Todd, based on the fact that this is a repair, as mentioned, AND the fact that you're replacing pipe that *should* have been calculated with a hazen-williams c-factor of 100 (black steel) with piping that has a c-factor of 120 (galvanized) - I would say you're probably going to be alright - but better safe than sorry - so why not run calcs?
-B- On 6/5/08, Todd Williams - FPDC <[EMAIL PROTECTED]> wrote: > > To do this job correctly (operative word) will require a lot more than just > pipe replacement and thus will need to be recalculated. As an example, to > properly pitch the pipe will require replacement of most of the dry pendents > feeding the floor below. The additional 30% increase and a few other things > have already been mentioned to the contractor. However, the job spec treats > this as a repair and doesn't really try to solve the problem of water > trapped in mains (except they want an add for an air dryer in the quote) > > My question was more academic in that if you replace one pipe with a > different type of pipe with a similar loss per foot and make no other > changes, would it necessarily have to be recalculated. When does repair > become modification? > > > > At 12:31 AM 6/5/2008, you wrote: > >> If I had high confidence of all the following, I wouldn't see the need for >> new calcs: >> - Strictly pipe replacement (no added offsets, elbows, riser >> nipples, etc) >> - The original calcs were accurate (done properly and reflect 'as >> built' conditions) >> - Water supply hasn't deteriorated. >> >> A bit of a side note - if the attic has a roof with slope greater than >> 2/12, >> the design area very likely didn't include a 30% increase for the slope. >> That requirement didn't appear in 13 until 1996. But since the pipe >> replacement is legitimately a repair, you probably don't need to meet any >> standard other than what was in effect 17 years ago. >> >> Ed Kramer >> Littleton, CO >> >> >> > I walked through an attic this afternoon where all of the existing >> > mains need to be replaced. The piping is 3" schedule 10 black steel, >> > that is developing leaks after 17 years (we found another one on our >> > tour). The proposal is out there to replace the existing with 3" >> > schedule 40 galvanized (and provide proper pitch). I did a couple of >> > quick calculations and at 250 gpm, the friction loss per foot for the >> > two pipes is very close to the same. (.077 for the sch 10 black v. >> > .075 for the sch 40 galv). My guess is that the difference in >> > pressure would be about 0.75 psi. The calc has about 12 psi >> > remaining. If this was strictly a pipe replacement (no other >> > modifications), would you recommend new hydraulic calculations? >> > >> > Todd G. Williams, PE >> > Fire Protection Design/Consulting >> > Stonington, Connecticut >> > www.fpdc.com >> > 860.535.2080 >> >> _______________________________________________ >> Sprinklerforum mailing list >> [email protected] >> http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum >> >> To Unsubscribe, send an email to:[EMAIL PROTECTED]<[EMAIL PROTECTED]> >> (Put the word unsubscribe in the subject field) >> > > Todd G. Williams, PE > Fire Protection Design/Consulting > Stonington, Connecticut > www.fpdc.com > 860.535.2080 _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:[EMAIL PROTECTED]<[EMAIL PROTECTED]> > (Put the word unsubscribe in the subject field) > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
