SDR Rating for Pipe?
SDR Rating for Pipe?
(OP)
Vertical sump 12 feet from surface to bottom and 4 feet in diameter. Design calls for a SDR of 21. If I am looking at this correctly, on a 48 inch pipe this would require a wall thickness of 2.28” for an SDR of 21. That seems like overkill. Thoughts?
TexChe
TexChe





RE: SDR Rating for Pipe?
Then there is internal forces. If you look at the force over a 1 ft section of this pipe at the ASME B31.8 MAWP of 80 psig you have about 1000 lbf pushing on this plastic pipe. No, 2.28 inches does not seem to be overkill at all.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: SDR Rating for Pipe?
[Edit]PE 100 means long term strength is 10 MpPa which means it has about 1/25 the astrength of basic steel.
PE tubes ability to withstand compressive forces is lower than internal pressure and needs to be pretty thick.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: SDR Rating for Pipe?
Dik
RE: SDR Rating for Pipe?
Funny that’s where this whole issue got started! Spec said 21 and contractor proposed corrugated pipe that was rejected.
RE: SDR Rating for Pipe?
That number really depends on the codes controlling. ASME B31.8 has a formula that limits the pressure of SDR 21 to 80 psig in water (about 58 psig in gas). B31.8 also says that no un-reinforced thermoplastic pipe can be rated above 100 psig. In Australia, one of the factors (which has values less than 1.0 in ASME) is removed and another has higher values than the ASME uses, and you get pressure ratings in the range you are talking about.
I think we'd need to define terms to understand your statement about the strength of PE to be 1/4 that of basic steel. If I do the standard coupon pull test, the numbers for HDPE are significantly less than 1% of steel for the same thickness. Manufacturers MAWP for Sched 40 6-inch pipe is 1210 psig. Even if you use your rating for SDR-21 (size is not a factor in MAWP, all sized of SDR-21 have the same MAWP) it has a MAWP of 115 psig, about 10%. Using ASME calcs it is about 5%.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: SDR Rating for Pipe?
Dik
RE: SDR Rating for Pipe?
RE: SDR Rating for Pipe?
RE: SDR Rating for Pipe?
We still have no idea what the forces are that the pipe is exposed to.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: SDR Rating for Pipe?
You hit e nail on the head. It's to hold back the pressure exerted by the soil. Could probably assume saturated soil being that it's a sump.
Terry
RE: SDR Rating for Pipe?
https://books.google.com/books?id=8DS7kyexZOsC&...