We just ripped out a late 60's installtion that had been wet, then preaction, then wet, and maybe it was something else for awhile. Anyway, there was sludge that filled the pipes. Office occupancy, single occupant (major health insurance provider). So larger piping would have helped if there was a fire, with the mains hopefully less clogged than the 1" arnover I saw that was almost solid muck. Not solid and brittle, but you'd have to use Darcy to calc it.
I'd assume that the projects Rahe gets involved in are generally major jobs, you probably have to screw with showing metric when submitting, etc. anyway, so changing the C factor- while I'm not a fan of this- is one way to accomplish building in a cushion, and some "fat" for when Joe Carpetbagger ties in and runs 6 heads off 1" from it a couple decades from now. I far prefer to use accepted C factors so we can discuss the job with insurance and local AHJs and we all know what we're talking about- instead of talking to the A/E in his language of 15 PSI cushion using 20% degraded water supply and with C=70, while the rest of us see a 40 PSI cushion based on our industry's reality. glc -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, January 15, 2007 2:21 PM To: [email protected] Subject: RE: max velocity Help me out here, while limiting those two items may seem well and good, I fail to see how limiting the pipe velocity to 20fps will extend the life of a sprinkler system. This is not like a plumbing system where water it flowing constantly. In the typical 50 year lifespan of the buildings you know of, how many times has the sprinkler system discharged? How long has it been left in a flowing condition? I dare say that in most cases you've probably had few discharges and even if the system is allowed to flow for a couple of hours, in that length of time and use, the deterioration on the piping couldn't even be measured. I assume you're specifying that the designer use a C-factor of 100 in his calcs. Again, how will that increase the life of the system? All that's doing is changing pipe sizes being used because they have to overcome a fictional friction loss that isn't really there until 50 years from now. If you had that much accumulation it would have to be based on a system that never saw any maintenance or flushing for 50 years? If the systems are modified as often as you say, then it seems like piping is being changed on a regular basis and the longevity issue is a moot point. Might want to reconsider the practicality of requiring the installation of piping in systems that's larger than necessary. Craig L. Prahl, CET Fire Protection Group Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [EMAIL PROTECTED] http://www.lg.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, January 15, 2007 1:55 PM To: [email protected] Subject: RE: max velocity Folks, Here is some more food for thought. I provide the sprinkler specification for all of my federal projects. I use 20 fps velocity as a limit and a maximum C of 100 to insure that I have a system that has a chance to last for the life of the building (approximately 50+ years). Our buildings are always being changed with the sprinkler system being drained and modified many many times by all sorts of contractors, from the best to the worst. Once the building is constructed and occupied, the local GSA service center does all of the work in the building, usually with the lowest bidder. Therefore, we need some sort of hedge against all of this. Once the building is built, it is out of my control. I see no problem specifying these limits as long as everyone is bidding the same job. Any suggestions? Thank You Rahe Loftin, P.E. Region 7 - GSA Office - 817-978-7299 Fax - 817-978-8644 Cell - 817-371-3102 _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
