Yes Jim. Pressure in the retard chamber is relieved through the drain when the alarm port is closed.
On Fri, Mar 20, 2009 at 10:26 AM, <[email protected]> wrote: > I had not been following the thread because the subject title hasn't > changed, but am I correct in assuming this problem does not occur with > pressure switches at the top of retard chambers? > > James L.(Jim) Roberts, PE/SET > Fluor Corporation > 100 Fluor Daniel Drive - C104F > Greenville, SC 29607 > 864.281.5149 > 864.281.4916(Fax) > > > > > > Jay Jay Blocker <[email protected]> > Sent by: [email protected] > 03/03/2009 08:09 PM > Please respond to sprinklerforum > > To > [email protected] > cc > > Subject > Re: statistics > > > > > > > > Rodney i do not believe you are a nut im just not sure we are looking at > the same equipment. Maybe no one else is admitting this is a problem > because it may not be. I say that to say this. > Lets look at basic common science here. If you have a flow switch set at > 76 seconds and an air pocket tripped it that would suggest that there was > enough air in one single pocket to not only move the paddle but hold it > in the activated position. THis would mean the velocity of the air would > have to have enough force to over power the spring and hold it for 76 > seconds. None moving air could not perform this action. So if there is a > pocket of air that can do this i do not believe moving the ITC would > help. I would have to work with the water dept. and find a way to prevent > these air pockets from entering the system. Maybe even check with > businesses near bye the affected buildings and see if there domestic water > has had any problems. I dont see how air pockets would discriminate > between systems (honestly seems like the domestic would be more > susseptible to this problem). Im not saying your wrong i am just really > lost as to how this > could happen. Have you tied changing out the flow switch? > > Jay > > > > > ________________________________ > From: Rodney Hamm <[email protected]> > To: [email protected] > Sent: Tuesday, March 3, 2009 3:26:47 PM > Subject: Re: statistics > > Jay, > > It is really not a "theory" at this point. I have found this problem at so > many locations and resolved the issue that I am absolutely convinced the > large trapped air pockets are causing the false alarms. > > I have placed my digital LPT Data Logger on the downstream side of wet > systems and recorded the system pressure on 30 second intervals for 7 day > periods. The graph shows the gradual pressure increases/decreases caused > by > temperature changes and the exact time of the false fire alarms are always > indicated by a distinct pressure increase which lasts for more than 60 > seconds. This happens when the water supply increases at the same time as > a > cold front (or significant drop in temperature). Public water supply > systems > typically fill gravity tanks at night and temperature changes usually drop > at night during Spring and Fall (this is typically the time of year these > false alarms are most common). I use the weather channel to determine the > greatest temperature drop on the night when the false fire alarm occurred. > > After I bleed as much air from the system as possible, the LPT Data Logger > verifies that the pressure fluctuations are much less severe and the false > fire alarms are a thing of the past. > > I have one customer where this problem occurred when there was a > temperature > drop and the jockey pump filled the system EVEN WITH THE DELAY ON THE FLOW > SWITCH SET AT 76 SECONDS! After we bled the air from the system, the > problem > was resolved. LPT Data Logger was also used on this system. Yes that is > correct same problem even with a fire pump......the jockey pump at this > facility typically requires 20-25 seconds to start/stop, but when the > underground main pressure is just right and the air pocket/temperature > issue > combines.......we had false fire alarms. I checked the electronic water > flow > switch 7-8 times and the delay was always between 70-80 seconds! > > In summary, air will expand and contract with temperature changes while > water will not. All system have some air, but systems with a significant > percentage/volume of air will allow water to flow into the system to > equalize the system pressure when the pressure downstream of the alarm > check > valve drops below the upstream pressure. When the time required to > replenish > the system exceeds the flow switch delay.....the fire alarm will activate. > It is even more common for systems which have pressure switches on the > retard chambers. > > The flow switch cycling issue is also a huge problem in some instances! > Refer to my previous post regarding the typical test method used by alarm > technicians. > > I sincerely hope this helps. I imagine some of the people on this forum > think I am a freak'n nut. I'm really not crazy! I will admit that I seem a > little obsessed with this issue, but I am getting tired of finding the > problem and none of my buddies in the Fire Sprinkler Industry want to > admit > this is an issue. It has become a bit of a pet-peeve of mine I suppose. > > Take care, > > Rodney K. Hamm, P.E. > President/Owner > Falcon Fire Protection > Office (478) 953-1677 > Cell (478) 396-6988 > > -----Original Message----- > Date: Mon, 2 Mar 2009 17:07:39 -0800 (PST) > From: Jay Jay Blocker <[email protected]> > Subject: Re: statistics > To: [email protected] > Message-ID: <[email protected]> > Content-Type: text/plain; charset=iso-8859-1 > > Rodney could you please elaborate on your theory of the air pocket > tripping > the flow switch. Several of us in my office are baffled. > > Jay > > > _______________________________________________ > 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]<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]<to%[email protected]> > (Put the word unsubscribe in the subject field) > > ------------------------------------------------------------ > The information transmitted is intended only for the person > or entity to which it is addressed and may contain > proprietary, business-confidential and/or privileged material. > If you are not the intended recipient of this message you are > hereby notified that any use, review, retransmission, dissemination, > distribution, reproduction or any action taken in reliance upon > this message is prohibited. If you received this in error, please > contact the sender and delete the material from any computer. > > Any views expressed in this message are those of the individual > sender and may not necessarily reflect the views of the company. > ------------------------------------------------------------ > _______________________________________________ > 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]<to%[email protected]> > (Put the word unsubscribe in the subject field) > -- Ed Vining 4819 John Muir Rd Martinez CA 94553 925-228-8792 _______________________________________________ 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)
