Metallurgical Analysis Determines Root Cause of Line Failure

//Metallurgical Analysis Determines Root Cause of Line Failure
Metallurgical Analysis Determines Root Cause of Line Failure2017-09-25T15:39:45+00:00

Project Description

Project

Metallurgical Failure Analysis

Background

Our client experienced a rupture failure on a 16-inch OD by 0.250-inch WT API 5L X42 electric resistance welded longitudinal seam pipe. The pipeline was installed in 1947.

Challenges

The client called on EN Engineering to perform a failure analysis on the rupture and to determine the root cause of the failure.

Solutions

EN Engineering performed a formal metallurgical evaluation on the pipe rupture failure that included a visual examination of the fracture and the failed pipe; nondestructive examination of the internal and external pipe surfaces; and scanning electron microscope (SEM) evaluation. In addition, the engineers documented the fracture dimensions, including pipe wall thickness along the fracture surface, and the circumferential position of the electric resistance weld longitudinal seam. They also visually examined the pipe for internal and external corrosion; conducted a metallographic examination of the fracture surface, including preparation and examination of metallographic cross sections under a light microscope; and completed a chemical analysis.

The team’s mechanical testing included:

  • Transverse pipe body and transverse weld tensile test samples were prepared, and rings were taken from the pipe upstream and downstream where the fracture arrested
  • Transverse pipe body and transverse weld Charpy specimens prepared from both the upstream and downstream pipe rings
  • Vickers mircro-hardness tests conducted in the area of the fracture origin

Upon completion of the project, EN Engineering delivered a report showing the cause of the rupture was high-pH stress corrosion cracking.

Based on physical evidence, EN Engineering determined the cause of the rupture was high-pH stress corrosion cracking

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