1, Domestic and foreign steel wedge gate valve standard profile In a variety of pipelines and equipment such as fluid delivery system, the valve is one of the most widely used valve varieties. The main features of the gate valve are: (1) flow resistance is small; (2) the torque required by the switch is small; (3) the direction of the flow of the medium is not limited; (4) ) Simple and compact body structure; (6) good manufacturing process. Currently widely used in petroleum, chemical, metallurgy, power plants, medicine, food and other industrial installations. With the increasing international economic and technological exchanges, the valve is an important industrial accessory pipeline accessories in the international market is also rapidly increasing circulation, the national standards for the valve is different, the results of the valve length and flange standards Not the same, which caused great inconvenience to the circulation of international valves. At present, the world's advanced countries in the world for the valve design, manufacture, testing have developed their own national standards, the valve standard used in the main metric units are metric and British two systems. China GB, Germany DIN, France NF, the Soviet Union and other countries have adopted the standard valve standards; the United States ANSI, API standards in the past have been used in English, and now also added a metric schedule. Select the national standard gate pressure - temperature rating benchmark is not uniform. Metric countries, usually the maximum working pressure at room temperature is defined as the nominal pressure, such as the GB standard: the nominal pressure of carbon steel WCB valve PN 10MPa that the maximum working pressure at room temperature, when the temperature rises to 425 ℃ when its maximum Working pressure is only 5.3MPa; the United States and other countries using the British system, according to different materials at a specified temperature of the working pressure nominal pressure. For example, a 150 lb. carbon steel gate valve of the American National Standard ANSI A216 WCB material has a permissible working pressure of 150 psi (lbf / in2) at a service temperature of about 560 ° C and a maximum service temperature of 800 ° C , The corresponding allowable working pressure is 80psi (lbf / in2). Valve Metering pressure benchmark and other technical parameters of the valve is not uniform, a serious impediment to the exchange and use of valve products, the issue of international standardization is highlighted. On valve international standardization, in September 1971 held its twenty-fifth council meeting in Geneva, decided to set up a common valve industrial valve Technical Committee TC153 "valve", the secretary country is the British Standards Institution. Since the founding of TC153, its activities have been frequent and many meetings have been held each year to discuss and formulate relevant international standards. ISO / TC153 has carried out a great deal of international standardization work on the basic dimensions of general valves, pressure, temperature grade, material test and name terminology , It formulates the valve basic standard, generally applies to the valve industry in the developed country and the developing country, some standards such as ISO: The general industrial valve sign; The general industrial valve term; The metal valve structure length; The valve bonnet bolt Connected steel gate valve; valve material, inspection and pressure test and more. At present, most of these international standards have been adopted by countries to varying degrees, most of them are adopted (equivalently adopted) and others are equally and unequally adopted (see). ISO International Organization for Standardization in the coordination of valve standards in various countries have done a lot of efforts, ISO international standards that take into account the existing industrialized countries in the valve industry, but also to absorb advanced technology standards in developed countries, as far as possible to harmonize, ISO standards are widely used in all countries in the world. The adoption of international standards is an important technical policy of our country. With the standardization of our valve, the valve standard has been rapidly developed. By actively participating in the international activities in the valve industry, our country can keep abreast of developments in the international standardization and revision of the valves and tracking of international standards Situation, formulate and amend the standards of our country in real time and keep up with the international situation. At the same time, foreign counterparts to understand China's valves, valve enterprises in China to more quickly enter the international market to create the conditions. By comparing the main standards of foreign steel gate valves and our national standards, we try to find out the differences between domestic and foreign standards in several aspects such as the shell part, the sealing part, the stem part and the inspection test of the gate valve. Valve design and manufacture for reference. 2, the shell part of the domestic and international standards comparison Common steel gate shell wall thickness, the basic standards at home and abroad by the correction coefficient of thin-walled cylinder wall thickness formula is calculated, ISO, ANSI, JIS and other standards are basically used The following formula: t = 1.5 [p.d2s-1.2p] where: t-- calculated thickness in inches p - pressure rating in lbf / in2 d- nominal diameter in inches s- basic stress factor Material allowable stress) This formula, close to the medium-pressure valve in China III standard wall thickness formula used: S = 1.32p.DN2 [σ] -1.2p + c American Petroleum Institute API standards, Japan Petroleum Institute JPI Standard valves take into account the special conditions for oil and petrochemical needs, wall thickness than the value of the valve for general industrial use to increase, with 6? -300Lb cast steel gate valve, for example, the corresponding ANSI and ISO standards The minimum wall thickness is 9.6 Å and 8.8 ‰, respectively. However, the minimum wall thicknesses required by the API, JPI and BS standards are 16 Å, 16 Å and 15.9 Å, respectively. Gate valve structure length of different countries have different standards, the current unified by the ISO standard for the length of the two series of sizes, while ISO, ANSI, API and BS standards: End flange can be cast with the valve body forging, welding can also be used to connect. At present, the shell material valve standards in all countries have a special shell material table, the standard specifies the maximum carbon content of the material, such as WCB steel carbon content standard C ≤ 0.3%, but the API, JPI, BS further consider gate valve used in petroleum, chemical and other high-sulfur medium and other special conditions, with reference to NACE MR0175 oil field equipment sulfur stress cracking metal material requirements, selection of shell material carbon content C ≤ 0.25%, hardness HRC 22 Japan's JPI standard shell materials, in addition to the required carbon content of C? 0.25%, but also provides the content of other elements. On the bonnet seal structure API, JPI, BS and our new standards have emphasized the bonnet must have on the seal structure, when the valve is fully open when the stem seal of the seal contact, API, JPI, BS and other standards The seal is generally stainless steel bushing, but must be fixed on the valve cover, work can not be loosened, only the seal on the austenitic stainless steel valve allows body processing or surfacing carbide sealing surface. The valve body and the valve cover connected flange bolts, the early domestic standard universal cast steel gate flange bolts and nuts and more use of high-quality carbon steel, and the United States, Britain, Japan and other advanced industrial countries in the flange bolts The use of alloy steel 35CrMo, the use of high-quality carbon steel nuts, flange bolts in the use of alloy steel, can improve the creep strength of the material, to avoid high temperature creep caused by bolt deformation and leakage or accidents. In this way, even in the use of high temperature conditions, repeated use can still maintain a stable seal, in order to ensure safety, API, JPI and our new standards have emphasized the use of heavy-duty flange bolts hexagonal nuts, studs all Threaded, to avoid and reduce the phenomenon of thermal stress concentration. About flange gasket, GB standard according to the pressure range and temperature of the different provisions of the metal corrugated mat, flat mat, toothed pad and other seven types of gaskets, the United States API, the British BS and Japan JPI standards are on Flange gasket made strict requirements, at work temperature, gasket material should have a certain degree of flexibility and plasticity, and sufficient strength, and to withstand the corrosion of the medium. 3, part of the seal Domestic and foreign standards compared to the seal part of the valve, mainly refers to the sealing surface of the valve seat and the gate. National standards are generally based on the different conditions of the valve provides a series of optional sealing pair, the standard foreign gate material and hardness of the sealing surface have strict requirements, API600 lists fourteen kinds of materials, it also provides When the valve seat sealing surface are made of Cr13 material, the hardness value of not less than HB250, so to improve the sealing surface sealing performance and extend the service life are beneficial. In addition to the metal-to-metal seal pair, the British Standard states that the seat can also be made of a soft seal, but the seal of the metal part can still provide a seal when they are worn or damaged. China's valve standard Until 2006, the GB standard on the sealing surface of the valve sealing layer thickness is provided as follows: after processing the sealing surface surfacing layer thickness of at least 2 ?; API, BS standard regardless of the specifications are provided: Processing The thickness of the sealing layer after surfacing is at least 1.6. The new API602 standard stipulates that the thickness of the sealing layer after processing should be at least 1.0 ?, compared to the conservativeness of our standard. Without affecting the sealing performance and sealing life, reducing the overlay thickness of the sealing surface can save expensive sealing surface materials. At present, the new GB / T12234-2007 standard has referred to the relevant data adopting API and BS standards. 4, on the valve stem and stem seal stem in the valve opening and closing operation, in addition to withstand the pull, pressure and torque of the force, but also direct contact with the media and packing, stem material must be guaranteed at the specified temperature Sufficient strength and impact toughness, and have a certain corrosion resistance, wear resistance, early valve stem material in our country to use more stainless steel, and the standard without the specific requirements of the stem hardness; international standards and foreign standards API, BS, JPI, etc. Attaches great importance to the stem quality control, a clear rule stem material used at least stainless steel Cr13, and made its hardness requirements. Foreign standards and GB standards on the packing area stem diameter gives the minimum specified value, also provided for the overall stem forging the structure, does not allow the use of welded stem assembly. National standards for the stem on the seal have common requirements, the provisions of the valve stem should be provided on the sealing surface, when the valve is fully open state, it seals with the valve seat seal to ensure reliable sealing. On the structure of the stem head, the national standards are provided for "T" type. The BS and JPI standards also add that the stem and gate should not be threaded or pinned to prevent the stem from rotating or disengaging from the gate. In order to ensure the safety of the operation, API, BS and new GB standards stipulate that when the new valve is in the closed position, the length of the stem thread protruding from the stem nut should be at least equal to the required wear stroke. For valves with a nominal diameter less than or equal to DN150, the stem thread extends over the stem nut up to 5 times the wear stroke and up to 3 times the wear stroke for valves larger than DN150. 5, on the gate valve test, inspection and inspection International Organization for Standardization and the world's advanced industrial countries have developed a common valve inspection and test standards, ISO5208 industrial valve test methods, API598 valve inspection and testing, MSS steel valve Pressure test and other standards have clearly defined the valve test items, while the test pressure, test medium, the duration of the test and allows the amount of leakage and so made a detailed provision. Gate valve test include shell test, low pressure seal test, the seal test and high pressure seal test. US API standards: the gate valve shell strength, the upper seal test and low pressure seal test three necessary tests, and high pressure seal test is optional. Japan's JIS standard gate valve only need to shell, seat seal and seal on the three tests. China's GB standard reference API598 standard requirements. Contrast the national standards for the test valve, the shell strength test Most countries require the standard 1.5 times the rated pressure at room temperature as the test pressure. The duration of the test required by national standards varies according to the nominal size of the valve, but consistent with the provisions of the shell strength test is not allowed any leakage. Liquid test medium commonly used at room temperature water, GB, API, ISO and other standards also stressed that the test medium should contain anti-rust agent, but also allows the use of liquid viscosity is not greater than the test. Low-pressure seal test commonly used air or inert gas, China's standard test pressure of 0.5-0.7Mpa, the upper seal test is carried out in the fully open state, and its test pressure is generally 1.1 times the nominal pressure, both domestic and international standards Provisions do not allow any leaks. The above five aspects of the steel gate valve conducted a comparative analysis of domestic and international standards, regardless of the use of that national standard, users should also seriously study and consult the relevant standards to understand the content of the standards and special provisions of the standard. Only in this way can we use the standard flexibly and fully reflect the standard interchangeability and consistency in the design and manufacturing work. Zhejiang Zhongtai Valve Co., Ltd. Senior Engineer Song Qiang More Keywords: Valve