General faults and solutions

Valve body leakage

Cause: The valve body has sand holes or cracks

Solution: Replacing the valve

Valve bonnet sealing surface leakage

Cause:

1. The fastening force of bolts is insufficient or tight;
2. Gaskets do not meet the requirements or are damaged;
3. The sealing surface is defective.

Solution:

1. Retighten the bolts and ensure that the gap between the valve bonnet and flanges is consistent;
2. Replace the gasket.
3. Remove valve cover and repair sealing face or replace valve.

Valve internal leakage

Cause:

1. Lax closure;

2 .Valve disc, seat sealing surface damage;

3. The gap between disc and stem is too large, resulting in poor contact disc;
4. The disc is tightly stuck.

 Solution

1. Improve the operation, reopen or close;
2. Remove the valve, and regrind the disc and seat sealing surface;
3. Adjust the gap between the disc and the stem or replace the disc;
4. Remove the valve to eliminate the tightness;
5. Replace the valve.

 Stem damaged or bent

Cause:

1. Improper operation, excessive force when switching.
2. Too many operations and too long service life.

Solution:

1. Improve the operation, do not force too much;
2. Replace the valve.

 Disc detaches from stem

Cause:

1. Improper repair;
2. The joint of disc and stem is corroded;
3. The switch force is too large, causing the joint of the disc and the valve stem to be destroyed;
4. The disc thrust gasket is off and the connection part is worn.

Stem lift is not flexible

Cause:

1. If it is closed too tightly in cold state, it will swell to death after being heated;
2. The packing is too tight;
3. The valve stem clearance is too small and bloated dead;
4. The stem thread is too tight with the nut;
5. Pressure bias of packing gland;
6. Stem bending.

Solution:

1. Open the valve body slowly after heating;
2. Slightly loosen the packing gland and test open;
3. Appropriately increase the valve stem clearance;
4. Replace the valve stem;
5. Readjust packing gland bolts;
6. Straighten or replace the stem;

 Packing leakage

Cause:

1. The corrosive, temperature and pressure of packing and working medium are not suitable;
2. Incorrect loading method;
3. The packing gland is not pressed or biased;
4. Stem machining accuracy or surface finish is not enough;
5. Stem bending;
6. The filler is aged after being used for too long;
7. The operation is too fierce.

Solution:

1. Select filler correctly;
2. Filling correctly;
3. Check or adjust the packing gland to prevent press bias;
4. Repair or replace stem;
5. Straighten or replace the valve stem;
6. Replace the filler;
7. Pay attention to stable operation, open and close slowly, to prevent sudden temperature changes or medium impact.