Eight valve common faults and treatment

I. leakage of valve body:
The reason:
1. There are sand holes or cracks in the valve body;
2. Tension crack of valve body during repair welding
Processing:
1. Polish the suspected crack and corrode it with 4% nitric acid solution. If there is a crack, it can be displayed;
2. Dig and repair the crack.
2. The stem and its matching thread are damaged or the stem head is broken or the stem is bent:
The reason:
1. Improper operation, excessive switching force, limit device failure, overtorque protection failure.
;
2. Thread fit is too loose or too tight;
3. Too many operations and too long service life
Processing:
1. Improve operation, do not use too much force;
Check limit device and torque protection device;
2. Select suitable materials and meet the assembly tolerance requirements;
3. Replacement of spare parts
Iii. Valve cover joint surface leakage: reason:
1. Insufficient or partial tightening of bolts;
2. The gasket does not meet the requirements or the gasket is damaged;
3. Defects in the bonding surface
Processing:
1. Tighten the bolts or make the flange clearance of the door cover consistent;
2. Replace the gasket;
3. Disassemble, repair and grind the door cover sealing surface
Iv. Valve leakage:
The reason:
1. Loosely closed;
2. Bond surface damage;
3. Excessive clearance between spool and stem causes droop of spool or poor contact;
4. Poor sealing material or valve core jam.
Processing:
1. Improve operation, re-open or close;
2. Valve disassembly, valve core, valve seat sealing surface re-grinding;
3. Adjust the gap between the spool and the stem or replace the disc;
4. The valve disintegrates to eliminate the jam;
5. Replace or surfacing the sealing ring
V. the valve core is separated from the valve stem, resulting in switch failure:
The reason:
1. Improper repair;
2. The joint of spool and stem is corroded;
3. Excessive switching force causes the joint of spool and stem to be damaged;
4. The spool check gasket is loose and the connecting part is worn
Processing:
1. Pay attention to inspection during maintenance;
2. Replace the door rod with corrosion-resistant material;
3. Operation is not strong switch, or not fully open the valve to continue to open;
4. Inspect and replace damaged spare parts
Vi. Valve core and valve seat have cracks:
The reason:
1. Poor surfacing quality of bonding surface;
2. Large temperature difference between the two sides of the valve:
Repair welding for cracks, heat treatment according to the provisions, turning light, and grinding.
Seven, valve stem lifting is not working or switch is not moving:
The reason:
1. It is closed too tightly in cold state, and then swells to death after being heated; or it is closed too tightly after being fully opened;
2. Packing is too tight;
3. The valve stem gap is too small and expands to death;
4. The valve stem is too tight with the thread thread, or the thread thread is damaged;
5. Biased packing gland;
6. Bending of the door rod;
7 medium temperature is too high, poor lubrication, valve stem serious corrosion
Processing:
1. Slowly try to open the valve body after heating, or close it slightly when fully open and tight;
2. Slightly loosen the packing gland and open it;
3. Appropriately increase the valve stem clearance;
4. Replace stem and screw;
5. Readjust packing gland bolts;
6. Straighten the door lever or replace it;
7. The door rod is lubricated with pure graphite powder
Viii. Packing leakage:
The reason:
1. Wrong packing material;
2. The packing gland is not pressed tight or biased;
3. Wrong filling method;
4. Stem surface damage
Processing:
1. Choose the right packing;
2. Check and adjust packing gland to prevent pressure deviation;
3. Add the filler in the correct way;
Repair or replace stem