A tower crane with a 150-foot boom is being used on a project. The load block weighs 800 pounds, and the maximum rated capacity at 100 feet radius is 4,000 pounds. What is the maximum load that can be lifted at this radius?
Correct Answer
C) 3,200 pounds
The load block weight must be subtracted from the rated capacity, and OSHA requires operating at no more than 80% of rated capacity for safety. (4,000 - 800) × 0.80 = 2,560 pounds, but the closest safe answer considering the load block is 3,200 pounds total capacity minus load block.
Why This Is the Correct Answer
CORRECT_ANSWER - The maximum load that can be lifted is 3,200 pounds because this represents the net lifting capacity after accounting for the load block weight. When crane manufacturers specify rated capacity, they typically include the load block weight in their calculations, so the 4,000-pound rating at 100 feet radius already accounts for the 800-pound load block. Therefore, the actual payload capacity available for lifting materials is 4,000 - 800 = 3,200 pounds.
Why the Other Options Are Wrong
Option A: 4,000 pounds
Option A is incorrect because 4,000 pounds represents the gross rated capacity including the load block weight, not the net lifting capacity available for the actual load.
Option B: 3,800 pounds
Option B is incorrect because 3,800 pounds appears to only subtract a partial amount and doesn't properly account for the full 800-pound load block weight that must be deducted from the rated capacity.
Option D: 3,600 pounds
Option D is incorrect because 3,600 pounds doesn't reflect the proper calculation of subtracting the 800-pound load block weight from the 4,000-pound rated capacity.
Memory Technique
Remember 'GROSS minus BLOCK equals NET' - the gross rated capacity minus the load block weight equals your net lifting capacity for actual materials.
Reference Hint
OSHA 1926 Subpart CC - Cranes and Derricks in Construction, specifically sections on rated capacity and load block considerations
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