valve sealing surface faults and troubleshooting methods
1.The sealing surface of the valve is not tight
Reason: The connection between the valve stem and the closing part is incorrect, worn or suspended
Method: The connection between the valve stem and the closing part meets the design requirements, and those that do not meet the requirements should be trimmed. When the closing part is closed, the top center is not suspended and has a certain direction adjustment function
Reason: The valve stem is bent or improperly assembled, so that the closing part is skewed or misaligned
Method: During the acceptance of the new valve and the repair of the old valve, the curvature of the valve stem should be carefully checked, and the valve stem, valve stem nut, closing part, valve seat and other parts should be on a common axis
Reason: The sealing surface is not closed tightly or the cold shrinks after closing, and there are fine seams, resulting in erosion.
Method: The opening and closing of the valve should be marked and check whether it is closed tightly with the help of instruments and experience. After the high temperature valve is closed, there will be slits due to cooling, and it should be closed again at a certain interval after closing.
Reason: The sealing surface is dropped due to too small processing reserve or due to wear
Method: The new sealing surface should have sufficient reserve. Before assembling the valve, measurement and coloring should be carried out to check the reserved amount. If the reserved amount is too small, it is estimated that the sealing surface can not be maintained for one operation cycle, and it should be repaired or replaced.
2.Damage to the sealing surface
Reason: The sealing surface is not flat or the angle is wrong, not round, and the sealing line cannot be formed
Method: The method of processing and grinding the sealing surface should be correct, the coloring inspection should be carried out, and the shadow circle should be printed and continuous before assembly.
Reason: improper selection of sealing surface material or valve not selected according to working conditions, resulting in corrosion, erosion, wear and other phenomena
Method: Select the valve or replace the sealing surface strictly according to the working conditions. For batch products, the performance test of sealing surface such as corrosion resistance, wear resistance and scratch resistance should be done.
Reason: The surfacing and heat treatment of the sealing surface are not operated according to the regulations. Wear due to low hardness, corrosion due to burning of alloy elements, and cracks due to excessive internal stress
Method: Surfacing and heat treatment should comply with regulations and specifications, and there should be a strict quality inspection system
Reason: The surface-treated sealing surface peels off or loses its original performance due to excessive grinding
Method: The sealing surface surface quenching, nitriding, boronizing, chrome plating and other processes are carried out in strict accordance with its regulations and specifications. When repairing, the cutting amount of the permeable layer of the sealing surface should not exceed 1/3.
Reason: The shut-off valve is used as a throttle valve and a pressure reducing valve, and the sealing surface is eroded
Method: The valve used for cutting off is not allowed to be used as throttle valve and pressure reducing valve, and its closing part should be in the fully open or fully closed position. If the flow and pressure of the medium need to be adjusted, the throttle valve and pressure reducing valve should be set separately
Reason: When the closing part reaches the fully closed position, and continues to exert excessive closing force, the sealing surface is crushed and squeezed
Method: The closing force should be moderate. After the valve is closed tightly, stop closing the valve immediately to correct the wrong operation method of “the tighter the valve is closed, the better”