A single example of very cold from several years ago when I used to work for a living. An unoccupied section of a warehouse. Wet sprinkle system. All the branch lines on that side of the riser end in that space. The heat has been turned off. Several freeze and break due to freezing. We can assume that there is no air trapped in the new ends of the broken lines since the ice plugs are keeping the system intact. There probably is trapped air at the other end and in the frozen end where branch lines have not broken. I'm called out because the riser is leaking around the flow switch. When I get there there is also water weeping out around all the face plate bolts. The gauge reads zero. As I'm standing in front of this riser I rap on the gauge a couple of time and get not "wiggle" in the needle. I look closer and the needle is pegged on the back side of the zeroing pin, ergo 300+ psi. Quick little dance to the side and I try to open the main drain to bleed this sucker off. No chance even though my personal little hell there is literally frozen over. I finally cracked the main drain using a Texas Ten (ten-inch pipe wrench with a cheater that extends the handle to the same leverage as an 18" wrench) on the stem. I felt like I was in one of those submarine movies where flange bolts are going to start shooting off. The power ice. So question of the day: If thermal expansion causes pressure to rise/fluid to expand when heat is applied and to contract when heat is removed what then causes water to also expand when it reaches it's freezing point and is this true for all fluids. This two-part question is worth 50% of your final exam relative to this thread.
And Rodney, thanks for your final comments. I for one was thinking you were being more than a little contentious, arrogant and argumentative (in the negative context of that word), but after stating your intent throughout the thread all is forgiven. As in all institutions the Forum has a culture and sometimes it takes a new guy a bit of time to settle in. John Drucker can probably remember this crazy guy that entered the alarm forum, pretty much told everyone they were idiots, and at one point attacked me with a verbal violence I reserve for Hitler & his ilk because he took some offense at a joking comment I made to another member thinking I was insulting him. I offered a left-handed apology which he accepted, missing the sarcasm, and eventually left the forum. You seem to have gotten the culture here right, so welcome. On Sun, Mar 22, 2009 at 10:11 AM, Steve Leyton <[email protected]> wrote: > Excellent information. So to summarize, it's agreed by all that excess > pressure issues are valid and should be dealt with by way of valves or > accessories designed for that application, such as PRV's. And alarm test > connections can be located anywhere downstream of the device they're intended > to test. > > Steve Leyton > Protection Design & Consulting > San Diego, CA > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Rodney Hamm > Sent: Friday, March 20, 2009 9:13 AM > To: [email protected] > Subject: RE: Excessive system pressure > > > I FULLY INTEND THAT THIS WILL BE MY LAST POST REGARDING THIS SUBJECT. I > promise to make a concerted effort to make this statement true. I would also > like to state that you should probably read this entire post if you have not > completely tuned out regarding this subject! > > > I obtained my Bachelors Degree in Mechanical Engineering and I am also a > FPE; I am fully aware and I understand thermal expansion. A few forum > participants posted data regarding water, but refrained from including any > thermal expansion data for air. My point is that thermal expansion effects > both water and air. The following two paragraphs were copied from the > internet: > > > Charles's law states that when pressure is kept constant, there is a direct > relationship between volume and temperature. As a gas heats up, its volume > increases, and when it cools down, its volume reduces accordingly. Thus, if > an air mattress is filled in an air-conditioned room, and the mattress is > then taken to the beach on a hot day, the air inside will expand. Depending > on how much its volume increases, the expansion of the hot air could cause > the mattress to "pop." > > > > > That is to say, he discovered that if a container of air were to be sealed > at 0*C, at ordinary atmospheric pressure of 15 pounds per square inch, and > then heated to 100*C but kept at the same volume, the air would now exert a > pressure of about 20 pounds per square inch on the sides of the container. > (Of course, strictly speaking, the container will also have increased in > size, that would lower the effect-but it's a tiny correction, about ½% for > copper, even less for steel and glass.) Remarkably, if the air were > initially at a pressure of thirty pounds per square inch at 0*C, on heating > to 100*C the pressure would go to about 40 pounds per square inch-so the > percentage increase in pressure was the same for any initial pressure: on > heating through 100*C, the pressure would always increase by about 33%. > > > > Water on the other hand: On heating from 0*C through 30*C, the pressure will > stay essentially constant, while heating from 30*C through 100*C, the > pressure will increase by about 4%. Check out the thermal expansion > properties of air and water if you think I am wrong. Web site: > http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html > > > > In summary, I guess I am simply trying to state that trapped air pockets > will create a more significant pressure increase or decrease in a closed > sprinkler system than water when the temperature changes. > > > > I will absolutely admit that I cannot explain mathematically why we see such > drastic pressure increases in the numerous wet sprinkler systems where we > have identified and resolved these issues (based strictly on Charles's Law, > the pressure increases should not be so extreme), but I can state that the > excessive pressure problem is completely resolved after we bleed off a > significant amount of the trapped air pockets. This is not a theory, this is > absolute real world action with undeniable results. Some systems relieve air > for 20-40 minutes through multiple sprinkler heads (loosened enough to hear > and feel the air escape from the system at the various high points). After > we remove a significant amount of the trapped air, the problem is resolved. > And to address the obvious question, the problem is resolved even without a > 175 psi PRV (we do not always provide the 175 psi PRV, but we typically > recommend them for gridded systems; some clients agree to provide them, but > some decide against paying for the 175 psi PRV). > > > > I will officially let it go. I have planted a few seeds through this forum > and hopefully caused a few people to think about the subject to some degree. > > > > > I sincerely hope that I have not caused any animosity or hurt feelings......if > so, PLEASE know that I had no intentions of making anyone feel bad in any > way, shape or form. > > > > I also feel compelled to state that I am really not trying to win an > argument........arguing or an obsession of being right is usually a fruitless > and ultimately negative exercise. That being said, I imagine that I am now > officially "branded" as argumentative and/or obsessive. I hope this is not > the case, but I am a "Big Boy" and I can deal with it I guess! Over time, I > sincerely hope everyone on this forum will realize that my overall > intentions are to have a positive impact, learn from the forum participant's > experiences and share a few of my personal experiences along the way! > > > > Take care, > > > > Rodney K. Hamm, P.E. > President/Owner > Falcon Fire Protection > Office (478) 953-1677 > > Cell (478) 396-6988 > > > > Date: Thu, 19 Mar 2009 09:26:38 -0500 > > From: "Chris Cahill" <[email protected]> > > Subject: RE: Excessive system pressure > > To: <[email protected]> > > Message-ID: <4ea8e8951e2342039812650e425c4...@chris2005> > > Content-Type: text/plain; charset="us-ascii" > > > > I find it VERY interesting that you find it VERY interesting there has been > > no findings. Hint of insecurity in your position? > > > > Why would anyone try your experiment when it is irrelevant to the constant > > volume container of a sprinkler system? > > > > No one "believes water compression" is responsible for anything. It's > > thermal expansion without compressible air. > > > > "Or could it possibly be that water and air act differently to temperature > > changes in Georgia than any other place in the world?" I guess that's as > > valid a theory as trapped air causes excess pressure. I have only driven > > through the great state of Georgia once so I'll defer to your expertise on > > matters in Georgia. > > > > You have made an extraordinary claim thus it is incumbent upon you to > > provide extraordinary evidence. Your claims go against the text book > > ('02-7.1.2.2, A.7.5.3.2 and the handbook) and the vast field experience of > > this forum. There's even the fancy math thingies with letters, subscripts > > AND symbols which us PE's like. > > > > I have the upmost confidence in my position so I'm not in any big hurry to > > propose and try a valid model experiment of the situation. If I had doubts > > it would be a higher priority. Given a choice I'll spend my time with > > friends and family. When those priorities allow (and I have my Guitar Hero > > fix for the day) you'll get feedback. > > > > And as far as your trees and grids. Sure sounds like what 7.1.2 describes. > > Imagine that the trees are OK and the grid is not and that's what the text > > book covers. Coincidence I'm sure. Granted I concede once text books had > > the center of the universe as Earth and the Earth was flat. I'd like to > > think we've come a long way and today's text couldn't be that wrong. But hey > > those that wrote those old texts probably thought the same thing, they > > couldn't be that wrong. Good news if you are right we'll probably name the > > principal after you. Bernoulli, Pascal, Hazen-Williams, Hamm! > > > > If you believed your theory why are you recommending the PRV? Shouldn't > > removing the air only be what you would advocate? If the PRV wasn't > > required when installed then it was and still is code compliant. Why would > > you need both seemingly counter solutions? > > > > 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) > -- Ron Greenman at home.... _______________________________________________ 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)
