×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Common reasons for Bellows failure
2

Common reasons for Bellows failure

Common reasons for Bellows failure

(OP)
Dears

Can you pls share me the common reasons for the Bellows failure in PSVs other than listed below.

1. If the PZV has been exposed to excessive backpressure(constant/variable) then the bellows will damage.
2. If the PZV starts to chatter (rapidly opening and closing), as well as flow instability, could inevitably cause valve damage such as premature fatigue failure of the bellows.
3. If the operating pressure is too close to the set pressure, then pzv spindle is moving (maybe just simmering rather than popping open), causing enough movement to fatigue the bellows.
4. If there is any corrosion, bellows may damaged.


Thanks
Nasim

RE: Common reasons for Bellows failure

5. Badly designed bellows / Bellows manufacturing faults / Non OEM bellows replacements.
6. PRV seeing service other than what is specified in data sheet.
7. Solidification of media.
8. Impact from loose objects in outlet stream (welding rod bits etc)

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

RE: Common reasons for Bellows failure

Engineers intuitively understand that all metals will eventually experience fatigue failure when they're exposed to compression forces. What's not understood (and not intuitive) is that the number of bellows compression cycles is not equal to the number of PSV open-close cycles. Almost all PSVs experience flutter instability during the opening phase and during the closing phase. And in many cases there are periods of flutter instability during the time the PSV is open. All of this flutter instability is generally unnoticed by the observer. It can only be seen by using specialized (high speed and highly sensitive) instrumentation on a test stand.

When the PSV goes though a single opening/closing cycle, the bellows may experience hundreds of compression cycles. So the key to preventing bellows failure is to prevent the PSV from opening in the first place. And when bellows failures do occur, one shouldn't jump to the conclusion that the bellows has some defect. The use of Inconel as the bellows material will help minimize failures. Inconel resists fatigue failure better than other alloys, which is why Inconel is one of the standard materials offered by manuafcturers.

Bellows PSVs should be checked for leakage after each opening. It's an easy test - use a Drager Tube device to "sniff" the bonnet vent. If the bellows is cracked, gas from the PSV outlet piping system can/will freely flow through that crack, and out to the atmosphere through the bonnet vent.

RE: Common reasons for Bellows failure

(OP)
Thanks for your feedback. Existing PSV bellows material is SS316l & PSV manufacturer already recommended to replace with Inconel Bellows, which is advice by don1980.

Regards
Nasim

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now
The Great Project Profitability Debate
A/E firms have a great opportunity to lead the world into the future, but the industry’s greatest asset—real-time data—is sitting wasted in clunky, archaic ERP platforms. Learn how real-time, fully interactive dashboards in a modern ERP allow you to unlock data that will shape the future of the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close