Thomas, I'm sorry to hear you're having health issues. Never fun for anyone. So for the sake of distraction let's ponder this: All questions and discussions about split rings and Sammy's aside what exactly is the performance criteria the NFPA rules are based on. Now we've discussed the 250 extra pounds "cushion" ad nauseum being the fitter grabbing the pipe so let's put aside more discussion about that point for now. Makes us feel good about knowing some apocrypha (Jeopardy question?) but doesn't advance knowledge too much. Back to the point. If the point load hass to support five times the weight of the water filled pipe and that fat guy at the maximum allowable spacing what is the point load at lesser spans? Why would the failure of one hanger necessarily precipitate the collapse of the entire system, or even the next hanger? Is the "schedule" provided in 13 for hanging spacing that close to the edge? Since these are life-safety systems shouldn't the prescribed information provided exemplify a pretty robust performance criterion? If you're a fan of disaster video I'm sure you've seen Galloping Gertie, the collapsing suspension bridge. Not going into the details of why that harmonic feedback (think Jimi Hendrix) you're watching occurred note that the bridge was not re-built in the same way. The new bridge does not respond to the wind energy in the same way so that isn't a concern. As to failure of the suspension each end of the transverse girders are supported by four vertical cables (suspenders) attached to a main cable. For any section of the bridge to collapse all four suspenders on four adjacent transverse girders must fail. I imagine if you lose fifteen of these sixteen suspenders you'd have a pretty dangerous bridge but one still standing to be dangerous. So back to the original question. What is the performance criteria for hangers that the prescription in 13 represents? Until we know that we can't have a meaningful discussion about deviations from that prescription.
On Wed, Oct 13, 2010 at 5:54 PM, Thomas Watt <[email protected]> wrote: > Sorry for the delayed response. I am currently in the cardiac unit awaiting > a heart cath in the morning. > I remember the retaining nuts being provided with the Sammy screws and never > thought of them as being optional. (no sarcasm intended) However, when the > boss says ""Just do it" I did as I was told. > > On the other hand, I remember reading here that 1 1/2" split-ring hangers > are only rated at 160#. Far short of NFPA13 requirements. Since reading > that, I have only used them as stand-off rings for attaching pipe to walls > and floors. > > With this heavy galvanized dry system hanging from all these weak links, do > I really have nothing to fear when that valve trips? If one hanger fails, > then the next closest ones fail, etc.... > I think I just want something to worry about other than my health. > > Thomas Watt > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.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 Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: AFSA, SFPE, ASCET, NFPA, NFSA, AFAA, ASEE, NIBS, WSAFM, WFC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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)
