What to do when valve doesn't close completely?

1. Impurities are stuck on the sealing surface, and debris is deposited at the lower part of the valve or between disc and seat; Treatment: when this happens, do not close it by force.  People can try to open and close for several times. Usually, the problem will be resolved after several trying. The medium shall be kept with impurities as little as possible.  

2. Valve stem threads are rusted and valve cannot be rotated; Treatment: for valves that are normally open, when it is accidentally closed, the valve stem threads are already rusted, and the valve may not close tightly. In this case, the valve shall be repeatedly opened and closed, and the bottom of valve body can be struck with a small hammer, then the valve will be closed, and grinding and repair are not required.

3. Valve sealing surface is destroyed, which causes the leaking;
Treatment: if the valve is still not closed completely after several opening and closing, then it is for the reason that the sealing surface has been damaged or scratched by the particles in medium and valve shall be repaired by the factory.
4. Valve stem and disc are not connected well, thus the disc and valve seat are deflected and can't be totally contacted. Treatment:  it is necessary to inject lubricant oil between valve stem and stem nut. There must be a formal maintenance program to enhance the maintenance of the valve.