When is a safety valve required on an air reciver 6

[KevinNZ]

We have a remote, out door, compressed air vessel. This vessel can not be over pressured from the air source.

Is fire the only reason to have a safety valve on the vessel? Is this an ASME requirement? What would be enough of a fire risk to require a valve?
How to size the valve for fire?

 

[LittleInch]

This vessel can not be over pressured from the air source

Hmmm, I've heard that before, but this usually implies either a high tech redundant shutdown system or a relief valve somewhere on the pressure source? Has it gone through a HAZOP and LOPA assessment.
If you've got buy in from everyone on that then yes, fire is your key issue.

To prevent against fire needs a credible fire scenario to arise. If there isn't one then you have no fire risk.

But why do all this for a relief valve on an air tank??

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

 

[racookpe1978]

Murphy's Law = What can go wrong will go wrong.
Murphy's Law of Equipment Installations = What cannot go wrong will go wrong.

 

[MJCronin]

In the USA, vessels designed, fabricated and constructed IAW the ASME VIII code requires a relief device on the vessel or in the system. Exceptions include very small vessels or vessels of very low pressure.

The device setpoint is specified as the maximum allowable operating pressure (design pressure) for the vessel

Most other international codes are similar .... What doe your local building code authority require ?

Consider posting on the "Safety and Relief valve" forum

MJCronin
Sr. Process Engineer

 

[KevinNZ]

LittleInch

The receiver is feed from another receiver with safety valves. So that source can not over pressure our vessel.

We are now being asked to look at the fire case. The vessel is located on a gravel outdoor site. No source of fuel (process is water and steam) unless the weeds grow.

To put this is prospective, the vessel is not much different the valve pneumatic actuators near by.

 

[LittleInch]

KevinNZ,

you should know by now it's the details we need....

This sounds like a pneumatic accumulator on the end of a pneumatic system to allow valve operation without flattening the system and hence a fairly low volume which probably takes it out of Pressure Vessel regulations.

What volume and pressure are we talking about?

But Fire case - No source of fire, no need for fire pressure relief.

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

 

[moltenmetal]

Every ASME pressure vessel that is used as an ASME pressure vessel (i.e. pressurized in service or in emergency, and relieved at a pressure above 15 psig) requires a pressure relief device by code. It can be a pressure relief valve, rupture disk, buckling pin device, a vent with a P trap, or perhaps even an engineered, high availability active safety instrumented system depressurization device etc., but it cannot be NOTHING- even if no cases for overpressure are identified.

That relief device can be either dedicated to the vessel itself, or it can be shared with other vessels of the same MAWP or lower that it is connected to by pipe, of adequate size, and without valves which can be closed or a fluid which can freeze etc. which would thereby defeat the pressure relief protection of the vessel. Typically, valves which are locked or car sealed in the open position may be permitted in the interconnecting lines after a HAZOP review.

That's the way I read and interpret ASME VIII-1. If others disagree, and can quote chapter and verse from either ASME VIII or API 520/521 that says otherwise, I will be happy to stand corrected.

 

[Ehzin]

Moltenmetal, this is a common statement that I've seen in a lot of older posts but I don't believe I've ever seen it discussed in detail since 2010. The idea that a pressure relief device is needed regardless of whether or not there's any scenarios that demand it. Between the 2007 and 2010 versions of ASME Section VIII Div. 1 section UG-140 was added titled "Overpressure Protection By System Design." UG-125(a) requires, irrespective of size or pressure, overpressure protection in accordance with the requirements of UG-125 through UG-138 and/or overpressure protection by system design per UG-140. UG-140(a) states "A pressure vessel does not require a pressure relief device if the pressure is self-limiting..." then lists multiple requirements on how to satisfy this exemption to requiring a relief device.

Is there some language I'm missing within the 2010 or later editions that still requires a relief device regardless of circumstance even if the requirements of UG-140 are met? I'd be interested in whether or not I'm misunderstanding something or missed some language elsewhere that says otherwise.

Thanks,
Ehzin

 

[georgeverghese]

Relief protection for overpressure and fire provided upstream at other connected vessels or piping is the protection for this vessel also, provided there are no isolation valves interposed. If there are block valves, it would be adequate to have these locked open if these are purely for maintenance isolation, and not in some operating flexibility service.

 

[moltenmetal]

Ehzin: thank you very much for posting the reference to UG-140- a well-deserved LPS for you! You can see by my post that I couched my answer in case I'd missed something like this, which in this case I definitely did miss. That is a very valuable reference, and is very likely to permit a designer to not install a for-purpose relief device if the rest of the design satisfies UG-140.

 

[GenB]

per ASME Code, your air receiver does not need a fire rated safety r.valve but a pressure relief valve.
consult your local fire chief and fire Codes to asses fire safety. If you want to instal an alternate safety for fire, you can probably use a Fuse Plug, the same that are used on Boilers.

General Blr. CA,USA