Concrete Saddle Support for exposed pipe

[JG5255]

I am a structural engineer, so above ground pipe systems are not part of my everday expertise. I am hoping some people here can help me with thier experiences/expertise.

I am planning to use a reinforced concrete saddle (Pipe)support for the piers on my project. I was wondering what others have done between the concrete saddle and steel pipe to allow for movement. The M-11 code simply states "several layers of felt with graphite between" or "joint filler material". I am not particually found of either of these as I see them "walking out" (or falling off) eventually. Any Ideas? What have you called for on your projects? Total movement I'm expecting is about 1.5".

Thanks,

 

[bimr]

See if you can get a copy of the publication:
MSS SP-58-2002 Pipe Hangers and Supports - Materials, Design and Manufacture Manufacturers Standardization Society.

 

[rconner]

AWWA Manual M11 also contains the guidance sort of leading off the section on supports, "When subjected to temperature changes causing considerable longitudinal movement, steel pipe is frequently set on concave rollers." An old Steel Plate Fabricators manual I read several years ago referred to an apparent arguably alternative approach, "When pipe is laid aboveground, "hold down" or anchor straps should be wide and suitably padded to limit stress applied to the pipe. The purpose of these straps is to limit pipe movement." Indeed, the Figures that I believe your quotation on apparent suggested padding material points to appear to depict such a bolted strapping mechanism, strapping the pipe down to the pier. It appears what you are apparently attempting to do is something that may be sort of a hybridization of these perhaps at least some different schools of thinking on support (while I'm not sure of what the terminology authorities for such designs are, I would call this a "sliding support"), and whether or not there would be a problem with only 1-1/2" movement I think I understand your concerns re "walking" etc. of this padding.
In this regard, I believe there is a whole industry of various "sliding support" designs for piping (that can be searched with Google or other search engines) spawned in this sort of design middle ground. While I am not an expert in such sliding support designs, I would think to absolutely prevent any "walking" of loose padding materials etc. at some level of relative (rebating?) axial movement it would perhaps be necessary to at least partially contain same in the axial direction (with a recessed housing of some sort attached or integral to either the pier pipe or shoe affixed to same etc., and of course also employ low friction, high wear materials in any design sliding zone?) You might want to consider also whatever temperature variations are involved, effects of localized stress on pipe, as well as contact/sliding wear effects whatever the exterior coating system is, and also whatever is happening due to any strap contact and movement as well.

 

[bimr]

Rereading your post again, and am not clear exactly what you mean by "saddle". Pipe supports are usually piers. It is also unclear what type of pipe that you are using other than the piping is steel M-11.

The MSS reference contains a number of standard designs for consideration.

The type 35 may be appropriate. That type consists of an embedded steel plate for the pier. A T section pipe shoe is welded to the pipe and slides on the embedded steel. The design also has guides to prevent lateral movement.

Sliding Supports: MSS SP 58, Type 35. Welded steel attachments to pipe and building structure with Teflon or graphite sliding surfaces bonded to the attachments. Provide steel guides, except at expansion bends, to prevent lateral movement of the pipe.

http://www.empireindustries.com/files/2004 Spec Catalog_09122005.pdf

The pipe roller mentioned by rconner is a type 44. Rollers are normally used only for long piping runs.

Pipe runs are normally securely anchored in the middle of straight pipe runs. The piping is allowed to expand away from the mid points at the ends where the pipe changes direction. On very long straight piping runs, pipe expansion loops are installed at intervals to limit the overall expansion.

 

[stanier]

You should not be working outside your sphere of expertise. All learned societies have that as one of their tenets. Not only is it unprofessional it puts your company at risk with its insurers and you at risk of an ethical dilemma with whatever professional body you belong to.

In your shoes I would seek the advice of a professional piping engineer. Learn as much as you can from the engineer in the design of the saddles. Next time do it yourself but get the engineer to check it. the third time you can do it yourself.

You do not give sufficient information to enable an engineer to give advice. Even if you did you would be seeking free design. Your company would have no hesitation engaging a lawyer or plumber if they didnt have the expertise in house.

 

[JG5255]

Thank you all for the information, I decided to go in a slightly different direction. But I do appreciate all the assistance.


to stainer:

I'll argue that I am not working outside my realm expertise, although true I don't deal with pipe daily. I have an extensive background in hydraulics and personally design structural steel components daily. This is a very simple irrigation pipe with zero internal pressure, in fact its bone dry 8 months of the year. Besides my question was more detail related than technical, plus I did consult our department hydraulics expert and the other local government water engineers. In addition, the owner of the project is "my company". So I don’t need you to recite board rules and regs to me.

 

[stanier]

JG5255

The message was not directly aimed at you but the myriad of forum members who sometimes ask questions that plainly demonstrate that they are out of their depth. Your response clarifies the situation and this will be a lesson learnt for those who do wish to go outside the area of expertise. The points I made are still valid.