Diver-less Cofferdam: Pioneering in Permanent Hull Repair for Floaters at Malaysia's Upstream
Authors: Ghani Suhaimi Mat , Hamidon Zaidi 
Published: November 2024

Water ingress incident occurred inside an Engine Room of FPSO Berantai in December 2022 due to hull leaks located at approximately five (5) meters below sea level. The permanent in-situ hull repair approach for "Crop and Renew" approved by CLASS was adopted by utilizing Diver-less Cofferdam technology which eliminated diving operation as normally required by conventional hull repair method. This paper provides sharing of successful execution of novel repair approach in Malaysia and the value creations offered by the Diver-less Cofferdam technology.

Prior to selection of the technology, several repair techniques were assessed based on the proven technology capable of providing in-situ repair method that can offer elimination of diver intervention and provide reduction in the cost of repairs. Based these criteria, the Company had conceived an approach for diver-less concept methodology and utilized the Diver-less Cofferdam technology method for hull repairs of FPSO.

The technology has provided an innovative solution for deployment of Cofferdam without diving intervention, wherein the Cofferdam is lowered from the FPSO deck while being guided to the exact final position by the guide wires. These guide wires are attached to winches fastened inside the hull and that pass-through holes accurately located on the vessel side shell. Water ingress into the void spaces is eliminated via hot tap and winching system penetrating the side shell from hull internal. The technology has obtained several credentials and recognitions including patent and it has been widely used for over seven (7) years with successful projects on various floaters worldwide.

The execution of hull repairs commenced in October 2023 and successfully performed in within three (3) months. The works were completed in January 2024 as per plan, including removal and replacement of several hull plating at four (4) different locations, which included both flat and curved surfaces. The mini-inspection ROV was used to monitor and support the operations including visual inspection at Cofferdam the repair duration. The repair works were thoroughly witnessed by CLASS surveyor and finally accepted as permanent hull repairs by CLASS surveyor.

Based on successful execution, this method of hull repairs has provided various benefits and value creations: Elimination of high HSE risks associated with diving activities due to no requirement for diver intervention.Significant cost reduction cost due to no requirement for Diving Support Vessel (DSV) and work-class ROV as normally required by conventional Cofferdam method.Minimal weather dependency and lower operational disruptions since works can be safely performed during the monsoon season.No shutdown requirement during repair duration since the works can be performed in concurrence with production operations with the presence of risk assessment.

The successful execution of this innovative technology has established new industrial benchmark for permanent hull repairs for floaters at Malaysia's upstream due to its notable benefits and value creations. It has demonstrated that the permanent hull repairs can be safely performed without diving requirements which eliminate high HSE risks and contribute to significant reduction in the cost of hull repairs. In addition, similar diver-less methodology approach utilizing high performance mini ROV can be adopted and extended to the other inspection activities such as UWILD for floaters and underwater inspection for fixed structure.