During a strong cold front in Pascagoula, Mississippi in March 2022, mobile offshore drilling ship Valaris DS-16 broke free from its moorings. The vessel drifted across the Bayou Casotte channel and collided with bulk cargo vessel Akti. While, fortunately, all onboard personnel remained unharmed, the incident caused an estimated $5 million in damages.

The risk of bollard failure

As ever larger ships use our ports, the risk of bollard failure grows. The increase in tension exerted on the mooring bollards by larger vessels can lead to them being pulled out of the quayside with significant force.

Bollard failure and vessel breakaway can lead to severe damage and operational disruptions. The Valaris incident was traced to the failure of a modified bollard securing the drillship’s bow mooring lines. An investigation by the National Transportation Safety Board emphasised the need for routine inspections of mooring infrastructure, warning that increasing vessel sizes and environmental exposure can compromise bollard integrity, even in the absence of regulatory requirements.

Other such incidents have led to the complete failure of mooring dolphins, or bollards being catapulted into nearby buildings. The main causes for these incidents are generally strong winds off the berth, and the use of too many mooring lines on a single bollard.

The importance of mooring analysis

Testing bollards can determine the maximum load a bollard can withstand before failure. It is also important to know how much force is being exerted by moored vessels using the berth, and what environmental conditions would lead to bollard failure.

The Oil Companies International Marine Forum (OCIMF) prescribes methods and calculations to determine the forces involved with moored vessels under different environmental conditions within their Mooring Equipment Guidelines (MEG4).

Mooring analysis is also pertinent when developing new berths. It can help ensure that appropriately rated and positioned bollards are included in the design for the specific vessel class that will be using the berth.

Supporting your mooring requirements

ABPmer’s dedicated maritime specialists are regularly commissioned to support port authorities accepting a vessel for the first time. Using specialist software, we calculate the forces on a vessel’s lines and bollards to determine the maximum conditions in which a vessel can remain securely alongside and keep forces on mooring bollards within their safe working load.

We also determine the movement of a vessel on the berth under metocean conditions and suggest the most appropriate mooring configuration including storm bollarding to avoid line failure.

To learn more about our mooring assessment services, or book an appointment, call +44 (0)23 8071 1892 or email Monty Smedley.

Prepared by Harry Aitchison, Maritime Specialist

Header photo courtesy Karl Andre Photography