Load Charts and Capacity Flashcards

A load moment indicator (LMI) primarily helps the operator by:

Answer: Warning when the load approaches or exceeds the rated capacity for the current configuration

The LMI monitors load, radius, and angle to alert the operator before rated capacity is exceeded.

An LMI is a useful aid but must never be relied on as a substitute for:

Answer: The operator's own load chart calculations and judgment

The operator remains responsible for verifying lifts against the load chart; the LMI only supplements that.

Soft or unstable ground under an outrigger most directly threatens which type of capacity limit?

Answer: Stability-based (tipping) capacity

Settling ground reduces the effective stability base and can lead to tipping.

Why are charts for lifting on rubber (tires) typically much lower than charts for lifting on outriggers?

Answer: Tires provide a smaller, less rigid stability base than fully deployed outriggers

Outriggers create a wider, firmer support base, allowing much higher rated capacities than tires.

Wind acting on a large, sail-like load can effectively:

Answer: Increase the load radius and side forces, reducing safe capacity

Wind pushes the load out and adds side loading, which lowers the capacity you can safely use.

Side loading the boom (dragging or pulling a load sideways) is dangerous because load charts assume:

Answer: The load is freely suspended directly below the boom tip

Chart capacities are valid only for freely suspended vertical loads, not side-pulled ones.

Before every lift, the operator should confirm the chart matches the crane's current setup, including counterweight, boom configuration, and:

Answer: Outrigger position and quadrant of operation

Capacity depends on outrigger spread and the working quadrant, so both must match the chart in use.