I believe another reason was fear of main relief valve sticking OPEN as flows increase, so the water that should go to 10 open heads is out in the parking lot.
We address by using Clarke diesels w/PLD, 170 pSI output from churn to demand. About as good as it gets at base of riser. Sometimes your water delivery has a "need for speed". Glc -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Roland Huggins Sent: Friday, April 02, 2010 12:43 PM To: [email protected] Subject: Re: Pressure relief valves to flatten the pump curve doing a very bad thing all the time is not grounds for continuing to do it. NFPA 20 did not allow it in the past although the sloppy wording lead many to jump to that conclusion. The problem is during the weekly churn test, you are dumping a boat load of water in the parking lot etc. It now emphasizes that one is to design the system appropriately and account for higher pressures by selection of components (including not casually going to a bigger pump just to get a little more pressure and down size the pipes just a touch more). That's about as bright a light as I can shine. Roland On Apr 2, 2010, at 8:54 AM, Frans Stoop wrote: > 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) _______________________________________________ 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)
