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

Processing:

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

Processing:

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

Processing:

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.

Processing:

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

Processing:

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

Processing:

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

Processing:

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

Processing:

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