What is the cause of the pneumatic valve leakage?

Pneumatic valve leakage problem seriously threatens the normal operation of the device, and operation of the valve and it's hard to find whether there is leakage, results show that the existence of the petrochemical enterprise to use different degree of the valve leakage problems. The reasons of disc, seat sealing surface of the material do not conform to the requirements of the use, the machining accuracy is not enough, the valve plate gate valve, the seat of the wedge Angle is not matching, sealing surface width different, alignment, closed tightly and other factors. Analysis of the reason may be the following: the structure of the pneumatic valve seal design is not reasonable or manufacture and assembly accuracy can not meet the requirements; The valve installation failure to construction and make its bear too much force; In the construction process of welding slag, sand, scrap metal, such as impurities into the valve cavity, the sealing function is affected. , is practical, is also the fundamental reason is that in the manufacturing, transportation and installation of a process is not stipulated in the standard requirement to do. And as a pipeline system chose the wafer butterfly valve, valve seat adopt ptfe sealing materials. From the point of working condition, demand is not high, atmospheric pressure, but found that the number of the valve in the process of commissioning is lax, severe leakage, so can't normal use, and then need to replace the gate valve. Tear open come down to check found that closed the valve plate and valve seat there is a big gap, pervious to light.