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Corrosion Fatigue Behaviour of Cathodically Protected Welded Steel Tubular Joints of Offshore Structures

IR@SERC: CSIR-Structural Engineering Research Centre, Chennai

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Title Corrosion Fatigue Behaviour of Cathodically Protected Welded Steel Tubular Joints of Offshore Structures
 
Creator Gandhi, P.
Raghava, G.
Seetharaman, S.
Ramachandra Murthy, D.S.
Anil Bhardwaj
Sankara Rao, S.V.N.S.S.
 
Subject Corrosion
Fatigue behaviour
Cathodically protected
Welded steel tubular
Offshore structures
 
Description Steel offshore structures are widely used for production and processing of oil and natural gas from offshore areas. In addition to regular sea waves, these structures are subjected to natural hazards like cyclones and hurricanes and also to severe hydrodynamic forces during the monsoon periods. In addition to these natural hazards, these structures would also undergo severe corrosion which can be viewed as hazard due to environmental exposure. To mitigate the corrosion damage to offshore structures, aluminium alloy sacrificial anodes are used as cathodic protection system. The anodes near the water surface are subjected to severe environmental action since they are in splash zone. The wave force is maximum in this region and there is a possibility of detachment of these anodes, more so during severe cyclonic storms. Often, during inspection, some anodes are found to be detached from the structure and/or missing, hence affecting the corrosion fatigue performance of the structure. An alternative solution to this is the provision of bracelet type of sacrificial anodes which are generally used for offshore pipe lines. With an objective of studying the applicability of bracelet type of sacrificial anodes to offshore jacket structures, detailed analytical and experimental investigations were carried out. Analysis of a typical platform was carried out to find the possible reduction in wave forces due to the use of bracelet anodes near sea water surface in place of stand-off anodes. The experimental studies comprised a static test on an internally ring-stiffened steel tubular T joint to determine the stress distribution at the joint location and stress concentration factor for the joint configuration, and, two corrosion fatigue tests on cathodically protected joints, one with flush welded stand-off type sacrificial anodes and the other with half shell bracelet type sacrificial anodes, in synthetic sea water environment. This paper presents the results of analytical and experimental work carried out
 
Date 2009
2009
2007
 
Type Journal article
 
Identifier Journal of Structural Engineering, Vol.34, No.4, June-July 2007, p.141-147
http://hdl.handle.net/123456789/393
 
Language en
 
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Publisher Structural Engineering Research Center, Chennai