11.4 Wind conditions
Strong winds impose additional loads on a crane and affect the crane’s stability. A maximum permissible wind speed of 10 m/second (36 km/hour) is specified for mobile crane operation by some crane manufacturers. Crane configurations designed for wind speeds other than 10 m/second should have the design wind speed marked on the rated capacity chart.
Where wind speeds exceed the maximum figure stated by the crane manufacturer for a specific mobile crane, crane operations should cease, and the crane be placed out of service. Crane operators should recognise that dependent on the boom length, the wind speed may be greater at the height of the load compared to the wind speed at the height of the crane’s cabin.
A crane manufacturer will generally only specify a maximum wind speed to operate the crane, ignoring the type of load to be lifted. In some cases, there may not be a maximum wind speed specified for the crane itself. Wind speed may be much greater above the ground level than next to the operator’s cabin. Also, the effect of wind gusts will have a different effect on the crane than a constant wind. Given these variables, crane operators must base their decision to make a lift on information provided by the crane manufacturer and their experience as a crane operator. If the operator believes it is unsafe to lift the load, written certification should be obtained from the crane manufacturer or an engineer prior to lifting taking place.
Mobile cranes must be operated within their engineered design capacity. To ensure the stability of a mobile crane in windy conditions, the following factors should be addressed:
- The crane manufacturer should state the maximum wind speed that the crane may be operated in. Generally, the safe operation of a crane becomes difficult to ensure when the wind speed exceeds 36 km/hour, irrespective of the size of the load. However, in many situations, this speed may be excessive, particularly where the load and boom have large surface areas.
- Where the crane is lifting close to its rated capacity, the wind will have a greater effect on the crane stability and the potential application of a side load on the crane’s boom.
- Where the lift is a non-standard lift, with a suspended load or large surface area to be undertaken in windy conditions, a competent person should provide written advice on safe lifting conditions.
- Consider attaching wind gauges to mobile cranes or providing another reliable method of measuring wind speed (e.g. handheld wind gauge). Where wind gauges are to be attached to the crane, they should be mounted at the top of the main boom, and calibrated at predetermined intervals, to ensure they provide accurate readings. Guidance on this issue should be obtained from the crane manufacturer or supplier. The provision of wind gauges on mobile cranes is strongly recommended where the maximum rated capacity of the crane is 100 tonnes or greater.
Last updated June 9, 2006