Load Moment Indicators and Safety Devices Flashcards

An LMI system displays 98% of rated capacity, but the operator notices the boom angle sensor reads 2° higher than the physical boom angle indicator on the crane. Which action is MOST appropriate before proceeding with the lift?

Answer: Recalibrate or have the LMI sensor discrepancy investigated before continuing operations

A discrepancy between the LMI boom angle sensor and the physical indicator signals a potential sensor fault or calibration error. At 98% capacity, even a small error in boom angle reading could mean the crane is actually at or beyond rated capacity. OSHA and ASME B30.5 require that LMI malfunctions be investigated and corrected before continued use; operating with a known sensor discrepancy violates safe operating procedures regardless of the displayed percentage.

Under ASME B30.5, when an Anti-Two-Block (ATB) device activates during a lift, which crane functions must be automatically PREVENTED or INTERRUPTED?

Answer: Hoist-up, boom down, and boom telescope-out functions simultaneously

ASME B30.5 specifies that the ATB device must interrupt or prevent hoist-up, boom down (which closes the distance between block and boom tip), and boom telescope-out (which also reduces clearance). These three motions all reduce the gap between the load block and the boom point, risking two-blocking. Hoist-down, boom-up, and telescope-in are still permitted because they increase clearance. A manual reset by the operator is sufficient after the hazard is corrected.

A crane LMI is programmed with a configuration for a 100-foot main boom. The operator extends the boom to 110 feet without updating the LMI configuration. How is the rated capacity MOST likely affected compared to the actual chart value?

Answer: The LMI will display a higher percentage of capacity than actually exists, creating an unsafe condition

If the LMI is configured for a shorter boom length than is actually rigged, it references a load chart for a stiffer, shorter structural configuration. At extended boom lengths, rated capacities decrease significantly. The LMI's calculated rated capacity will be higher than the true chart value for 110 feet, meaning the displayed percentage (e.g., 85%) may actually represent a load that exceeds the real 110-foot rated capacity — a dangerously misleading reading. Operators must update LMI boom length configuration whenever the boom is changed.

An LMI's load moment is calculated as 180,000 ft-lb and the rated moment for the current configuration is 175,000 ft-lb. The LMI alarm sounds but does NOT cut out the hoist. Which condition BEST explains this scenario under ASME B30.5?

Answer: The LMI warning alarm should trigger at or before 100% rated load; the absence of automatic cutout may indicate the device is set up with an alarm-only (no cutout) configuration, which is non-compliant if cutout capability exists

ASME B30.5 requires that the LMI provide a warning at or before 100% rated capacity. If the crane is equipped with a load moment limiting device (cutout capability), it must prevent further load-increasing motion at or before exceeding rated capacity. A configuration where the system only sounds an alarm at 103% of rated moment without initiating a cutout — when cutout hardware is present — is non-compliant. The common misconception is that LMIs are alarm-only; modern compliant systems must also restrict motion when cutout is available.

During a pick-and-carry operation on a rough terrain crane, the LMI shows 72% of rated capacity on a level surface. As the crane begins to travel across a 3° side slope, what is the PRIMARY reason the operator must reassess the LMI reading?

Answer: Most LMI systems reference static on-level load charts; a side slope shifts the crane's effective center of gravity, reducing actual tipping resistance below what the LMI displays

LMI systems are typically calibrated to level, firm surfaces. A side slope causes lateral shift of the crane's center of gravity toward the downhill side, effectively reducing the crane's resistance to tipping — especially in the downhill direction of swing. The LMI continues to display capacity based on the level-surface load chart, meaning the displayed 72% may actually represent a higher percentage of real remaining stability margin. Operators must consult manufacturer specifications for slope derating and restrict swing toward the downhill side. Most LMIs do not automatically correct for operational side slopes unless specifically equipped with a tilt-compensation module.

A crane operator is replacing a load block and installs one that is 400 lbs heavier than the block stored in the LMI's rigging configuration. The LMI is not updated. At a working radius of 40 feet, the operator lifts a load the LMI indicates is at 95% of rated capacity. What is the ACTUAL situation?

Answer: The LMI underestimates the load moment; actual loading is higher than 95% because the heavier block's weight is not accounted for in the LMI's moment calculation

LMI systems calculate load moment using the configured block weight as part of the lifted load (hook weight + rigging + cargo). If the actual block is 400 lbs heavier than configured, the LMI underestimates total suspended weight. At a 40-foot radius, an extra 400 lbs adds 16,000 ft-lb of unaccounted moment. The displayed 95% therefore understates actual loading — the crane may already be at or beyond 100% of rated capacity. ASME B30.5 and manufacturer guidelines require that rigging and block weights be accurately entered into the LMI before each lift.