Safety Valves

[Sixflat]

I am in the process of registering several ASME VIII heat exchangers and vessels with the state jurisdiction. These are new vessels supplied by our contractor. Part of the information required to register is the safet/relief valve information.
I have been informed by the contractors engineer that overpressure protection is not required for heat exchangers/vessels where the source pressure,i.e. pump, is lower than the MAWP of the exchanger/vessel. I have never heard this interpretation of UG-125. Anyone run across this scenario before?

 

[EGT01]

Can't say I'm familiar with registering equipment but there may be a Code Case (2211) that may apply. Here's a couple of threads referencing it.

thread135-46044
thread794-40785

However, whether pump deadhead is the only concern for your exchanger is a totally different issue. Tube rupture and fire exposure are two others that need to be documented as being not an overpressure concern as well as any other scenarios that may apply.

Also, ASME Sec VIII UG-133 and Appendix M-5 will allow a "system" to be protected by a single relief device so you may not necessarily need a separate relief valve on your exchanger but you should have supporting documentation for that.

 

[metengr]

Sixflat;
If you review UG-125, paragraph (e), the wording implies that a pressure relief device does not need to be located directly on the vessel PROVIDED the source of the pressure in the vessel is external to the vessel can be controlled and is below the MAWP of the vessel at operating temperature.

I would use extreme caution on this, and would engage the owners Authorized Inspection Agency (AIA) and Jurisdiction where the vessels will be installed. The Jurisdiction's word is FINAL (if applicable) and if they require a pressure relief device to be installed directly on the vessel, it must be done.

 

[deanc]

Both of the earlier posts apply.

Contact your local Jurisdiction,Insurance Carrier,and local Fire Inspector/Chief for the final word.

It is apparent you do not feel good about it. That would be enough for me.

 

[psafety]

Sixflat,
The comment regarding checking with your inspector is right on. As far as CC2211 I think you need to know this up front and U1A's need to reflect this intent. Unless I'm mistaken the "Code" now says a relief device "shall" be provided. This does present a dilema sometimes as far as determining a relieving case (if there is no potential for fire exposure), some folks go ahead and use this as their relieving case to be safe and save time.
don coffman

 

[GenB]

Your contractor may be right, the safety valve at the target exchanger can be avoided only if the sorce has its own safety relief vale and if it matches the pressure on the exchanger(MAWP); it must not be a valve between the source and the exchanger.
ER