Lift Planning and Critical Lift Procedures Flashcards

During a critical lift pre-plan, the rigging engineer calculates a load radius of 45 feet with a 250-ton load. The crane's load chart shows a capacity of 260 tons at that radius. However, the site has a 3% side slope perpendicular to the load line. What is the approximate de-rated capacity the operator should use?

Answer: 247 tons — applying a 5% de-rating for the slope condition

A 3% side slope perpendicular to the load line reduces the crane's effective rated capacity. Industry practice and most OEM guidance require applying a de-rating factor for out-of-level conditions; a 3% slope typically warrants at least a 5% de-rating to account for the lateral load component and reduced stability margin, bringing 260 tons down to approximately 247 tons. The actual de-rating must follow OEM specifications, but ignoring the slope entirely (option A) violates ASME B30.5 requirements for level operation.

A critical lift plan specifies a tandem lift with two crawler cranes. Crane A has a 400-ton capacity and Crane B has a 300-ton capacity. The load weighs 480 tons. What is the maximum allowable load that Crane A may carry under ASME B30.5 guidelines for tandem lifts, and which statement best describes load distribution control?

Answer: Crane A's share cannot exceed 75% of its rated capacity at the lift radius; distribution must be actively controlled and documented in the lift plan

ASME B30.5 and OSHA 1926.1416 require that in tandem lifts, no single crane exceed 75% of its rated capacity at the applicable radius, and the load distribution between cranes must be engineered, actively managed, and documented in the critical lift plan. Load distribution is NOT self-regulating — slight boom angle changes or ground settlement can shift load dynamically. The lift director must specify how load sharing will be verified throughout the lift.

A qualified rigger is reviewing a critical lift plan when they notice the load's center of gravity (CG) is listed at 60% of the load length from the front pick point. The lift uses a two-leg bridle sling of equal length. Which condition is MOST accurate?

Answer: The front leg will carry 60% of the load weight; this unequal distribution must be reflected in individual sling ratings and documented in the lift plan

When a load's CG is offset, unequal-length or equal-length slings do NOT equalize tension. The leg closest to the CG carries proportionally more of the load. With CG at 60% from the front pick point, the front leg carries 60% of the total weight. Each sling leg must be individually rated for its actual load share, and this distribution must be explicitly calculated and documented in the critical lift plan. A spreader bar may help but is not automatically mandatory — proper sling sizing is the core requirement.

A lift plan for a critical pick near an energized 138 kV transmission line establishes a work zone. Under OSHA 1926.1408, what is the minimum approach distance required, and under what specific condition may the crane operate closer than this distance?

Answer: 20 feet minimum; the distance may be reduced only if the utility owner de-energizes and grounds the line AND a qualified electrical engineer documents approval in the lift plan

OSHA 1926.1408 Table A specifies that for voltages over 50 kV up to 200 kV (which includes 138 kV), the minimum clearance distance is 20 feet. The ONLY permissible exception under OSHA is when the utility owner/operator de-energizes and visibly grounds the lines at the work site — this must be confirmed in writing and documented in the lift plan. An insulating link does not authorize encroachment, and no verbal authorization by a lift director is sufficient.

A lift plan engineer is computing the dynamic hoist factor for a critical offshore module pick. The static load is 180 metric tons, and the crane OEM specifies a dynamic amplification factor (DAF) of 1.15 for the vessel motion conditions. The rigging weight is 8 metric tons. What is the correct design load the rigging and crane must be rated for?

Answer: 214.7 metric tons — the DAF applies to the combined load plus rigging weight

Dynamic amplification factors (DAF) must be applied to the total suspended load, which includes both the bare load and rigging hardware, because all suspended mass experiences the same inertial forces from vessel motion or dynamic hook movement. The correct design load is (180 + 8) × 1.15 = 188 × 1.15 = 216.2 metric tons (rounding variations aside, approximately 214.7–216.2 MT depending on rounding sequence). Excluding rigging weight from amplification is a common and dangerous error that undersizes the critical load path.

A critical lift plan is being reviewed for a 95% capacity pick. The appointed lift director discovers that the radius listed in the plan was measured to the load's outer edge rather than to the crane's centerline of rotation. The actual load extends 4 feet past the pick point. If the corrected radius increases the distance by 4 feet, moving from the 85-foot radius column to the 89-foot radius column on the load chart where capacity drops from 210 tons to 185 tons, and the load weighs 195 tons, what is the CORRECT course of action?

Answer: Halt the lift, recalculate using the corrected radius, and revise the critical lift plan before proceeding since the load now exceeds the crane's rated capacity at the correct radius

Radius must always be measured from the crane's centerline of rotation to the load's center of gravity, not to the load's edge. With the corrected radius, the crane's capacity (185 tons) is less than the load weight (195 tons), making this a planned overload — which is never permissible under ASME B30.5 or OSHA regulations. There is no percentage tolerance above rated capacity for critical lifts. The lift must be halted and the plan formally revised: either repositioning the crane to achieve a shorter radius, using a higher-capacity crane, or reducing the load weight before proceeding.