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The sealing performance of a valve is an important indicator for measuring its function and quality.
The problem of internal leakage in valves seriously threatens the normal operation of the equipment. Moreover, it is difficult to detect whether there is internal leakage in the valves in operation. The investigation results show that various valves used by different petrochemical enterprises have internal leakage problems to varying degrees. The reasons include that the sealing surface materials of the valve plate and valve seat do not meet the usage requirements, the processing accuracy is insufficient, the wedge angles of the valve plate and valve seat of the gate valve do not match, the widths of the sealing surfaces are inconsistent, the fit is poor, the gate plate is not in place, and it cannot be closed properly, etc. For the Z41Y-25, the sealing surface material code Y should refer to the relatively softer sealing surface material in the sealing pair. The corresponding other sealing surface material should also be at least hard alloy. However, in reality, some valves only have hard alloy surfacing on one of the sealing surfaces, while the other sealing surface is made of carbon steel. Shortly after being put into use, internal leakage occurred due to wear and tear. For instance, in a certain pipeline system, wafer-type butterfly valves were selected, and the sealing material of the valve seat was polytetrafluoroethylene. From the perspective of operating conditions, the requirements are not high, all at normal temperature and pressure. However, during the trial operation, it was found that quite a few valves could not be closed tightly, with severe internal leakage, making them impossible to use normally. Eventually, they had to be replaced with gate valves. When it was disassembled for inspection, it was found that there was a large gap between the valve plate and the valve seat in the closed state, and even light was transmitted. The possible reasons for this could be as follows! The structural design of the valve sealing pair is unreasonable or the manufacturing and assembly accuracy does not meet the requirements. The valve was not installed as required, causing it to bear excessive force. During the construction process, impurities such as welding slag, sand and metal shavings entered the valve cavity, affecting the sealing effect. In fact, the more practical and fundamental reason is that during a certain process of manufacturing, transportation or installation, the requirements stipulated by the standards were not followed.
Article Link: Industrial Control Network (100 Stations