Teflon Pad Under Shoe Support and Pipe Expansion 1

[Amir35]

Following support arrangement is used in our project:
42 inches pipe has been welded to shoe support then shoe sits on base plate on concrete sleeper. between these two members Teflon pad has been installed .During the construction after changing ambient temperature ,The pipe expands and Teflon pad Slips under Shoe.Pad comes out gradually like what you see in the attached picture.I am searching for a corrective action to stop pad moving.
Has anyone been experiencing same issue?I appreciate any feedback and advice

 

[KevinNZ]

The pad needs to be retained. Either to the support or the pipe shoe.

 

[Amir35]

thanks for your answer but how?

 

[3DDave]

I would avoid Teflon because it is really soft and tends to flow under pressure. If you use UHMWPE you can make it larger than the shoe. I would use a couple of plates on either side of the shoe, thinner than the slip pad and held from sliding on the base plate with weld studs and nuts.

 

[LittleInch]

I don't know lots about Teflon pads, but that pad looks way too small for the size and load.

Even assuming there are two (one either side) this is too small and may even be being extruded out the end, and not slipping.

Usually Teflon pads are glued to either the base or the support - usually the base I think - to stop it sliding. Like this

https://pipingtech.com/products/slide-bearing-plates/ptfe-25-glass-filled-slide-plates/

Also the smaller it is the greater the shear force on the pad and hence it moves as opposed to letting the support slide.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Amir35]

thanks for your recommended solution,it seems to be applicable ...42" Pipe length from nearest anchor is almost 110 meters so the expansion causes high shear force at shoe sitting point,I hope glue can withstand this force and can hold the pad.

 

[racookpe1978]

No, simple "glue" will not work.

1. What temperature is the pipe at operating conditions?
2. What is the actual displacement of the pipe axially at this position?
3. What thickness Teflon pad is now in place?
4. IS the Teflon degrading or de-laminating?
5. What is the load vertically on this support?
6. Is there any vertical movement at all, of any sort?

The solution will depend on the answers provided.

 

[Compositepro]

The link in the OP is to a file on the OP's hard drive.

 

[KevinNZ]

If the friction forces of the pipe shoe and foundation are analysed. The OP may find a low friction pad is not required at all. Steel on steel may be OK. There are many long pipelines that use steel on steel.

 

[pmover]

LittleInch post is spot on.

there is a supplier somewhere in Ohio & i forgot the mfg name. but the pad size is calculated based on the load, 4"x4", 5"x5" , etc. and it is welded to the pipe support pad.

see below.

good luck.

 

[IFRs]

I have seen Teflon pads used extensively to reduce axial loads on pipe supports with inadequate strength in that direction. They bought two steel plates with Teflon bonded to them. The larger one goes on top and is welded to the pipe shoe. The Teflon surfaces face each other. The smaller one is welded to the pipe support. The vertical load applied at the shoe determines the smaller bottom pad size. The amount of expansion determines the size of the top pad. One vendor is

https://pipingtech.com/products/slide-bearing-plates/ptfe-25-glass-filled-slide-plates/

 

[dhengr]

Amir35:
RE: Pmover’s detail of 9APR10, 01:46. One supplier of this material is Fiberglide. The PTFE thickness and bearing area size are based on wear life characteristics and allowable bearing stresses. We usually used a somewhat thicker PTFE base pl. to facilitate edge welding and to tolerate a slightly irregular concrete surface and still provide a flat bearing surface. We often wanted/provided a somewhat polished surface on the SS bearing pl. on the pipe support shoe, although in short order it becomes impregnated with Teflon. The supplier can comment on these issues w.r.t. their products. The size of this upper SS bearing pl. is such that it insures that the lower Teflon bearing pl. always remains well covered under all potential movements, so as to keep most crud out of (off of) the bearing surface.