Sometimes if air is trapped in a system, especially if a gridded configuration is used, and the inspectors test is flowing, more water is rushing into the system then is flowing out the inspector's test, compressing the air and causing a reverse flow back to the alarm valve closing the clapper. Once the water flowing out the inspector's test decreases the system pressure, the check valve reopens and the same thing occurs again. This results in an intermittent alarm. If there is no alarm valve, and just a backflow preventer with a waterflow detector switch is being used for the riser, the same phenomena may result causing the checks on the BFP to close intermittently. Try draining the system and filling the system back up slowly while venting the system piping at the hight point(s). Regards, Salvatore Izzo, P.E. Manager - Reliable Technical Services
________________________________ From: [EMAIL PROTECTED] on behalf of John Drucker Sent: Mon 4/30/2007 16:24 To: [email protected] Subject: Ames RPZ BFP During waterflow alarm testing on a Wet Pipe NFPA-13 System I witnessed a phenomena wherein the vane type waterflow switch fluctuated back in forth appx every 10 seconds making it impossible to set a 30 second retard. Supply Pressure is 60 psi static, 55 psi Residual at 2" Main Drain Test. The WF Switch is mounted horizontally in a straight length of 6" Sch 10 48" from closest change in direction. Inspectors test is located downstream end of a branch line 1/2" orifice in place. The sprinkler contractor suspects theres a problem with this particular BFP. Anyone had a similar problem. Thanks John Drucker Fire Protection Subcode Official (AHJ) New Jersey _______________________________________________ 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)
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