Relief Valves requirement according to ASME 1

[davidet68]

One of our clients pointed out that as per clause No. UG-125 of ASME Sec VIII, Div 1 (see attached), all pressure vessels designed as per ASME, should be provided with relief valves. Is this clause applicable to every vessel? Is there any excheption?

 

[DSB123]

davidet68,
The pressure relief valves could be located on the attached pipework provided there is no valve between the PV and the RV connection. No matter what the PV should be protected from overpressure.

 

[davidet68]

Thank you for your prompt reply.
A RV is required from ASME even if no overpressure is foreseen in our PV? (vessels are indoor and pump shut off pressure is lower than PV MAWP)

 

[metengr]

Please read UG-125 a) in ASME B&PV code, Section VIII, Div 1. It states that all pressure vessels within the scope of ASME Section VIII, Div 1 require a pressure relieving device. As far as location, paragraph g) does allow for the the pressure relieving device to not be installed directly on the vessel, provided you have means for controlling pressure in the vessel to avoid exceeding the allowable pressure of the vessel.

However, you still need to have some type of pressure relieving device in the process stream of the vessel to meet the requirement in UG-125 a. Please note, the owner is responsible for this requirement, the vessel manufacturer is not obligated to supply a pressure relieving device.

 

[davidet68]

UG-125 c) states that all PV () shall be protected by a pressure relief device that shall prevent the pressure from rising more than 10% or 3 psi () above the MAWP. Our Pressure vessels are feeded by pumps with a shut off pressure lower than vessels MAWP and no heat imput is foressen from the athmosphere or process, therefore in our system pressure will not rise above MAWP of the vessel. No hazardous situation is foreseen.
Is a relief device required also in this case? How can I size this device if I don't foresee any overpressure?

 

[unclesyd]

What shuts your pumps off?

 

[metengr]

In situations like this, I would ask the Jurisdiction where the vessel will be installed if your pump pressure shut-off meets the requirement for a pressure relieving device. If there is no Jurisdiction, and the vessel is insured, the Inspector (Insurance company) will provide you with an answer to this question, as well. Either way, the Jurisdiction or the Inspector will provide guidance.

 

[jte]

I think metengr hit on the most important issues with regard to discussing the situation with the Jurisdiction and insurance company. Depending on your client's jurisdiction, you may or may not be able to use Code Case 2211-1 which may provide a way to not provide pressure relief for the vessel. For what it's worth, I work under a Jurisdiction which (to my knowledge) has not allowed the use of 2211. Just be sure to include a fire scenario in your analysis of potential problems...

jt

 

[GenB]

You are trying in getting away from the pressure relief device by invoking the pump lower pressure shutoff.
unless your pump has a safety relief device without any valve or other obstruction between the pump piping and the vessel you are okay. you have to prove it to the inspection body to get acceptance and also state in the mfrs data report remarking the safety device location.
ER

 

[davidet68]

What I don't understand is that ASME don't state to consider fire in any case, but only as an additional case (UG-125 (c) (2) ... an additional hazard CAN be created by exposure of a PV to fire...).

If I don't consider fire a possible hazard, my only source of pressure is pump (my vessel are full of water and located indoor). Pump shut off is lower that MAWP of the vessel. How could I have overpressure? And consequently, how can I size a pressure relief device?

Moreover, there is a minimum flow connection on the pump discharge. This is a pressure relief device. Can I consider this also for ASME requirement? Even if this does not make sense considering that the pressure is lower then MAWP in any case.

Frankly speaking I don't understand this requiremnt if I'm not forced to consider the possibility of a fire. And ASME don't state this.

It seem to me that the result of this UG-125 is: if you realy need a relief device you have to install it, if you don't need a relief device install "something" even if this "something" is not usefull and you don't have any possibility to size this with a sense.

Thank you to everybody.

 

[jte]

davidet68-

Take a look at API-520 and API-521 just to cover yourself from a HAZOP / Process Safety Management perspective. If your facility doesn't fall into the scope of federal

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9760

or state compliance then you have a bit more flexibility in interpreting overpressure scenarios.

As I mentioned in an earlier post, a Section VIII vessel must have a pressure relief device unless the user of the vessel writes the Code Case 2211 exemption into the purchase documentation and the fabricator includes the use of the Code Case in the vessel's Code paperwork. In your case, it sounds like a small rupture disk would be the easiest solution. All you'll need is a tee on some piping connected directly to the vessel. Not too painful, and it'll keep the jury happy.

jt

 

[GenB]

davidet68
you are tryiing to get away from a requirement by bypassing a "Gov. mandated Code", you can go around and around w/o success.
A safety relief valve is a Code mandated in most vessels.
If your needs one you better put it.
I make some vesselsthat do not require safety valves.
some others require not one but two or more safety valves.

Fire safety is under the NATIONAL FIRE Code, NFPA, you can contact them for requirements.
Sizing" if you do not know, ask a valve manufacturer, since they make valves they know most Codes and can help you size the valves, you will be surprised what they can do for you.
I am sure they will not help you to get away from using the valves!
Good luck, and be safe than sorry,
I am through with this one.
ER

 

[davidet68]

Thank you for your suggestions,

I have alredy decided to instal a little rupture disk on the vent pipe if my client insist to require a relief device. But if someone ask me on which basis I have sized this disk what can I reply?
I'm trying to understand this UG-125.
Generalblr: you suggest me to ask to a valve manufacturer.
I've already asked to one of our relief valves supplier and also they are not sure on how to consider the requirement of UG-125. Moreover, I can size a relief valve, but on which basis? Not pump flowrate because it is not a problem. You can say: be safe and size for fire. But if I size for fire I have to install the valve directly on the vessel and moreover, in my particoular case, all my vessels are stainless steel, but all the piping is GRP!
So, if required, I will install a rupture disk as suggested by jte, but which size? After all this discussion it seems to me that there is no applicable criterion. I will install a "reasonable" disk. But it remain without any sense.

Thank you and have a nice week end!