High pressure rating = vacuum rating..?
High pressure rating = vacuum rating..?
(OP)
Dear sirs,
I'd would appreicate some expert comments on the below statement..
I've read the comment " a vessel with a 50
psig (or higher) ASME pressure rating is frequently capable of withstanding a full vacuum". How valid is this general comment?
Our Engineering contactor has ordered boilers that were not requested to have a vacuum rating. But they are designed to withstand at least 20 barg / 300 psig pressure. ( I am a process guy).,. what would be required to estimate if these vessels would implode if we shutdown below 100 C?
We had all kinds of conserns about o2 issues if we install a vacuum breaker on the boilers.. the conserns are o2 cuases corrision.
The current spec for the boilers is a rating of 0.8 bar or 10 psia (-5 psig).
I'd would appreicate some expert comments on the below statement..
I've read the comment " a vessel with a 50
psig (or higher) ASME pressure rating is frequently capable of withstanding a full vacuum". How valid is this general comment?
Our Engineering contactor has ordered boilers that were not requested to have a vacuum rating. But they are designed to withstand at least 20 barg / 300 psig pressure. ( I am a process guy).,. what would be required to estimate if these vessels would implode if we shutdown below 100 C?
We had all kinds of conserns about o2 issues if we install a vacuum breaker on the boilers.. the conserns are o2 cuases corrision.
The current spec for the boilers is a rating of 0.8 bar or 10 psia (-5 psig).





RE: High pressure rating = vacuum rating..?
RE: High pressure rating = vacuum rating..?
But as it has been designed for 20barg internal pressure I am quite sure that she could withstand -5psig i.e -0.34barg.
However the comment you have read is no valid. In any case you must advise the Code.
RE: High pressure rating = vacuum rating..?
An internal pressure of 50 psi frequently will not result in a shell capable of full vacuum without stiffening rings.
You should run some numbers based on the original code of construction. If you are using ASME VIII then, making a few assumptions, my numbers show that your vessel will be ok for full vacuum as long as the tangent to tangent length is not more than 7 times the diameter. Consider this a rough guide, and please consult a qualified vessel engineer for the final answer. Remember, this answer is worth every penny you paid for it.
jt
RE: High pressure rating = vacuum rating..?
RE: High pressure rating = vacuum rating..?
RE: High pressure rating = vacuum rating..?
RE: High pressure rating = vacuum rating..?
There are a few more hoops to jump through if you want to rerate the drum though. If the boiler fabrication is not started, then it may be possible to revise the design (with some financial pain and suffering).