Min vol of vessel to require PSV ? 1

[jamesbanda]

Dear sirs,

I recall guidenace on min vessel volumes that require a PSV.. but now can i find it no.. is it in API or the pressure vessel codes? and what defines it.. i assume is an engineering judgement.. eg when the equipment is not much bigger than pipe..

 

[moltenmetal]

If it falls within the definition of a vessel per ASME VIII, it needs a relief device. ASME VIII lists the sizes, volumes and pressures above which it applies. Indeed what matters is NOT the design or operating pressure- it's the relief pressure that determines whether or not ASME VIII applies.

You can protect multiple vessels with a single relief device if they are connected by pipe of adequate size with no valves in the line.

Even sub-ASME devices which walk and talk like a vessel and have relief cases which cannot discounted, need protection via a relief device. Even a 500 mL laboratory reactor pressure "vessel", which is far too small for ASME VIII to apply, needs a relief device (generally a rupture disc is used).

 

[Latexman]

My company follows the requirements of the ASME BPVC. In your application, PIP VESSM001 would be applicable.


Good luck,
Latexman

 

[psafety]

Introduction U-1 Scope as far as ASME is concerned. Still moltenmetal gives good advice

 

[Latexman]

PIP VESSM001 speaks to when and what type (U or UM) of ASME Code Stamp is required. In general, > 6 inches ID requires an ASME Code Stamp.

PIP VESSM001 does not speak to PSV requirements.

Good luck,
Latexman

 

[jamesbanda]

So, on this basis.
If i have
> Vessel design P 20 Barg.
> Pipework design P 10 barg.

RV on the vessel has to be 10 barg or can it be 20 barg ?
if i did not have a vessel in the system i would not have an RV.. so why can i not use 20 barg..

but it seems wrong.

 

[zdas04]

If you use 20 barg, then there is a good chance that in an overpressure scenario the pipe would fail, which would serve to protect the vessel. You are not wrong, but I would rather have a PSV lift than a pipe come apart, it is usually easier to fix.

In this scenario, I usually look for the lowest MAWP in continuous contact (not including piping downstream of a pressure regulator) and set the PSV to protect that. I hate it when people rely on pipe failing to prevent a PSV from lifting.

David

 

[786392]

Dear David Hello/Good Afternoon,

I 100% endorse and feel the same way about

any pipeline segment serving as passage of relieved material

to safeguard any vessel's/containment's mechanical integrity.

Best Regards
Qalander(Chem)

 

[moltenmetal]

Since ASME VIII doesn't address piping, ASME VIII doesn't address the relief protection of piping. It is crazy to assume that this means the piping needs no overpressure protection!

Either your piping has the same or higher design pressure than the vessel it is connected to such that the code-required protection on the vessel is also protective of the piping, or the piping needs separate relief- or there is some other protective scenario at play in the design.

 

[786392]

Thanks!

Best Regards
Qalander(Chem)

 

[Duwe6]

ASME piping typically falls under ASME B31.1 or B31.3 [there are other Codes] Pipe cannot fall under Sect VIII - it is only for pressure vessels. That being said, small vessels are usually made from a piece of pipe and 2 pipe caps. Now a Sect. VIII vessel.

As for safety relief devices; Will your CFO and/or insurance carrier have a problem with a medium to huge bomb complete with shrapnel? [scarcasm off] Anything that can be isolated with valves needs a pressure relief device. For most items, there is a Code that requires that device. Just because you can't/didn't find a Code requirement, it doesn't mean that protection is not required or prudent.

ASME Code became law [in the 1930's?] because too many people got tired of explosions and carnage.

 

[jamesbanda]

Thankyou good comments: For what is worth we were always going to set the relief to the lower of vessel pressure and pipe pressre but wanted to understand background discussion.
thankyou for your information very helpful

 

[don1980]

There are some real good comments in this thread. I want to add that, as a general rule, the piping connected to a vessel should never be weaker than the vessel itself. To me, that's a fundamental point that process engineers should understand and practice.

An exception can be made if a surplus vessel, with a high MAWP, is retrofitted into a lower MAWP system. In such cases, the PSV needs to be set at the design pressure of that system and not at the MAWP of the vessel.