Load Moment Indicators and Safety Devices Flashcards

An LMI displays 98% of rated capacity while the crane is picking a load on a 15° side slope. The operator notices the LMI was calibrated on level ground. Which of the following best describes the actual safety margin?

Answer: The actual margin is less than displayed because side slopes shift the crane's tipping axis, reducing true rated capacity below the calibrated value

LMIs calibrated on level ground do not account for the shifted tipping axis caused by a side slope. A 15° side slope meaningfully reduces the effective rated capacity, so the true safety margin is smaller than the 2% the display suggests. Operators must never rely solely on LMI readings when working off-level.

During a tandem lift, Crane A's LMI reads 85% of rated capacity and Crane B's LMI reads 72%. The lift plan assumes equal load sharing. What is the MOST likely cause of the imbalance, and what is the correct immediate action?

Answer: Unequal headroom angles or rigging length differences shifting load share; stop the lift and reassess rigging geometry before continuing

Unequal load sharing in a tandem lift most commonly results from differences in sling angles, rigging lengths, or attachment point geometry. The correct response is to stop the lift immediately and reassess rather than continuing, because the imbalance can shift dynamically and cause one crane to become overloaded. Overriding safety devices or continuing with a known geometry problem is never acceptable.

An anti-two-block (ATB) system activates and cuts power to the hoist. The operator bypasses the ATB using the manufacturer-approved override to complete a pick-and-carry operation over a short distance. Under ASME B30.5, which condition MUST be met for this bypass to be permissible?

Answer: The bypass is permissible provided it is a temporary measure and a competent person continuously monitors the block-to-boom-tip distance

ASME B30.5 permits ATB bypass only as a temporary measure when a competent person directly monitors the distance between the load block and the boom tip to prevent two-blocking. Simply having a second device or limiting travel speed does not fulfill the standard's requirement; active human monitoring by a competent person is mandatory during bypass operation.

A crane's LMI suddenly shows 'SENSOR FAULT' mid-lift with approximately 75% of rated capacity on the hook. Which response is correct according to OSHA 1926.1416 and manufacturer guidance?

Answer: Immediately lower and secure the load, then have the LMI serviced before resuming lifts that require the device

OSHA 1926.1416 requires that safety devices be operational before use. A sensor fault means the LMI is not functioning as required. The correct action is to set the load down safely and remove the crane from service until the LMI is repaired and verified. Continuing the lift — whether at reduced speed, via manual estimation, or through bypass — does not satisfy the regulatory requirement for functioning safety devices.

A luffing jib crane's LMI is configured for main boom only. The operator is using the main boom plus luffing jib in a 'fly jib' configuration. The LMI shows 60% of rated capacity. What critical error is present in this scenario?

Answer: The LMI is not configured for the jib configuration and may not reflect the correct rated capacity for the actual boom-jib combination in use, potentially displaying a falsely safe percentage

An LMI configured for main-boom-only operation does not reference the correct load chart for a boom-plus-luffing-jib configuration. The rated capacities differ substantially between configurations, and the LMI may be comparing the load against the wrong capacity, displaying a falsely safe percentage. Before any lift, the LMI must be configured to match the exact boom configuration in use.

During cold weather operations at -20°F (-29°C), an operator notices the LMI's load cell readings fluctuate ±5% even with no load on the hook. The crane is otherwise mechanically sound. What is the MOST technically accurate explanation for this behavior and the correct course of action?

Answer: Extreme cold causes thermal contraction in strain gauge load cells, altering their electrical resistance and zero-point calibration; the LMI should be re-zeroed per the manufacturer's cold-weather procedure before lifts begin

Strain gauge load cells rely on precise resistance measurements. Extreme cold causes thermal contraction of metal components, shifting the zero-point calibration and producing false readings even under no-load conditions. Manufacturer cold-weather procedures typically require re-zeroing or recalibration of the LMI before operations begin. Proceeding without addressing the calibration drift can result in the LMI displaying inaccurate load percentages throughout the lift.