eight valves common faults and treatment methods
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