1. 1 The status quo of China's valves and piping selection China's petroleum, chemical, electric power, machinery and other industries were developed in the 1950s along the former Soviet Union model. Therefore, the piping accessories used in the process equipment (such as valves, Flanges and flange fittings, etc., are also produced in accordance with the standards of the former Soviet Union. Therefore, the mechanical and petrochemical pipeline accessories used in the former Soviet Union standards have already formed a system in China and have a long history of use. JB standard flanges and valves have been used in pipeline design for decades. In particular, some old equipment upgrades and modifications require some matching pipeline accessories, which cannot be eliminated in a short period of time and require long-term transition.
Since the reform and opening up, China has introduced many large and medium-sized petrochemical plants. Most of these imported devices use European and American technology.
Most of its pipeline valves are American ASME, API standard, German DIN standard, British BS standard and so on. At present, a considerable number of valve factories in China can produce corresponding valves according to foreign standards. However, there are many problems with JB valves. Therefore, the superior performance of foreign valves, especially API valves, in domestic production and application is becoming more and more obvious.
1. 1. 1 API and JB valve performance comparison 1 API standard valve structure length is shorter, the valve takes up less space, light weight, and JB valve structure length is long, the structure of the ram and bracket is not reasonable. The API valve adopts the elastic ram structure, which has good sealing effect and reduces internal leakage. In addition, the elastic ram can avoid over-tightening and seizure caused by thermal expansion. Stainless steel diaphragm valve;
2 JB standard valve One type represents a fixed type, and the model provided by the standard is very limited. If the user makes a slight modification, the manufacturer considers it to be a non-standard valve, and proposes a fare increase or a delayed delivery. If the design changes the valve according to the operating conditions. The seal pair or packing structure is considered by the manufacturer to be non-standard, and the API standard does not exist.
3 user use shows that JB valve is easy to leak and leak, short life, inconvenient operation, narrow selection, and
API valves can overcome these deficiencies.
The API valve has a quality demonstration mechanism, which can effectively guarantee the quality of the valve, and the API standard has detailed regulations on the structure, materials, test and inspection of the valve, which is easy for the manufacturer and the user to use.
In addition, in 1989, China introduced a set of GB valve standards, but this set of standards has not been widely promoted and applied. The flanges paired with them are the so-called "large outer diameter" series, and the temperature and pressure curves of A. GB valves and JB valves. It is not the same, the two can not be used together; GB valve standard system is not perfect, it uses the temperature and pressure curve specified by GB 9131, and the material listed in GB 9131 standard is less, which limits its use. At present, the valve varieties in the domestic market A variety of stainless steel manholes, various valve standards in the transition period between the old and the new, a large number of JB standard valves are still in production, GB standard valves have been introduced, in addition to a large number of foreign standards such as API STD. 600, API STD. 602, API STD 6D, ASME/ANSI B 16-34, JBI-
Valves manufactured by 7S-36, BS5352, E101, etc., can meet different needs.
1.1.2 Matching of Valves and Fittings Since the valves are installed in pipes, we will first introduce the series of pipe flanges and piping standards currently selected in China. At present, the international standard for pipe flanges is mainly composed of two systems: the European flange system and the American flange system. The European flange system is represented by the German and former Soviet pipe flanges; the American flange system is represented by the American ANSI pipe flange; the flange sizes of the two systems are not interchangeable with each other.
Most of China's petrochemical industry was established in the 1950s according to the former Soviet model. Therefore, the JB standard series is close to the European flange system. At present, there are two sets of outer diameter series of pipe specifications in China's steel pipe standards, sanitary diaphragm valves, one set is "small outer diameter" pipe; the other set is "large outer diameter" pipe. The nominal diameter of the valve flange commonly used in petroleum and chemical plants and the matching pipe series are shown in Table 1-14. The meaning of "large and small outer diameter pipe" refers to the size of the outer diameter of the pipe required for the pipe fittings (valves, flanges, and fittings) under the premise of the nominal pipe diameter of the same pipe. Large outer diameter tube.
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