Multiple Fire Pumps in Parallel (NOT for redundancy) 2

[sl3656]

I know NFPA 20 has a specific chapter that governs fire pumps in series (the state building code uses the 2013 edition to be specific at the moment).

Does anyone know if there are any requirements governing multiple fire pumps in parallel? Note that the pumps would be required as part of the design - there is no redundancy. We have a project currently in design development that may require a 'lead' and 'lag' fire pump, where the pumps are started in a cascading fashion with a 5-10s time delay in between, primarily to reduce the starting current drawn. Any thoughts greatly appreciated.

As always, I find the advice from the experts in the forum helpful as a guide!

 

[TravisMack]

What are you looking for? We have had to do parallel pumps in the past for various reasons. Flow in parallel is additive. So, if you have two 2500 gpm pumps, you have to size your common suction / discharge piping as though it were a 5000 gpm pump. If you have common relief valve discharge, that would be sized for 5000 gpm.

For the example above, your common suction line will be 16". You will have individual 10" feeds going to each pump. When you tie back in to a common discharge, that will need to be 14" minimum. The individual pump relief valve discharge (assuming diesel pumps) would be 10". If you have them in a common line back to tank, then that common line would be 14". The last one I did like this (but larger pumping capacity), we did a test header sized to test a single pump. So we would have a 10" test header with 8 valves in this example. In the last job I did, we had hydrants downstream of the pumping assembly. We used the hydrants to test at full capacity with both pumps going.

I hope this gave some ideas. I'm not sure I really answered your question.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, LLC

http://www.mfpdesign.com

 

[skdesigner]

See 20-2013 10.5.2.5 for sequence starting of multiple pumps. The sequential time delay is a requirement.

10.5.2.5.3 indicates that the pumps are to start at intervals of 5 to 10 seconds.

 

[sl3656]

Yes both answers addresses my concerns. I was looking for some anecdotal advice on whether parallel pumps were possible. It seems like it is permitted per NFPA.