Hello Chris, Hmmmmm CPVC in the microwave.... Ha Ha
Wednesday, March 11, 2009, 11:22:41 AM, you wrote: >SNIP > Do your same experiment with > capped steel pipe and see the results through a pressure gauge. You might > need the oven or a pot of hot water. The misses at home or the boss at work > might get upset if you put steel in the microwave. The other problem I see > with your experiment is the scale. The changes in the water volume may be > imperceptible to the naked eye. > 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 Rodney Hamm > Sent: Tuesday, March 10, 2009 8:27 PM > To: [email protected] > Subject: Re: Test/Drain at the Riser > I am sorry to be so blunt, but you need to think a little about what you > have stated. Air is compressible and water is not compressible. Temperature > increases or decreases do not affect the pressure of a section of pipe > filled with 100% water until the water begins to boil. Temperature increases > will cause the pressure to increase if the same section of pipe is filled > with air. Temperature decreases will cause the pressure to decrease if the > same section of pipe is filled with air. > If you do not believe me, try a quick little experiment. Take a completely > 100% full glass of cold water (plastic would be best) pull some saran wrap > over the top very tight and add a rubber band really tight to make sure no > air leaks out. Make sure there are no air bubbles on top. Put the full glass > of water in the microwave on HIGH for 2 minutes. No pressure builds up > inside the glass because water is not compressible and does not expand. > Pressure will eventually build if you let the water start to boil. THEN do > the same exact thing with a glass half full of cold water. Using saran wrap > and a tight rubber band, you will see the pressure increases dramatically > and eventually will burst the saran wrap after the balloon effect! > If you have significant trapped air pockets in a sprinkler system, the ONLY > time you do not need a PRV is if you are absolutely certain the sprinkler > piping does not experience significant temperature changes. High temps to > low temps will cause the pressure to decrease and can potentially allow > water to enter the system (i.e. false fire alarms) and low temps to high > temps will cause the pressure to increase and can potentially cause damage > to the sprinkler system piping (i.e. leaks, ruptures, deformation of > sprinkler plugs, etc.). > You stated the following: "With a static system increasing in temperature > the air compresses and stabilizes the pressures." Actually, in this instance > increasing the temperature the air does not compress it actually expands and > instead of stabilizing the static pressure it drastically increases the > static pressure. > > Rodney K. Hamm, P.E. > President/Owner > Falcon Fire Protection > Office (478) 953-1677 > Cell (478) 396-6988 > > Date: Tue, 10 Mar 2009 08:53:14 -0500 > From: "Chris Cahill" <[email protected]> > Subject: RE: Test/Drain at the Riser > To: <[email protected]> > Message-ID: <e86bfbe0cd6e4eae97886a3b39d3d...@chris2005> > Content-Type: text/plain; charset="us-ascii" > > Rodney said "It is an indisputable fact that trapped air is a huge problem > in gridded systems and THE reason why pressure relief valves are required on > gridded systems is specifically because of the trapped air in these > systems." > > Sorry it's the LACK of trapped air that is the problem as it relates to > pressure. I suggest you read '02-7.1.2.2 and the handbook. If you have air > you don't need a pressure relief on a system. Why? It's right in the text > of the standard. Air is compressible. A spring if you will. For our > purposes water is not compressible. With a static system increasing in > temperature the air compresses and stabilizes the pressures. That's what > the pressure tank on your well is doing, that is what an expansion tank on > an anti-freeze is doing. Take the air out and there is nothing to compress. > Minor temperature fluctuations then radically change pressure. I can show > you systems that all the air has been deliberately removed. It takes a cup > of water to change the pressure a couple psi. > > Ever opened an inspector test valve and waited 30-60 sec for the flow switch > to change position. That's the trapped air expanding. Ever opened one and > the flow switch moves immediately that's no air. For this purpose ignore > the delay watch the lever/paddle position. > > A generalization gridded systems don't have air in them is also false. It's > exactly related to the location of the ITV. If the ITV is at the end of the > system on a grid air might be removed while filling or testing. If the ITV > is at the riser (and there is no air relief remote) there is a similar > amount of air in the system as a tree. OK all things being equal a gridded > system has less volume compared to a tree system because of pipe size. But > the volume of the system is similar in magnitude. > > I'm with Mark riser ITV with air relief remote and pressure relief someplace > as the best of practice for all systems but I'll add not the minimally > acceptable practice. > > Chris Cahill, P.E. > Fire Protection Engineer > Sentry Fire Protection, Inc. > _______________________________________________ > Sprinklerforum mailing list > http://lists.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 > http://lists.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) -- Best regards, Charles Thurston mailto:[email protected] Coastal Fire Protection _______________________________________________ Sprinklerforum mailing list http://lists.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)
