Proper heat bending of PVC conduit, buldge!

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Gkarl

Gkarl

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Seattle area
After installing 4" PVC conduit in a fully concrete encased duct bank the 90's that turn upright to head to the next level ended up being waayyyy out of plumb once the next section of conduit was fitted to them. Basically we have about 3 inches of the 4" conduit sticking out of the concrete duct bank with a glue on threaded coupling for metal conduit to be run vertical next. Once these metal conduits were screwed on the inaccuracy of the plumb condition really showed. The contractor took a weed burner torch and slowly heated the 4" conduit just below the glue on coupling in order to bend the conduit enough to get it plumb. In the process, the 4" pvc pretty much stretched on one side but buldged quite a bit on the other side (where the compression was). It's one ugly piece of work BUT... will this method do any real harm... it will eventually become a vertical concrete duct bank completely buried. Can't seem to find any "best practice" information on means and methods for heat bending 4" pvc. Can anyone help with this issue or provide a best practice sort of "code"?:confused:
 
Gkarl said:
After installing 4" PVC conduit in a fully concrete encased duct bank the 90's that turn upright to head to the next level ended up being waayyyy out of plumb once the next section of conduit was fitted to them. Basically we have about 3 inches of the 4" conduit sticking out of the concrete duct bank with a glue on threaded coupling for metal conduit to be run vertical next. Once these metal conduits were screwed on the inaccuracy of the plumb condition really showed. The contractor took a weed burner torch and slowly heated the 4" conduit just below the glue on coupling in order to bend the conduit enough to get it plumb. In the process, the 4" pvc pretty much stretched on one side but buldged quite a bit on the other side (where the compression was). It's one ugly piece of work BUT... will this method do any real harm... it will eventually become a vertical concrete duct bank completely buried. Can't seem to find any "best practice" information on means and methods for heat bending 4" pvc. Can anyone help with this issue or provide a best practice sort of "code"?:confused:
Click to expand...

110.3(A)(2) comes to mind.

iwire said:
354.24 is worth a look.
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You mean 352.24?
 
My first thought is if it is getting completely embedded in concrete why did they change over to steel pipe ? The PVC could have been used to correct the angle then transitioned over to steel.
 
I should add make sure to run a mandrel through it before going to much farther. You may save a lot of work if you check it now and find a problem.
 
There's going to be a construction joint above so the steel was specified in order to keep a shear problem from happening. PVC could shear if the upper slab moved in relation to the lower slab.
 
Gkarl said:
Thanks everyone, 352.24 says it all... no weed burner torches and no damage.
Click to expand...

You can add 352.12D to the list as well.The flame required to bend the conduit is over 122 degrees.

D) Ambient Temperatures. Where subject to ambient temperatures in excess of 50?C (122?F) unless listed otherwise.
 
RUWired said:
You can add 352.12D to the list as well.The flame required to bend the conduit is over 122 degrees.
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So is the temp inside a conduit heating box or blanket.

D) Ambient Temperatures. Where subject to ambient temperatures in excess of 50?C (122?F) unless listed otherwise.
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In my opinion this section does not apply. (OK it says what it says but it can't mean what it says or heat type benders are no good :D)
 
RUWired said:
You can add 352.12D to the list as well.The flame required to bend the conduit is over 122 degrees.

D) Ambient Temperatures. Where subject to ambient temperatures in excess of 50?C (122?F) unless listed otherwise.
Click to expand...

Wouldn't that only apply after installation and not during the installation of the conduit?
 
iwire said:
Well I don't know, but I am willing to bet it has to be higher then 122F to soften up the conduit for bending. :D
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Next time I fire up the blanket, I'll get my IR thermometer out.

122?F is not too hot to touch (it gets that hot in the Southwest US!). My blanket is far higher than that!
 
Gkarl said:
After installing 4" PVC conduit in a fully concrete encased duct bank the 90's that turn upright to head to the next level ended up being waayyyy out of plumb
Click to expand...

4" PVC 90's are more like 85?.
 
480sparky said:
Nope.... one of these.
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I have this one

31QR60EM1BL._SL500_AA280_.jpg


So far the only work related thing I have used it for has been to verify the temperature of a lobster tank was cooling after I made some repairs to it.
 
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