Fixed and floating object (FFO) damage incidents in container terminals can be complex and their cost significant. When these incidents involve ship-to-shore container cranes the specialist nature of the equipment and the potentially high cost of the property and business interruption claim call for specialist attention
Constructive Total Loss (CTL)
A CTL will require the safe demolition and removal of the crane from the berth. This is a complex operation and can be further complicated if the crane has fallen onto an adjacent crane or if the berth’s structure has been damaged and weakened. Complexities increase if the terminal is in a remote location, particularly if the required heavy lift equipment and specialised expertise is not available.
A decision must then be made whether to replace the crane with an equivalent used crane or to install a new crane. The search, assessment and cost of a used crane is time consuming and may result in little cost difference between used and new when all the additional costs for modification, transportation and installation are included.
When dealing with a repairable crane accident there two key phases: the recovery phase, and the repair and re-commissioning phase.
The recovery phase comprises the initial survey, stabilisation of the crane and the isolation and containment of the damaged crane(s) to enable ongoing terminal operations. Once this has been achieved and notifications and initial discussion with insurance and port authorities are carried out, a more detailed structural survey and damage assessment can be performed. It is important that the attending surveyor ensures that corrective procedures are in place to avoid unnecessary property and business interruption costs, and further damage to the crane or berth occurring.
After the crane structure has been made safe it must be decided what repairs are necessary. The repair and re-commissioning of a damaged crane will require a number of activities and involve parties representing both the vessel and terminal.
Cranes are not designed to withstand horizontal impact forces and in order to understand the behaviour of a crane damaged in a major allision, it may be necessary to perform a Finite Element Stress Analysis (FEA). This will identify the extent of the structure that has been affected in the incident, any points of damage previously unseen and the remaining useful life of the crane will be assessed to determine whether repair is commercially viable. The correct points of support required during the repair will also be determined.
Crane repair and Recommissioning
If the crane can be repaired it must first be decided if it is to be repaired on the rails or moved. Here the attending surveyor will have to review the options, and advise his client if the terminal’s proposals for where the crane is to be repaired are reasonable.
If the crane is to be moved, temporary supports will be required to reinforce it for the move and a system for moving the crane from its damaged location to the place of repair will need to be installed. Here again, care needs to be taken to avoid further damage to the crane or berth.
The most frequent crane damage incident is to the boom, which is often repairable. But if the boom needs to be taken down for repair or replacement, this can be problematical and costly as the boom’s positional height and weight will require the mobilisation of a large mobile or floating crane.
The next most frequent crane damage is to the crane’s frame and if the frame or leg is twisted/deformed the leg(s) will need to be supported from a tower to relieve the load in the legs whilst the corrective repairs are undertaken. However, if the leg is straight an expensive temporary tower support is not required and local structural support (stiffening) can be used to transfer the loads across the damaged section of the leg while the repair is carried out. Again the attending surveyor will need to ensure that the most appropriate and cost effective repair option is used.
Repairs to the crane’s structure normally involve cutting away and replacing the damaged plating. This operation will allow the distorted structure to recover its original form; but jacking or heat application may also be needed. These repairs are frequently carried out at height on the crane’s leg, which is a slow and costly operation.
Damage to a crane’s electrical system is normally confined to the power supply trailing cables being pulled out of their protective trench (Panzerbelt) and over-stretched or broken if the crane is derailed, or the cable reel being hit directly and crushed or bent. These items have long delivery times and to avoid delay in re-commissioning the crane an order for a new cable or cable reel should be placed early in the repair process.
The final stage in the repair and re-commissioning process involves the nondestructive testing (NDT) of the repaired areas and other critical weld joints that may have been affected in incident. Crane geometry dimensional checks will also be performed for perpendicularity, diagonal tolerance and boom hinge alignment.
Lastly re-commissioning load testing will be carried-out before the crane can be approved for operation.