First, Leakage of valve body:

    the reason:

    1. The valve body has blisters or cracks;

    2. The valve body is cracked during repair welding

    deal with:

    1. Polish the suspected cracks and etch them with 4% nitric acid solution. If there are cracks, they can be revealed;

    2. Dig and repair the cracks.

Second, The valve stem and its mating female thread are damaged or the stem head is broken or the valve stem is bent:

    the reason:

    1. Improper operation, excessive force of the switch, failure of the limit device, and failure of over-torque protection. ;

    2. The thread fit is too loose or too tight;

    3. Too many operations and long service life

    deal with:

    1. Improve the operation, do not use excessive force; check the limit device, check the over-torque protection device;

    2. Choose the right material and the assembly tolerance meets the requirements;

    3. Replace spare parts

Third, Leakage of bonnet joint surface: 

     Reason:

    1. The bolt tightening force is insufficient or tight;

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

    3. Defects in the joint surface

    deal with:

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

    2. Replace the gasket;

    3. Disassemble and research the sealing surface of door cover

Fourth, the valve internal leakage:

    the reason:

    1. Lax closure;

    2. Damage to the joint surface;

    3. The gap between the valve core and the valve stem is too large, causing the valve core to sag or contact poorly;

    4. Poor sealing material or jammed valve core.

    deal with:

    1. Improve operation, re-open or close;

    2. The valve is disintegrated, and the sealing surface of the valve core and valve seat is reground;

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

    4. The valve disintegrates to eliminate jams;

    5. Replace or overlay the sealing ring again

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

    the reason:

    1. Improper repair;

    2. The joint between the valve core and the valve stem is corroded;

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

    4. The spool stop gasket is loose and the connection part is worn

    deal with:

    1. Pay attention to inspection during maintenance;

    2. Replace the door stem of corrosion-resistant material;

    3. The operation is not to force switch, or to continue to open the valve after fully open;

    4. Check and replace damaged spare parts

Sixth, there are cracks in the valve core and valve seat:

    the reason:

    1. The quality of the bonding surface is poor;

    2. Large temperature difference between both sides of the valve

    Repair the cracks, perform heat treatment, car polish, and grind as required.

    Seven, the valve stem does not work well or the switch does not move:

    the reason:

    1. When it is cold, it is closed too tightly after being heated, or it is too tight after being fully opened;

    2. Packing is too tight;

    3. The valve stem gap is too small and swells;

    4. The valve stem is too tight with the nut, or the matching thread is damaged;

    5. Packing gland pressure deviation;

    6. The door pole is bent;

Seventh, The medium temperature is too high, the lubrication is poor, and the valve stem is severely corroded.

    deal with:

    1. After heating the valve body, try to open slowly or open it fully and then close it slightly;

    2. Test open after loosening the packing gland;

    3. Properly increase the valve stem clearance;

    4. Replace the valve stem and nut;

    5. Readjust the packing gland bolts;

    6. Straighten the door pole or replace it;

    7. The door pole uses pure graphite powder as lubricant

 Eighth, packing leakage:

    the reason:

    1. The packing material is wrong;

    2. The packing gland is not compressed or biased;

    3. The method of adding packing is wrong;

    4. Damage to the stem surface

    deal with:

    1. Choose the correct filler;

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

    3. Add packing according to the correct method;

    4. Repair or replace the valve stem