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
On Tue, 05 Mar 2013 13:22:02 -0500, email@example.com wrote:
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
One reason given why a pipefitter would not do my external gas barBQ
line in black pipe was he "won't work with that shit" anymore.
On Tue, 05 Mar 2013 18:09:40 -0500, firstname.lastname@example.org wrote:
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.
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.
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.
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.
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,
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
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.
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