flat pad, wave pad And toothed pad metal flat pad, metal wave pad Generally used for medium and high pressure valves, pipes and equipment flanges with small diameters. The use pressure is based on the temperature, the former is 1.568~31.36MPa, and the latter is 1.568~3.92MPa. The gasket material is selected based on the media and temperature. Octagonal pad and oval pad The octagonal pad and elliptical pad for the trapezoidal groove face flange (commonly known as “soil ring” in the refining industry) have good sealing performance. On the tapered surface of the groove, the octagonal pad is in face contact and the elliptical pad is in line contact. Therefore, the elliptical pad has a good fit under a low fastening force, but needs to be tightened twice; and the octagonal pad is generally less likely to leak after being fastened once. Their shortcomings are that they require a large bolt tightening force. When used for low pressure and high temperature conditions, the flange grade must be above pg25kg. Source: China Gaskets Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

A TV program many years ago, about China’s construction of nuclear power plants, foreign experts instructed Chinese workers to tighten the screws three times and then back half a circle. 1. Why not tighten, but half off? 2. If it is necessary to withdraw half of the buckle, can it be screwed to the retracted position instead of being tightened and released? The rigor and persistence of the Germans in the spirit of craftsmen has been praised by the people of the country. Some friends will ask if you just screw two laps and half a half is not finished? But is this the case? In most German high-end machinery and equipment factories, when assembling special parts, the screw is strictly guided by the operation manual, and the torque applied is clearly defined. In fact, after the screw is tightened, in order to prevent loosening, an additional pre-tightening force should be applied, so the pre-tightening force will be eliminated after the loose half-turn, and the screw is elastically deformed after tightening, especially under the condition of high temperature and shock load. In the long run, the continuous pressure will cause creep, and after the screw becomes plastically deformed, its strength will drop or even fail. Retracting a half turn is to restore the elastic deformation and eliminate the pre-tightening stress. After the screw is subjected to continuous pressure deformation or elastic deformation, the probability of plastic strain and failure is greatly reduced, so that the screw can maintain a constant high-strength pressure. And directly twisting two and a half turns can not achieve this effect. Tell a detailed story again The same brand model of the car has original imported and domestic assembly points. In the domestic assembly, a detail makes the manager quite a headache. In the original German, the worker screwed the screw strictly in accordance with the requirements of the operation instructions and then returned to the circle for three times; the assembly factory in China also requested this, but the assembly workers finally returned. There are more lazy people in the half circle, but this is the difference that is invisible to the naked eye. As time goes by, the influence of that half circle appears. The same car model, some parts of the domestic car is significantly higher than the imported car failure and maintenance rate. Let me tell you a detailed story told by a German car brand executive friend: The same brand model of the car has original imported and domestic assembly points. In the domestic assembly, a detail makes the manager quite a headache. In the original German, the worker screwed the screw strictly in accordance with the requirements of the operation instructions and then returned to the circle for three times; the assembly factory in China also requested this, but the assembly workers finally returned. There are more lazy people in the half circle, but this is the difference that is invisible to the naked eye. As time goes by, the influence of that half circle appears. The same car model, some parts of the domestic car is significantly higher than the imported car failure and maintenance rate. Car assembly The rigor and persistence of the Germans in the spirit of craftsmen has been praised by the people of the country. Some friends will ask if you just screw two laps and half a half is not finished? But is this the case? In most German high-end machinery and equipment factories, when assembling special parts, the screw is strictly guided by the operation manual, and the torque applied is clearly defined. Screw In fact, after the screw is tightened, in order to prevent loosening, an additional pre-tightening force should be applied, so the pre-tightening force will be eliminated after the loose half-turn, and the screw is elastically deformed after tightening, especially under the condition of high temperature and shock load. In the long run, the continuous pressure will cause creep, and after the screw becomes plastically deformed, its strength will drop or even fail. Retracting a half turn is to restore the elastic deformation and eliminate the pre-tightening stress. After the screw is subjected to continuous pressure deformation or elastic deformation, the probability of plastic strain and failure is greatly reduced, so that the screw can maintain a constant high-strength pressure. And directly twisting two and a half turns can not achieve this effect. Brief analysis of the tightening process 1, 541 rules (ie 50%, 40%, 10%) See Figure A: Normally, during the tightening of the bolt, the torque actually converted to the bolt clamping force is only 10%, the remaining 50% is used to overcome the friction under the bolt head, and 40% is used to overcome the thread pair. The friction, which is the “541” rule, mainly reflects the relationship between clamping force and friction. However, if certain improvement measures (such as applying lubricant) or defects in the thread pair (such as impurities, bumps, etc.) are applied, the proportional relationship will be affected differently. Figure A, 541 rules 2, the characteristics of the bolt connector Figure B: Bolt Connector Features Main variables of the tightening process Torque (T): The tightening torque applied, in units of cattle (Nm); Clamping force (F): the actual axial clamping (pressure) tightness between the connecting body, unit cattle (N); Friction coefficient (U): the torque coefficient consumed by the bolt head and the thread pair; Corner (A): Based on a certain torque, the bolt will reproduce a certain amount of axial elongation or the thread angle at which the connecting member is compressed and needs to be rotated. German connection experts clearly explain the bolt calculation animation demonstration Bolt tightening control method 1. Torque control method Definition: When the tightening torque reaches a certain set control torque, the control method of tightening is stopped immediately. Advantages: The control system is simple and straightforward, and it is easy to check the quality of the tightening with a torque sensor or a high-precision torque wrench. Disadvantages: The control accuracy is not high (pre-tightening error is about ±25%), and the potential of the material cannot be fully utilized. 2, torque – angle control method Definition: After screwing the bolt to a small torque, start from this point and screw a control method of the specified corner. Advantages: The bolt axial preloading precision is high (±15%), and a large axial preloading force can be obtained, and the values can be concentratedly distributed around the average value. Disadvantages: The control system is more complicated, and it is necessary to measure the two parameters of torque and rotation angle; and the quality inspection department is not easy to find an appropriate method to check the tightening result. 3. Yield point control method Definition: A method of stopping the tightening after tightening the bolt to the yield point. Advantages: The tightening accuracy is very high, and the preload force error can be controlled within ±8%; however, the accuracy depends mainly on the yield strength of the bolt itself. Disadvantages: The tightening process requires dynamic and continuous calculation and judgment of the slope of the torque and the angle curve. The real-time performance and operation speed of the control system have high requirements. Source: China Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Screws are known as industrial meters, though small but not small. Especially the plane rocket this high-tech content of the object, bolts can not be ignored, once loose, the consequences are unthinkable! How do bolts prevent loosening? Bolted connections of aircraft generally have anti-loosening measures, such as fuses, open pins, bumpers, safety screws, etc., smaller plate nuts through the elliptical hole to achieve self-locking, the nut is not installed when the hole is elliptical, and through the nut tail groove clamping. Fuse A thin metal wire is used to connect two or more fasteners together. Two. When a component has loose tendency, it will be blocked by the fuse and stop developing. Material: low carbon steel, stainless steel and brass, etc. commonly used is low carbon steel wire. In insurance, you can choose single or double fuse form, generally twisted into a braid in the form of double most widely used, as shown in the following figure. Single-stranded fuses are commonly used in small groups of screws with very close spacing or in places that are difficult to reach, as shown in the figure. Generally speaking, if threaded fasteners are clustered together, the form of mutual series insurance is much superior to separate insurance. The number of components that are insured in series should be determined on specific occasions. Cotter pin The installation of the cotter pin is as follows: Insurance film Insurance screw In addition, thread self-locking is one of the most common anti-loosening measures, thread self-locking is generally achieved by a special thread tooth type, self-locking thread pitch (pitch) is small. Self-locking performance generally depends on the nut, unless the screw damage is particularly serious, so self-locking too small fault can generally be solved by replacing the nut. What are the ways to prevent screw loosening in work? General screw and nut connections are self-locking, under static load and working temperature changes little, will not be self-loose. However, under the impact, vibration or variable load, and when the working temperature changes little, the connection may be loose, affect the work, and even cause accidents. In order to ensure the safety and reliability of connection, effective anti loosening measures must be taken for connection between screw and nut. Size to choose the right, slightly large or small screws, may be reluctant to use at the moment, but in the long run, will occur loose, or lock. Processing special engineering plastics on the screw teeth can make the screw cap produce strong friction torque and reaction force during the locking process because the engineering plastics are pressed and extruded, produce contact of all teeth, provide absolute resistance to vibration, make the general screw become permanent strong anti-loosening screw, thoroughly solve the problem of loose connection between screw and screw. It’s a problem. Loosening method to increase friction. This kind of anti-loosening method is to make the screwed threads do not lose pressure because of the change of external load, so there is always friction resistance to prevent the connection from loosening. The loosening methods for increasing friction include installing spring washers and using double nuts. Mechanical loosening. This kind of anti-loosening method is to use a variety of stop parts to prevent the relative rotation of the thread and parts to achieve anti-loosening. Mechanical loosening is more reliable, so there are more applications. Commonly used mechanical anti-loosening measures include open pin and groove nut, back washer and round nut, stop washer and nut, Shenlian steel wire and so on. No loosening method can be dismantled. By means of positioning welding and spot riveting, the nut can be fixed on the bolt or the connector, and the screw can be fixed on the connector, thus achieving the effect of anti-loosening. Source: China Fasteners Manufacturer – wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)

Threads, do mechanical daily dealings, especially hydraulic and pneumatic, a long time domestic, metric, imperial, straight cone, sealed non-sealed, inside and outside, 55 degrees and 60 degrees . In short, I am often confused. I use it once to check it from start to finish. I am here to summarize it and hope to help. My approach is to print it out and put it on the table. When you use it, you can check it at any time. After a long time, you will naturally remember it. (One) NPT is a general-purpose American standard taper pipe thread with a tooth angle of 60° The PT tooth is an inch taper thread with a tooth angle of 55°, which is most commonly used in sealing. The inch pipe thread is a fine thread, because the tooth depth of the coarse thread will seriously reduce the strength of the pipe with the outer diameter of the thread. The PF tooth is a parallel thread for the tube. G is a 55 degree non-threaded sealed pipe thread, belonging to the Wyeth thread family. Marked as G for cylindrical thread, G is the general name for the pipe thread (Guan), 55, 60 degree pision is functional ZG is commonly called tube cone, that is, the thread is made of a conical surface. The general water pipe joints are like this. The old national standard is labeled as Rc. The metric thread is expressed by the pitch of the thread. The US and British thread is expressed by the number of threads per inch. This is the biggest difference. The metric thread is a 60-degree equilateral tooth type, and the inch thread is an isosceles 55-degree tooth type. 60 degrees. Metric threads are used in metric units, and American-English threads are used in imperial units. The pipe thread is mainly used for the connection of the pipe, and the inner and outer threads are closely matched, and there are two kinds of straight pipe and tapered pipe. The nominal diameter refers to the diameter of the pipe to which it is connected. It is obvious that the diameter of the thread is larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameter of the inch thread in inches. (Two) 1, inch uniform thread Widely used in inch countries, this type of thread is pided into three series: coarse tooth series UNC, fine tooth series UNF, extra fine tooth series UNFF, plus a fixed pitch series UN. Marking method: Thread diameter – number of teeth per inch series code – accuracy level Example: Coarse tooth series 3/8-16UNC-2A Fine tooth series 3/8—24UNF—2A Extra fine tooth series 3/8—32UNFF—2A Fixed pitch series 3/8-20UN-2A The first digit 3/8 indicates the outer diameter of the thread in inches. The conversion to the metric unit mm is multiplied by 25.4, ie 3/8×25.4=9.525mm; the second and third digits 16, 24, 32, 20 are The number of teeth per inch (the number of teeth in the length of 25.4mm); the character code UNC, UNF, UNFF, UN after the third digit is the serial number, and the last two digits 2A are the precision grades. Conversion of 2, 55° cylindrical pipe threads 55° cylindrical pipe thread, which is derived from the inch series, is widely used in metric and inch countries. It is used to connect liquid pipe, gas and wire fittings to pipes. However, the codes of different countries should be pressed. The foreign code in the table (control table) is converted into the code name of our country. The 55° cylindrical pipe thread code of each country is listed in the following table. Country code China G Japan G, PF UK BSP, BSPP France G Germany R (internal thread), K (external thread) Former Soviet Union G, TPУБ ISO Rp 3, 55 ° conical pipe thread conversion The 55° conical pipe thread means that the thread has a profile angle of 55° and the thread has a taper of 1:16. This series of threads is widely used in the world, its code name, different national regulations, see the table below. According to the foreign code in the table below, it is converted into our country code. Country code China ZG, R (external thread) UK BSPT, R (external thread), Rc (internal thread) France G (external thread), R (external thread) Germany R (external thread) Japan PT, R ISO R (external thread), Rc (internal thread) 4, 60 ° conical pipe thread conversion 60° conical pipe thread refers to pipe thread with a tooth angle of 60° and a taper of 1:16. This series of threads is used in China’s machine tool industry and the United States and the former Soviet Union. Its code name, China’s past regulations for K, and later for Z, is now changed to NPT. The thread code comparison table is shown in the table below. Country code China Z (old) NPT (new) United States NPT Soviet B 5, 55 ° trapezoidal thread conversion The trapezoidal thread is a metric trapezoidal thread with a tooth angle of 30°. This series of threads is relatively uniform at home and abroad, and its code name is also quite consistent. See the thread code below. Country code China T (old) Tr (new) ISO Tr Germany Tr Former Soviet Union Tr