NCCER Crane Crane Safety Devices & Operational Aids — Questions and Answers
Question 1: What does an anti-two-block device prevent?
- The crane tipping over the rear
- The outriggers retracting under load
- Contact between the load block or overhaul ball and the boom tip (Correct answer)
- The swing brake overheating
Correct 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.
Question 2: Under OSHA 1926.1416, if an operational aid such as a boom angle indicator stops working, what is the general rule?
- The crane must be removed from service immediately and permanently
- The crane may keep operating indefinitely
- The operator may bypass it without alternative measures
- Repairs are generally required within 7 calendar days, and temporary alternative measures must be used in the meantime (Correct answer)
Correct 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).
Question 3: Which of these is a SAFETY DEVICE under OSHA 1926.1415, not an operational aid?
- Crane level indicator (Correct answer)
- Load moment indicator
- Boom angle indicator
- Anti two-block device
Correct 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.
Question 4: What does a load moment indicator (LMI) or rated capacity limiter primarily monitor?
- Engine oil pressure
- Load weight in relation to radius and configuration, compared with chart capacity (Correct answer)
- Wind direction only
- Fuel level
Correct 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.
Question 5: Why must the operator correctly set the configuration (outrigger position, counterweight, parts of line) in the LMI before lifting?
- The LMI only affects the cab display brightness
- Configuration only matters for travel
- The LMI picks its capacity limits from the selected configuration, so a wrong setting gives false capacity readings (Correct answer)
- So the horn works
Correct 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.
Question 6: What should an operator treat a functioning LMI as?
- A replacement for reading the load chart
- Proof that any lift it allows is safe
- Something to disable during critical lifts
- An aid that supplements, but never replaces, the operator's knowledge of the load chart and lift conditions (Correct answer)
Correct 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.
