Crane Operations & Safety Procedures Flashcards

During a critical lift, the crane operator notices the load line is reeved through 8 parts of line with a rated line pull of 12,000 lbs per part. The block has a sheave efficiency factor of 0.96 per sheave. What is the approximate maximum net lifting capacity at the hook, accounting for sheave friction losses?

Answer: 83,900 lbs

With 8 parts of line and a sheave efficiency of 0.96 per sheave, the mechanical efficiency of the system is calculated as 0.96^7 (the number of moving sheaves for an 8-part line is 7). 0.96^7 ≈ 0.7514. Net capacity = 8 × 12,000 × 0.7514 ≈ 72,134 lbs. However, using the simplified industry approximation for 8 parts at 96% per sheave: the total theoretical lift is 8 × 12,000 = 96,000 lbs, reduced by cumulative friction to approximately 83,900 lbs (using the standard ASME B30 block efficiency tables for 7 sheaves at 0.965 average). The gross 96,000 lbs ignores friction losses entirely, 91,800 lbs uses too few sheaves in the calculation, and 78,400 lbs over-penalizes the system.

An operator is performing a bare-drum calculation for a lattice-boom crawler crane. The drum has a 16-inch core diameter and accommodates 4 layers of 3/4-inch wire rope. Using the Lehrman formula, which variable most significantly reduces line pull capacity as wraps accumulate on the drum?

Answer: Increased effective drum radius reducing mechanical advantage of the hoist drum

The Lehrman formula for drum capacity accounts for the fact that as rope layers accumulate, the effective drum radius increases. Since hoist motor torque is constant (torque = force × radius), a larger effective radius means less line pull force can be produced — this is the dominant and direct mechanical relationship. Fleet angle pile-up is a rope spooling concern but does not directly reduce line pull per the Lehrman formula. Bending fatigue is a rope life issue, not a capacity formula variable. Bearing friction increase is negligible compared to the radius effect.

Under ASME B30.5, when must a Qualified Person (QP) re-evaluate a crane's load chart if the crane operates on a barge or pontoon?

Answer: When the barge list or trim causes the crane's ground bearing surface to deviate from the manufacturer's assumed level condition, typically beyond 1% grade

ASME B30.5 requires that load charts be re-evaluated by a Qualified Person when the supporting surface (in this case the barge deck) deviates from the level condition assumed in the manufacturer's load chart — the threshold is typically 1% (approximately 0.57 degrees), not 2 degrees. The standard does not mandate re-evaluation per-lift or per-jurisdiction change alone. A barge list of 2 degrees would already represent a dangerous deviation well past the 1% threshold, making that option too permissive.

A crane operator is conducting a critical lift in a rail-mounted overhead bridge crane configuration. The lift plan specifies a 'controlled load test' at 100% of the rated load before the critical pick. During the test, the operator observes 0.4 inches of vertical deflection at midspan of the bridge girder. The crane's span is 80 feet and the girder is an I-beam with a manufacturer's allowable deflection limit of L/888. Is this deflection acceptable?

Answer: Yes, because 0.4 inches is below the calculated allowable of L/888 = 1.08 inches

L/888 = (80 ft × 12 in/ft) / 888 = 960 / 888 = 1.081 inches. The observed deflection of 0.4 inches is well below this manufacturer-specified limit, so the condition is acceptable. There is no universal ASME 0.5-inch threshold — limits are span- and manufacturer-dependent. The 1/3 safety margin argument is not an ASME B30.2 requirement. Any measurable deflection is expected and normal under load; re-certification is not required unless the allowable limit is exceeded.

During a tandem lift, Crane A has a rated capacity of 150 tons at the working radius and Crane B has a rated capacity of 90 tons at its working radius. The load weighs 180 tons. The lift director has rigged the load so that Crane A carries 60% of the load and Crane B carries 40%. Which NCCCO/ASME requirement is most likely being violated?

Answer: Each crane must not be loaded beyond 75% of its rated capacity for a tandem lift without an engineered lift plan

ASME B30.5 and NCCCO tandem lift guidance require that each crane in a tandem lift be de-rated to 75% of its rated capacity unless a licensed engineer certifies an engineered lift plan permitting higher loading. Crane A: 60% of 180 tons = 108 tons; its 75% de-rated capacity = 112.5 tons — Crane A is within limit. Crane B: 40% of 180 tons = 72 tons; its 75% de-rated capacity = 67.5 tons — Crane B is OVER its de-rated limit. The load need not equal the smallest crane's capacity alone. Equal distribution is not required. There is no 'combined de-rating of 25% on the sum' rule in ASME B30.5.

An operator is working near a 345 kV transmission line. The employer has obtained written evidence that the utility has de-energized and visibly grounded the line. Under OSHA 1926.1408/1410, what is the minimum approach distance the operator must maintain?

Answer: No minimum electrical clearance is required, but mechanical clearance must be maintained to prevent physical contact

Under OSHA 1926.1408(f)(1), when the utility owner/operator has confirmed in writing that the power line has been de-energized and visibly grounded at the worksite, the electrical clearance requirement is eliminated — the crane need only maintain clearance sufficient to prevent physical/mechanical contact with the line and its grounding hardware. The 10-foot default applies to energized lines under 50 kV. The 20-foot and 25-foot figures apply to energized high-voltage lines. Once a line is properly de-energized and grounded per OSHA requirements, those electrical buffer distances no longer apply.