An operator is planning a tandem lift where two cranes will simultaneously hoist a pre-fabricated concrete beam weighing 80 tonnes. Crane A has a capacity of 50 tonnes at the required radius, and Crane B has a capacity of 60 tonnes at the required radius. What is the minimum percentage of the load that Crane A must be capable of lifting independently for this tandem lift to be considered safe and within typical planning guidelines?

Question: An operator is planning a tandem lift where two cranes will simultaneously hoist a pre-fabricated concrete beam weighing 80 tonnes. Crane A has a capacity of 50 tonnes at the required radius, and Crane B has a capacity of 60 tonnes at the required radius. What is the minimum percentage of the load that Crane A must be capable of lifting independently for this tandem lift to be considered safe and within typical planning guidelines?

Answer options:

• 40%
• 50% ✅ 60%
• 70%

Correct answer: 60%

Explanation: For tandem lifts, a common industry practice (e.g., CSA Z150) suggests that each crane should be independently capable of supporting at least 60% of the total load to account for dynamic loading and load distribution imbalances. In this case, 60% of 80 tonnes is 48 tonnes. Since Crane A's capacity is 50 tonnes, it meets this minimum threshold (50 tonnes / 80 tonnes = 62.5%).