Publications

ExxonMobil Cepu Ltd (EMCL) operates Floating, Storage and Offloading (FSO) Gagak Rimang which was converted from a Very Large Crude Carrier (VLCC) M/T Chios (originally built in 1993). The converted hull and supporting structures have been upgraded to meet expected environmental and operational loads including remaining at the location, Tuban Sea, for 25 years, operating uninterrupted as an FSO without dry-dock or requiring major repair/maintenance work while on station. The FSO Gagak Rimang is a dual classification vessel (ABS and BKI). The FSO’s cargo tanks store Banyu Urip’s crude oil (~70 deg C) prior to transferring to buyer’s vessel. A Risk-Based Inspection (RBI) program was developed for structural aspects of the FSO hull to ensure its integrity. The RBI program integrated a detailed structural analysis (strength and fatigue), with past operational performance (as M/T Chios) to understand the risk profile (quantitative and qualitative) and determine a fit for purpose In-Service Inspection Program (ISIP). The RBI approach ensures inspection is proportionally focused on the systems and/or components which greatly contribute to the overall integrity of the facilities, while still meeting Class requirement. Additionally, it offers benefit to the operator by reducing personnel exposure to hazards associated with work execution, minimizing operational interruption and ultimately improving cost efficiency. FSO Gagak Rimang’s RBI program was approved by Class in late 2016. Upon approval, a thorough execution plan was reviewed to address complexities such as confined space entry, heat stress management and simultaneous operations. One unique challenge to address when executing the RBI program is related to heat stress management. Due to the high temperature of crude (~60C) and radiant heat impacts, proper mitigations needed to be carried out to ensure personnel safety & health when conducting inspections inside crude oil and void tanks. The Thermal Work Limit (TWL) methodology was developed to determine the safe work environment based tank atmosphere ambient temperature and relative humidity. This TWL methodology permits a maximum sustainable metabolic rate that allows well-hydrated, acclimatized individuals to be maintained in a specific thermal environment, within a safe core body temperature. Through implementation of the TWL methodology, the first tank inspection campaign was safely executed in 2017 with all required inspection data for Class recertification captured.