I don't think you are over thinking. Which side of the FS does the JP pump into? Is there no water running past the FS after the initial surge? And if the pressure has dropped that far why hasn't the FP kicked in? That might be the actual problem.
Chris Cahill, P.E. Fire Protection Engineer Sentry Fire Protection, Inc. 763-658-4483 763-658-4921 fax Email: [email protected] Mail: P.O. Box 69 Waverly, MN 55390 Location: 4439 Hwy 12 SW Waverly, MN 55390 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Todd Williams Sent: Monday, November 02, 2009 10:54 AM To: [email protected] Subject: RE: pump failure/flow alarm Just had another conversation with the fitter. When the IT is opened, the paddle goes up for about 3 seconds and then settles back to neutral. My guess is that the majority of water is discharged in the first few seconds and the pressure pretty quickly dissipates to elevation head only and the flow would be only a trickle. At 50 psi, a 1/2" sprinkler would discharge 39.6 gpm initially, rapidly declining. How long would the 8 gpm need to be maintained for the flow switch to activate? The duration of the delay? The 39.6 gpm translates to 0.66 gallons per second. If that 50 psi remained steady, it would take 12 seconds to discharge 8 gallons, well under the 30 second setting on the FS. The minimum 8 gpm flow requires a 2 psi discharge out of a 1/2" orifice. Will the pressure at the orifice drop from 50 psi to 2 psi in 30 seconds in a closed system? Probably. Am I over thinking again? At 11:21 AM 11/2/2009, you wrote: >Are the jockey and fire pump not using sensing lines? > >Joe Burtell > >-----Original Message----- >From: [email protected] >[mailto:[email protected]] On Behalf Of Todd Williams >Sent: Monday, November 02, 2009 9:07 AM >To: [email protected] >Subject: pump failure/flow alarm > >A situation came up this morning that I probably should know the >answer to, but I don't. A building is protected by a 500 gpm at 40 >psi diesel pump taking suction from a tank (no public water). The >pump feeds to 2 sprinkler risers with riser checks and flow switches. >The jockey pump pressure is set to approximately 50 psi. If the >inspector's test opens and the pump does not turn on, there is not >enough flow in the system to activate the flow switch. Consequently, >if a sprinkler goes off and the pump does not activate, then no alarm >is sent. Having never run into this or heard of it being tested, I >don't know if this is normal but it seems like it shouldn't be. Is >this normal? Is it ever tested? > >My first reaction is what is the delay on the flow switch set to (30 >seconds). I told them to set to delay to 0 and see what happens. It >may be just a situation of getting the setting right. Thoughts? > >Todd G. Williams, PE >Fire Protection Design/Consulting >Stonington, Connecticut >www.fpdc.com >860.535.2080 >_______________________________________________ >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) Todd G. Williams, PE Fire Protection Design/Consulting Stonington, Connecticut www.fpdc.com 860.535.2080 _______________________________________________ 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)
