Crude oil export pipeline NGL risk 1

[123harv]

We have a crude oil export pipeline that we want to introduce NGLs into. Is it a possibility that if we have an impact/damage which results in small ductile tear that the escaping NGLs could cause a subsequent drop in metal temperatures and potentially a brittle failure? The pipeline was designed for ambient use and there is now low temperature impact data. Is this a real concern and if so what % NGLs would be considered a problem? Any ideas/help would be appreciated.

 

[JLSeagull]

NGL product is normally transported in carbon steel piping. Assure that the pipeline is suitable for the operating and maximum pressure. A tear in a pipeline is a serious failure, not a normal event.

 

[SJones]

If the pipeline has already been ruptured by means other than a brittle or ductile fracture, the driving force for crack extension should have been lost. It wouldn't be normal to compute a minimum design temperature on the basis of a pipeline rupture but the process engineers should look at the implications for a pipeline blowdown scenario. Then, in the absence of toughness data for pipe (and welds?) you may have an integrity assessment to perform.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/