Pipe Hangers 1

[andyfabian]

I have to design secondary members to support pipes and their hangers. I stumbled upon the fact that there may be some special design consideration for the allowable stresses. Apparently, MSS SP58 (Manufacturers Standardization Society) requires 16.6 ksi maximum allowable bending stress when designing the secondary support members.

Is this correct and are there other requirements that I should be aware of?

I do not have a copy of the publication mentioned above. It is $95, and I do not know if it is worth buying.

Any info will be helpful.

Thank you.

 

[ERV]

Unless you are actually designing the mechanical system there is no need to buy SP-58-2002 (Pipe Hangers and Support Materials, desing and Manufacture). I would think that all the information you would need is available from the mechanical engineer or designer, including spacing of secondary support members.
Have you asked him for this information?

 

[andyfabian]

ERV - The spacing of the secondary members is not of importance. The information that I need deals with special design requirements for the members, regardless of the loads imposed on the members. In other words, I looked at another engineers calc and found that they used an allowable bending stress of 16.6 ksi per MSS SP-58. Per AISC, there is no reason for this allowable stress.

Do you know if this an actual requirement?
Do you know why it is 16.6 ksi specifically?
Do you have any other information on possible design restraints imposed by that code related to allowable stresses, etc?

 

[ERV]

andyfabian,

I don't know the parameters or the requirements for the specific design (e.g. seimic, loads imposed, etc.), so I can't give information. As far as I know this is not a requirement, however, if specified by the Mech. Eng., it should be followed. SP-58-2002 will have the information that can point you in the proper direction, so in that respect I recommend you obtain a copy.

http://www.mss-hq.com/

 

[talmage]

andyfabian,

My understanding of MSS SP-58 is that it establishes fabrication, design and inspection criteria for standard types of pipe hangers and components.
It does have some guidelines for reduction criteria for stresses based on thermal (service temperatures) considerations for the hangers and components.
Unless the 'secondary support' members are being affected by temperature variations outside of normal creep considerations (i.e steam lines), I think that the appropriate (assuming steel of some sort) steel and building code requirements for bending should apply.

Hope that helps more than confuses
talmage

 

[haynewp]

The first thing I thought of is thermal also, I have not used this code but it would seem that the stress shouldn't be set at 16.6. I would check to see if the allowable stress varies with the temperature that the hanger is expected to be subjected to.

 

[bvi]

There are pipe support elements, such as hanger rods and the clips that attach to the structural frame and the pipe. These are within the scope of the mechanical, piping codes. The structure these elements attach to are within the scope of the civil codes. MSS SP 58 deals with the pipe supports, such as hanger rods, spring supports, etc., not the structure to which they attach. MSS SP 58 is a requirement only to the extent that it is referenced in the relevant piping code (e.g. B31.1, B31.3, etc.).

 

[andyfabian]

cb4 - Here is everything. I have pipes hung with angles and rods that form trapezes. The rods are supported by channels. The channels are supported by the primary building steel beams, girders and concrete walls.

1. Based on what you said, it is obvious that the primary members (steel beams and girders and the concrete walls) are governed by the material codes (AISC and ACI). No problem here.

2. Most likely, the rods and angles would be governed by the piping code.

3. The gray area is if the channels are governed by AISC or the piping codes. Not 100% sure which way to go here.

To a degree, you have helped clarify the situation. Can you take it a step further by letting me know if the piping codes address the latter two issues?

To whatever extent the issues are addressed by the piping code, I do not have the direct means of reviewing it for myself. I wish I could, but I do not have any piping codes.

If you can help, I would appreciate it. I could get you my fax info if necessary.

 

[bvi]

The rods and angles forming the trapezes are pipe supporting elements governed by the piping code.

The channel to which the trapeze is attached is a structural support, governed by the structural code.

The piping code limits the allowable stres in pipe supporting elements to the piping code allowable stress.

 

[bvi]

If you really need and want consulting help after the prior explanations, you can provide contact info if you wish.

 

[andyfabian]

Thanks for your help......what i need to be able to do now is simply determine what the allowable stresses are in the hanger supports based on the piping codes.

if it is not too many pages to bother you, and it isn't too cumbersome, could you please fax it to: 302-996-9537

Thanks in advance!

 

[bvi]

The allowable stress tables are long. What is the material you are concerned about?

 

[andyfabian]

I'm not sure if you mean the supporting member materials or the material transmitted through the pipes:

Steam, condensate and mostly water (chilled) are running through the pipes.

The double channel supports are steel.

 

[bvi]

Allowable stress for A36 is 17.6 ksi at ambient temperature (up to 100F).

 

[andyfabian]

cb4 - thanks for your help. i appreciate it. if you ever have a structural question, i'd be glad to help if possible.