1. Valve body leakage:

Reason:

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

2. Pull-out Crack of Valve Body during Repair Welding

Handle:

1. For polishing of suspected cracks, etching with 4% nitric acid solution can reveal cracks.

2. Digging and repairing the cracks.

2. Damage to the stem and screw threads with which it fits or breakage of the stem head or bending of the stem:

Reason:

1. Improper operation, excessive switching force, failure of limit device, over-moment protection did not operate. ;

2. Thread fit is too loose or too tight;

3. Too many operations and too long service life

Handle:

1. Improve the operation, do not use too much force; check limit device, check over-moment protection device;

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

3. Replacement of spare parts

3. Leakage of valve cover joint: Cause:

1. Bolt tightening force is not enough or tightening deviation;

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

3. Defects in the joint

Handle:

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

2. Replacement of gaskets;

3. Dismantling and repairing the sealing surface of door cover

IV. Valve leakage:

Reason:

1. Lack of closure;

2. Joint surface damage;

3. Excessive clearance between spool and stem causes sagging or poor contact of spool.

4. Bad sealing material or stuck spool.

Handle:

1. Improve operation, reopen or close;

2. The valve disintegrates and the sealing surface of the valve core and seat is re-grinded.

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

4. Valve disintegration to eliminate jamming;

5. Replacement or surfacing of sealing rings

5. The valve core is separated from the stem, which causes the switch to fail:

Reason:

1. improper repair;

2. The joint of spool and stem is corroded.

3.开关用力过大，造成阀芯与阀杆结合处被损坏;

4. Loosening of spool backstop gasket and wear of joint

Handle:

1. Pay attention to inspection during overhaul;

2. Replacement of door poles made of corrosion-resistant materials;

3. Operation is not a strong switch, or can not be fully opened after the valve continues to open;

4. Inspection and replacement of damaged spare parts

6. There are cracks in the spool and seat:

Reason:

1. The quality of surfacing on the joint surface is poor.

2. Treatment of large temperature difference on both sides of valve:

Repair welding for cracks, heat treatment according to regulations, car polishing and grinding.

7. Stem lifting or switching is not working properly:

Reason:

1. Close too tightly in cold state and die after heating or close too tightly after full opening;

2. Packing pressure is too tight;

3. Stem clearance is too small to expand.

4. The valve stem is too tight with the screwdriver or the screwdriver is damaged.

5. Packing pressure offset;

6. Bending of the door pole;

7. Excessive medium temperature, poor lubrication and serious corrosion of valve stem

Handle:

1. After heating the valve body, try to open it slowly or close it slightly when it is fully opened and tight.

2. Trial opening after slightly loosening packing cap;

3. Increase the stem clearance properly;

4. Replacement of stem and screw mother;

5. Re-adjust packing bolt;

6. Straightening or replacing the door pole;

7. Pure graphite powders are used as lubricants for the door poles.

8. Packing leakage:

Reason:

1. The packing material is not right.

2. The packing gland is not tightened or deflected.

3. The method of filling is incorrect.

4. Stem surface damage

Handle:

1. Correct selection of fillers;

2. Check and adjust packing cap to prevent bias.

3. Packing according to the correct method;

4. Repair or replace valve stem