The objective of this paper is to evaluate the use of a mini-ROV (Remotely Operated Vehicle) for conducting intermediate Underwater Inspection in Lieu of Dry-Docking (UWILD) surveys as well as various underwater inspection & maintenance works in the Floating Storage & Offloading (FSO) Gagak Rimang (turret-moored FSO) operated by ExxonMobil Cepu Limited (EMCL).

UWILD is divided into Intermediate Survey & Special Survey which differs in scope. Intermediate UWILD Survey consists of General Visual Inspection, Cathodic Protection (CP) readings on offshore vessel's hull, weld inspections, and marine growth assessments. Meanwhile, Special Survey includes all the Intermediate Survey scope with additional sea-valves internal & external examination and operational test. Typically, the UWILD inspection utilizes conventional method by using divers and/or work-class ROV which require dive support vessel. With two underwater campaigns every five year – it is considered an operational challenge for offshore vessel to optimize cost since in many countries the drydock / UWILD requirements are tied with government regulation.

EMCL demonstrate initiative of mini-ROV utilization for Intermediate UWILD Survey on FSO vessel, namely Gagak Rimang. The mini-ROV was trialed as it has the capability to perform comprehensive inspection as well as cleaning with minimum cost.

The use of the mini-ROV was successful in completing the intermediate UWILD survey pioneered in 2022. The ROV was able to access and inspect areas that would have been challenging or implausible for divers to reach, such as the underside of the platforms and tight spaces between structures. In addition, the use of the ROV eliminated the need for divers to enter the water, improving safety and reducing the cost and logistical challenges of diver-based surveys.

Compared with conventional methods, the utilization of mini-ROV has provided significant cost saving until the end of facility life. The first mini-ROV implementation in EMCL has demonstrated that its use is a feasible and effective alternative to conventional method for intermediate inspections of offshore vessels. Mini-ROV also provides one-stop solution by allowing mount-ability of certain attachment tools to enable cleaning & measurement works. The use of mini-ROVs can improve safety and reduce cost and logistical challenges, making them a valuable tool for the maintenance and integrity management of offshore assets.

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