I believe if you look in the "discharge pipe" section of 25 and the associated annex material you'll find the sizes are intended to keep the velocity below 20'/sec. There really isn't any exception, but the discharge size is only mandated between the fire pump discharge flange and the discharge shutoff valve, normally there's only a couple fittings and valves in that space, anything after the discharge shutoff is considered NFPA 13 governed system pipe and can be any size supported by calcs. Mike Morey, SET, CFPS Sprinkler Designer BMW Constructors, Inc. O: 317.651.0596 | C: 317.439.2695 www.bmwc.com
________________________________ From: [email protected] on behalf of Matt Grise Sent: Tue 7/19/2011 11:56 AM To: '[email protected]' Subject: Pump Discharge Piping Are there any exceptions out there for the minimum pipe sizing on fire pump discharge as listed in NFPA 20 2007 5.25? We have calc'd a pump and all of the down stream piping to work with a smaller diameter than the one listed in the table. Is there additional thrust blocking or supports that can be added to allow a smaller pipe size? I am thinking that the goal is to keep the velocity down to reduce water hammer effects? Is that the case - are there other considerations? Matt Grisé PE*, LEED AP Sales Engineer Alliance Fire Protection 130 w 9th Ave. North Kansas City, MO 64116 *Licensed in KS & MO 913.888.0647 ph 913.888.0618 f 913.927.0222 cell www. AFPsprink.com _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
