Cranes and Lifting Material

When a crane is used to lift materials or equipment, it is commonly understood that a thorough lift plan is created and reviewed ahead of time.  However, it is not universally accepted that all lifts must be thought out and planned ahead of time.  All lifts must be reviewed to prevent injuries and/or property damage, whether a delivery truck or a mobile crane is used. 

A quick review of the headlines and we find “crane falls over, causing damage to 2 homes”, “Truck crane tips over onto building under construction,” “crane falls to the ground,” and more.  Some of these incidents involved mobile hydraulic cranes, and others involved delivery truck cranes. 

The lift is planned out in detail in a typical crane lift.  The weight of the item being lifted, the rigging details and weights, the ground bearing pressure of the outrigger floats, the details on the mats to be used under the outrigger floats, the radius and boom length of the crane, etc.  The plan is reviewed before mobilization and then again on the day of the lift to ensure that everything is consistent with the plan.

When it comes to delivery truck cranes, some think that a lift plan isn’t needed.  Most delivery truck crane accidents are due to operating outside of the safe working area of the load chart or not having the crane set up correctly.  As shown in the picture below, the outriggers were not extended on the back side.  In addition, the crane was operating outside the load chart’s safe working area. 

A load chart is a diagram that assists a crane operator in determining the most appropriate configuration and positioning.  The load chart diagram shows the boom length needed to pick up and lift a load.  The range diagram is also helpful when setting up near structures.  A load chart may appear like a diagram or a spreadsheet.  In the spreadsheet version, the numbers on the top row represent the boom lengths of the crane.  The numbers in the left column represent the operating radius.  The gross capacity of the crane can be determined by either following the radius column and intersecting boom length or following the boom angle and intersecting the radius or boom length column.  Each crane’s load chart will have specific footnotes pertinent to the particular crane type that must be considered to ensure the crane’s safe operation. 

The capacities listed in a crane’s load chart are not the actual loads that can be lifted on the hook.  The values given in the charts are “gross capacities: or “rated capacities.” The actual load the crane can lift is referred to as the “net capacity.”  The maximum load must never exceed the crane’s net capacity!  The gross capacity must include the weight of anything, and everything mounted or stowed on the crane boom or hanging from the boom tip.  These items are called “capacity deductions.”  Some capacity deductions include:

  • Weight of the main load block
  • Weight of the headache ball or overhaul ball
  • The effective weight of the jib (stowed or erected and not used)
  • Weight of all hanging cable
  • Weight of all rigging
  • Weight of the load

A rule of thumb is that the load must never exceed 75% of the net capacity of the crane.  Anything beyond 75% falls into a category known as a critical lift.  When it comes to crane work, a small mistake could be costly.  Take the time to properly plan all lifts and ensure that the equipment can complete the work.     

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