Calculating number of rollers to use

[weldquals]

Good Day To All!

I have a 3000lb capacity Pandjiris positioners and I want to use it to rotate a 42" dia pipe (18000 lbs).
My question is how many rollers (rubber/ steel) do I need to use? I know there will be friction on the rollers.

Thank You in advance

 

[kiwitom235]

You need to clarify and provide more details.

 

[SandCounter]

The easy answer for the sake of the rollers is a minimum of six (6), that's (18,000lb pipe divided by 3,000 lb capacity rollers). However, you should also consider the pressure area of the roller against the pipe and potential for pipe deformation at those locations. Further, you should run a beam calc to check the unsupported length against bending.

Unfortunately the OP does not inform of the pipe thickness or length. Once you have those, you can check the shear force against the area and the moment against the section modulus.

I used to count sand. Now I don't count at all.

 

[Tmoose]

What are you trying to do to this 18000 lb pipe.

I'm left to guess that your 3000 lb capacity positioner looks like this -

http://www.pandjiris.com/html/positioners.html

http://www.pandjiris.com/specsheetpdf/Positioners/30-12specsheet-s.pdf

And, that the rollers you are asking about would form a "steady rest" to support the 18000 lb pipe, because it is way more than the capacity of the positioner.

https://i.ytimg.com/vi/vPsGjC4tptA/maxresdefault.jpg

Getting more than two rollers toward the "bottom" aligned so well they will support the pipe equally will be a good trick.
Two rollers will likely make the pipe look like this to some degree, either permanently, or as it turns -

https://encrypted-tbn0.gstatic.com/...MNYCYb2Td85ztUrMlDwxyG7VTeLjf4NerlQ36ehthqS-f

You may need to have the rollers bear on the face plate of the positioner, or put "spiders" inside the pipe for temporary support to maintain roundness, or, something else altogether.