In the HG/T20570.2 "safety valve settings and selection" mentioned in these kinds of safety valve, but did not give a clear definition, meaning clear, want to find a more formal definition. Which standard is better if it is inside?.
Bellows type safety valve refers to the valve in the valve plate support and guide between the bellows, the main balance valve disc upper and lower back pressure area, the bellows shape similar to the old-fashioned washing machine drain pipe. Of course, the bellows is not only balanced back pressure, it also allows the media has no chance to enter the spring chamber, in the valve chamber and the spring chamber between the better sealing effect. Closed or open valve cap, as the name suggests, is to see whether the bonnet is sealed, and wrench is not too much, there are wrenches can also be closed valve cap, but also is an open valve cap.The above is my personal explanation, if you want to further understand, you can refer to the relevant standards of API520. Or find some safety valve samples, which will be described in detail.
Open help jump wrench, enclosed is a helpless jump wrench, safety valve bellows safety valve is inside the system with back pressure, the bellows safety valve, it can eliminate the effect of back pressure on the safety valve, bellows is mainly to eliminate back pressure. I hope I can help you!!
The selection of safety valve is generally based on displacement, set pressure and other related parameters, calculation of throat diameter level and other parameters, API standard formula, or directly to the safety valve manufacturer selection software, it is better.
