I. leakage of valve body:

The reason:
1. The valve body has sand holes or cracks;
2. The valve body cracks when rewelding

Processing:
1. Polish the suspected crack with 4% nitric acid solution. If there is any crack, it can be shown.
2. Dig and repair cracks.
2. Damaged stem and its mating thread, broken stem head and bent stem:

The reason:
1. Improper operation, excessive force of the switch, malfunction of the limit device and no action of overtorque protection. ;
2. The thread is too loose or too tight;
3. Excessive operation times and long service lif

Processing:
1. Improve the operation and do not use too much force; Check the limit device and check the torque protection device.
2. Suitable material selection and assembly tolerance meet the requirements;
3. Replace spare parts

Iii. Valve cover joint surface leakage: reason:
1. Insufficient bolt tension or deviation;
2. The gasket does not meet the requirements or the gasket is damaged;
3. There are defects in the binding surface

Processing:
1. Tighten the bolts or make the flange clearance of the cover consistent;
2. Replace the gasket;
3. Disassemble the sealing cover of the door cover

Iv. Valve leakage:
The reason:
1. The closure is not strict;
2. Bond surface damage;
3. The clearance between the valve core and stem is too large, causing the valve core to sag or poor contact;
4. Poor sealing materials or stiff valve core.

Processing:
1. Improve operation, restart or close;
2. The valve disintegrates and the sealing surface of the valve core and seat is re-ground;
3. Adjust the clearance between the valve core and stem or replace the valve disc;
4. The valve disintegrates to eliminate the stickiness;
5. Replace or stack the sealing rings

5. The valve core is separated from the stem, causing the switch failure:
The reason:
1. Improper repair;
2. The joint between the valve core and stem is corroded;
3. Excessive force of the switch causes damage to the joint between the valve core and stem;
4. The core check gasket is loosened and the connecting part is worn

Processing:
1. Pay attention to inspection during maintenance;
2. Replace the corrosion resistant door stem;
3. The operation is not to force the switch or to continue to open the valve after full opening;
4. Check and replace damaged spare parts

Vi. There are cracks in the valve core and seat:
The reason:
1. Poor quality of bonding surface surfacing;
2. Large temperature difference between two sides of valve:
Repair welding of cracks, heat treatment, polishing and grinding as required.

7. The valve stem fails to lift or switch properly:
The reason:
1. It is closed too tightly in the cold state; it will swell to death after being heated; or it will be too tight after being fully opened;
2. The packing is pressed too tightly;
3. The stem clearance is too small and dies of distension;
4. The valve stem is too tight with the screw base, or the screw buckle is damaged;
5. Packing gland pressure deviation;
6. Bent door bar;
7. The medium temperature is too high, the lubrication is not good, and the valve stem is seriously corroded

Processing:
1. After heating the valve body, slowly try to open or fully open and close slightly when it is tight;
2. Slightly loosen the packing gland and try to open it;
3. Appropriately increase stem clearance;
4. Replace the stem and thread holder;
5. Readjust packing gland bolts;
6. Straightening the door lever or replacing it;
7. The door bar is lubricated with pure graphite powder

Viii. Packing leakage:
The reason:
1. Wrong stuffing materials;
2. The packing gland is not compacted or deviated;
3. The filling method is wrong;
4. Valve stem surface damage

Processing:
1. Select the correct packing;
2. Check and adjust packing gland to prevent deviation;
3. Add the stuffing in the correct way;
Repair or replace the stem