Generally speaking, if the valve is not tightly closed, first confirm to see if the valve is closed in place. If the valve has been closed in place, or there is leakage can not be sealed, then check the sealing surface. Some valve sealing pairs are removable, then take them out for grinding and re-testing, of course, if it is still not tightly closed, It must be repaired or replaced in order to avoid affecting the normal use of the valve and operating conditions accident.

If the valve is not tightly closed, we should first find out where the problem occurs, and then solve it according to the corresponding methods. Generally, there are several reasons why the valves are not tightly closed:

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(1) Impurities are stuck on the sealing surface and deposited at the bottom of the valve or between the disc and the seat.
(2) The valve stem threads are rusty and the valve can not rotate.
(3) The sealing surface of the valve is damaged, resulting in leakage of the medium.
(4) Stem and disc are not well connected, so that disc and seat deflection can not be tightly contacted.


The treatment method of valve closing is not strict:

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(1) Contamination of valve sealing surface
Sometimes the valve suddenly closes lax, it may be that there are impurities between the sealing surfaces of the valve. At this time, the valve should not be forced to close. The valve should be opened a little larger, then try again and again, which can generally be eliminated. Otherwise, it should be checked and the quality of the medium should be kept clean.

(2) Rust on valve stem threads
For valves normally in open state, occasional closure can also occur when the stem threads have rusted. In this case, the valve can be repeatedly switched on and off several times, while tapping the bottom of the valve body with a hammer, that is to say, the valve can be closed tightly without grinding and repairing the valve.

(3) Valve sealing surface is damaged
For the case that the switch is still not tightly closed after many attempts, that is, the sealing surface has been damaged and should be repaired; or the sealing surface has been damaged by corrosion, particle scratches in the medium, etc., should also be repaired.

(4) Poor connection between stem and disc
Lubricating oil is often added to the stem and stem nut to ensure flexible valve switching. There should be a formal maintenance program.