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Square and round pipe strengths and differences
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farmall30    Posted 09-19-2004 at 19:11:41       [Reply]  [Send Email]

Can anyone tell me if square tubing is stronger, weaker, or the same as round tubing (pipe). I am leaning towards building a barn here. I can weld square tubing easier than I can round pipe. Which would sag more held up on each end. Isa square tubing stronger if turned so that the end looks like a diamond rather than a square? im talking say 4in, same thickness

Doc    Posted 09-20-2004 at 06:59:45       [Reply]  [No Email]
My 2 cents. From my experience in gas line welding, round is by far the strongest, BUT; that is for pressure exerted in all directions at the same time such as submarine, gas pipe, water lines etc.
Square is stronger for pressure exerted in Omni direction or one way pressure such as against the longest side (if rectangular) or in other words pressure exerted directly in line with one of the sides, but not very good at internal pressure pushing out or diagonal pressure (i.e., from corner to corner from the outside).

For low pressure water lines, square tubing would probably be fine but for anything high pressure, say over 60 lbs. you really should use pipe.

Probably Engineer Joyce could explain it better. You may want to ask her. Her's is textbook learning and mine is from having lines blow up.

Dieselrider    Posted 09-20-2004 at 04:26:30       [Reply]  [No Email]
Try this link. Alot of info there.

Rowdy Yates    Posted 09-19-2004 at 20:23:12       [Reply]  [No Email]
From my experience, I would have to say that square tubing is stronger than round when you are applying pressure downward on the side of each. If you are installing it vertically the square will hold up better because of the vertical sides of the tubing, built more like an I-beam so to speak. It depends alot on what kind of span you are talking about and how much bracing, load, etc., that you will be putting on it. Those metal "carports" that you see are all square tubing. Round pipe is more designed to withstand pressures from within pushing outward. In my opinion, I would go with the square. I have built several dune buggies and you are right, it isn't easy getting all the tubing to fit together in order to weld it, square would be a whole lot easier.

Jet9N    Posted 09-19-2004 at 20:14:51       [Reply]  [No Email]
I would think that a square tube of the same dimension
as a round tube would be stronger. First the perimeter
of a square is about 1 1/4 that of the circumference
of a round, hence more material. Also, when a round
or a diamond is bent it will squat (become smaller
in height and wider. A square will have the sides
vertical and have the top and bottom having direct
compression and extention strengths applied.
Keep in mind I'm not an engineer, just a farm boy
with quite a bit of experience.



Grove r    Posted 09-19-2004 at 19:59:25       [Reply]  [No Email]
Got a little experiment for ya that I saw on TV the other nite; take a piece of writing paper, not onion skin, and roll it into a roll so the ends overlap a bit, can be taped so it will hold it's shape.... take a secound piece. fold it into a box with same amount of overlap as the round one, tape; now use a fairly good size book, and with the round tube on end on the table, put the book gently on top of the do the exact same thing with the square tube, using the same book....if nothing was crushed, go to a bigger book...if both were crushed, start over with new paper and a smaller book....I think that will answer your question.. have a gooder, R.E.L.

mojo    Posted 09-20-2004 at 04:23:57       [Reply]  [No Email]
Round is stronger, but what you want is stability. If you're so close to failure that round versus square is a factor, you don't want to use the structure;^)! Both would require bracing to support any roof structure and side loads (winds).

Clod    Posted 09-19-2004 at 19:50:57       [Reply]  [No Email]
I am not an expert ,But we use both pipe and square tube. If the thickness of the wall is equal I would say sqare tube is equal in strength.Or stronger.Much easier to weld up.But I expect the price will be higher for square tubing.

Grove r    Posted 09-19-2004 at 20:10:13       [Reply]  [No Email]
Pipe isn't too bad to join end to side, if you take the time to make a cardboard template for the end of the pipe, so it can be cut to fit nearly perfect, with the cutting torch. Dressing with the angle grinder to remove all slag and leave the metal brightly clean and to do the final "true up", even a slight bevel, is also conducive to strong weld joints. Do hope this is of some miniscule help in your project, have a gooder, R.E.L.

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