The original standard for valve seat leakage rating of control valves was established by the American Institute of Standards and implemented by the American Institute of Fluid Control (ANSI BI6.104 FC170-2). The leakage level standard in the Technical Conditions for Regulating Valves of Power Plants in China is formulated with reference to this standard. Purpose of specifying the seat leakage class. It is to provide users and manufacturers with a method to test the closing performance of the regulating valve or control the leakage capacity of the valve seat. The content discussed in this article can only be used as an example. The valve seat leakage test shall refer to the latest ANSI standard. The actual allowable valve seat leakage of a certain valve depends on the valve diameter and type published by the manufacturer.

2. The wafer type pneumatic butterfly valve, after being used for a long time, is prone to wear of the valve core seal ring, damage of the valve stem and valve seat, resulting in gas leakage in the valve, slow action of the valve or abnormal reversing and other failures. At this time, the sealing ring, valve rod and valve seat should be replaced, or the wafer type pneumatic butterfly valve should be replaced.