Why must the center of gravity be maintained within the crane's working envelope?

• A. It prevents tipping and ensures stability during lift.
• B. It has no effect on safety.
• C. It only affects the color of the rigging.
• D. It determines how fast the load moves.

Answer: (A)

Maintaining the center of gravity inside the crane's working envelope keeps the lifting system balanced and stable. The crane and the load together have a combined center of gravity, and as you reach out with the boom or move the load, that point shifts. If the combined center of gravity moves outside the crane’s base of support, the overturning moment produced by the weight can exceed the stabilizing moment from the outriggers and ballast, making the crane prone to tipping.

The working envelope defines the safe combinations of boom angle, reach, and load offset where those forces stay within the crane’s stability limits, even when dynamic effects like starting, stopping, swinging, and wind are involved. Staying within this envelope ensures the resultant force remains within the base and prevents loss of balance.

The other options miss the point: safety is directly affected by CG location, rigging color has no bearing on stability, and how fast the load moves is not determined by where the CG lies in the envelope.