Although I don't have any specifics, I heard there have been cases where the main relief valve was improperly set and thus hindering fire fighting operations. The handbook to section 5.7.6.2 (2007 edition) states the reason for excluding them is because they are maintenance intensive.
Ken Isman, from that 'other' association, may have more information. I know he was heavily involved with the re-write of this section of code and has been involved with the fire pump handbook in the past. Duane Johnson, PE Program Manager Division of the Fire Marshal (Support Contractor) Office of Research Services National Institutes of Health 301-496-0487 -----Original Message----- From: Frans Stoop [mailto:[email protected]] Sent: Friday, April 02, 2010 11:55 AM To: [email protected] Subject: Pressure relief valves to flatten the pump curve Forumites, NFPA 20 - 2007 par. 5.7.6.2 ( = 2010 par. 4.7.7.2) says: "Pressure relief valves and pressure regulating devices in the fire pump installation shall not be used as a means to meet the requirements of 5.7.6.1." (= 2010 par. 4.7.7.1) I ask this question because it seems to be not unusual in my country to fit fire pumps with a pressure relief valve to limit the churn pressure below 175 psi in systems that need a high pressure (e.g. 165 psi) in the point of operation. Thus flattening the first part of the curve up to the point of operation. This happens to both, engine driven as well as electric driven fire pumps. In engine driven pumps they use for this purpose the same relief valve as mentioned in section 5.18 "Relief Valves for Centrifugal Pumps" (= 2010 section 4.18). Can anyone tell me why this par. 5.7.6.2 says: "shall not be used" ? Why did the committee put this in the code ? I remember times when it was not in there. Is this based on bad experiences? When I point other technicians to this rule a common response is "Why ? We do it all the time! " Can anyone of you shed some light on this issue? Frans Stoop TOS architecture & fire protection Netherlands <[email protected]> Tel. +31-24-324 0112 _______________________________________________ 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)
