A single point mooring operation depends on more than the availability of a supporting vessel. The tanker, terminal, mooring system, towing arrangement and environmental conditions form one operating system. Pull-back support may help maintain a vessel’s position relative to the installation, but the required capability and method are specific to the location and operation.
Planning should therefore establish the task before selecting the resource. This guide sets out questions for owners, terminal teams and marine contractors arranging offshore support and towage services. It is a planning aid, not a towing procedure or a substitute for a competent, site-specific engineering and operational assessment.
1. Define the operation and its boundaries
Describe the purpose of the support, the vessels involved and the planned operating sequence. Identify whether the scope includes approach assistance, connection, maintaining a pull-back force, disconnection, towing or standby. Different phases may require different equipment, personnel and decision-making arrangements.
Confirm the terminal’s procedures and the responsibilities of the master, pilot or mooring master, terminal control and supporting vessel. Record who directs each phase and who may stop the operation. Avoid wording that leaves commercial coordination, navigational control and technical authority indistinguishable. Everyone should understand the boundaries of their role before arrival.
2. Assess the vessel against the actual task
Review propulsion, manoeuvrability, deck arrangement, towing equipment, endurance and relevant certification. Bollard pull is one input rather than a complete measure of suitability. Its relevance depends on the operating environment, available power, connection arrangement and the forces the vessel must manage in the specified position.
Consider the whole operating envelope
Assess how wind, current, wave conditions and the tanker configuration affect the task. Consider machinery redundancy and the consequences of a loss of capability. Confirm that the vessel’s crew have relevant experience and that the planned duties fit the safe manning and work-rest arrangements. A capability statement should connect evidence to the proposed operation.
3. Verify the towing system as an assembly
Review towing points, winches, wires or ropes, shackles and other connecting components as a complete load path. Check certification, condition, compatibility and the limitations of every relevant component. The strongest item does not determine the capacity of the assembly; a weak connection or unsuitable geometry can govern the risk.
Plan the lead of the tow, protection against chafing and the effect of vessel movement. Establish safe working areas and recognise potential snap-back and crush hazards. Connection and release arrangements need particular attention because personnel may be close to loaded equipment. Equipment-specific instruction and competent supervision are essential throughout these phases.
4. Agree environmental limits and decisions
Use the terminal’s approved operating criteria and a competent assessment to establish limits for starting, continuing and stopping. Consider forecast reliability and how rapidly conditions can change. A limit should have an associated action, decision-maker and lead time; a number without an agreed response is incomplete.
Plan how conditions will be monitored and reported. Establish what happens when different sources disagree or a sensor becomes unavailable. The decision to suspend an operation may need to be made before conditions reach a point at which disconnection is difficult. Build that reality into the sequence and resource plan.
5. Test communications before connection
Agree channels, call signs, working language and standard terms for critical instructions. Distinguish an order to change force or position from a request for information. Use repeat-back for essential instructions and establish an agreed response if communication fails. Test the arrangement with the actual people who will conduct the operation.
Include the deck team as well as the bridges and control room. A bridge-to-bridge conversation does not ensure that personnel handling the connection understand a change. Keep the communication plan simple enough to use in poor weather and high noise. Record how emergency messages take priority over routine traffic.
6. Examine credible failure scenarios
Review loss of propulsion, towline failure, winch problems, unexpected vessel movement, deteriorating weather and a medical emergency. For each scenario, consider immediate actions, navigational room, escape options and the effect on the other parties. Avoid relying on a standby resource without checking its location, readiness and response time.
Emergency release arrangements require a shared understanding of their operation and consequences. Define when they may be used and how other vessels will be warned. Rehearse the decision process in a briefing or table-top discussion. The objective is to expose conflicting assumptions while there is time to resolve them.
7. Manage execution through clear hold points
Before each critical phase, confirm that personnel, equipment, communications and conditions remain suitable. Hold points might include entering the operating area, connecting, applying load and disconnecting, depending on the approved procedure. Use positive confirmation rather than assuming silence means readiness.
Monitor load and vessel behaviour through the agreed arrangements. Record significant changes and deviations. If the planned method cannot be followed, pause and assess the change with the appropriate people. A series of small informal adjustments can move an operation outside its assessed envelope without anybody making a deliberate decision to do so.
8. Close out with useful operational evidence
After the operation, inspect equipment as required, report damage or unusual loading and restore readiness. Log significant times, conditions, instructions and any limitations encountered. Keep the record factual. The purpose is to support maintenance, learning and the next plan, rather than to reconstruct an ideal sequence after the event.
Review the task with the terminal and supporting crews. Ask whether the vessel was suitable, communication was clear and contingency assumptions were realistic. Include resulting actions in the next mobilisation package. Relevant service discussions can begin with Lilly Maritime’s offshore services scope, supported by the site information needed to assess a particular operation.
