Mobile Crane Operator Flashcards

During a tandem lift using two mobile cranes, the load shifts unexpectedly toward Crane A, increasing its share to 65% of the total load. If Crane A's rated capacity at that radius is 80,000 lbs and the total load is 100,000 lbs, what is the minimum required net capacity Crane A must have had before the shift began, assuming the original plan allocated loads equally and NCCCO tandem lift derating was applied at 75%?

Answer: 66,667 lbs

In a tandem lift with NCCCO derating at 75%, each crane's usable capacity is 75% of rated. With a 50/50 split on 100,000 lbs, each crane carries 50,000 lbs. So the required net (derated) capacity = 50,000 / 0.75 = 66,667 lbs rated capacity. After the shift, Crane A carries 65,000 lbs — which exceeds its derated capacity of 60,000 lbs (80,000 × 0.75), creating an overload condition. The pre-shift minimum rated capacity needed was 66,667 lbs.

A mobile crane is traveling on a highway with a 13'6" height restriction. The boom is fully retracted and the load block is secured. The operator notes the load block's sheave pin is 12'10" from the ground, and the hook and block assembly adds 14 inches. What must the operator do before proceeding?

Answer: Remove or restrain the hook and block assembly to bring the total height within 13'6"

The total travel height is 12'10" + 14" = 14'0", which exceeds the 13'6" restriction. The operator must either remove the hook and block assembly or secure it in a way that reduces the overall height to comply with the posted limit. Simply noting the sheave pin height is insufficient — the entire load hook assembly must be accounted for.

Per ASME B30.5, when operating a mobile crane with a luffing jib, the operator observes that the jib angle indicator is malfunctioning. Which action is required?

Answer: The crane must be taken out of service until the indicator is repaired

ASME B30.5 requires that all operational aids, including jib angle indicators, must be functional before lifting operations proceed. A malfunctioning angle indicator on a luffing jib is a safety-critical deficiency — the crane must be removed from service until repaired. Visual monitoring by a rigger and capacity reductions are not approved substitutes under B30.5.

An operator is picking a load near an energized 115 kV overhead power line. The employer has NOT obtained a power line clearance from the utility. What is the minimum required clearance distance the crane must maintain from the power line?

Answer: 20 feet

Under OSHA 1926.1408 (the Cranes and Derricks in Construction standard), when no utility determination has been made and no encroachment prevention plan is in place, the crane must maintain at least 20 feet of clearance from all power lines up to 350 kV. The 10-foot rule only applies after a qualified person has determined the voltage AND the utility has been notified. Since no clearance was obtained, the 20-foot default applies.

During a pick-and-carry operation on a rough terrain crane, the load begins to pendulum. The operator should FIRST:

Answer: Stop all travel and use the load line to dampen the swing before resuming

When a load pendulums during pick-and-carry, the safest immediate action is to stop all crane travel, allowing the pendulum to dampen naturally, and then use controlled load line movement or a tag line to arrest the swing before resuming travel. Accelerating to match or exceed pendulum frequency risks tipping. Extending outriggers during travel is prohibited. Releasing the load brake is dangerous and uncontrolled.

A crane's load chart lists a capacity of 42,000 lbs at a 40-foot radius with outriggers fully extended on a firm, level surface. The operator is working on a 2% side slope with outriggers partially extended (75% of full extension). Applying NCCCO guidance, which of the following best describes the correct approach?

Answer: The rated chart capacity does not apply; a new capacity must be determined by the crane manufacturer or a qualified engineer before making the pick

Load charts are only valid under the exact conditions specified — typically fully extended outriggers on a firm, level surface. When conditions deviate (partial outrigger extension AND side slope), the chart capacity cannot be applied using simple derating formulas unless the crane manufacturer has published specific correction factors for those conditions. NCCCO requires that a qualified person or the manufacturer determine actual capacity for non-standard configurations. Arbitrary percentage derates are not an approved method.