Telescoping Boom and Jib Configuration Flashcards

Before extending a telescoping boom section, the operator must first ensure the boom is:

Answer: Free of any suspended load

Telescoping a boom under load is prohibited unless the manufacturer's documentation specifically permits it, because the load moment changes as the radius increases.

When a mobile crane's telescoping boom is extended to a longer length, the rated lifting capacity will:

Answer: Decrease as the increased radius increases the load moment

Extending the boom increases the working radius, and since load moment equals load multiplied by radius, the rated capacity decreases to stay within structural limits.

The fly jib 'offset angle' on a mobile crane refers to:

Answer: The angle between the jib and the main boom centerline

Offset angle is the angle formed between the centerline of the jib and the centerline of the main boom, and separate load charts exist for each rated offset angle.

What is the primary purpose of a fly jib (boom extension) on a mobile crane?

Answer: To extend the crane's reach in height or radius beyond the main boom

A fly jib adds length beyond the main boom tip, allowing the crane to reach greater heights or radii that the main boom alone cannot achieve.

When using a jib attachment, which load chart must the operator reference?

Answer: The jib-specific chart for the exact jib length and offset angle being used

Each jib length and offset angle combination has its own rated capacities; using any other chart would result in an unsafe or incorrect capacity determination.

Mechanical locking pins on telescoping boom sections are critical because they:

Answer: Secure the boom section in position if hydraulic pressure is lost

Hydraulic systems can lose pressure due to seal failure or line damage; mechanical pins prevent catastrophic boom retraction under load if pressure is lost.

Before operating with a newly assembled jib configuration, an operator must verify that:

Answer: All connecting pins are fully inserted, secured, and properly cottered

Improperly secured connecting pins can allow the jib to separate from the boom tip during a lift, causing catastrophic failure.