Minimum design Pressure requireed for applicability of ASME BPVC Sec VIII part 1

[gasoperations]

Dear experts
I need a clarification about applicability of Sec VIII part-1. Under section "U1" one of the conditions where code is not applicable is
Quote "(-1) vessels having an internal or external pressure not exceeding 15 psi (100 kPa)" Unquote

I believe it should be psig and Kpag.

Expert comments required.

Thanks

 

[LittleInch]

Only process engineers use psia or bara...

However this could also be interpreted as a pressure difference of 15 psi, positive or negative.

For instance an open pipe or vessel dropped to 20m water depth will be at 30 psig pressure, but no differential pressure.

Have you searched in the Boiler and Pressure Vessel forum for this?? If not it may already be answered.

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

 

[david339933]

See UG-21

 

[gasoperations]

psig or psi will make a big difference. If we consider 15 psi that is mentioned in the code as 15 psia (which is quiet normal) then practically all vessels operating even at 0.1 barg would come under purview of code. That is highly unlikely.

in BPVC forum i am trying but yet to find this issue

 

[gasoperations]

@ david339933
I looked at UG-21 but did not find anything to clarify psi / psig. It only refer to UG-98 & sec 3.2.

Could you please clarify if I am missing something

 

[1503-44]

Yes it is "psig". Nothing else would make sense, but if you need to see to believe, I think I recall it is defined on the first page in Scope. Start there and read until you have your $775 worth. That is why psig traps need to qualify for the stamp.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[david339933]

UG-21: "For this condition, the maximum difference in pressure between the inside and outside of a vessel, or between two chambers of a combination unit, shall be considered."

What would be the difference in pressure between inside and outside if it was 15 psia?

 

[1503-44]

I don't recall ever seeing a differential pressure stated as psia, or psig for that matter, but it probably doesn't make any difference.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[MGZmechanical]

I agree, differential pressure are alway in kPa o psi. And,at least in European code, it clearly says that all pressures, unless otherwise stated, are manometric. So you only have to detail it if you are working with absolute pressure.

 

[TiCl4]

In the strictest sense of the terms, psia and psig are a specific designations that deal with a single pressure value (i.e. from a pressure gauge or when dealing with NPSHr for a pump, though that term is often in feet of water). PSI is used to indicate a differential pressure ONLY, not an absolute or gauge pressure reading.

I’m 99% sure the code references that all values for pressure are given in reference to standard pressure, but I don’t have it in front of me right now. I’ll try to find it tomorrow. In this case, 15 psi is the numerically same as 15 psig because both have the same reference pressure.

 

[1503-44]

It seems the link to Scope above was a little obscure. Scope.

https://www.asme.org/codes-standard...ules-construction-pressure-vessels-division-1

Product Scope / Abstract

This Division of Section VIII provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either [highlight #FCE94F]internal or external pressures exceeding 15 psig.[/highlight] Such pressure vessels may be fired or unfired. Specific requirements apply to several classes of material used in pressure vessel construction, and also to fabrication methods such as welding, forging and brazing. It contains mandatory and nonmandatory appendices detailing supplementary design criteria, nondestructive examination and inspection acceptance standards. Rules pertaining to the use of the U, UM and UV ASME Product Certification Marks are also included.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[gwalkerb]

I'm in the habit of never listing a pressure as just psi or kPa. There's too much ambiguity. I always use one of psig/kPag, psia/kPaa, or psid/kPad for differential pressures, to be as explicit as possible. I've come across too many scenarios where just psi or kPa was listed, and they actually meant either gauge or absolute pressure, not differential.