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 life

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:

The 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