Advice on how to move PSV discharge piping with PSV in service 1

[seasar]

Howdy...I have a facility which has ammonia relief valve discharge piping that is well under 15 ft from the ground. The protected equipment includes, among other things, the primary suction header for the facility and it can't be easily taken out of service (has never been in 30 years).

I'm trying to find a safe, PSM compliant and realistic way to rework the piping. I'm nervous having pipefitters working on it while the relief could go off, more nervous about leaving the equipment unprotected but in service and it doesn't seem practical to have them in full level A suits to do the work.

Thanks for any advice....this re-instills the mantra in me:
"5 minutes spent now means 5 hours saved later"

 

[Longinthetooth]

I think it about time you inspected that pipework.
It is way beyond any inpsection frequency that I have heard of.
As for working on a live PSV- just dont do it!

 

[iainuts]

The facilities I'm familiar with all have an outage at least once per year to accomodate these kinds of tasks. Having relief valves in service that long without maintenance or testing being done on them seems negligent. May I ask what country this is in?

 

[seasar]

Its the US...the relief valves themselves are configured in a dual arrangement with a selector valve. They share a common discharge pipe and that is the issue. The reliefs are recertified every 5 years.

 

[pennpiper]

Seasar<
You wrote:
"They share a common discharge pipe and that is the issue."

What do you mean by this? What is the issue?

 

[seasar]

The dual PRVS (of which one is in service and the other is in standby...done so that either one can be recertified without takind down the affected equipment) tee back into a common discharge pipe. Some of these discharge pipes are within 15 ft of the ground (not compliant with ASHRAE 15 which, for reliefs venting to atmosphere requires 15 ft from ground, 20 ft from windows/openings/exits and spray must be directed away from personnel).
How do I work on these discharge pipes to make them compliant? Taking the relief OOS means taking the equipment OOS and evacuating the ammonia. The facility in question doesn't take routine outages (annual or otherwise). In fact some of this equipment has been in service for 30 years and everything but the common discharge piping from the dual reliefs has redundancy installed to accommodate that (compressors, condensers, individual reliefs, even suction traps, thermosyphon receivers, etc, it can all be worked on safely while the rest of the facility is running).

 

[Duwe6]

How big is your discharge pipe? At 4"NPS and smaller, a socket-weld coupling would be a good answer. Prefab the new pipe and supports, then dress out a welder & a fitter. Slip the new pipe spool on and tack it fast. Then root the weld. Now the guys can go back to normal dress, with escape 'lollypop' respirators on their belts.

Bigger than 4", use a slip-on flange on the existing pipe. After it has the root welded, bolt on the new spool. Now they can 'undress'.

 

[seasar]

Duwe6....Thanks! I hadn't thought of doing the work partially in full level A suits.

 

[StoneCold]

What about re-orienting the PSV that is out of service and building a new relief vent header for that valve. Then switch to that PSV and then tear out the old header and built a second relief vent header for the second PSV.
Assuming that you can turn the PSV's 90 degrees and they are still headed in a direction you want to go.

Regards
StoneCold

 

[seasar]

StoneCold....thanks, this would work for some of them, most are too close together coming out of the selector valve though.

 

[EGT01]

Typically dual PSV arrangements on refrig units that vent to atmosphere have their own (separate) discharge pipe which would provide the greater flexibility for maintenance. Unless there is some other limitation for having a common discharge pipe, usually, you are not talking about a lot of pipe/dollars. Is that something worth thinking about now?

 

[seasar]

It's something they'll have when I'm done, that's for certain.