Happy Mid-Autumn festival
2019-09-12
Heating project pipe network design standard
2019-09-25

Valve body leakage

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 crack and etch it with 4% nitric acid solution. If there is crack, it can be displayed;
2. Excavation treatment of the crack.

The stem head is broken and the stem is bent


Reason
1. Improper operation, the switch is too strong, the limit device fails, and the over-torque protection does not work;
2. The thread is too loose or too tight;
3. Too many operations and long service life;
Deal with
1. Improve the operation, the force is not too large; check the limit device and check the over-torque protection device;
2. Select the appropriate material and the assembly tolerances meet the requirements;
3. Replace the spare parts.


   

Bonnet joint surface leakage


Reason
1. The bolt tightening force is not enough or tightly biased;
2. The gasket does not meet the requirements or the gasket is damaged;
3. The joint surface is defective.
Deal with
1. Re-tighten the bolts or make the gap between the door flanges consistent;
2. Replace the gasket;
3. Disintegrate the sealing surface of the door cover.


Valve leakage
Reason
1. Closed is not strict;
2. Joint surface damage;
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 valve cartridge jam.
Deal with
1. Improve the operation, re-open or close;
2. The valve is disassembled, and the sealing surface of the valve core and the valve seat is re-ground;
3. Adjust the gap between the valve plug and the stem or replace the valve flap;
4. The valve is disassembled to eliminate the jam;
5. Re-replace or weld the seal.


   

The spool is disengaged from the valve stem


Reason
1. improper repair;
2. The joint between the valve core and the valve stem is corroded;
3. The force of the switch is too large, causing the joint between the valve core and the valve stem to be damaged;
4. The spool retaining washer is loose and the joint is worn.
Deal with 1. Pay attention to inspection during maintenance;
2. Replace the door rod of corrosion resistant material;
3. Operation is not strong switch, or can not continue to open the valve after full opening;
4. Check for replacement of damaged spare parts.


Valve core and valve seat have cracks


Reason
1. The quality of bonded surface surfacing is poor;
2. The temperature difference between the two sides of the valve is large.
Deal with
Repair welding with cracks, heat treatment according to regulations, light and grind.


The stem lifts up or down or the switch does not move


the reason
1. When the cold state is closed, it is too tight to be swollen after being heated or too tight after being fully opened;
2. The packing is pressed too tightly;
3. The stem clearance is too small to swell;
4. The valve stem and the nut are too tightly matched, or the threaded fastener is damaged;
5. Packing gland pressure deviation;
6. The door stem is bent;
7. The medium temperature is too high, the lubrication is poor, and the valve stem is seriously rusted.
Deal with
1. After heating the valve body, slowly test it with force or open it tightly and then close it slightly;
2. After a little loose packing, try to open;
3. Appropriately increase the stem clearance;
4. Replace the valve stem and the nut;
5. Re-adjust the packing gland bolts;
6. Straighten the door lever or replace it;
7. The door rod uses pure graphite powder as a lubricant.


   

Filler leak


Reason
1. The filler material is incorrect;
2. The packing gland is not pressed or biased;
3. The method of adding packing is wrong;
4. Damage to the stem surface.
Deal with
1. Correct selection of fillers;
2. Check and adjust the packing gland to prevent pressure deviation;
3. Add the filler in the correct way;
4. Repair or replace the valve stem.

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