There are many technologies available to port operations to achieve compliance with the new SOLAS amendment, including weighbridges and weighing systems for ship to shore container cranes, mobile harbour cranes, RTGs, straddle carriers, reach stackers and container handling fork lift trucks. Each of these options has pros and cons that will impact port operations workflow. Ports should consider the following criteria when considering options.
Accuracy is generally defined as a margin of error from the true weight, either as a percentage (e.g. +/- 1%) or as a discrete error over the full scale (e.g. if the total range is 50 tonnes and inaccuracy is 1%, then the absolute weight inaccuracy is +/- 500 kg). This assumes correct operation of the system according to the manufacturer’s instructions.
Ports should consider the entire activity of weighing as part of an overall workflow. The exercise of weighing is quite quick, but the supplementary activities may introduce delays or additional workload. When weighing, the systems will not only weigh the container, but in many cases all the hardware required to lift the container. A quay crane trolley operator will need to deduct the weight of the spreader and headblock, crane cables and ropes. Some reach stacker scale systems will have these pre-programmed so the operator can change out implements and automatically deduct from the total, which reduces human error.