Square tube or SCH 40 round?

[FL Guy]

Came across this SCH 40 tubing.
I’m going to be building a gantry crane and I’m trying to decide if 5” SCH 40 tube is just as strong as 5” square tube assuming both have 1/4” walls?
This would be the upright posts on both ends.

 

[speed bump]

My shoot from the hip quick check math says it's about 10-12% weaker.

That being said if it was cheap enough I would go pipe all day over buying 5 inch box tubing ($$$$).

 

[strutaeng]

It's roughly equivalent to HSS5x5x1/4 in moment of inertia (or "stiffness"), so no huge difference. Edit: looking at my AISC steel manual.

However, HSS is usually 46 ksi yield strength vs 35 ksi for the standard pipe. There's also HSS round (42 ksi) which has slightly different dimensions and telerances.

I'd say in your case either will work. You probably won't be pushing the stress of the material into the yield limits.

 

[metlmunchr]

5 inch pipe should be fine as a substitute for 5" square tube as a column in this application, but unless you have some means of verifying the soundness of the pipe, I wouldn't recommend using some unknown piece of pipe that's been hacked out with a torch as a part of some demolition as the one shown in the picture. I've seen plenty of pipe like that where the wall is full thickness in one area and half the wall is eaten away by corrosion just a few inches away.

 

[Rusted Nut]

SCH 40 is pipe, not tube. Pipe is for carrying liquid, gas, etc… not really for structural stuff. You want tube for structural stuff.

 

[speed bump]

SCH 40 is pipe, not tube. Pipe is for carrying liquid, gas, etc… not really for structural stuff. You want tube for structural stuff.

Eh, lots and lots of structural stuff out there built with pipe. Your average building will have a truckload worth of pipe in handrail alone. Only major difference between tube and pipe is one is measured on the ID and one is measured on the OD. Otherwise for the same given specs they are the same.

 

[nadogail]

I would use the least expensive or the two. I have seen many gantry cranes built from pipe. The primary consideration will be how strong does it need to be.
Because you are building it yourself, I doubt that you will be exceeding any reasonable load.
If you need to pick up anything weighing multiple tons you should consult an Engineer.

 

[strutaeng]

Eh, lots and lots of structural stuff out there built with pipe. Your average building will have a truckload worth of pipe in handrail alone. Only major difference between tube and pipe is one is measured on the ID and one is measured on the OD. Otherwise for the same given specs they are the same.

Agreed. In structural steel design and fabrication for buildings at least, tube and pipe are pretty interchangeable terms, as long as ASTM designation and grade are understood.

In my mind it's more like pipe means round and tube means square or rectangular, again knowing the grade, etc.

 

[FordTruckWench]

I’m going to be building a gantry crane and I’m trying to decide if 5” SCH 40 tube is just as strong as 5” square tube assuming both have 1/4” walls?
This would be the upright posts on both ends.

I built a gantry crane designed to lift two tons in the center of the span, i.e. one ton per upright: The telescoping uprights are 2.53" x 1/4" wall square tube, i.e. hitch receiver tube. They slide into 3" x 3/16" wall square tube. That is supported by 2" x 4" x 3/16" wall rectangular tube. (Upside down Y configuration.) I did quite a bit of strength calculations: For the normal loading condition, for a load swung transversely to the tip over point, and for a load swung 15 degrees (I think) in the longitudinal direction. Assuming garbage grade 36000 psi steel, the above material was strong enough for a safety factor of 3.

I found the material specs for a commercial product built to the same design. Plugged its numbers into my spreadsheet. The result was almost exactly the same safety factor.

5" x 1/4" wall square tube for uprights would be insanely strong!

 

[ez-duzit]

...it's more like pipe means round and tube means square or rectangular...

Not even close. Read Rusted Nuts' post.

 

[strutaeng]

Not even close. Read Rusted Nuts' post.

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