I. leakage of valve body:

Reason:
1. The valve body has sand holes or cracks;
2. Crack during repair welding of valve body

Handle:
1. Polish the suspected crack and etch it with 4% nitric acid solution, if there is crack, it can be shown;
2. Repair the cracks.
II. The valve rod and its matching screw thread are damaged or the valve rod head is broken, and the valve rod is bent:


Reason:
1. Improper operation, excessive switch force, failure of limit device and failure of over torque protection. ;
2. The 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 the limit device, check the over torque protection device;
2. Select appropriate materials, and the assembly tolerance meets the requirements;
3. Replacement of spare parts


III. leakage on the joint surface of valve cover: causes:

1. Bolt tightening force is not enough or deviated;
2. The gasket does not meet the requirements or is damaged;
3. The joint surface is defective.


Handle:

1. Tighten the bolts or make the gap between the door cover flange consistent;
2. Replace the gasket;
3. Disassemble and repair the sealing surface of the door cover
IV. internal leakage of valve:


Reason:
1. The closing is not strict;
2. Interface damage;
3. The clearance between the valve core and the valve stem is too large, resulting in the valve core sagging or poor contact;
4. The sealing material is poor or the valve element is jammed.


Handle:


1. Improve operation, re open or close;
2. Disassemble the valve, regrind the sealing surface of valve core and valve seat;
3. Adjust the clearance between the valve core and the valve stem or replace the valve disc;
4. Disassemble the valve to eliminate jamming;
5. Replace or weld the sealing ring again


V. the valve core is separated from the valve stem, resulting in the switch failure:


Reason:

1. Improper repair;
2. The joint between valve core and valve rod is corroded;
3. Too much force on the switch causes damage to the joint between the valve core and the valve stem;
4. The check gasket of valve core is loose and the connection part is worn.


Handle:


1. Pay attention to inspection during maintenance;
2. Replace the door rod with corrosion-resistant material;
3. It is not allowed to turn on or turn on the valve after full opening.
4. Check and replace the damaged spare parts

Vi. cracks on valve core and valve seat:


Reason:

1. The welding quality of the joint surface is poor;
2. Large temperature difference treatment on both sides of the valve:
Repair welding shall be carried out for cracks, heat treatment shall be carried out as required, turning and grinding shall be carried out.

VII. The valve stem does not lift or the switch does not move:


Reason:

1. When it is cold, it is closed too tightly, and when it is heated, it will swell up or when it is fully opened, it will be too tight.
2. The packing is pressed too tightly;
3. The valve rod gap is too small and expands;
4. The valve stem is too tight with the screw nut, or the screw thread is damaged;
5. Pressure deviation of packing gland;
6. The door rod is bent;
7. The medium temperature is too high, the lubrication is poor, and the valve rod is severely rusted.


Handle:

1. After heating the valve body, open it slowly with force or close it slightly when it is fully opened and tightened;
2. Slightly loosen the packing gland before trial opening;
3. Properly increase the valve rod clearance;
4. Replace the valve rod and screw nut;
5. Readjust the gland bolts;
6. Straighten the door rod or replace it;
7. Pure graphite powder is used as lubricant for gate rod.


VIII. Packing leakage:


Reason:
1. The filler material is incorrect;
2. The packing gland is not compressed or biased;
3. The method of adding packing is wrong;
4. Valve rod surface damage

Handle:

1. Select packing correctly;
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 rod