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Fire Relief for a Centrifugal Pump

Fire Relief for a Centrifugal Pump

(OP)
I have a centrifugal pump. It cannot overpressurise the discharge in a dead head (no flow) scenario. Do I need to provide a PSV for fire relief?

Thanks.

RE: Fire Relief for a Centrifugal Pump

There is no regulation or Code that mandates a fire scenario relief for a pump to my knowledge.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: Fire Relief for a Centrifugal Pump

Latexman is correct. There are no code requirements.
If suction side of the pump remains with an open path during fire, hydraulic expansion will have no consequences.

You may consider installing a TSV on pump suction or discharge piping if there is a significant volume of trapped liquid between two isolation points (suction/discharge) and the system qualifies for hydraulic expansion due to absorption of heat.

Dejan IVANOVIC
Process Engineer, MSChE

RE: Fire Relief for a Centrifugal Pump

Pumps are usually treated as piping components and piping is not typically protected against fire. That's not to say you can't though I can't say I've ever seen a fire case PSV on a pump.

RE: Fire Relief for a Centrifugal Pump

I can say I've never done or seen a fire case for a pump.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: Fire Relief for a Centrifugal Pump

I agree the answer is no you don't

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Fire Relief for a Centrifugal Pump

I agree that there is no code that dictates piping be protected against fire. But on my experience, to be conservative on relief load, pipings are accounted to the PSV on the upstream drum of the pump.

RE: Fire Relief for a Centrifugal Pump

choack,

What does that mean? Can you explain further with more detail?

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

RE: Fire Relief for a Centrifugal Pump

Pump casings are not constructed to PV codes, so that may explain why PSVs' are typically not installed on pumps. Pump casings are made with much thicker walls. However, if a pump is blocked in during a fire, dont know at what pressure the shaft seals will blow out - if this pump is in some high HSE risk application, may be worth asking - a pump or seal specialist may comment?

RE: Fire Relief for a Centrifugal Pump

As mentioned earlier, the problem with pump catching fire occurs only if liquid is trapped between the suction and the discharge isolation points. In all other cases, there is an open path that will allow for hydraulic expansion of the fluid and hence there are no further concerns.

The only scenarios in which a pump can catch fire while being isolated on suction and discharge side, are:

1) Sitting in a flammable liquid pool created by leakage from a nearby source (another pump or tank/vessel);
2) Impinged by jet flame from a nearby vessel or piping.

If these two prerequisites exist (isolated pump and source of fire), one may argue if fire relief is required. If one of the two factors is not present, there is absolutely no need to consider fire case relief. Being conservative, you can calculate heat flux for the isolated system and see whether a common TSV will provide the required relief rate. If it doesn't do so, you may go for a higher size orifice.

Based on the description in the OP query, we cannot conclude if any of these criteria are met for this particular pump. You can review the fire scenarios and isolation philosophy in your plant and see if the pump qualifies for further fire safety assessment.



Dejan IVANOVIC
Process Engineer, MSChE

RE: Fire Relief for a Centrifugal Pump

Pump casings contain a small amount of liquid volume, so even if one was isolated and engulfed in flame, the explosion radius would be small. PSV is not needed for fire protection.

However, if it is in LNG service, sometimes a TERV will be installed on the piping for over pressure due to ambient heat input.

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