ASME Stamped Vessels Have No Relief Devices
ASME Stamped Vessels Have No Relief Devices
(OP)
I have several solvent storage tanks stamped at U-Stamped at 40 psig/150 F with a Conservation Vent/Vacuum vent installed on the tank. A secondary emergency manway vent is also on the tank. Typical pressures do not exceed atmospheric/ambient conditions, however I need to consider a Fire Scenario and Pump Overpressure. Vapor Pressure of the solvents at normal Temps do not exceed the MAWP. There is also not Nitrogen or purge gas connected to the tanks. The reported capacities appear to be ok for these even at the low set pressures (4 oz vent -6 oz hatch) The problem I see is that these devices are not stamped with capacities or set pressure.
Do I need an additional Relief Valve/Rupture Disc etc to satisfy the code? Are the conservation vent and hatch all that are necessary or is an ASME certified relief device at a stamped capacity required? i.e. do all ASME Stamped vessels need Stamped/Certified Relief Devices on them even when they are typically run at conditions much less than what the MAWP is on the vessel? And, can these be set at pressure below 15 psig?
Do I need an additional Relief Valve/Rupture Disc etc to satisfy the code? Are the conservation vent and hatch all that are necessary or is an ASME certified relief device at a stamped capacity required? i.e. do all ASME Stamped vessels need Stamped/Certified Relief Devices on them even when they are typically run at conditions much less than what the MAWP is on the vessel? And, can these be set at pressure below 15 psig?





RE: ASME Stamped Vessels Have No Relief Devices
Per VIII-1 UG-125 you need a pressure relief device which complies with UG-125 through UG-137. Markings on valves are addressed in UG-129 and include, among other things, set pressure and rate. So it sounds as though you do need to add another valve.
You may set the set pressure however low you want - the Code only sets upper limits on opening pressure and pressure in the vessel while relieving.
One workaround for you may be to keep your existing setup for everyday protection and add a valve which complies with the Code at the 40 psig MAWP for your extreme scenarios. 'Course for your Code calc's you cannot take credit for the other non-Code devices. Might be able to use a smaller valve that way.
jt
RE: ASME Stamped Vessels Have No Relief Devices
I don't know if that is ScottPearson's situation and I hope this doesn't deviate too much from his post but it makes me wonder about the obligations of procuring a Section VIII code stamped vessel when you never needed it to be in the first place. Does that mean you have to maintain the vessel per code (code relief, code repairs, inspections, whatever else) even if your designated design pressure is less than 15 psig or, in other words, your intended service is never greater than 15 psig? I suppose it would make sense to do it that way but would you have to?
Anyway, even if the existing relief devices were sized following API 2000 for low pressure storage, I think that it requires the relief devices to be marked with set pressure and relief capacity (see section 4.6.2 Marking of Venting Devices).
RE: ASME Stamped Vessels Have No Relief Devices
I've read UG-125 through 134 several times and have found no exceptions to not having a Stamped Relief Valve/Rupture Disc even when there is a Conservation Vent/Non-code rupture manway in place and in essence are used as safety devices.
I would guess I need to only replace the hatch with a code stamped Rupture Disc of some kind.
RE: ASME Stamped Vessels Have No Relief Devices
You can always place the PSV on the attached piping (usually piping off the top of the vessel) per UG-135. In accordance with UG-135(d)(1) you may have block valves in between the vessel and PSV provided you CSO (car seal open) them or otherwise "positively control" them so they do not get closed while the vessel is in service. Chances are that a fairly small valve set at say 38 psi on a bleeder would do the trick.
Depending on your jurisdiction, you may be able to remove the "U" stamp therby allowing your existing setup to do its job. But "99.99% of the time" isn't enough. You'd have to convince me that your existing venting would keep the pressure below 15 psig 100% of the time.
Let the flames begin!
jt
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
I see two exceptions: First, with the written concurrence of the jurisdiction and consultation with the plant's insurance company, remove the U stamp. At that point the nameplate must also be replaced/modified to indicate a MAWP less than 15 psig. The second option is to use Code Case 2211 retroactively to avoid the need for a relief device altogether. See thread292-102991
jt
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
I do see that UG-130 has a footnote that says
"Vacuum relief devices are not covered by Code Symbol Stamp requirements."
I'm not sure how that may figure into the discussion but that got me thinking, are there ASME code vacuum valves? Then I found this thread that has some interesting information that ASME has no provisions for certifying valves below 15 psig though there is reference to a "NV" stamped valve.
thread292-35470
This also seems supported by the vendor data on a Kunkle model 215V & 337 vacuum and pressure relief valves.
ht
So it would seem that if you want relief protection below 15 psig, you are not going to get a ASME code relief valve. In that case, relief devices certified to API 2000 would seem to be as good a choice as any.
I'm still a little unsure about this as an argument but if nothing else, I'm getting the impression that to avoid any potential conflicts with code requirements, it is not necessarily a good idea to have a vessel ASME stamped for low pressure applications (<15 psi) just because the code would allow it.
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
So, I think we're going to talk about removing/rerating the tank instead of putting in more PSM/Inspection work and also thereby removing the U-Stamp requirements for upkeep.
Thanks for all of the input
RE: ASME Stamped Vessels Have No Relief Devices
So as I suspected, the jurisdiction requires the Code requirement for a Code stamped PSV to be maintained.
Did you speak with the jurisdiction about removing the U stamp or is that an internal discussion? I'm curious 'cus I'm building a case to remove the U stamp from some currently stamped vessels which could easily have been bought without the stamp as piping components. In the past, my jurisdiction has not permitted this approach...
jt
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
The inspector asked if there were inspection tags on the tanks and I had not seen them. He than told me there are literally thousands of pressure vessels in the state that they don't know about and they have not inspected.
RE: ASME Stamped Vessels Have No Relief Devices
RE: ASME Stamped Vessels Have No Relief Devices
if you pressurize the vessel then you will need the protection and the min will be the MAWP of the vessel or the mAWP of the attachng piping if the piping do not have the required Valves,
in your case i would install 15 psi valves because they are cheaper, more reliable, easy to maintain,
(see conbraco ind. web site,),
the max operating pressure o the valves can be 12 psi,
If opening for valve not on the vessel, you can install it on the inlet piping attached to the vessel right after the shutoff valve (no valve shall be between the vesel and the relief valve) 'hope this helps,
ER
RE: ASME Stamped Vessels Have No Relief Devices
This issue is still up in the air and a decision of either recertification or adding relief has not been made as of yet. I would lean toward recertifying, if only to get out of the inspection and upkeep of ASME vessels.
RE: ASME Stamped Vessels Have No Relief Devices
but if you pressurize the system you need some kind of relief or as you said.- you are waiting to hurt (kill) someone if the vessel overpressures- pumping or other.
it is sad to learn of you waiting to act on this.
ER
RE: ASME Stamped Vessels Have No Relief Devices