Chris, I think its because CRR isn't directly related to wall thickness. I was always led to believe that its simply a measure of pipe life in relation to SCH 40 threaded pipe. Thats why products like megathread and dynathread have a much higher carbon content in the steel, so they tend to resist corrosion much better. On the other hand, non-threadable lightwall has a much higher CRR as you're not cutting material out of the wall.
Like I said, that's what I've always been led to believe. Benjamin Young On Thu, Jun 17, 2010 at 10:21 AM, Chris Cahill <[email protected]>wrote: > Relating to CRR sounds reasonable. Is there anything threadable that has a > CRR of 1 or greater that is not sched 40? Wheatland GL is 0.61 to 0.25 for > 1"-2" for example. XL has virtually the same ID but no CRR listed but it > must be the same as GL. > > Now Dyna Thread is interesting. CRR stated of 1 but 3.6% larger ID than > sched 40. Not sure I follow that though. If the wall is less than sched 40 > how can it have a CRR of 1? If it's 3.6% less seems based on the formula > CRR = (X/X40)^3 should be a CRR of about 0.9. OK that's much better than > 0.61 BUT it's NOT 1. > > Chris Cahill, P.E. > Fire Protection Engineer > Sentry Fire Protection, Inc. > > 763-658-4483 > 763-658-4921 fax > > Email: [email protected] > > Mail: P.O. Box 69 > Waverly, MN 55390 > > Location: 4439 Hwy 12 SW > Waverly, MN 55390 > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Ed Kramer > Sent: Wednesday, June 16, 2010 4:52 PM > To: [email protected] > Subject: threaded thinwall hanger spacing > > Max hanger spacing is covered in section 9.22 and Table 9.2.2.1(a) (NFPA 13 > 2010). Threaded thinwall pipe has a max hanger spacing less than other > steel pipe in sizes 1 1/2" to 3". > > > > Maybe I'm just not seeing it, but is there a clear definition of > "thinwall"? > I've always assumed it meant any pipe with a wall thickness less than sched > 40/sched 30. Today I read the commentary in the handbook that follows > 9.2.2.1 - it says hangers on threaded thinwall need to be spaced closer > together "because of the reduced remaining pipe wall thickness between the > inside diameter and the thread root diameter". That sounds very similar to > Corrosion Resistance Ratio (CRR). > > > > So if my threaded "thinwall" has a CRR of 1.0 or greater, is it "thinwall" > in the context of 9.2.2.1? In other words, does the reduced hanger spacing > apply? > > > > Ed Kramer > > Littleton, CO > > > > > > > > > > _______________________________________________ > 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]<to%[email protected]> > (Put the word unsubscribe in the subject field) > > _______________________________________________ > 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]<to%[email protected]> > (Put the word unsubscribe in the subject field) > _______________________________________________ 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)
