Hello gentlemen. Yes, I am a fire sprinkler system designer by trade. To give you a little background, I have been working in the industry for five years, and I have a NICET III in sprinkler system layout, and a level II in special hazards systems.
I dabble in some low voltage work for special hazards systems, like Sapphire, FM-200, and other clean agent systems. Its all A&D work, though. My only involvement with high voltage systems would be electric fire pumps, and even then, most of that is handled by a note on the print saying "all electrical connections by others." But, I enjoy reading EC&M magazine, and try to learn a little bit when I can. Sometimes I wish the NEC was laid out like NFPA 72 and 13, because the article layout is sometimes hard for me to follow.
Anyway, moving on to your questions and responses...
DB, a "load bank" is nothing more than the biggest toaster you'll ever see. Lots of elements, getting red-hot. It is quite possible for an area near a load bank to get too hot.
Of course, if it does.... well, that's what the sprinkler heads are for. There are heads made with temperature ratings as high as 195 degrees.
renosteinke:
Ok. I didn't know what a load bank was, but I had a hard time believing that it could to that high a temperature if there are people working around it, and moving it. But hey, if you say it gets that hot, then I will take your word for it.
As for sprinkler head temperatures, they actually go a lot higher than 195 deg F. Standard temp is 155 deg F, but you can get certain sprinkler heads for very high temp applications up to 650 deg F. They aren't very common, though.
Der-
I agree that the odds of failure (IMO) would have to be designed to be impossibly low. However, the 175psi you quote seems low. My building has the siamese needing at least 176psi for top-floor demand (to check, I found a pressure guage in a stairwell reading 176psi at standby). Were you saying at least 175, or ... ? Just needing clarification, thanks.
trobb:
The 175 psi is the normal max pressure on system components. If a system doesn't have a fire pump, you normally aren't going to see anything this high for a system working pressure. The nature of the wet system clapper means that it opens up under water surges. This extra pressure gets trapped in the system when the clapper closes, and that is why you will sometimes see a higher pressure on the system side of the check valve.
176 PSI isn't that unusual, especially on a standpipe system where you have very few places for pressure to leak back, and I'm sure you know that there is always some percentage of error inherent in gauges. 176 PSI on the gauge is probably more like 173-177 in reality. Now if it was 275, yeah, I might be concerned.
As for the pressure requirements for the standpipe at the FDC... I'm not really sure what you're trying to tell me here. Its probably a terminology issue, though. What kind of building is it? How tall is it? What size fire pump does it have? Your insurance company may have required a higher working pressure at the standpipe outlet than required by NFPA 13 (100 psi). If the system is supplied by a fire pump, and it is an automatic wet standpipe, it shouldn't need anything from the fire department to meet that 100 psi requirement. Now, keep in mind that that is 100 psi at 250gpm flowing. Water pressure degrades with flow, so your 176 static may go down to 100 at the flow required for the standpipe flow, and that depends on your water supply.
Our house electrician saw a shadow on the wall where the sprinkler in the dry zone was leaking. I observed it after repairs were not quite complete.
JoeTestingEngr:
How does a leaking sprinkler head create a shadow on the wall? Was the sprinkler subject to mechanical damage at all? How old was the system? There are a lot of variables. Was this in a very cold area? Was it a dry head on a wet system? There is too much info missing for me to say what happened, obviously. And of course, I'm not going to claim that no sprinkler has ever leaked, that would be foolhardy, and not true. Its rare, though. I'm more mystified about the shadow thing!
10 inch check valves failed by crusting up inside. This caused leakage back through the electric and diesel fire pumps that they followed. This caused short cycling and ultimate failure of the jockey pump. This caused running of the electric pump with high pressure bursts of water dumping into city drains. The city of Evanston would dispute your claim that system operation would not be adversely effected.
Was regular maintanence performed on those check valves? If so, that much crust in a years time speaks highly of Evanston's water supply system. Maybe a strainer would help out a bit. Was there a backflow involved with this installation as well? Also, there are normally issues with discharging PRVs into public sewers. I would love to see this fire pump installation. Also, are the pumps in series or parallel?
