For the sake of both reliability and maintenance, I think you want to pick one or the other basis of design, i.e. create a lower zone with a double reducing valve manifold or (assuming the building isn't so tall as to preclude this) make the building a single zone and use point of connection reducing valves at each hose connection and sprinkler floor control assembly. I would not want PRV's inside of PRV's.
PR hose and control valves are either spring (totally field adjustable) or piston type and these designs will fail in the open state if they do. I prefer this type of valve because even if it hasn't been maintained and isn't working properly, water is still available to fire fighters. Pilot-type valves can fail open or closed, and the prospect of a full-close fail state is of highest concern, hence the NFPA 14 requirement for redundancy. (Sidebar note: if you pursue this approach, remember that you also need to account for the lowest flow of one or two sprinklers, so two smaller PRV's are likely also required.) The most critical element of all is the issue of maintenance - regardless of which approach, will these valves be ITM'd by the owner to assure functionality? Zone-by-PRV is likely the less expensive approach and there are fewer valves to test, but in a fire fight there is a higher (albeit still very low) chance of interruption of the water supply. Point of connection valves are more expensive and there are more of them to test and maintain, but are considered more reliable (again, the % chance of failure overall is very low in any case) and will fail open. But there is a critical difference and that is that POC valves can be ordered that are completely field-adjustable in flow and no-flow conditions, allowing firefighters the most flexibility during an operation. For me - as a consultant who isn't spending his own money - and knowing what I know about the available product technologies, I prefer the POC approach because at the end of the day a standpipe system is about r eliability of the water supply and firefighter safety. The preceding is MOST DEFINITELY my opinion only and does not represent the NFPA 14 Technical Committee or AFSA in that or any other regard. Steve -----Original Message----- From: Sprinklerforum on behalf of T. Silva Sent: Mon 5/25/2015 10:44 PM To: [email protected] Subject: Highrise Can you share your strategies for highrise buildings? Or direct me to a source for information? I am planning to reduce the pressure after the fire pump, using two pressure reducing valves in series. Then run two standpipes, one low pressure and the other, high pressure and use additional pressure reducing valves at each floor where the pressure exceeds 175 psi.This PRV at each floor will reduce the pressure (only where it exceeds 175) to both the sprinkler zone and hose connection. Any problem with that? Or do I have to use a PRV for only the sprinkler zone and a pressure reducing hose valve for the hose connection? The hose connections are 2 1/2" with 2 1/2" x 1 1/2" reducers. Any feedback will be appreciated. Thanks. Tony Call Send SMS Add to Skype You'll need Skype Credit Free via Skype _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
