What is the failure analysis and treatment of the bellows globe valve by gate valve manufacturers

　The leakage of the bellows globe valve of gate valve manufacturers is usually divided into external leakage and internal leakage, and there are many reasons for leakage. Under normal circumstances, the liquid medium contains solid impurities, which will destroy the sealing surface and lead to failure. Combined with the field application analysis, the main reasons for valve stem leakage of gate valve manufacturers are related to the operation mode, valve structure and working environment.

Gate valve manufacturer

1. Structure:

The valve stem adopts the double sealing structure of bellows and packing. The bellows are welded with the inner ring and outer ring to form a bellows assembly, and then welded with the valve stem and guide body to prevent media leakage through the valve stem. The stem is moved up and down from the flat key I until the upper face of the flat key I touches the lower face of the lower packing. Because the lower packing is teflon material, if the valve is opened excessively, the flat key I will be embedded in the packing, the valve will no longer be opened and closed, and the bellows assembly will be crushed, resulting in media leakage along the valve stem. The stretch length and compression amount of the bellows are determined according to the valve stroke. If stretched or compressed beyond the limit, the bellows may be damaged, causing the small braided tube to break and seal failure. Therefore, it is necessary to increase the valve opening and closing limit device, so that the bellows can expand and expand within the design range during the valve opening and closing process.

2. Working environment:

The poor working environment of the bellows globe valve of gate valve manufacturers is also one of the reasons for its failure. Because the bellows stop valve installed on the ship has been working in the salt spray environment for a long time, the upper part often drops condensate, resulting in corrosion of the upper thrust ball bearing. In severe cases, it will lead to valve stem contact corrosion.

3. Operation:

If the bellows stop valves of gate valve manufacturers open and close excessively in use, they may not meet the corresponding performance requirements. If the valve is closed too much, the sealing surface may be damaged, resulting in a failure of the seal when the valve is used again. If the valve is opened excessively, it may operate the bellows assembly and cause the valve to leak.

Gate valve manufacturers analyzed the problems of the valve, and improved its environment, structure and operation. One is to increase the limit welfare of flat key one, add 3mm thick stainless steel packing pad on the lower packing of polytetrafluoroethylene material to prevent the packing from becoming dirty and limit the valve stem.

When the valve is closed, if it is not possible to close the valve, it should not be forcibly closed, but should open the valve, flush with liquid for a period of time, and then close repeatedly. If it still cannot be closed, check the grinding sealing surface. When the valve is opened, when the valve is opened to a certain height and the valve stem encounters small resistance, try not to continue to force the valve to open to extend the service life of the valve stem and its seals.

When installing a stop valve with thrust ball bearing on the upper part of the valve stem, condensate should be avoided from dripping directly on the valve stem, causing valve stem corrosion.