Crane Safety Devices & Operational Aids Flashcards

What does an anti-two-block device prevent?

Answer: Contact between the load block or overhaul ball and the boom tip

Two-blocking happens when the hook block or overhaul ball is pulled into the boom tip sheaves, which can part the hoist rope and drop the load. Anti-two-block devices warn the operator and stop the motions that cause it.

Under OSHA 1926.1416, if an operational aid such as a boom angle indicator stops working, what is the general rule?

Answer: Repairs are generally required within 7 calendar days, and temporary alternative measures must be used in the meantime

OSHA allows limited continued operation while an operational aid is out of service, but the employer must use specified temporary alternative measures and generally repair it within 7 calendar days (30 days for some aids, such as load weighing devices).

Which of these is a SAFETY DEVICE under OSHA 1926.1415, not an operational aid?

Answer: Crane level indicator

1926.1415 lists safety devices such as the crane level indicator, boom stops, jib stops, foot pedal brake locks, integral holding valves on hydraulic outriggers and the horn. If one isn't working, operations must stop. LMIs, boom angle indicators and anti-two-block devices are operational aids under 1926.1416.

What does a load moment indicator (LMI) or rated capacity limiter primarily monitor?

Answer: Load weight in relation to radius and configuration, compared with chart capacity

An LMI or RCL compares actual load and radius (load moment) with the programmed load chart for the current configuration. It warns the operator, and on many systems stops motions that would increase load moment, as capacity is approached.

Why must the operator correctly set the configuration (outrigger position, counterweight, parts of line) in the LMI before lifting?

Answer: The LMI picks its capacity limits from the selected configuration, so a wrong setting gives false capacity readings

The LMI uses the load chart for the configuration entered. A wrong setting, such as full outriggers when the crane is on partial extension, makes the system allow loads beyond actual capacity and can lead to overload or tip-over.

What should an operator treat a functioning LMI as?

Answer: An aid that supplements, but never replaces, the operator's knowledge of the load chart and lift conditions

Manufacturers and ASME B30.5 make clear that operational aids assist the operator and don't replace their judgment or load chart knowledge. LMIs can be set up wrong, and they can't account for every factor, such as wind or side loading.