Can the leakage class of a self-acting control valve reach Class V? It’s usually grade IV, right?
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This post was last edited by Deep-water fish bpec2014 on 2015-6-19 at 13:45
It is carried out in accordance with the project specifications; for example, my current project requires that the leakage level of control valves be no less than grade V, and that of shut-off valves be no less than grade VI.
The leakage class of self-acting control valves can reach Class V, with Class IV being the common level. Levels IV and V mainly differ in their experimental standards. For Class IV valves, the experimental pressure difference is 0.35 MPa, and the allowable leakage amount is a fixed value ； The test pressure difference for Class V valves ranges from 0.7 MPa to the valve’s maximum operating pressure, and the allowable leakage is the pressure difference multiplied by a coefficient. So when the requirements for the valve reach a certain level, the leakage rating naturally increases. For example, the user specified a high working pressure difference; as a result, the manufacturer equipped it with a diaphragm head with high thrust, and as the thrust level increased, the sealing capability also improved to meet the requirements of grade V. I’ve seen people insist on avoiding grade V valves during bargaining, only for the manufacturer to still send grade V valves when they arrive. It seems that as long as the other requirements are met, the valves produced will inevitably be of grade V; even if you pay for grade IV valves, the manufacturer has no choice but to deliver grade V valves
Yes, I always use level IV when writing specification documents; I have never used level 5