Low leakage of pneumatic valve seal grade classification standard

low leakage of pneumatic valve is refers to the actual pneumatic valve leakage is very small, by conventional hydraulic pressure, air pressure seal test cannot determine, need to use more advanced methods and instruments to detect tiny leak. Pneumatic valve of the tiny leak is referred to as a low leakage to the outside environment. Pneumatic valve testing are frequently used in international at present low leakage standard basically has the following three kinds:
( The U. S. environmental protection agency EPA method 'volatile organic components leak detection.
( ISO (international organization for standardization Industrial pneumatic valves: low leakage measuring, testing and qualification program.
( SHELL oil company SHELL MESC SPE/' industrial pneumatic valve: low leakage measurement, classification system, qualification procedure and switch of pneumatic valve and control valve type approval and product test '.
only the U. S. environmental protection agency EPA Method standard the hierarchies of the detection Method without leakage, belong to the local standards and regulations, less application. The international organization for standardization (ISO and SHELL oil company SHELL MESC SPE/this two standard, for the performance of the pneumatic valve from close ranks, endurance level and temperature to assess three aspects. Close ranks against leakage of pneumatic valve stem seal and pneumatic valve body, is divided into A, B, C three levels, the ISO standard pneumatic valve seal leakage requirements of em/m or less, and pneumatic valve stem leakage of two standards are calculated according to the diameter of the pneumatic valve stem.
ISO grade A sealed highest grade, B, c level sealed with SHELLMESC SPE/standard. Usually low leakage of pneumatic valve seal below class B grade, and because bellows seal pneumatic valve in the pneumatic valve rod sealing parts adopt metal bellows seal, the seal grade lower than A level.

low leakage of pneumatic valve selection of bellows seal pneumatic valve is one of the low leakage of pneumatic valve. Past with pneumatic valve leakage level is generally selected have special requirements of working condition of bellows seal pneumatic valve, pneumatic valve f - but as a result of bellows seal JJm work difficulty is big, high technical requirements, the corrugated pipe material also can't fully realize localization, the cost is too high, so as to restrict its extensive use in the petrochemical industry. At present, as people's safety, strengthening environmental protection consciousness, cooperation with foreign technology, as well as the domestic pneumatic valve factory itself continuously strengthen technical force, the understanding of the domestic technical personnel for low leakage of pneumatic valves also constantly improve, make its application range is constantly expanding. For flammable and explosive, toxic medium in petrochemical enterprises choose the pneumatic valve if you can satisfy the standard of low leakage, it will greatly reduce the emissions of toxic, flammable and explosive medium in the device, avoid the pneumatic valve leakage fire, explosion, poisoning, etc. , which endanger the safety of the life accident. Meet ISO, SHELL MESC SPE/standard low leak compared with corrugated pipe pneumatic valve, pneumatic valve has simple structure and manufacture easy, its high cost compared with the general pneumatic valves about % ~ %. According to the former in the face of the levels of analysis and comparison, two standard seal tightly grade B pneumatic valve leakage is generally can meet the requirements of some special working condition of the low leakage, machining accuracy is relatively easy to achieve, manufacturing costs have gone up a lot, it can replace part of the use of corrugated pipe pneumatic valves. At present, the low leakage of pneumatic valve for high content of hydrogen sulfide gas purification system has more practical significance. Because hydrogen sulfide is a kind of highly toxic, flammable gas, heavier than air, can be gathered in the lowlands, a certain concentration of hydrogen sulfide can harm the body, and even lead to death, so for this type of natural gas purification facilities more strict leakage.