Analysis of valve sealing and valve function

The tightness of the valve is an important indicator of the function and quality of the valve.
The problem of internal leakage of the valve seriously threatens the normal operation of the device, and it is difficult to find whether there is any internal leakage in the valve in operation. The investigation results show that various valves used by various petrochemical enterprises have end leakage problems to varying degrees. The reason is that the sealing surface material of the valve plate and the valve seat does not meet the requirements for use, the machining precision is not enough, the wedge angle of the valve plate and the valve seat of the gate valve is not matched, the sealing surface width is narrow, the matching degree is poor, the ram is not in place, Not dead and other factors.
For Z41Y-25, the sealing surface material code Y should refer to the sealing surface material with relatively soft hardness in the sealing pair. The corresponding sealing surface material should obviously be at least cemented carbide, but actually there is The valve only welds hard alloy on one of the sealing faces, while the other sealing surface is the body material of carbon steel. When it is not used for a long time, it will leak due to wear.
For example, a pipe system uses a wafer type butterfly valve, and the valve seat sealing material is made of polytetrafluoroethylene. From the point of view of the working conditions, the requirements are not high, and they are normal temperature and normal pressure. However, during the trial operation, a large number of valves are not tightly closed, and the internal leakage is so serious that they cannot be used normally. Finally, they have to be replaced with gate valves. . After dismantling and checking, it was found that the valve plate and the valve seat in the closed state had a large gap and even light transmission. The reasons for the analysis may be as follows: The structural design of the valve sealing pair is unreasonable or the manufacturing and assembly precision cannot meet the requirements; "The valve installation is not subjected to the required construction and it is subjected to excessive force; #There is welding slag during the construction process Impurities such as sand, metal shavings and the like enter the valve cavity, which affects the sealing effect. In fact, the more practical and fundamental reason is that it is not required to be in accordance with the standard requirements in a certain process of manufacturing, transportation or installation.