Crack Analysis In Weld Joints Of Pipes In The Oil And Gas Industry

Mohd Zulfadli, Amiruddin (2008) Crack Analysis In Weld Joints Of Pipes In The Oil And Gas Industry. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

The idea and objective of this study is to analyze cracks that initiates in weld joints of pipes due to quenching phenomenon. The crack is analyzed using two Quality Control methods which are Mechanical Testing (MT) and Nondestructive Testing (NDT). The pipe material is as per API 5L Grade B and joined using Shielded Metal Arc Welding (SMA W) which is common for Process Piping in the oil and gas industrial application. The materials are prepared as- per ASME IX Welding Codes and Standards. In order to initiate the crack formation, the quenching phenomenon is simulated using tap water at post weld treatment. After the simulation process, NDT is conducted using Visual Inspection (VI), Ultrasonic Testing (UT), Magnetic Partic1e Inspection (MPI) and Dye Penetrant Testing (DP1) along with MT which is Hardness Test (HT), Charpy Impact Test (CIT) and Bending Test (B1). The VI conducted has determined the post weld temperature of the weld joint and the weld metal is the area with the highest temperature folJowed by the Heat Affected Zone (HAZ) and the base metal. The quality control testing conducted results no visible defects on the external surface of the pipes (face weld) through VI, MPI and _DPT but the root weld has four main defects which. are Incomplete Root Penetration, Concave Root, Root Undercut and Root Crnck determined using UT. The MT conducted indicated that the properties of the welded pipe material are affected. The weld metal and the face weld area have higher hardness value than the base metal, HAZ and root weld. The CIT conducted results, the base metal has higher toughness than the weld metal and HAZ. The face weld also has higher ductility than the root weld when root and face BT is conducted. There are no visible cracks at the face weld area because quenching process is only simulated at the internal surface of the weld joint and has only affected the root weld. The properties of the pipe material are affected due to the heat treatment that occurred from high temperature of SMA W process and quenching simulation.

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