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[redouane]

Hello,

Please, I need your comment about the operating philosophy of a group of fire pump:

Setting the pressostat:

The pressostat connected to the jockey pump (1) should be set to:
- A starting pressure of 9.5 bara
- A shut-off pressure of 11 bara

The pressostat connected to the pump jockey (2) must be set to:
- A starting pressure of 9.0 bars
- A shut-off pressure 11 bar.

The pressostat connected to the principal electrical pump set at:
- A starting pressure of 8.5 bars
- Manual Stop

The pressostat connected to the diesel pump set to:
- A starting pressure of 8.00 bars
- Manual Stop

Are there any requirements in the NFPA code?

Thanks in advance and have a nice day

R.B (Mehanical Engineer)

(Note: Sorry for my English)

[kkala]

Α. Comparison to an operating manual of a similar fire station for refinery, noted to comply with NFPI regulations in general, results in following.
1. Operational pressure range (OPR) of jockey pump No 1: 9.5 - 11.0 barg versus 7.2 - 8.3 barg.
2. OPR of jockey pump No 2: 9.0 - 11.0 barg versus 6.6 - 8.3 barg.
OPR 6.6 - 8.3 barg means pump starting at FW network pressure of 6.6 barg and stops at 8.3 barg.
3. Electric driven FW pump: starts at 8.5 barg versus 5.9 barg; manual stop in both cases.
4. Diesel driven FW pump: starts at 8.0 barg versus 5.2 barg (if 5.2 barg lasts 10 s); manual stop in both cases.
5. According to Operating manual max FW flow is covered by these two pumps; there is another FW pump as spare (but also starts at 4.5 barg, if 4.5 barg lasts 20 s).
Β. Details of NFPA are not known to me, however logic of set pressures looks similar in the two cases, with following remarks.
1. Corresponding pressures are roughly 2.5 bar lower in Operating manual, allegedly assuring 8 Barg everywhere in FW network from negligible to max FW flow. Referred FW pumps seem to aim at (say) 10.5 (instead of 8) Barg, which is more conservative.
2. Refinery fire fighting stations here (said to comply with NFPA) have spare FW pumps installed.
3. Comments / additions from others more familiar with NFPA would be welcomed.
Note: FW = fire water

Edited by kkala, 25 December 2012 - 02:45 AM.