When establishing a pipelines’ maximum allowable operating pressure (MAOP), many pipeline operators face uncertainties regarding the yield strength of the respective pipeline material. This specifically concerns “pre-regulatory” pipelines which, for example, constitute approximately 66% of all gas transmission pipelines in the U.S. as well as new pipelines to ensure laid steel pipes meet the contracted steel grade.

Conventional ILI technologies are capable of delivering relevant information for MAOP calculation, such as wall thickness and diameter. However, as missing element, in the past there have been no economic means for accurately measuring yield strength. Therefore ROSEN has developed and tested a novel ILI system for measuring yield strength of pipeline steel.

This paper introduces the fundamental principles of this new system and outlines first results.

Laboratory test results are obtained from samples covering the typical range of pipeline steels. The sensor readings are correlated with reference yield strengths of certified steels where the yield strength was determined by destructive tensile tests.

Initial pull tests with an ILI tool measurement are compared with the available yield strengths and tensile strengths according to the inspection certificates of the pull test pipes.

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