Improved Procedure to Prevent Hydrogen Induced Cracking for Welding Offshore Structures

• Main Author: Myra Azwinna Binti Sapian, Myra Azwinna
• Format: Final Year Project
• Language: English
• Published: Universiti Teknologi Petronas 2009
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://utpedia.utp.edu.my/670/1/Myra_Azwinna_Final_Report.pdf; http://utpedia.utp.edu.my/670/

The objectives of the study are to study the causes of failure due to hydrogen induced cracking and its method of prevention and improve the current offshore welding procedure thus reduces the occurrence of hydrogen induced cracking in offshore repair works. The project covered the condition and prevention methods of hydrogen induced cracking based on literature review and also some experimental works done as part of the study. In fabricating an offshore structure, multiple assemblies are joined together to get the final product. The materials used to assemble these assemblies are made from carbon steel and they are joined together by weld. In 1980’s research shows that 7% of failures in petroleum and gas industry are caused by weld defects. Therefore, the entire welding process played a vital role as far as the quality and integrity of the end product. The steel manufacturing industry has offered and developed improved steel strength properties to enhance resistance towards damage caused by hydrogen. A reliable and cost effective maintenance and repairworks for offshore structure are also required to promote long term product integrity. Thus, effective welding processes and procedures for repairworks that could reduce the risk of hydrogen induced cracking could be employed in the future. Some of the methodology for this project is to get hold of the problem definition which covers the problem statement of the project, background of study and setting the specific objectives. Researched and literature review regarding the project through resources such as engineering handbooks and journals were done. Methodologies done thorough out this project were material preparation, surface preparation, exposing the sample to hydrogen evolution by impressed current cathodic protection, testing on surface by using liquid penetrant inspection and also visual inspection by using optical microscope. From the results gained, the study concluded that hydrogen induced cracking tended to happen more when the sample was being overprotected by cathodic protection. When impressed current applied were very high, it would result a very high hydrogen evolution. Hence, the probability of hydrogen induced cracking to occur would therefore increase.