Out of Service Underground Piping

[atmengr]

Hi All,

We have some underground piping that has been out of service for 4-15 years depending on who I talk to. The line has not been under pressure, and we are assuming it was not decontaminated (product was ~clean butylenes). We want to put the pipe back into its original service.

I am interested in what kinds of NDE, inspection or testing others would require, if any, as well as other considerations that should be made. For some information, the system is 150 lb system, std pipe, cp readings are good, a buried check valve is in the system, and it will operate at a max pressure around 70 psig.

I would appreciate any thoughts around this, thanks in advance.

 

[zdas04]

I've looked hard for regulatory requirements for abandoning pipe in place and the requirements are spotty, confusing, and often missing. Consequently, you really can't rely on a regulatory-mandated decommissoning procedure to help you predict the current status.

When I've been in your situation, I've dug up enough of the pipe to be confident in the wall thickness (usually 1-2 test points per mile) and calculated a new design pressure (using ASME B31.8 equations) based on the smallest wall thickness I found. Then I hydrotested the line to 1.5 times the design pressure (regardless of the expected nominal pressure). At the end of this process I felt confident that the return-to-service procedure could be conducted safely.

There are many possible shortcuts, but they all feel pretty mushy to me.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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