General faults and solutions

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;

  1. The gap between disc and stem is too large, resulting in poor contact disc;
  2. 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.