I would do what the contractor did at my own house without a 2nd thought if there was not an easy way to bleed off the air.
Greg McGahan Operations Manager Living Water Fire Protection 1160 McKenzie Road P.O. Box 877 Cantonment, Florida 32533 (850) 937.1850 | Fax (850) 937.1852 | Cell (850) 554.3231 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris Cahill Sent: Wednesday, October 28, 2009 8:21 AM To: [email protected] Subject: RE: Homeowner needs advice I think Ed confused the issue. He's not wrong but I don't see it as applicable. Hydrostatic testing is not the question. The bleeding of air for test purposes is recommended because yes it will create a serious hazard if it ruptures. I'd venture though this bleeding is not actually done in the field. This testing is done at 200 psi. Your system most likely does not have this kind of pressure on it. And even if it did most of what is in the system is water not air. Air is compressible, water is not for these purposes. This is why air at pressure is dangerous and water not as much. The volume of the air is also a critical factor. A little air at very high pressure is not as big an issue as a lot of air at a lower pressure. Think when air is compressed energy is retained. The more volume of air, the higher the pressure the more retained energy. When the pipe breaks this energy is released. The water not being compressible does not retain as much energy. There is no reason really to bleed the air in the situation described. Actually some air in the system is a good thing. Because it is compressible is "absorbs" temperature changes and pressure surges much, much better than water. Think of it like a spring. If there was no air in the system and the temperature rose just a few degrees the pipe would break. This is the ratio of Pressure = Temperature from basic science. Taking an empty system at 0 pressure and filling it with water at street pressure leaves the air in the system, true. But after it's compressed to street pressure (much <200 psi, probably in the 80 range) there is very little volume left. Recall the ratio of Pressure * Volume = a steady value with no changes to Temperature from basic science. Double the pressure = 1/2 the volume. With average street pressure you are doubling the pressure many, many times. If one suspects trapped air is causing false alarms like George suggested the real problem is a leaking check valve. Each time the system surges from the city supply the new high pressure should be locked in. This could take a couple hours to a couple days to stabilize at the highest pressure. But at least in these parts surges in the street are not that common on scale or duration to cause false alarms. Again there is no reason to bleed the air in your situation. 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 [email protected] Sent: Tuesday, October 27, 2009 6:41 PM To: [email protected] Subject: Homeowner needs advice I'm not sure how this email forum works. I'm sending this out blind hoping one of you pros has some advice for me. I am a homeowner in a three-story townhouse. Recently, a company did some minor modification to our fire sprinkler system - moving a couple of heads for a basement remodel. When they were done with the pipe and heads, they simply re-pressurized the system without bleeding out the air trapped in the lines. From what little I know about it, I thought this step was very important to eliminate any pressurize air in the system and preventing dangerous surge pressures. It says so in big bold type on the product spec sheet for the CPVC pipe. When I asked the installer he said they don't need to bleed it, but couldn't explain why not. Before I go raising a stink about it, I want to know if your forum agrees that it's not necessary; or do I need to pester them into doing it correctly. Thanks. _______________________________________________ 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) _______________________________________________ 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)
