Mike, The 18 fps second surge is a UL test (UL 346, Section 34) to test the sensitivity of the device. Basically, the switch is exposed to flow rate that equals 18 fps velocity. The flow is reversed and the flow at 50% of the forward flow is sent past the switch. The switch is then tested again for sensitivity.
The UL/FM listings are far from what the Europeans require. The EN12259-5 standard requires almost double the flow velocity in order to pass those tests. As you can see these tests are much more stringent and the device is compliant with the more stringent listing. Kind Regards, Tim Tim Frankenberg, CFPS Fire Product Manager Potter Electric Signal Company www.pottersignal.com 800-325-3936 >>> "Peter Nadhazy" <[EMAIL PROTECTED]> 11/14/2007 9:17 PM >>> Mike, We use the Potter VSR-F flow switches for main and sectional control. I am sure you are aware that there is a max. design water flow velocity (surge) limit (18 FPS) allowed going through the water flow indicator switch per UL/FM listing/approval. Peter Nadhazy ----- Original Message ----- From: "Mike Brown (TECH- GVL)" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, November 14, 2007 4:48 PM Subject: RE: Maximum Velocity I guess being old and having been around for a long time. The 32 ft per sec came from some old water distribution engineering manuals and became sort of a rule of thumb for sprinkler calculations in that when you get above that velocity the friction loss gets larger in a hurry. At one time FM came out with a requirement for a maximum of 20ft per second in grid branch lines but they sort of backed off on that issue but did keep the requirement for the velocity in riser nipples or something like that. I am not sure what FM does now regarding velocity. Most of the computer hydraulic programs have followed the old rule of thumb that you need to keep your velocity at or under 32 ft per second and usually they will show you the various pipes that exceed that velocity and you can make the decision on changing the pipe size or not. But the velocity is not addressed in NFPA 13. Mike Brown -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Roland Huggins Sent: Wednesday, November 14, 2007 3:41 PM To: [email protected] Subject: Re: Maximum Velocity also look at 13: A.22.4.1 (last sentence) It is not necessary to restrict the water velocity when determining friction loss using the Hazen-Williams formula. This is also in the 02 edition. Roland On Nov 12, 2007, at 6:41 AM, Brian Harris wrote: > What's the general rule of thumb for maximum velocities in > hydraulic calc's? > I use Hydra-Calc and the default is set @ 32, I assume that's feet per > second. Where did that number come from, I didn't see anything in > the code > book. > > > Regards, > > <http://www.firstdefensefire.com/> > > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:Sprinklerforum- > [EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) _______________________________________________ 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) _______________________________________________ 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) _______________________________________________ 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) _______________________________________________ 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)
