2" sensing line placement
2" sensing line placement
(OP)
I'm not sure if this is the appropriate place to post this, so please direct as needed.
I'm curious about the sensing line placement in regards to a low pressure pressure relief valve. I was on a job site today while we were servicing equipment and noticed the 2" sensing line plumbed into a flange adapter spool accommodating a 10" pressure relief valve. My question is, what is the potential effect of having a pressure sensing line so close to a unit designed to relieve pressure? I presume that normally the VRU would come on before the PV operates. Thoughts? Thanks,
I'm curious about the sensing line placement in regards to a low pressure pressure relief valve. I was on a job site today while we were servicing equipment and noticed the 2" sensing line plumbed into a flange adapter spool accommodating a 10" pressure relief valve. My question is, what is the potential effect of having a pressure sensing line so close to a unit designed to relieve pressure? I presume that normally the VRU would come on before the PV operates. Thoughts? Thanks,





RE: 2" sensing line placement
Hypothetically, if the flowrate was high enought to create a vacuum where the sensor line is connected, and the vac device opened, then it would experience reverse flow. Effectively, it will supplement the pressure relief device. That's very unlikely to happen, but if it did there's no harm - certainly no safety hazard.
RE: 2" sensing line placement
The 10" was a weight loaded unit, set at 1.0 Oz pressure and 0.5 Oz vacuum. Generally for the scope of work we deal with, sensing line will connect to Varec 180/181 (weight loaded as well) or S&J Oil regulators, set at between 0.8" WC and 0.2" WC. Other times its a switch device connected to some computer logic that will either tell the compressor or make up gas to come on depending on the pressure readings. Again, most times the operation range is measured in 0.1"WC. I guess from a design stand point, you could have have issues reading tank pressure if the valve is leaking or failed open, sending false readings. Every day I seem to have more questions, so I appreciate all the time taken to address them.
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