Bending electrical PVC with a heating blanket.

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Mark Patterson

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Can some of you tell me a good wed site to show some ways to use a PVC heat blanket to bend 3/4 " pvc and 1/2" and 1". what is the amount of time we need to pre heat the pvc pipe before bending it into offsets and 90% sweeps.
 
Its not very hard to bend with a blanket.
Just wrap the blanket around the PVC and heat until the conduit is pliable, then bend to the desired angle.

It is best to have some water and rags standing by to cool the PVC and set the bends.

It you want to make some consistent offsets, you can make a simple jig buy using a piece of plywood and some nails.

Make sure the conduit is heated enough so you don't kink it.
Sometimes you may want to heat a longer section than the blanket to make longer bends, slide the blanket down the conduit and try to heat a longer section.

The best thing to do is try it and you will be surprised how easy it is.
 
Put duct tape on each end of the pipe so wind doesn't let the hot air out. Keep a small bucket of water with a sponge nearby to quickly cool the pipe.

The time depends on alot of things. Shouldn't take more than 5 minutes each bend if the blankets already hot. But a strong wind, and it will take a lot more time.
 
For what it is worth the NEC requires you bend PVC with a tool identified for doing so.

2008 NEC
352.24 Bends — How Made. Bends shall be so made that
the conduit will not be damaged and the internal diameter
of the conduit will not be effectively reduced. Field bends
shall be made only with bending equipment identified for the
purpose. The radius of the curve to the centerline of such
bends shall not be less than shown in Table 2, Chapter 9.
Click to expand...



Article 100
Identified (as applied to equipment). Recognizable as
suitable for the specific purpose, function, use, environment,
application, and so forth, where described in a particular
Code requirement.


FPN: Some examples of ways to determine suitability of
equipment for a specific purpose, environment, or application
include investigations by a qualified testing laboratory
(listing and labeling), an inspection agency, or other organizations
concerned with product evaluation.
Click to expand...


What you do from here is up to you. :)
 
tkb said:
So applying some PVC cement and lighting it on fire is out? ;)
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Or the exhaust of a generator, or the duct from a large temporary job heater, or two heat guns and a 2" hot box for 4" PVC or a torch .....

Of course I would not no how well any of those way work.
 
They sell a tool which is a spring sized for the pvc conduit . insert the spring inside conduit and use a pipe bender to make your bend. Works pretty good. Never found one for sched 80 . check with your supply house. used it on 1/2 3/4 1"
 
puckman said:
They sell a tool which is a spring sized for the pvc conduit . insert the spring inside conduit and use a pipe bender to make your bend. Works pretty good. Never found one for sched 80 . check with your supply house. used it on 1/2 3/4 1"
Click to expand...

You have a pipe bender that's listed for use on PVC?

352.24 Bends — How Made. Bends shall be so made that
the conduit will not be damaged and the internal diameter
of the conduit will not be effectively reduced. Field bends
shall be made only with bending equipment identified for the
purpose. The radius of the curve to the centerline of such
bends shall not be less than shown in Table 2, Chapter 9.
Click to expand...
 
K8MHZ said:
OK, Smarty Pants. Where does it say I need a tool listed to HEAT the PVC with?
Click to expand...

Not listed, identified. I would say that is a lower standard.

I don't even know of a tool in existence that is listed to actually bend PVC.
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Identified PVC blankets, PVC hot boxes, or heat guns etc.

The shop has a couple of Hotbends

 
I am going to play the devil's advocate here. Just for fun and because it's Iwire and he is probably used to it by now.

iwire said:
Not listed, identified. I would say that is a lower standard.



Identified PVC blankets, PVC hot boxes, or heat guns etc.
Click to expand...

Where does it say I have to use identified tools or devices to heat PVC? .24 specifies bending equipment, not heating or any other kind of preparation eqipment. A blanket does not bend, thus it is not bending equipment.

The shop has a couple of Hotbends
Click to expand...

Nice product. BUT it's purpose is to heat. Bending is done by hand and I have never seen anyone's hands listed for bending PVC.
 
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iwire said:
As I said in my first post in this thread, what you do from here is up to you. :grin:
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I hereby recognize my heat gun as suitable for heating PVC conduit and recognize my hands as suitable for bending said PVC conduit and will continue to recognize them both in the future thus making them both recognizable for the purpose therefore rendering both the aforementioned as 'identified' as defined by NEC Article 100.
 
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So inserting the PVC conduit into the exhaust pipe of a truck in order to heat it is not an approved method ?
Ive seen it done for both electrical conduit and plastic plumbing pipe !
For larger sizes that wont fit into the exhaust, slip the end of the pvc over the exhaust in order that the hot gasses pass through the pipe and heat it.
 
Blankets are great if you only need a bend or two. They're compact (I carry two on the truck at all times), but are too hot to handle once you've pulled 'em off the pipe. They need to cool down quite a bit in order to put it on the next stick. I have found, though, that using gloves like this helps.

Another issue is.... they only work on straight sections of pipe. Once you've bent it, the blanket won't make good enough contact to make it pliable any more.


So for production work, they suck.
 
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