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

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)

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)

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)

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

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)

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)

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

Liquefied gas is mainly produced in oilfields and refining and chemical enterprises. It has the characteristics of less pollution, high calorific value, easy transportation and simple storage, so it is widely used in civil, commercial services, industrial production and other fields. Table 1 shows the global supply of liquefied petroleum gas and forecast data from 2015 to 2021. As can be seen from the table, in recent years, global LPG production has continued to increase, with annual growth rates of more than 2%. In addition, the average annual compound growth rate of LPG consumption and output in China has reached 15.69% and 9.95%, respectively. In 2016, China’s liquefied gas production was 35.539 million tons, an increase of 19.41% year-on-year. LPG has become an important part of China’s energy structure. Table 1 Global liquefied gas supply and forecast for 2015-2021 Table 3 Partial parameters of the amine solution

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)