Crane Institute of America

Crane Blocking: How Much is Enough?

500 Ton Crane-OverIt is always important to consider ground support around the entire working area, not just where the load will be lifted.

It is common to think that if the ground is firm enough under the outriggers toward the lift, then the crane will be supported. However, this 500 ton All-Terrain crane has several tons of counterweight being supported by the outriggers on the opposite side of the crane.

If the crane swings over an outrigger, thousands of pounds per square inch of pressure impacts the float and the ground beneath it. Generally, the times three rule for blocking is adequate, but the actual load pressure on the ground for a crane configured similarly must be calculated. Additionally, a compaction test should be conducted to determine ground support.

After obtaining this information, a proper size blocking can be chosen for lifting the load safely.

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