Thom, I ran into a very similar scenario in one of the cities along the Front Range. A commercial/light industrial area was being served by two municipal water pumps - the 1st being a 'small' pump intended to supply non-emergency/domestic water to the development; the second being a much larger pump that kicks in when the flow through the system exceeds approx 1500 gpm. We discovered that all hydrant flow tests in that area were being done with the larger pump operating.
Long story short, we had the city do an additional flow test with the larger pump off. We used the lesser test data for design. The scary part was that it wasn't obvious. If we had asked for the basic Static/Residual/Flow numbers and nothing more, we would have designed & installed a number of deficient systems. Ed Kramer Littleton, CO >We have a municipal water system which operates at 48 psi most of the >time, however when the flow exceeds 350 Gpm the fire pump kicks in and >boosts the system to 145 Psi, @ 2000 gpm. Whenever a flow test is >performed the results are always based upon the fire pump flow. >As we all know most fires are contained or extinguished by one to three >heads. Obviously this isn't enough to make the fire pump kick in. >The local Fire Chief has started to question the operation of systems >installed using the full flow of the fire pump, since even in flow >conditions over 350 Gpm it can take as long as 2 (Two) minutes for the >pump to kick in. The bigger concern as I see it is that the design for any >system up to 350 Gpm should be based upon "NO" fire pump, with two sets of >calculations one for flow up to 350, and another for flow over 350. This >way we can be sure that the sprinkler heads will have the min. pressure >and flow even if only a few go off. The other calc should be easy to >prove, as over 350 there will be a large increase in pressure available. >The caveat is that the higher flow calculation cannot be used to reduce >the pipe size below those used for the lower calc. It is just a "Proof" >calc. > >Does this sound like the right approach? >No the city has no intention of changing the pump set up any time soon. > >Thom McMahon >Firetech, Inc. >2560 Copper Ridge Dr >Steamboat Springs, CO 80488-2136 >Tel: 970-879-7952 >Fax: 970-879-7926 _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
