This is a real-life story of Elimination vs. Engineering Control
We see some odd designs in our work around the world, but recently we came across a setup that defied any logic for a relief valve design basis. For some reason, the OEM and Installer of this process equipment wanted it enclosed for “efficiency”; however, they did not feel the need to vent the relief valve(s) outside of the space/area.
To be fair, I will admit the enclosed process area is normally unoccupied. However, when the PSV lifts, the discharge is about 80-90% Nitrogen gas. This N2 is discharges into the fully enclosed area/space in volumes that could create an oxygen-deficient atmosphere within this working space. To counter this CREATED hazard, the OEM specified an O2 monitoring system and alarmpanels located at the entry doors (however, NOT ALL doors have these alarm panels!).
The simple fact that the foreign OEM (outside the USE) specified such an expensive safety system for installation tells me they are concerned about this N2 discharge into the room/space. But rather than vent the PSVs out of the room/space (Elimination), they chose to manage this life-safety hazard with an O2 monitoring system (Engineering Control), which flies in the face of our RAGAGEPs in the USA.
I lost the debate about simply discharging the PSVs (3 of them) outside. So now the O2 monitoring system becomes a Safety Critical System, requiring it be in the CMMS/PM program for calibration every three (3) months (Detector OEM frequency) with functional testing every 6-months. Of course, this cost and work was NOT part of the Hand-Over from the OEM, so once again I get to be the “bad guy” forcing the hand to do this by the book. These added costs for calibration and functional testing are estimated at $4,000/year. NOTE: The cost to modify the PSV vents to the outside was $20,000, with a 5-year ROI. This of course does NOT take into account the following: 1) these are NOT repair costs and 2) the process can NOT run if the O2 system is not functioning as designed.
All of this, rather than venting the PSVs outside the building!