National Commission for the Certification of Crane Operators (NCCCO) Mobile Crane Practice Exam

Which of the following is classified as duty cycle work?

1. Pile-driving

2. Setting trusses

3. Clam-shell digging

4. Unloading trucks

The correct answer is: Clam-shell digging

Duty cycle work is characterized by tasks that involve repeated lifts, lowerings, or movements as part of a cyclical operation, often requiring the crane to perform a specific cycle of actions rather than simply lifting and moving loads from one place to another. Clam-shell digging fits this description perfectly, as it involves the crane repeatedly cycling through the process of digging into the ground, lifting dirt, and then releasing it at another location. In this context, pile-driving involves driving piles into the ground using a hammer action, which is less of a cyclical operation and more focused on repetitive impact. Setting trusses involves placing beams or girders, typically requiring more straightforward lifting rather than a cycle of actions. Unloading trucks generally consists of lifting and moving cargo but lacks the repetitive, cyclic nature that defines duty cycle work. Therefore, clam-shell digging stands out as the clear example of duty cycle work due to its repetitive motion and operational characteristics.