About the valve common faults and processing methods

date:2018/8/29 13:23:12 source:

1. Leakage of valve body:

The reason:

1. There are sand holes or cracks in the valve body;

2. Pull crack of valve body during repair welding


1. Polish the suspected crack and etch it with 4% nitric acid solution. If there is a crack, it can be shown;

2. Excavate and repair the crack.

2. Damage of stem and its matching thread, or break of stem head, bending of stem:

The reason:

1. Improper operation, excessive force on the switch, malfunction of the limit device, and no action of over-torque protection. ;

2. Too loose or too tight thread fit;

3. Too many operations and too long service life


1. Improve the operation without excessive force; Check the limit device, check the torque protection device;

2. Material selection is appropriate and assembly tolerance meets the requirements;

3. Replacement of spare parts

3. Valve cover joint surface leakage:

The reason:

1. Insufficient bolt tightness or deviation;

2. The gasket does not meet the requirements or the gasket is damaged;

3. Defects in the joint surface


1. Tighten the bolts or make the flange clearance of the door cover consistent;

2. Replace the gasket;

3. Disassemble the sealing cover of the door

4. Leakage of valve:

The reason:

1. Loose closure;

2. Joint surface damage;

3. Too large gap between spool and stem, resulting in droop or poor contact of spool;

4. Poor sealing materials or spool sticking.


1. Improve operation and reopen or close;

2. Disintegrate the valve and re-grind the sealing surface of valve core and seat;

3. Adjust the gap between the spool and the stem or replace the disc;

4. Disintegrate the valve to eliminate the astringency;

5. Replace or weld the sealing ring

5. The valve core is separated from the stem, causing the switch failure:

The reason:

1. Improper repair;

2. The joint of spool and stem is corroded;

3. Excessive force on the switch causes damage to the joint of valve core and valve stem;

4. Loose gasket of spool check and wear of joint


1. Pay attention to inspection during maintenance;

2. Replace the door rod with corrosion-resistant material;

3. The operation shall not be forced to switch, or continue to open the valve after full opening;

4. Check and replace damaged spare parts

6. Cracked spool and seat:

The reason:

1. Poor quality of joint surfacing;

2. Large temperature difference on both sides of valve


Weld the cracks, heat treatment, finish and grinding according to regulations.

7. The valve stem is not lifting or the switch is not moving:

The reason:

1. In cold state, close too tightly and become swollen after heating;

2. Packing pressure is too tight;

3. The valve stem clearance is too small and expands dead;

4. The stem is too tight with the screw or the screw buckle is damaged;

5. Packing gland pressure deviation;

6. Door rod bending;

7. High temperature of medium, poor lubrication and severe corrosion of stem


1. Slowly open or close the valve body after heating;

2. Open the packing gland slightly loose;

3. Appropriately increase the valve stem clearance;

4. Replace valve stem and thread;

5. Re-adjust the packing gland bolt;

6. Straightening the door rod or replacing it;

7. The door rod is lubricated with pure graphite powder

8.Packing leakage

The reason:

1. Wrong filler material;

2. Packing gland is not pressed or deflected;

3. Wrong filling method;

4. Valve stem surface damage


1. Correct selection of filler;

2. Check and adjust packing gland to prevent pressure deviation;

3. Add packing according to the correct method;

Repair or replace stem


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