Good day seniors,

Im currently working on a project that would use HPPE material for Underground firewater ring main. I learned that in pipelines, B31.3 is not an applicable code. Im just wondering if it is appropriate to use B31.4 because the FW's main purpose is for the distribution and transportation of Liquid. but the code specifies that (400.1.2) "this code does not apply to (a) auxiliary piping such as water, air, steam, lubricating oil, gas and fuel". Please enlighten me with this, it may sound crazy for others.

One more thing is HPPE PE-100 is the preffered material. Is there any good advice on this material?

Many thanks,
BRYM

If you mean HDPE (high density polyethylene pipe), then HDPE is quite a common material for B31.3 underground firewater ring mains. Performing a CII analysis though would just be a waste of time. Do some hand calcs in accordance with the manufacturer's guidelines. Keep it simple.

As above. Also remember that ceasar II gives a result for only 1 material property. You might want to do a short term and long term calculation though.

What about the metallic UG firewater ring?
Does it need stress analysis?

It depends on the Project specification and client preference.

Most probably we never do pipe stress anaysis for FW ring line.

You would only consider doing stress analysis when you expect to see... well... stress.

Typical sources of stress are temperature swings and outside forces acting upon the piping. "Outside forces" can also include forces from the contents of the pipe acting upon the material that constitutes the pipe.

Firewater piping in of itself generally doesn't need to be analyzed for stress unless someone asks for it, or it's unusual.

Cases where it might be unusual?

1) The piping is of significant diameter, and is empty by default - which I'm sure would be against various fire codes.
2) The piping is subject to external weather loads (snow, wind) - but as you said, your piping is underground.
3) The piping has to be designed to withstand the temperature effects of extended fire - again, yours is underground. Note that CII may not give you the correct answer if there's a significant differential of temperature between the top and bottom of your pipe.

What the pipe is made from does not dictate stress analysis. What the pipe is used for does.