How do I calculate the frictional force resisting overturning on a banded pipe saddle?
How do I calculate the frictional force resisting overturning on a banded pipe saddle?
(OP)
Hello,
I was tasked to design a standardized guided banded pipe saddle. Our worst case simulation models from AutoPIPE are coming up with large ratios of horizontal to vertical loads, so we are investigating overturning as an issue. With the numbers we came up with, it seems to prevent the worst case overturning from all realistic client pipe classes/situations, we would have to use very wide base plates which are unrealistic for pipe spacing requirements. Now we are looking at how the friction of the saddle band against the pipe might help prevent overturning. Assuming the saddle would rotate around the very outer corner of the base plate, my project manager suggested using the equations/method below. I was wondering if this was an oversimplified approach. I realize frictional force is calculated by F=µN, however it is not a single point of contact and I feel there should be some kind of angular component or something involved. It seems from an internet search that the formulas for disk breaks etc. are more somplicated, and while it's a different problem it's still friction on metal stopping the rotation of metal. Am I over complicating this?

Here is a side view so that you can see how the bands attach. Thanks
I was tasked to design a standardized guided banded pipe saddle. Our worst case simulation models from AutoPIPE are coming up with large ratios of horizontal to vertical loads, so we are investigating overturning as an issue. With the numbers we came up with, it seems to prevent the worst case overturning from all realistic client pipe classes/situations, we would have to use very wide base plates which are unrealistic for pipe spacing requirements. Now we are looking at how the friction of the saddle band against the pipe might help prevent overturning. Assuming the saddle would rotate around the very outer corner of the base plate, my project manager suggested using the equations/method below. I was wondering if this was an oversimplified approach. I realize frictional force is calculated by F=µN, however it is not a single point of contact and I feel there should be some kind of angular component or something involved. It seems from an internet search that the formulas for disk breaks etc. are more somplicated, and while it's a different problem it's still friction on metal stopping the rotation of metal. Am I over complicating this?

Here is a side view so that you can see how the bands attach. Thanks





RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Piping Design Central
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Ah. It looked like those 3/8" "diaphragm plates" had something to do with being mis-drawn longitudinal stops on either side of the HSM. They still don't look correct as drawn.
Piping Design Central
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Piping Design Central
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Piping Design Central
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
This pipe clearly moves about a bit and you're concern is that the horizontal forces will mean the pipe hits the side stops and then rotates.
If you think this is a concern, I can't see why your side stops don't just become an angle that the plate slide within which has a few mm clearance of the plate (say 5) so that at worst your plate will lift off one side, but only by a few mm.
normally you wouldn't really want your side stops to see much force, so if you're getting very high loads then you might need to re-think the anchors and expansion loops.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Thanks!
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
https://www.asme.org/products/courses/detail-engin...
http://www.elsevier.com/books/piping-engineering-l...
http://accessengineeringlibrary.com/browse/piping-...
http://www.wermac.org/pdf/piping_engineering.pdf
http://cwsfiberglass.com/docs/smithfiberglass/E500...
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
You did not mention if the line is very hot, or cold. Maybe you want spring loaded pipe hangers instead of just resting on the structure???
Regards
StoneCold
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
If you really need to stop rotation you need to weld a short pipe on the main pipe and lock in the position on the saddle. This short pipe can also transfer longitudinal main pipe loads if you design that way too. The loading/stresses on the weld and/or location of acting lateral and/or longitudinal forces will determine the short pipe geometry.
Hope it helps.
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
If I understand correctly you are concerned that the saddle itself will tip over rather like a tortoise rolling onto it back.
that being the case then if you take moments about one corner of the saddle to the centreline of where all the vertical mass acts ( which would be half of dimension F in this case) then compare that with the moment due to the horizontal force on the pipe at the pipe centerline at a vertical distance from the same saddle corner as before.
If the latter moment is greater than the first the saddle will tip over, if it isn't it's okay.
If I have misunderstood you're post then why not post another front view of the pipe and saddle and show where you think the forces are acting and that way there will be no doubts.
Regards desertfox
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
http://www.pipingtech.com/blog/2015/06/21/insulate...
RE: How do I calculate the frictional force resisting overturning on a banded pipe saddle?
Thanks for the picture it does help, so from my prospective Inwould think taking moments about one edge of the base as I described in my earlier post is applicable.
It appears the OP must have got an answer as the threads been quiet for a while now.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein