On Site Mobile Crane Lift Calculator

Before Calculating, you need the following:

• Load weight (W): Total weight of the object to be lifted (including rigging).
• Boom length (L): Length of the crane’s boom at the time of the lift.
• Load radius (R): Distance from the crane’s center of rotation to the center of the load.
• Boom angle (θ): Angle between the boom and the ground.
• Crane capacity chart: Manufacturer’s load chart for the specific crane model.
• Ground conditions: Ensure firm and level ground.

Basic Lift Capacity formula:

Lifting Capacity =

Crane Capacity from chart x Efficiency Factor
Safety Factor

where:

• Crane Capacity = the maximum lifting capacity of the crane at a given radius. It also considers the boom length from the crane’s load chart.
• Efficiency factor = Adjusted based on wind speed, ground condition and boom length ( ranges from 0.7 to 1.0).
• Safety Factor = A multiplier ( typically 1.1 to 1.5 ) to ensure safe lifting operations.

Alternatively use the Load Moment equation.

Load Moment = Load Weight x Load Radius

Available Load Moment = crane capacity x Load Radius

Ensure that the Load Moment does not exceed Available Load Moment.

Checking Against the load Chart

• Used to check the Crane’s Load Chart to find the maximum capacity at the given boom length and load radius.
• Ensure that the calculated load is within safe limits for the crane’s configuration ( boom extension, counterweight, outrigger position).

Additional Considerations

• Rigging Load: Consider the weight of slings, shackles, and hooks.
• Wind Load: If working outdoors, account for wind speed and boom deflection.
• Boom Deflection: A longer boom can cause deflection, changing the load radius.
• Outriggers vs. Crawler: Cranes on outriggers have higher capacity than those on rubber tires.
• Swing Effect: Swinging a load dynamically affects crane stability.

Example Calculation

Given:

Load weight = 10,000 kg

Load radius = 5 m

Boom length = 15 m

Crane capacity from the chart at 5 m = 20,000 kg

Efficiency factor = 0.85

Safety factor = 1.3

Calculation:

Lifting Capacity = 20,000 x 0.85 / 1.3 = 13,076.92 kg

Since the required load (10,000 kg) is less than the adjusted capacity (13,076.92 kg), the lift is safe.

Final Checklist Before Lift

✅ Verify the load chart and calculation.
✅ Inspect the crane, slings, and shackles.
✅ Confirm outriggers are fully extended.
✅ Check for obstacles (power lines, structures).
✅ Ensure proper communication between operator and signalman.
✅ Monitor wind conditions and load swing.

Note: This calculator is for educational purposes only and now in Testing mode.