Load Moment Indicators and Safety Devices Flashcards

A crane's Load Moment Indicator (LMI) is showing 92% of rated capacity while the operator is picking a load at 40-foot radius. The operator then begins a simultaneous operation: booming down while slewing. What is the primary concern with this combined movement?

Answer: Booming down increases the radius, which increases the load moment and can push the LMI into an overload condition even without adding weight

Booming down (lowering the boom angle) increases the load radius. Since load moment = load weight × radius, increasing radius at 92% capacity can quickly exceed 100%, triggering an overload condition — even though no additional weight was added. This is a critical dynamic hazard in crane operation that the LMI will reflect in real time.

During pre-shift inspection, an operator notices the LMI's anti-two-block (ATB) device warning light is illuminated but the hook block is not near the boom tip. What is the correct course of action?

Answer: Tag out the crane and remove it from service until the ATB system is repaired

A malfunctioning ATB device that gives a false alarm indicates the safety system is compromised. ASME B30.5 and NCCCO standards require that defective safety devices render the crane out of service. Operating with a known faulty ATB — even if the hazard seems absent in the moment — is prohibited. The crane must be tagged out and repaired before use.

An LMI is rated and calibrated for a specific boom length and jib configuration. The operator reconfigures the crane to a shorter boom with a longer jib but does not update the LMI configuration. What is the most dangerous consequence of this error?

Answer: The LMI will overestimate remaining capacity, allowing the operator to unknowingly exceed the actual rated load for the new configuration

LMI systems reference the rated capacity chart for the configuration they are programmed with. If the crane is reconfigured to a shorter boom with a longer jib but the LMI still references the original configuration's load chart, the displayed capacity may be higher than the actual rated capacity for the new setup. This means the operator can believe they are within limits while the crane is actually overloaded — an extremely dangerous condition.

A lattice boom crawler crane equipped with an LMI is working on a barge. The barge develops a 3-degree list toward the load side during a pick. The LMI does not account for barge trim. What effect does this list have on the actual load moment compared to what the LMI displays?

Answer: The actual load moment is greater than displayed because the effective radius increases as the crane tilts toward the load

When a crane tilts toward the load side (list), the effective horizontal radius of the load from the crane's centerline increases beyond what the LMI measures based on boom angle alone. Since the LMI calculates radius from the boom angle relative to the crane's own reference plane, not a true horizontal plane, the actual load moment is greater than what the LMI displays. This is a well-documented hazard in marine crane operations.

An LMI override (bypass) switch is activated by a qualified operator to complete a critical lift after the LMI triggers an overload warning at 97% capacity. The operator has manually verified the load weight and rigging and believes the LMI is reading incorrectly due to a wind load compensation error. Under ASME B30.5, which statement best describes the permissibility of using the override?

Answer: Override use is permissible only when authorized by the appointed person and additional safety measures are implemented, and its use must be documented

ASME B30.5 acknowledges that LMI override switches exist but requires that their use be authorized by the appointed person responsible for the lift. Additional measures — such as a spotter, independent load verification, and restricted operational envelope — must be in place. The use must be documented. Overrides are not blanket permissions; they are tightly controlled exceptions for specific, justified circumstances.

During a tandem lift, each crane is equipped with its own LMI. Crane A is at 78% of its rated capacity and Crane B is at 71%. As the load is lowered and one crane's load line goes slack, what happens to the load distribution and what risk does this create for the LMI of the crane still bearing load?

Answer: Load redistribution causes the active crane to absorb a greater share of the total load, potentially exceeding its LMI's overload threshold without the operator commanding more load

In a tandem lift, if one crane's load line goes slack, the entire suspended load transfers to the other crane. The active crane's LMI will suddenly show a dramatic load increase — potentially far beyond its rated capacity — even though the operator did not intentionally pick up more load. This is one of the most dangerous failure modes in tandem lifting and is why ASME B30.5 requires continuous communication and a designated lift director during tandem operations.