Effect of Excessive Towing Load on The Motion and Tension Behaviour of 50,000 DWT Single Point Mooring System

Catenary Anchor Leg Mooring (CALM) systems are vital for offshore oil and gas operations to moor Tankers and transfer cargo. A common issue arises when Tankers exceed the mooring system’s design capacity, leading to shifts in the Single Point Mooring (SPM) coordinate. This study examines the structural integrity of a 50,000 DWT CALM-type SPM system under excessive mooring loads, simulating conditions with Tankers of 55,000, 75,000, and 100,000 DWT. The analysis follows API RP 2SK, DNV OS E301, ABS standards and includes three stages: (1) Hydrodynamic analysis to obtain the Response Amplitude Operator (RAO); (2) 3D coupled dynamic time-domain simulation to determine mooring line tension; and (3) Von Mises stress analysis of the Y-connection. Results show that increasing tow loads elevate mooring line tension, with the highest force found in Chain 1C under beam sea with a 100,000 DWT Tanker. The maximum stress occurs at the Y-connection in hole C facing the seabed, failing to meet safety requirements. These findings highlight the critical need for adherence to design load limits to ensure safe and reliable mooring system performance.