Pressure Vessel Under 15 psig in United States
Pressure Vessel Under 15 psig in United States
(OP)
If a vessel is being operated under the 15 psig rating which keeps it from needing to be a stamped pressure vessel, what other codes or specifications does a manufacturer need to follow in the United States to be sure they design the vessel to cover them selves as well as make sure the vessel is safe?





RE: Pressure Vessel Under 15 psig in United States
Multiple outlet reservoir for LN2 at atmospheric pressure.
Approximately 5-10 gallons.
RE: Pressure Vessel Under 15 psig in United States
Since the vessel is small, it may also be economical to construct two and proof test one to failure.
RE: Pressure Vessel Under 15 psig in United States
RE: Pressure Vessel Under 15 psig in United States
RE: Pressure Vessel Under 15 psig in United States
"Whom the gods would destroy, they first make mad "
RE: Pressure Vessel Under 15 psig in United States
RE: Pressure Vessel Under 15 psig in United States
Cheers,
gr2vessels
RE: Pressure Vessel Under 15 psig in United States
I also disagree with any one who says that"building to the Code" w/o final
stamping and certification is the same but it just short of data report and national board number. No, it is not the same, if the final Item has not been processed with the proper procedure and been intended to be stamped and certified has no value.
An ASME Code Shop does have a reputation and may get jobs that will not be stamped I agree. I make a lot of vessels for customers who wants to enjoy a cheaper vessel w/o stamping and certification. I must tell them that I will follow the ASME Cod ein the construction.
It's tricky too and note that my responsibility is greater if I do not stamp it.
think about it. I save the customer money, I get the Job on that basis but at the end I loose because my exposure is greater. The customer saves money and his/her exposure is greater. It's a game. Lets stamp most items please.
15 PSI. I have stamped 5 psi vessels by following the Code It shall be designed to 30 psi as a minimum.
RE: Pressure Vessel Under 15 psig in United States
I will take a bit of an issue with tmast2, specifically with the wording used in the original post:
What pressure a vessel is operated at is irrelevant. So is the PSV setting. What is relevant in making the "not exceeding 15 psi" call is the MAWP. So it would not be ok to take a piece of pressure equipment which is stamped for 16 psi and say that it does not need a U stamp [where the jurisdiction requires stamped vessels] simply because we put a PSV on it which is set for 14 psi and we operate it at 5 psi. It is ok to take the same equipment, put a 15 psi (or 14 psi if you want to be abundantly clear) MAWP on the nameplate, and then consider it exempt from stamping.
RE: Pressure Vessel Under 15 psig in United States
As to the design and construction of devices below the scope of ASME VIII: it's the owner's call. Devices below the scope of the code on size (volume, diameter or both) but relieved above 15 psig are typically designed to either ASME VIII or B31.3 piping code, without stamping. Devices above the volume but operating below 15 psig get treated differently depending on size and what they contain, i.e. the hazards to be expected if the container were to fail.
There's an interesting thought experiment to consider when determining what code should apply to a device. Consider two large pressure vessels connected by a 24" pipe line. The pipe line is clearly B31.3 pipe, correct? Some might designate it a vessel in its own right, but really, it's pipe. Now assume there's a 2" reduction at either end of this 24" pipe, such that the lines connected to the large vessels are 2" at either end: most would still consider it to be pipe. Disconnect one end and replace with a blind flange- voila, it's a vessel. Connect one end to the atmosphere instead and it becomes non-code by virtue of relief below 15 psig. It's all a bit silly, don't you think? What really makes it a code vessel is its risk of harm on failure, relative to the risk of harm of failure of other components in the system: THAT is what merits the extra inspections and paperwork and rigour associated with designating something as a pressure vessel rather than as pipe.
RE: Pressure Vessel Under 15 psig in United States
I have had experience with many "vessels" that were specified, designed and operated at less than 15 psig...
My suggestions:
- Please do not refer to them as "pressure vessels", you will run afowl of psychotic town, state and other regulatory people all to willing to accuse you of "getting away with something" and breaking the law ! ! . Call them "low pressure tanks" or something..... I realize that this is petty, but in the eyes of a government regulator, this can be a big idea !
- Be aware of the fabrication shops that have done this many times in the past. They are willing to provide all necessary testing, inspection and other documentation you will want to keep in your records. Consider the type of identification plate that you want to attach to your vessel and what it will say.
- I have found that the so-called "savings" amounts to very little when a vessel is fabricated to but not stamped to the ASME code. This usually amounts to only 3-5% of the total. Try to always get two cost quotes. One with the vessel designed to the actual max operating pressure (no stamp) and another at 15 psig (with a stamp).
Another consideration is the long term yearly "state fee" charged by some for the privledge of having a stamped pressure vessel on the plant site. Theoretically, the non-stamped "low pressure tank" should not have to pay this fee/tax.
MJCronin
Sr. Process Engineer
RE: Pressure Vessel Under 15 psig in United States
My perspective is clearly biased towards the life-cycle cost - without compromising reliability and safety - of running a plant. Others will have different perspectives based on their own experinces, whether it be only dealing with greenfield projects, running fab shop work (even if they see the occasional repair job), or otherwise.
I recently was involved in the short term repair of a vessel which will be replaced within a few months. Simply put, the "proper" long term repair would have had an effective cost well above the replacement cost of this vessel. And this wasn't some little filter, it was somethig I'd classify as a medium sized vessel, replacement cost is six figures for the shop PO alone.
So, to each his own. Again, a good discussion, glad E-T is here to facilitate it.
RE: Pressure Vessel Under 15 psig in United States