Pressure Vessels Reliefs or System Design Proctection
Pressure Vessels Reliefs or System Design Proctection
(OP)
Hi
I have an installation with 5 shell and tube steam (@85 psi) to hot water heat exchangers used to heat a building. I had an insurance inspector come by for an annual inspection and identify that each individual exhanger was not protected by a safety relief valve on the steam/shell side. I indicated that these were protected by a saftey relief upstream at my boiler which was set at 125 psi. My exchanger MAWP is 150 psi so I thought it was protected by code.
I was informed later by another inspector that this is only acceptable when there are no isolation valves present between the system safety relief and my exchangers.
It will be quite difficult to install properly sized safeties on each exchanger, is there any variance in the ASME to this code?
I have an installation with 5 shell and tube steam (@85 psi) to hot water heat exchangers used to heat a building. I had an insurance inspector come by for an annual inspection and identify that each individual exhanger was not protected by a safety relief valve on the steam/shell side. I indicated that these were protected by a saftey relief upstream at my boiler which was set at 125 psi. My exchanger MAWP is 150 psi so I thought it was protected by code.
I was informed later by another inspector that this is only acceptable when there are no isolation valves present between the system safety relief and my exchangers.
It will be quite difficult to install properly sized safeties on each exchanger, is there any variance in the ASME to this code?





RE: Pressure Vessels Reliefs or System Design Proctection
RE: Pressure Vessels Reliefs or System Design Proctection
I will contact the insurance agent to see if there is any way to get around this. However, I am only the maintenance contractor for the building I will probably report this to the owner so they can make a proper decision
RE: Pressure Vessels Reliefs or System Design Proctection
If there is an isolation valve installed in a line, sooner or later it will be closed, otherwise it would never have been installed in the first place.
It sounds as if you will need to both lock open the valves and add a 3/4" thermal relief valve directly to a PV nozzle.
"Nobody expects the Spanish Inquisition! "
RE: Pressure Vessels Reliefs or System Design Proctection
This would help my case, but I will probably need to install something for the fire case to make sure I'm code compliant there. Also, some contractors have quoted larger reliefs to evacuate the entire running capacity of the unit which is significantly more expensive and will require a lot more work.
Has anyone ran into this case in M-5?
Thanks
RE: Pressure Vessels Reliefs or System Design Proctection
"Nobody expects the Spanish Inquisition! "
RE: Pressure Vessels Reliefs or System Design Proctection
Under the system design scenario (which is what you appear to be proposing) it is the user's responsibility to request a manufacturer's data report indicating that overpressure protection is provided by system design and to conduct a detailed analysis examining all potential over pressure scenarios described in ANSI/API Std. 521. At this point you may be better off following your AI's recommendations and installing the individual PRVs on each PV.
RE: Pressure Vessels Reliefs or System Design Proctection
RE: Pressure Vessels Reliefs or System Design Proctection
I'll have to continue reviewing the code, there seems to be many interpretations and contradictions within the asme. Not sure why it was written to be so complicated.