Improved Methodology for Boat Impact Analysis of Fixed Platform

Abstract Improved methodology for Boat Impact Analysis (BIA) for fixed platform is applied for Malaysian water. Brownfield structure boat landing, riser guard and jacket may have designed with old API code. Offshore platforms frequently receive visits from vessels during their operation. Access from the vessel to the platform is achieved via the boat landing, which must be designed to absorb impact to prevent fatalities and significant economic loss. The riser guard is crucial in preventing vessel collisions with the riser to avoid hydrocarbon spills and potential explosions. Additionally, the jacket structure must be robust enough to withstand accidental boat impact energy without compromising its integrity, thereby minimizing risk. BIA criteria are not standardized and vary between operators. In the Malaysian region, over 350 platforms in brownfield structures require updated boat impact analysis reports due to changes in vessel operations, unavailable or partial BIA reports, and metocean variations. Three-dimensional structural models have been updated to reflect the present conditions, including corrosion, flooded or damaged members, updated metocean data, and structural anomalies identified from topside and underwater inspection reports. Non-linear plastic collapse analyses are conducted at boat landing zones, riser guards, and jacket members, which are probable areas of boat collision, using the non-linear finite element software package USFOS. A one-year operating environment load is applied in conjunction with vessel impact energy, and results are examined under both operational and accidental boat impact scenarios. Impact locations and directions are standardized based on the locations of the impacted members. Multiple members are impacted, and the least energy from various impact cases was designated as the maximum capacity of the structure. The boat landing height is evaluated based on vessel freeboard and updated metocean criteria. Boat landing/ riser guard shall be able to demonstrate the following damage tolerances: Plastic deformation to the boat landing/ riser guard structural members are tolerable and plastic strain shall be limited to 15% except for the supporting elements connecting to the substructure.All primary substructure members and their joints connected to the boat landing shall remain elastic without yielding.The jacket displacement shall be within allowable limit for all boat impact case.All boat impact cases satisfy the pile safety factor requirement. To conclude, the structure requires to have sufficient reserve strength and able to dissipate energy from the boat impact cases without complete loss of integrity and fit for intended usage. Acceptable criteria include pile FOS, structural dent ratio, and global deflection, etc. New BIA procedure introduced as per PTS to mitigate fit for purpose brownfield requirements. It is recommended to group similar platforms and conduct a BIA for one platform, applying the results to the group to minimize the amount of analysis. Impact energy and vessel size is optimized for marine operations. Few notable features for are Marine operation manual for region, functional design specification of BIA, PTS update, USFOS software use, standard improved design worksheet, boat landing level check, standard report, etc. This study explores the current design and maintenance challenges of boat landing and propose the criteria adopted for brownfield structure. The Marine Manual of Permitted Operation (MOPO) should be periodically updated to guide vessel Captains on limiting displacement and velocity near the platform.