What condition occurs when the tower load block or hook assembly contacts the upper limit?

Two-blocking is a condition that occurs when the load block or hook assembly makes contact with the upper limit of the crane's vertical travel. This situation can result in dangerous conditions, including potential damage to the crane and its components, as well as risk to the operator and other personnel on site.

In crane operations, the concept of two-blocking is critical; it indicates that the crane is at its maximum elevation and can no longer lift the load safely. The hook or block is designed to travel freely within a specified range, and reaching the upper limit may trigger safety systems to prevent further lift, as it signifies that the way the load is being handled is not compliant with safe operational standards.

Understanding two-blocking is essential for crane operators, as it emphasizes the importance of being aware of the mechanisms within the crane operation. It reinforces the need for regular inspections and proper training to avoid this condition, ensuring safe lifting practices.