Reza, In my industrial experience, I've never quite seen what you are proposing. You have a couple issues I think you are trying to address -
Basic NFPA requirement - single automatic water supply; in your case, most simply a single pump with a single water supply; in that case, personally, I would start by looking at a single 3500 or 4000 gpm pumps(using the pump at 110-135% of rated is OK); I'm not sure why you would split that into two 50% pumps; in the few cases where 50% pumps have been used in my experience , 3 - 50% pumps are used so that the loss of any one pump doesn't impact your ability to supply demand. Also, using that arrangement doesn't buy that much from an insurance perspective, since the 3 pumps are supplied by a single water supply. Typically the key issue for underwriters is redundant WATER SUPPLIES, not necessarily pumps when those are required. So if there is no owner or insurance underwriter requirement requiring two supplies, I would start with the single pump arrangement to meet your demand and I would be looking at making a 3500 or 4000 gpm pump work if possible. Your 90 psi requirement isn't that high, so you've got some room to work with at churn and be able to use at 110-135% of rated. HP requirement for those pumps will be in the 350 HP +/- range. Iterate your selection between keeping the curve flat as possible without making a costly jump in motor/engine sizing. Diesels are available from typical suppliers, Clarke (JD), Cummins Fire Power. I have made two water supplies work to supply a single large demand if the owner, underwriter doesn't require redundant supplies. That is developing a combined supply and designing the sprinklers, water spray, etc. to that supply. I usually don't start with that in a greenfield scenario - usually existing where a new large demand is somewhat greater than what either single supply can provide and it is far more cost effective than upgrading either supply. Electric vs. diesel depends on electrical power reliability and again if the owner or insurance underwriter have a position on it. You would have to estimate electrical vs. diesel drive costs if electric drive is an option, I think you need the estimates to be accurate. If you are actually required to install redundant pumps on a single water supply or two pumps on redundant water supplies, typical arrangement is one electric drive and one diesel drive or two diesel drives. These both would be 100% pumps. Just one last quick comment. 4600 gpm is a pretty large demand and in my experience would be industrial deluge system related. If you are working with a large industrial site, I always look at potential demands, not just what happens to be the largest demand associated with the current pump install. That would be a discussion with the owner typically since they need to support the larger pump install. My experience would indicate if this is an industrial application, a pair of 4000-5000 gpm pumps would be installed off two water supplies. Pressure rating would be basically to limit underground mains to 125-150 psi max. Hope this helps, Rich Richard Malek [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Reza Esmaeili Sent: Sunday, September 02, 2007 7:37 AM To: [email protected] Subject: Fire Pump Selection Hi friends, The estimated water demand for a sprinkler system and hose stream is 4600 GPM at 90 Psi, I want to select 2 x 2500 GPM at 90 psi pumps. I know that electric fire pumps are duty pumps and diesel fire pumps are standby pumps and will run in power failure situation. If I have to use 2 x 2500 GPM electric pumps as duty pumps and 2 x 2500 GPM diesel fire pumps as standbuy pump, it will cost me too much. Is using of diesel fire pumps necessary for all fire sprinkler systems as per NFPA-20? I think I should better use 1 x 2500 GPM electric fire pump and 1 x 2500 GPM diesel fire pump, however in this case my diesel fire pump will not be as an standby pump and will run when water demand exceeds than 2500 GPM. is it a right arrangment as per NFPA-20? What about If I use 2 x 2500 GPM electric fire pump, is it against NFPA-20? What is the best arrangment to according NFPA and also economical? Thanks in advance for your kind help, Reza --------------------------------- Sick sense of humor? Visit Yahoo! TV's Comedy with an Edge to see what's on, when. _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
