Which device prevents contact between the load block and the boom tip?

The anti-two-blocking device is specifically designed to prevent the load block from making contact with the boom tip, a condition known as two-blocking. This situation can lead to serious accidents or damage to the crane and its load. The device works by using sensors that detect the proximity of the load block to the boom tip and will typically sound an alarm or engage a safety feature to stop the crane's operation before contact occurs.

This safety measure is critical in crane operations as it helps to avoid the risk of entanglement or structural failure of the crane due to excessive load or improper handling. The anti-two-blocking device is a vital safety feature on cranes that are used in lifting operations, ensuring operational safety and compliance with industry regulations.

In contrast to other options, the anti-tipping device is focused on preventing the crane from tipping over when lifting loads, while a signal alarm merely alerts operators but doesn’t prevent mechanical contact. Similarly, a load limit switch is designed to prevent lifting beyond a predetermined weight but does not address the issue of two-blocking. Thus, the anti-two-blocking device is the correct answer as it directly addresses the prevention of load block and boom tip contact.