Enhancing Crane Load Testing

Traditional crane management in the US is based upon periodic inspection, routine maintenance and (depending on regulation) load testing up to 125% of safe working load.

Periodic inspection tends to limit itself to the externally visible structure and the mechanical components. Proof load testing of cranes gives a snapshot of the asset’s capability at the time of testing and an overview of the general mechanical condition of the asset. It does not give any information with regard to the internal structural integrity of the asset or indeed any future structural verification. Risk based NDE will be used on a very limited basis. Many facility cranes were installed in the 1960’s and are now reaching the end of their design life. This leaves the alternatives of replacement or life extension to support the extended life of the facilities they serve.

Water Weights Inc. works with Imes who approaches the management of cranes in a different way. This approach requires a full understanding of the structural integrity of the asset, the effect of corrosion on the rated capacity, an assessment of fatigue cycle history and a thorough understanding of the remaining life of the asset.

The Imes technology has the capability to establish these parameters for existing cranes and is able to develop a long term management plan to achieve the maximum life from these assets. The capability of the asset is determined by inspection using visual, acoustic and other non-destructive techniques (depending on the particular asset). This is coupled with a corrosion study and the degraded material properties are modeled in a Finite Element package. This model is used to determine the capacity and capability of the asset as it currently is, compare it to its original design code and establish its performance against current design codes. Predictions of performance against the load test can be made and verified by instrumentation mounted on the crane during test. Areas of weakness can be identified and an engineering plan put in place to re-establish the asset integrity before a load test is failed. The ability to predict failure modes with this methodology also enhances the safety argument for maintaining ageing assets in operation

The difference between periodic inspection and testing and condition / reliability based approaches is that, in the latter, the condition of the asset is constantly understood, monitored and managed. Instrumentation is provided on the crane to record load history and other appropriate parameters to the asset. Predictive techniques are employed to support maintenance/replacement on condition instead of period, and life expectancy of the asset can be accurately forecast for budget and capital finance planning.

Water Weights working with Imes are able to offer this service as an enhancement to load testing. In the event where a full load test is not possible for any reason, using this technology without a full proof load or where critical lifts are being made enables the management and mitigation of risk.