Air compressor question

We have PVC in our full time shop for 23 years. Never a problem. Just clean
and seal all the joints right. Have 120 psi.

Larry

(Fitzair4) wrote in message ...
We have PVC in our full time shop for 23 years. Never a problem. Just clean
and seal all the joints right. Have 120 psi.

Larry

Been in lots of places that used it and seen lots of failures. You do
know that Sch 40 and 80 both have an ultimate tensile strength of
only 7400psi at 73 deg. F.,( black iron is about 10-15 times that )
and that by the time you get to around 90deg F., that is reduced by
almost 50%? By the time you run the numbers for the data given in ASTM
D1784, the code that your pvc pipe is rated by, when you do all the
required derates and apply all the safety factors required for sound
engineering practices, 1" PVC is rated to handle about 4psi working
pressure. It also might interest you, in that the code specifically
states that the rating is good for incompressible liquids only and
that pvc and cpvc are to never be used in a compressible gas system
without revising the pressure ratings to those found under ASME B31.3.

BTW...if you are a commerical shop, the use of pvc like this will get
you some nice little code violations if the inspectors ever look
notices it, or OSHA visits.

Craig C.

!doctype html public "-//w3c//dtd html 4.0 transitional//en"
html
I'm no engineer and don't have a lots of formal smarts but common sense
tells me  if the following is true, then PVC is useless as tits on
a boar hog for any use. 4 psi???
p"when you do all the required derates and apply all the safety factors
required for sound engineering practices, 1" PVC is rated to handle about
4psi working pressure."
pL.D.
pCraig wrote:
blockquote (Fitzair4) wrote in message ...
br We have PVC in our full time shop for 23  years. Never a problem.
Just clean
br and seal all the joints right. Have 120 psi.
br
br Larry
pBeen in lots of places that used it and seen lots of failures. You do
brknow that  Sch 40 and 80 both have an ultimate tensile strength
of
bronly 7400psi at 73 deg. F.,( black iron is about 10-15 times that )
brand that by the time you get to around 90deg F., that is reduced by
bralmost 50%? By the time you run the numbers for the data given in ASTM
brD1784, the code that your pvc pipe is  rated by, when you do all
the
brrequired derates and apply all the safety factors required for sound
brengineering practices, 1" PVC is rated to handle about 4psi working
brpressure. It also might interest you, in that the code specifically
brstates that the rating is good for incompressible liquids only and
brthat pvc and cpvc are to never be used in a compressible gas system
brwithout revising the pressure ratings to those found under ASME B31.3.
pBTW...if you are a commerical shop, the use of pvc like this will get
bryou some nice little code violations if the inspectors ever look
brnotices it, or OSHA visits.
pCraig C.
/blockquote
/html

"L.D." wrote in message
...
I'm no engineer and don't have a lots of formal smarts but common sense
tells me if the following is true, then PVC is useless as tits on a boar
hog for any use. 4 psi???
"when you do all the required derates and apply all the safety factors
required for sound engineering practices, 1" PVC is rated to handle about
4psi working pressure."

L.D.

Craig wrote:

It works great at what it is intended for, when installed correctly, and
that is cold water supply. The temperature is the big issue, when dealing
with pressure. Any building inspector has a piece of pvc blown up from 3/4"
up to about 3", found after someone incorrectly installed it hooking up a
hot water heater.
--
Jim in NC

"Craig" wrote
Been in lots of places that used it and seen lots of failures. You do
know that Sch 40 and 80 both have an ultimate tensile strength of
only 7400psi at 73 deg. F.,( black iron is about 10-15 times that )
and that by the time you get to around 90deg F., that is reduced by
almost 50%? By the time you run the numbers for the data given in ASTM
D1784, the code that your pvc pipe is rated by, when you do all the
required derates and apply all the safety factors required for sound
engineering practices, 1" PVC is rated to handle about 4psi working
pressure. It also might interest you, in that the code specifically
states that the rating is good for incompressible liquids only and
that pvc and cpvc are to never be used in a compressible gas system
without revising the pressure ratings to those found under ASME B31.3.

OK, I can accept at face value that PVC isn't meant to handle compressed air
Compressible vs incompressible fluids, no problem.

But out of curiosity, how do you get from a 7400 psi under ANY conditions to
a safe working pressure of 4 psi?
That requires dividing 7400 by 2 almost TWELVE times!!!
Are there twelve (or more) separate conditions that each compromise the
tensile strength by 50% (or more)??!?!?

Just wondering, Eric