Pull-off force: hose, pipe, clamp

[jbenedet]

Was surprised by a study recently where we tested 6 samples for pull-off force at a 10% reduction in clamp Torque and noticed negligible shift in results. Is it possible that at higher torque the clamp is deforming the pipe, reducing the surface contact (friction) between the hose and pipe?

The pipe is a soft plastic, the hose is rubber, the clamp is steel. The pipe is inserted into the hose and a clamp is torqued down over the connection.

 

[berkeman]

What is different about this versus your previous thread?

https://www.physicsforums.com/threads/joint-physics-hose-pipe-connection.1059052/

And you refused to post a diagram in your previous thread; will you please post a diagram in your new thread here?

 

[jbenedet]

It’s similar but different. This is a study focused on the torque of the clamp. The other was for clamp position. This assembly also has no groove unlike the other example and is a plastic pipe, instead of a steel pipe. I am being careful not to provide proprietary information while still including enough info to work through the concept. Also, the community provided good ideas/brainstorming based on the info I provided previously. It was helpful. Thanks.

 

[berkeman]

It’s similar but different. This is a study focused on the torque of the clamp. The other was for clamp position. This assembly also has no groove unlike the other example and is a plastic pipe, instead of a steel pipe. I am being careful not to provide proprietary information while still including enough info to work through the concept. Also, the community provided good ideas/brainstorming based on the info I provided previously. It was helpful. Thanks.

Do your managers know that you are having to resort to Internet forums to do your proprietary work? Are you working as an ME?

 

[jbenedet]

Do your managers know that you are having to resort to Internet forums to do your proprietary work? Are you working as an ME?

This is so incredibly out of line it’s ridiculous. I’m not “resorting” to anything. I’m thinking about this because I enjoy it, not because I can’t get my work done.

 

[Baluncore]

It is often the case that you can more easily push a hose on, or off a pipe, but you cannot pull it off. When you pull on a hose, the tension causes the hose becomes slightly longer, while the diameter of the hose is reduced. The surface area of the hose effectively remains constant. That is the source of the positive feedback.

The hose must be clamped sufficiently to the pipe, that the internal fluid under pressure, does not penetrate between the pipe and the hose, under the band of the clamp.

Is it possible that at higher torque the clamp is deforming the pipe, reducing the surface contact (friction) between the hose and pipe?

No.
Very little initial clamping is necessary to start the positive feedback multiplication. Once the clamp is snug, additional clamping will be unnecessary.