Whats the Pipe Sag limit for Sustained load case ?

Hi All,

As per my Knowledge ASME B 31.1 is the Father among all B31 codes because of having the basis for everything.

My query is regarding the Pipe Sagging limit in Sustained case.

B 31.1 has mentioned it as 0.1" in suggested span for the Pipe support chapter -II.( provided conditions in the Notes below the table-121.5).Whereas B.31.3 says nothing for the same. Every design consultancy has its own SOPs & Design criteria, if I want to prepare a Piping Stress Design Criteria doc. as SOP / Design Guide for my Organisation then in th e sustained pipe load case for B 31.3 whats the Pipe Sag limit we take? Does any one have basis for this( or which code tells about it?).

No doubt that we should keep that sagging within certain limit so that our Sustained stresses will be less.

But in realty during facing such challenges in such cases ,some times we need to convinced the client that the with exceeded sagging the Piping system is still safe. Any smart Client will ask the basis for this then what to do?( ya.. It depends how one can convince the Client but is the only way ?) to meet the requirements of Code & Client.

My kind request to all respected Piping Stress Engineer that please answer my question.

With Rg,
MVS

"Piping Stress Engineer = The Real Master Blaster of Piping Engineering"

If you wanted to be all-encompassing, you'd need to factor in at least the following in no particular order.

•Aesthetics
•Allowable Stress
•Pocket acceptability
•Vibrations Risk
•Interference

So, a water pipe in the middle of nowhere with a low flow rate and no risk of hammer could have an acceptable sag of "whatever doesn't fail."

Conversely, a high velocity line in a crowded rack with high visibility could have an incredibly small allowable.

As such, my opinion is that designing for a specified sag value across the board can be unnecessarily costly, or it could result in under-engineered piping as described in the above bullet points.

With that said, most of the time, this is indirectly specified through maximum piping span charts, which are based upon deflection and/or sustained stress values.

Thanks Michael for your valuable reply.

I totally agreed with you but my question is specifically on B 31.3 sagging limit value;written/figure out somewhere in code/standard( as suggested in B31.1 it is 0.1")that we generally recommend/suggest & even show the basis for it.

With Rg,
MVS

"Piping Stress Engineer = The Real Master Blaster of Piping Engineering"