If I may chime in - this is all very confusing. The term PRV is applicable to the terms pressure RELIEF, pressure REDUCING, pressure RESTRICTING or just plain ole' pressure REGULATING valves. Methinks it would be better to speak to the specific type of valve.
Once we get into discussion of pressure reducing valves - which is the right term for this application if I'm following it correctly - then we should focus on the type of reducing valve. The POC valves for hose and sprinkler connections are either spring or piston type, but the in-line valves are pilot type. So Todd's question about "Cla-Valves" could be directed at pilot-type valves in general. So, if I'm still guessing right, here's the deal: pilot valves are reputed to be less reliable and in the big to-do over NFPA 14 I heard this from numerous professionals. Another issue is that they are capable of failing full open or full closed, unlike spring and piston valves which only fail part-open and still offer some pressure reduction in fail mode. There is also the issue of minimum flow, which is often overlooked. Cla-Valve makes a listed reducing valve that is rated for 3100 GPM continuous and 3900 GPM intermittent flows, but also carries a 200 GPM MINIMUM flow rating - this is the part that almost everyone overlooks. You can't leave that valve (or a 6" or 4" for that matter) in line on a combined system if you expect the flow of a single sprinkler to make it through, which is why both 13 and 14 speak to the possibility that you'll need to manifold more than one valve for the full range of expected flows. And of course 14 now requires redundancy. If you have a project where "the relief valve was removed and replaced with a PRV" that has since become a nightmare because it can't be set properly, then you have the wrong valve in place and if the water supply doesn't work properly the downside scenario could be catastrophic. In all likelihood, a complete re-evaluation of the design should be undertaken. And all of this is subject to aggressive ITM, which will help to assure longer-term functionality of "PRV's". Steve Leyton Protection Design & Consulting The foregoing is the opinion of the writer alone, and does not necessarily represent the intent of the NFPA 14 Technical Committee, nor constitute a formal or informal interpretation of the standard. -----Original Message----- From: Greg McGahan [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 14, 2007 9:24 AM To: [email protected] Subject: RE: pump tricks We have never used one for an entire facility unless we could do it with 2-1/" prv. The relief valves really can create a lot of problems and we have seen them not work at all and no one know for long periods of time. You can get 500 gpm out of 2-1/2" PRV so we try to stay with them. Are you talking about a PRV or a Clay Valve being unreliable? PRV's usually relax over time. That is why the requirement is to limit the pressure to 165 psi on the system side of the valve. Living Water Fire Protection, LLC 1160 McKenzie Road Cantonment, FL 32533 850-937-1850 Fax: 850-937-1852 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Todd Williams - work Sent: Wednesday, March 14, 2007 12:19 PM To: [email protected] Subject: RE: pump tricks >Greg McGahan wrote... > >We do not use Relief valves any more. We rely on the proper rated fittings >and Pressure Reducing Valves. The relief valves we have seen do not operate >quickly enough to save the system from being exposed to higher pressure and >they discharge so much water that they destroy property. > > Interesting. I am working on a project where the relief valve was removed and replaced with a PRV. The PRV has become such a nightmare since we can't reliably set it and just don't trust it to work right, that we are replacing it with a standard relief valve. What is you experience with PRVs over time? What kind of maintenance are you doing with them? Todd G. Williams, PE Fire Protection Design/Consulting Stonington, Connecticut 860-535-2080 www.fpdc.com _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
