Crane boom angle

The distances from the pivot point to outrigger or tire support points on the side or ends typically are not the same. The limits differ for a load lifted over the side compared to a load over the front or the rear of the vehicle. Moving a load to different positions may cause structural failure or tipping of a mobile crane. The boom angle and length also affect what load is safe. When cranes operate in tight spaces, there is a need to make precise measurements for making a safe lift. 

Boom cranes have special safety devices for their unique hazards. One device is a boom angle indicator or boom radius indicator. A reading from this device provides the operator with information to help determine if a load is within safe Umits. There are also devices, called load-moment indicators, that combine boom angle and load. If there is a load with the boom set at a certain angle, the moment may exceed the allowed moment and cause a crane to tip over. The device sounds an alarm for the operator when approaching or exceeding the limit. 

All movable cranes must have boom angle indicators those cranes with telescoping booms must have some means to determine boom lengths, unless the load rating is independent of the boom length. Load rating charts must be posted in the cab of cab-operated cranes. All mobile cranes do not have uniform capacities for the same boom length and radius in all directions around the chassis of the vehicle. 

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