1

Valve body leakage 

The valve body has sand holes or cracks, and the valve body is cracked during repair welding.

For the suspected crack, treat it with 4% nitric acid solution . If there is crack, the crack is repaired.  

2

The stem and the mating thread are damaged or the stem is bent 

(1)Improper operation,   

(2) excessive force when opening and closing,   

(3) failure of the limit device,     

(4) no action of torque limiter ,   

(5) Too tight or loose thread.     

(6) Too many operations   

(7) long service life   

(1)Improve the operation method,   

(2) Check the position limiter and torque limit device,   

(3) Use appropriate screw and thread nut to match,   

(4) Replace the matching easy worn-out parts   

3

Leakage of the bonnet .

It is defined as

the medium leaks from the valve to the outside of the valve , which will cause material  loss, pollute the environment, and related accidents in severe cases.

(1) The bolts are loose or tight on one side.      

(2) The gasket is damaged.     

(3) The gasket joint surface is defective.   

(1)Adjust the bolt tightness   

(2) Replace the gasket.     

(3) Disassemble body and grind seal face of bonnet.   

4

Seat leakage of the valve .

It will affect the ability of the valve to cut off the medium. For the shut-off valve, seat leakage is not allowed.

(1)Leaks after closing.     

(2) Sealing surface wear.   

(3) The clearance between valve   disc and the valve stem is too large, causing the valve disc to sag or poor contact.     

(4) Poor sealing treatment or disc  jam.   

(1) Open and close valve repeatedly.     

(2) Disassemble the valve to repair the valve disc and seat sealing surface or replace the sealing ring.     

(3) Adjust the clearance between the disc and the stem or replace the disc.     

(4) Disassemble the valve to eliminate jams or replace the sealing seat .   

5

Loose connection between the valve stem and disc, causing the switch to malfunction.

(1)Corrosion for a long time   

(2) Improper repair.     

(3) Excessive force causing damage to the valve disc  and stem connection.     

(4) The disc stop is loose or the joint is worn.   

(1)Check or replace corrosion-resisting parts   after inspection.     

(2) It is not advisable to use excessive force for opening   

(3) Replace the valve disc or valve stem during    operation.