FULL VACUUM DESIGN 1

[hassann]

what is reason that Pressure Vessels subject to partially vacuum should be designed for full vacuum?
I have seen many pressure vessel data sheet that have for example 70 KPa absoloute with full vacuum desighn pressure.
thank for any respond

 

[shvet]

1/ Intention to extend service life so way a principal/auditor does not notice as full vacuum design give a lot more metal thickness.
2/ Inadvertent condensation or siphoning due to human error or control system failure. Search word "vacuum" and you find a lot of versatile cases with pictures and description:
- Sanders's Chemical Process Safety
- BP's booklets "Hazards of Steam" and "Hazards of Trapped Pressure and Vacuum"
- Kletz's What Went Wrong and and Still Going Wrong

 

[DriveMeNuts]

Full vacuum often only makes the stiffeners slightly thicker making the extra cost negligible..
Upset conditions or human error may result in FV being applied.

 

[SJones]

It's commonly applied for when vessels are subjected to steam out cleaning procedures. The results of condensing steam are evident in the post above.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[shvet]

Full vacuum often only makes the stiffeners slightly thicker

For info - vessels on photos above have no stiffeners. It is not a widelly spread practice in process industry.

@hassann
Note that tall vessels are subject to vacuum during draining. Deep of vacuum depends on ratio of vent to drain nozzles area, so 70 kPaa may relate to draining conditions.

 

[LittleInch]

An example of previous discussion and you'll find a lot more in the search function.

https://www.eng-tips.com/viewthread.cfm?qid=366746

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r6155]

1)Out-of-round tolerances are tighter, see UG-80(b). Some inspectors forget about this.
2)The collapse due to the vacuum is suddenly.
3)The vacuum relief valve can fail or be improperly maintained, therefore the best practice is to design for full vacuum.
4)In some scenarios, wind pressure (external pressure) must be considered.

Regards