BRITANNIA LOSS PREVENTION MAY 2024 A SHIP TO SHIP (STS) TRANSFER OPERATION IS THE TRANSFER OF CARGO BETWEEN TWO SHIPS ALONGSIDE EACH OTHER, EITHER WHILE STATIONARY OR UNDERWAY. SHIP TO SHIP OPERATIONS PREPARE TO ABORT Bringing two ships together and separating them while underway is an unusual occurrence for many ships and the crews onboard. Consequently, heightened risks are associated with these operations, where skill and experience play crucial roles. This article examines the risks involved in manoeuvring the ships while they are underway and the necessity to be ready to abort the operation should circumstances change. Before engaging in an STS operation, each ship follows its own set of protocols, typically integrated into the ships Safety Management System (SMS) and risk assessment. Tankers will have a Ship to Ship Transfer Operation Plan (STS plan) approved by their flag to consult and follow, and we recommend that the latest version of the ‘Ship to Ship Transfer Guide ’ is consulted when preparing for this operation. 2 | BRITANNIA LOSS PREVENTION | GUIDANCE DURING THE PREPARATION STAGE, THERE ARE SEVERAL FACTORS TO CONSIDER, INCLUDING: • Ship dimensions and the likely interaction effects between the vessels involved • Mooring supervisors and their quantity • Method of communication to be agreed and function tested. A common language should be agreed, and alternative means of communication prepared should the primary means fail • Clarify which ship will maintain course and speed during the operation (the Constant heading ship) and which ship will be the Manoeuvring ship • Daylight hours: For certain transfers, especially Very Large Crude Carrier (VLCC) to VLCC transfers, the availability of daylight hours may be stipulated by the company, influencing the timing of the operation • Wind velocity and direction: There is a defined threshold for wind velocity, often set at 30 knots, with even lower limits for larger ships. The wind direction can make manoeuvring difficult, particularly if in opposition to any tidal currents • Constraints on swell: Restrictions on swell conditions, typically around 3 meters, are implemented, although VLCC transfers may observe a reduced limit of 1.5 meters • Meteorological predictions: Weather forecasts must remain within acceptable parameters, and allowances for potential time extensions should be made to account for unforeseen delays • Unobstructed clear sea area: An unobstructed clear sea area, spanning a specified distance such as 10 nautical miles, is essential for safe manoeuvring • Approach velocity and heading: The approach velocity should be carefully maintained, often at a speed of 5 to 6 knots, to ensure controlled and safe mooring. The velocity may also be limited by the load limits of the fendering arrangement. The difference in relative heading of the manoeuvring ship should not be excessive and the approach is most commonly from the quarter of the side of mooring (Figure 1) • Fender requirements: A minimum of 4 jumbo fenders is a standard requirement to protect the vessels during the transfer. The fenders can be rigged on either vessel, but a common arrangement is to rig on the manoeuvring ship • Side of berthing: This may be determined by the respective vessels manoeuvring characteristics (e.g. taking into account the effect of transverse thrust on the manoeuvring ship) or other reasons such as anchor availability on the constant heading ship • Mooring arrangement: Moorings should be r