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Bellows failure
Posted: 06 Jun 2026, 17:54
by novice123
What are the major reasons of frequent bellows failures in a pressure safety valve?
We observed an increase of failures recently and probing into this.
Re: Bellows failure
Posted: 09 Jun 2026, 14:46
by ben
A sudden increase in bellows failures in Pressure Safety Valves is usually a symptom of a change in process conditions, installation configuration, operating practices, or valve selection rather than a random reliability issue. When investigating the problem, it is important to recognize that bellows are relatively delicate components subjected to pressure cycling, temperature effects, corrosion, vibration, and mechanical stresses throughout their service life.
Backpressure is often the first area to investigate.
Balanced bellows PSVs are designed to tolerate a specified level of backpressure. If actual backpressure exceeds the design limit, the bellows can experience excessive stress and fatigue.
Potential causes include:
1. New equipment tied into the relief header
2. Increased relief loads
3. Undersized flare or relief system
4. Flare header restrictions
5. Condensate accumulation in relief lines
6. Closed or partially closed isolation valves
You will get to know the actual failure upon testing for backpressure and any leak.
Have you identified multiple cases of such failures, one system, spread on multiple systems? what's the pattern of this finding?
Re: Bellows failure
Posted: 13 Jun 2026, 09:28
by neo
Practically, ben has listed all the potential causes. However, when bellows failures suddenly increase across several PSVs, the most common root causes are typically:
Increased backpressure in the flare/relief system.
Process pressure cycling causing fatigue.
Corrosion or stress corrosion cracking due to chemistry changes.
Frequent PSV lifting caused by operating closer to set pressure than before.
Each of these causes are to be distinctly evaluated with right evidence.
Re: Bellows failure
Posted: 13 Jun 2026, 09:56
by sys1
Yeah, how an all of a sudden bellows failures?
Identified during the testing at the bench?
Have you recently started testing bellows through backpressure test?
ben wrote: 09 Jun 2026, 14:46
A sudden increase in bellows failures in Pressure Safety Valves is usually a symptom of a change in process conditions, installation configuration, operating practices, or valve selection rather than a random reliability issue. When investigating the problem, it is important to recognize that bellows are relatively delicate components subjected to pressure cycling, temperature effects, corrosion, vibration, and mechanical stresses throughout their service life.
Backpressure is often the first area to investigate.
Balanced bellows PSVs are designed to tolerate a specified level of backpressure. If actual backpressure exceeds the design limit, the bellows can experience excessive stress and fatigue.
Potential causes include:
1. New equipment tied into the relief header
2. Increased relief loads
3. Undersized flare or relief system
4. Flare header restrictions
5. Condensate accumulation in relief lines
6. Closed or partially closed isolation valves
You will get to know the actual failure upon testing for backpressure and any leak.
Have you identified multiple cases of such failures, one system, spread on multiple systems? what's the pattern of this finding?
Re: Bellows failure
Posted: 15 Jun 2026, 10:10
by Dlew
You know what I was thinking, the actual PSV lifts place substantial stress on bellows.
Frequent lifting may indicate operating close to set pressure, control system instability, process upsets, plants often discover that valves with repeated lift histories have significantly shorter bellows life.
In my opinion, review lift records, DCS pressure history and near-miss overpressure events.
This may provide you some lead.