Safety Valve Reseating Pressure Too Low: How to Adjust the Blowdown Ring
Diagnose the Condition
Before adjusting, confirm that the low reseating pressure is a ring setting issue and not a seating surface defect. If the valve leaks continuously after closure or fails to pop cleanly, the disc and seat may require cleaning or lapping. If the valve opens and closes normally but reseats too early, proceed with ring adjustment. Note that reseating pressure is typically specified as a percentage of set pressure, often 7 to 10 percent blowdown for gas service. A valve reseating well below this range indicates the blowdown ring is set too far from the nozzle or disc.The main safety valve product names of China safety valve Network include:,900 DIN Safety Valve,Air Compressor Safety Valve,A69Y Main Safety Valve(W Series) Welding Safety Valve,Anti-sulfur Spring Type Safety Valve,ANSI Bellows Safety Valve,Air, Gas Valve,Ammonia-used Safety Valve,A28X Air Compressor Safety Valve,AD Safety Valve Muffler,Bellows Spring Fall Lift SafetyValve,Built-in Safety Valve,Butterfly Spring Type Safety Valve,Copper Safety Valve,Duplex Safety Valve,Double Lever Safety Valve.
Adjustment Direction and Procedure
The adjustment direction depends on the ring type and the desired correction. For a valve reseating too low, the blowdown must be reduced, which means the ring position must be lowered. On most designs, turning the blowdown ring to the left (clockwise when viewed from the top) lowers the ring and decreases blowdown, raising the reseating pressure. On some Emerson/Crosby designs, turning the guide ring to the right raises it and decreases blowdown, so the direction must be confirmed against the specific manufacturer’s manual.
The procedure is as follows. Reduce the inlet pressure below 90 percent of the set pressure before touching the ring, to prevent the valve from popping unexpectedly during adjustment. Remove the ring locking screw or pin and insert a screwdriver or thin rod into the exposed notch. Rotate the ring by a small increment, no more than five notches per adjustment on most designs, and never more than ten notches without retesting. Reinstall and tighten the locking screw or pin immediately, ensuring it seats in a notch without bearing on top of a tooth.
Retest and Verify
After each adjustment, retest the valve by raising inlet pressure until it pops and then observing the reseating pressure as pressure falls. Repeat the adjustment in small increments until the reseating pressure falls within the specified blowdown range. Reseating pressure testing requires a test bench with sufficient flow capacity to fully open the valve; a small bench that cannot achieve full lift will produce a false reseating pressure reading. Once the correct setting is achieved, seal wire the adjusting ring and record the final ring position.
If ring adjustment alone cannot achieve the required reseating pressure, the adjusting screw may be used as a secondary control on some designs, but it should only be changed when ring settings fail to produce the desired result. A spring with an incorrect pressure range or a damaged seating surface can also prevent proper reseating and must be corrected before adjustment.
Summary
A safety valve reseating too low is corrected by lowering the blowdown ring to reduce blowdown and raise the reseating pressure. Adjust in increments of no more than five notches, retest after each change, and always resecure the locking pin. Confirm the correct rotation direction for your specific valve model, and ensure the test bench can fully open the valve for a valid reseating pressure reading.
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