Mobile Crane Operator Fundamentals Flashcards

A mobile crane is configured with a 150-foot main boom and a 35-foot fixed jib offset at 15°. The load chart shows a rated capacity of 18,200 lbs at a 60-foot radius. If the actual load including rigging weighs 17,500 lbs and the load radius unexpectedly shifts to 65 feet mid-lift due to boom flex, what is the operator's correct immediate action?

Answer: Stop all swing motion and slowly boom up to reduce the radius back to 60 feet before continuing

When radius unexpectedly increases mid-lift, the rated capacity at the new radius may be significantly lower than at the planned radius. The operator must stop all movements that could worsen the condition (especially swing, which adds centrifugal force), then carefully boom up to reduce the radius. Rapidly booming up or continuing the lift without correction risks exceeding the chart limit at the new radius. Releasing the load is never an appropriate response.

Under ASME B30.5, when must a mobile crane operator refuse to make a lift even if the lift plan has been approved by a qualified engineer and the load is within the crane's rated capacity?

Answer: When the operator has any reason to believe the lift cannot be made safely, regardless of approvals

ASME B30.5 explicitly grants the operator the authority and responsibility to refuse any lift they believe cannot be performed safely, regardless of engineering approvals, lift plans, or management pressure. This operator authority is absolute and cannot be overridden by supervisors or engineers. The other options describe specific conditions that may or may not require refusal depending on context, but they do not capture the unconditional nature of operator authority under the standard.

A lattice boom crawler crane has been reconfigured as a rubber-tired carrier (truck crane) for a road move. During the move, the operator notices the load moment indicator (LMI) alarm is sounding with the boom in travel position and no load on the hook. What is the most likely cause?

Answer: The crane is on a side slope exceeding the manufacturer's travel limit

LMI systems measure the relationship between load moment and crane stability. During road travel, if the crane traverses a side slope exceeding the manufacturer's specified travel limit, the system detects a tipping hazard condition and alarms even with no suspended load. The crane's center of gravity shifts laterally on a slope, and the LMI interprets this as an overload/instability condition. Recalibration for travel mode would silence spurious alarms, but a legitimate slope alarm should not be silenced—it's warning of a real condition.

When calculating the net capacity of a crane using a jib, which combination of deductions must be applied to the gross load chart capacity before determining if a load can be lifted?

Answer: Deduct the total weight of all auxiliary rigging, the hook block, the jib, and any jib pendants from the gross capacity

Net capacity equals gross chart capacity minus the weight of all items between the crane and the load: hook block, overhaul ball, load line, jib, jib pendants, auxiliary rigging, and any other attached equipment. Jib load charts include structural derating for the jib configuration but do NOT subtract the physical weight of rigging hardware—the operator must do this. Failing to deduct all auxiliary weights is a common cause of overloads during jib lifts.

A crane operator is performing a critical pick near energized 345 kV transmission lines. The appointed signal person instructs the operator to move the load within 12 feet of the lines, stating that a qualified electrical utility representative is on site. Under OSHA 1926.1408, what must the operator verify before complying with this instruction?

Answer: That the utility owner has provided written confirmation that the lines have been de-energized and visibly grounded, OR that an encroachment permit with site-specific minimum approach distance has been established in writing

OSHA 1926.1408 prohibits crane equipment from coming within the Table A minimum approach distances of energized lines unless either: (1) the lines are de-energized AND visibly grounded by the utility owner with written confirmation, OR (2) an encroachment permit has been established with the utility owner specifying a revised minimum approach distance based on voltage. For 345 kV, the Table A distance is 25 feet. No verbal assurance, signal person certification, or insulated link substitutes for these specific written requirements.

A mobile crane's load chart has separate sections for 'on outriggers fully extended,' 'on outriggers extended 50%,' and 'on rubber.' The crew needs to make a lift at a 45-foot radius over the rear quadrant. Fully extending outriggers on one side is blocked by an excavation. The foreman suggests using the '50% extended' chart for the blocked side and 'fully extended' chart for the clear side and averaging the two values. What is the correct response?

Answer: The lift must not be made until the crane is configured in a rated configuration matching a published load chart, unless a qualified engineer performs a site-specific analysis

Load charts are published only for specific, manufacturer-tested configurations. Asymmetric outrigger extension (one side fully extended, one at 50%) is not a rated configuration and no published chart applies. Averaging two chart values is not an engineering method and is not permitted under ASME B30.5 or OSHA standards. The only compliant options are: reconfigure the crane into a published configuration, relocate the crane, or have a qualified engineer perform a site-specific engineering analysis that accounts for the actual asymmetric condition.