Chill water piping and B31.2 1

davemccombs · Sep 14, 2004

I am currently fabricating 4" sch 40 carbon steel pipe for an HVAC unit to be located off-shore. My client is holding me to B31.3 and APR RP-14E on fitup,welding, installation and testing since this will be installed off-shore in a refinery/production environment. This piping will have no more than 20 feet of material with 35psi of chilled water flowing at about 45*F. Also, specifically, under code I will have to test this system at 350psi which is way above many of the components of the chiller and air handler units.
In my opinion the "spirit" of B31.3 and RP-14E is not intended to apply to this type of piping installation, although it is installed in a petroleum environment. I could use a clear definition of "Process Piping".
I have not been able to find any reference in either code that will allow me to present a argument against meeting code with this application. Any ideas?

jte · Sep 14, 2004

I guess I'm curious as to what you are afraid of? A 4" Sch 40 CS pipe should be capable of withstanding a *design* pressure well over 1000 psi. We normally would test this pipe to 450 psi and that's limited by the CL-150 flange rating.

Are you really that worried about the quality of the welding? If so, I'm not sure I'd want to be the client...

jt

bvi · Sep 14, 2004

Ultimately, the owner has the right to select the Code they feel is most appropriate, regardless of your arguments. This is specifically stated in the B31 Codes.

An approach you can take is to ask that it be classified as Category D Fluid Service, in which case the requirements are less stringent (e.g. no radiographic examination). The subject system can be classified Category D, based on how you described it.

davemccombs · Sep 14, 2004

Hello jt. No, I'm not worried about the welds. I have qualified a welder on the procedure and we're performing 10% x-ray, so we're turning out a great product for the client. I guess my real issue is with the hydro-test requirments. The weakest point in the system is <100psi. I will be hydro-testing the pipe sections to 350psi off the system, then once attached, performing another hydro-test to <100psi. That's really what I'm trying to get away from.

bvi · Sep 14, 2004

Well, I did not notice you mentioned you thought you needed to conduct a hydrotest at 350 psi. With a design pressure of 35 psi and the design temperature you mentioned, the required hydrotest pressure would be 1.5 times 35, or 52.5 psi, not 350 psi. Also, if it is Category D, no hydrotest is required, simply a initial leak test during start-up.

davemccombs · Sep 15, 2004

Thanks bvi. Problem resolved. I was able to justify that this piping installation is catagory D and thus reducing the hydrotesting pressure required to 1.5 times operating pressure.

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Chill water piping and B31.2 1

davemccombs

Industrial

Recommended for you

jte

Mechanical

bvi

Mechanical

davemccombs

Industrial

bvi

Mechanical

davemccombs

Industrial

Similar threads

Part and Inventory Search

Sponsor