It's not a good idea to use iron water pipe for rigid conduit, even though the sizes are similar, because water pipe usually has a rough and sharp longitudinal welded seam that will cut through the wire insulation during pulling. Conduit, being intended for wire, has a smooth-walled bore.
Joe Gwinn
Is either better for structural uses? jsw
Hey CP,
Never given it much thought, but to me "rigid" is always galvanized, while "pipe" is black unless specified. In most cases for electrical use, aluminum can be substituted for "rigid", but the cost needs to be offset in some way.
Hope you get some better answers.
Take care.
Brian Lawson, Bothwell, Ontario.
Yes and no -depends. Black Iron water/gas pipe today is pretty much an unknown, quality-wise. Cheap rough Chinese crap in many cases - in which case Rigid conduit MAY be stronger/more predictable.
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Neither is specifically intended although a lot is used for railings, etc., etc., etc., ...
Have to judge by comparative wall thickness and intended use/loading, etc. As noted earlier, GRC is slightly lighter than Sch 40 pipe of the same nominal dimension so will be somewhat less strong based solely on that difference in resultant bending moments, etc.
Rigid has an appearance benefit of generally a smoother surface but that's purely aesthetics, not functional.
For something like a railing where form is more important than function - in that you want something big enough to fall well to hand
- so 2 or 2 1/4", the strength of iron pipe is way more than necessary
- so the advantage of smooth, slightly less strong rigid conduit makes it the "better" material for that job. Lots lf other places where the small difference in strength is a non-issue, as the size used for aesthetic or other reasons, is overkill even for the weaker material.
ASTM A53 is the standard that covers common steel plumbing pipe in the US. Even Home Depot and Lowes cite that spec for the black pipe they sell, so I don't think it's fair to say that the quality of black pipe is an unknown. It may not be exactly what one might want for a particular purpose, but it is qualified for its intended use.
The steel dealers around here stock uncoated A53 pipe, which is much better looking than the black stuff, and preferable if you're welding or painting it.
Just because it SAYS it meets ASTM A53 spec doesn't necessarily mean it DOES, you know. A lot of "counterfiet" material around these days. And the crap will really hit the fan when they prove it was substandard pipe that caused a gas explosion that levelled a city block.
One reason given why a pipefitter would not do my external gas barBQ line in black pipe was he "won't work with that s*it" anymore.
I recently bought a black iron nipple to modify into something else. It was 1/2" pipe, 4 inches long. I parted off the threads on one end and turned it to .812. I then welded (actually I should say tried)one end into a mild steel plate. When turning the pipe it looked like there was porosity in the material but I told myself it must just be hardness differences in the material that gave it the appearance of having tiny holes in it. But when welding it the stuff acted like I was welding without shielding gas. All sorts of bubbles blowing out of the weld. So I tried running a bead on just the pipe away from the steel plate and the same thing happened. Running a bead on the steel plate worked just fine. It was the crappy black iron pipe. Eric
That should have read..... "I did NOT see anyone state that" Remove 333 to reply. Randy
I found that out awhile back, I was welding up platforms and putting on railings and found I could buy bare steel pipe. The stuff I got welded nicely. Came in 21 foot lenghts, same as plumbing pipe. Not sure what the ratings were. Remove 333 to reply. Randy
An imaginary future disaster is not evidence that there's currently a problem.
Nor is an opinionated plumber. (There's one for the Department of Redundancy Department.)
Well, in building airplanes we have found a LOT of so-called 4130 is nothing close to spec, and also a lot of 6061T6 aluminum. It's all stamped with the proper identification, but the 6061t6 will crack if bent to even twice the allowable radius, and doesn't weld worth crap, and the 4130 is WAY below spec for tensile and yield.
Don't want to fly with that - so we don't accept chinese material without independent confirmation of quality - and then only if American, Canadian, or European product is not available.
No idea; neither is made or rated for structural use.
Depending on what one means by "structural use", if the use is serious, I wouldn't use anything not so rated.
A very high rated burst pressure would be a pretty good indication, though.
Joe Gwinn
It's certainly reasonable to be suspicious of material used in a safety critical application where low factors of safety are typical.
Common black "iron" pipe is, as I mentioned in another post, qualified to ASTM A53, and suitable for structural use.
A53 grade B and A36 (the most common steel for structural rolled shapes) don't differ much in how they're treated by the AISC Steel Construction Manual.
A53 (grade A) and buried it in concrete as electrical rigid conduit. Rigid conduit comes according to ANSI C-80.1
Can this steel pipe installed be threaded or made compatible with "real" ER SC pipe?
My email is snipped-for-privacy@hotmail.com
Please help if you can.
I've bent miles of rigid pipe
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