Jockey Pump Selection 1

[arabei]

Hi all,

I'm really confused about how to select a jockey pump, and i mean in terms of flow.
I would dearly appreciate if any one can give me some refrenced info. about this subject Or how to predict the expected leakage rates in a conventional commercial system.

 

[sudheer]

There is a clause in NFPA-20 regarding selecting Jockey Pump capacity, based on leakage rate. This leakage rate depends upon length and number of joints in the system.
But calculating the pimp capacity based on the above clause results in very low figures (may be couple of gpm). Therefore, as an industry practice, a Jockey pump of 25 to 30 gpm is seleceted for a main firewater pump of 2000 to 3000 gpm capacity (i.e. about 1% of the main pump capacity. Pumps of this capacity are easily available, designed and approved by NFPA-20.

 

[Guidoo]

We often specify for offshore platforms that:
The jockey pump shall be rated to supply a flow of 30 m3/hour to enable the use of one hydrant without starting the main diesel driven fire pumps.

 

[kieffer]

The amount of leakage from your system is something that you have to monitor. These can vary widely depending on the amount of pipe the type of joints and the installation. The jockey pump is a small pump just used to maintain a resonably constant system pressure by running on an intermittent basis to prevent the larger fire pump from starting too frequently. Often a jockey pump is only 10 or 20 gpm with a rated pressure higher than the starting setting of the fire pump. eg. 15 gpm @ 125 psi.

If your jockey pump comes on more than every 4 hours it is probably operating to frequently. A chart recorder on the system will tell you how often it is running. You need to monitor this closely to see if the jockey pump is running too often and therefore, you have an unacceptable leakage rate.