When can blocking (cribbing) be placed under outrigger beams?

Blocking, or cribbing, under outrigger beams is generally not permitted. The primary reason is safety and structural integrity. When you support a crane's outrigger beams with blocking, it can alter the intended load distribution and stability. Outriggers are designed to extend and distribute the load of the crane on a predetermined design surface.

Placing blocking under them can lead to unsafe conditions, especially if the ground beneath is not properly assessed or if the blocking does not provide a stable base. Outriggers should always work on a level, firm ground to ensure proper weight distribution and prevent tipping or structural failure of the crane.

In contrast, the other options suggest scenarios where cribbing could be allowed, which may mislead operators regarding safe practices. Correct adherence to safety rules emphasizes that blocking under outrigger beams should never be done to maintain crane stability and operator safety.