6

Crack in the valve disc and seat

(1) Bad casting

Bad seat overlaying .

(2) The ambient temperature differen tial around the valve is large.

(1) Before welding repair , undergo heat treatment, and then grinding.     

(2) Replace the valve according to the actual situation.   

7

Stem lift is not flexible or opening and closing is not permitted

(1) Infrequently operation in a static state, causing corrosion, adhesion, etc. in the valve transmission.     

(2) The packing pressure is too tight or the seal is broken.     

(3) The stem clearance is too small, causing it to swell.     

(4) The valve stem and the nut are too tightly fitted or the threaded fastener is damaged.     

(5) The valve stem and the valve disc are bent.     

(6) The temperature of the medium is too high and the lubrication is poor, so the stem is severely corroded.   

(1) P eriodically operate the valve.     

(2) Loosen the packing gland .     

(3) Increase the stem clearance as appropriate.     

(4) Replace the stem and the nut.     

(5) Correct or replace the disc and stem   

(6) Pure graphite powder is used as a lubricant.   

8

Packing leak

(1) Packing has aged.     

(2) The packing gland is not pressed or biased.     

(3) The stem surface is injured.     

(4) The packing material is incorrect.   

(1) Replace the packing and place it circle by circle with 30 degrees.      

(2) Re-adjust the packing gland.     

(3) Repair or replace the valve stem.     

(4) Choose the packing correctly.   

9

Worm gear bite

(1) foreign matter or grease failure.     

(2) Inadvertent operation,   

(3) excessive gear wear   

(4) Bearing bite.   

(1) Remove foreign objects and repair them.     

(2) Replace the worm gear