Safety Valve Spring Aging: Hidden Failure You Cannot See
A safety valve may look fine, but when the set pressure is reached, it fails to open. In many such incidents, spring aging is the hidden culprit. Long‑term compression stress, combined with heat and vibration, causes the spring to lose force. The danger: you cannot see it from the outside.The main safety valve product names of China Safety Valve Network include:(W Series) Welding Safety Valve,Anti-sulfur Spring Type Safety Valve,ANSI Bellows Safety Valve,Air, Gas ValveAmmonia-used Safety Valve,A28X Air Compressor Safety Valve,AD Safety Valve Muffler,Bellows Spring Fall Lift Safety Valve,Built-in Safety Valve,Butterfly Spring Type Safety Valve,Copper Safety Valve
Why springs age
Springs under constant compression suffer stress relaxation. For every 10°C rise in temperature, the relaxation rate roughly doubles. Chrome‑moly springs on WC6/WC9 valves, after 3–5 years of service above 350°C, can shorten by 2–3 mm free height, significantly reducing preload. The result: set pressure drifts downward, even causing nuisance opening.
When to replace
During bench calibration, if turning the adjusting screw half a turn gives little set pressure increase, the spring is soft. Also, remove the spring and measure its free height – if shortened by more than 3% compared to factory data, discard it. For critical high‑temperature services, force replacement every four years instead of waiting for failure.
Risky field “fixes”
Some technicians over‑compress the spring to “restore” set pressure. This increases stress, accelerates relaxation, and may coil‑bind the spring, completely blocking opening. Never do this.
Better material choice
For high‑temperature springs, specify Inconel X‑750 or Inconel 718 instead of ordinary chrome‑moly steel. They resist relaxation much longer above 400°C.
Bottom line: Spring aging is a chronic disease of safety valves. Measure free height periodically, track calibration trends, and replace by schedule – far cheaper than dealing with an accident.
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