Impurities have stuck the sealing surface of valve
Sometimes the valve suddenly closed lax, may be the valve sealing surface between impurities stuck, at this time do not apply force to seal, should open the valve slightly larger, and then attempt to close, repeat try, generally can be ruled out, otherwise should be viewed, should adhere to the quality of the medium clean.
Stem threads are rusted
With regard to valves that are usually open, loose closing may occur occasionally when closed because stem threads are now rusted. In this case, the valve can be repeatedly opened and closed several times, while hitting the bottom of the valve body with a small hammer, that is, the valve can be closed without grinding the valve repair.
The sealing surface of the valve is damaged
On trying to switch many times still not tight, that is, the sealing surface has been damaged, should be reported to repair; Or corrosion, particles in the medium such as scratches damaged sealing surface, should also be reported for repair.
Stem and disc connection is not good
Stem and stem nut are often greased to ensure flexible valve opening and closing. Have a formal maintenance plan.
