A project requires lifting a 12-tonne (26,455 lb) structural steel beam using a 100-tonne (220,000 lb) capacity mobile crane. The crane operator determines from the load chart that at the required radius of 20 metres (66 ft) and boom length of 30 metres (98 ft), the crane's gross rated capacity is 15 tonnes (33,070 lb). However, the lift plan specifies a net load capacity of 80% due to site-specific conditions and wind. If the rigging tackle (sling, shackles, spreader bar) weighs 800 kg (1,764 lb), what is the maximum net load that can be safely lifted, considering this derating, and can the steel beam be lifted?

Question: A project requires lifting a 12-tonne (26,455 lb) structural steel beam using a 100-tonne (220,000 lb) capacity mobile crane. The crane operator determines from the load chart that at the required radius of 20 metres (66 ft) and boom length of 30 metres (98 ft), the crane's gross rated capacity is 15 tonnes (33,070 lb). However, the lift plan specifies a net load capacity of 80% due to site-specific conditions and wind. If the rigging tackle (sling, shackles, spreader bar) weighs 800 kg (1,764 lb), what is the maximum net load that can be safely lifted, considering this derating, and can the steel beam be lifted?

Answer options:

• Maximum net load: 12,000 kg. Yes, the beam can be lifted. ✅ Maximum net load: 11,200 kg. No, the beam cannot be lifted.
• Maximum net load: 11,200 kg. Yes, the beam can be lifted.
• Maximum net load: 12,000 kg. No, the beam cannot be lifted.

Correct answer: Maximum net load: 11,200 kg. No, the beam cannot be lifted.

Explanation: First, calculate the derated gross capacity: 15,000 kg * 80% = 12,000 kg. Then, subtract the rigging tackle weight to find the maximum net load: 12,000 kg - 800 kg = 11,200 kg. Since the beam weighs 12,000 kg, which is greater than the maximum allowable net load of 11,200 kg, the beam cannot be lifted under these specific conditions.