NCCCO Anti-Two-Block Devices and Safety Systems 2

Question 1

What is a two-block condition on a crane and why is it dangerous?

Accepted Answer

A condition where the load block or hook assembly contacts the boom tip sheaves, which can snap the hoist rope and drop the load

Answer

A condition where two loads are lifted simultaneously, doubling the stress

Answer

A condition where the crane is blocked from slewing in two directions

Answer

A condition where two brakes are applied simultaneously

Question 2

What is the function of an anti-two-block (ATB) device on a crane?

Accepted Answer

It detects when the hook block approaches the boom tip and automatically stops the hoist to prevent two-blocking

Answer

It prevents the crane from lifting loads heavier than its rated capacity

Answer

It locks the boom in position to prevent uncontrolled lowering

Answer

It prevents two cranes from performing tandem lifts without authorization

Question 3

An operator performing a pre-shift inspection finds that the anti-two-block device's warning weight is missing. What should the operator do?

Accepted Answer

Remove the crane from service until the ATB device is repaired or replaced

Answer

Proceed with the lift but keep a close watch on the hook block position

Answer

Use the crane only for lifts below 50% capacity where two-blocking is less likely

Answer

Tie a rope to the hook block as an alternative warning system

Question 4

Which of the following crane operations is most likely to cause a two-block condition if the operator is not vigilant?

Accepted Answer

Raising the boom angle while the hook is near the top of its travel with a short rope length deployed

Answer

Lowering the boom angle while the hook is at ground level

Answer

Slewing the crane with a load near maximum radius

Answer

Extending the outriggers while a load is suspended

Question 5

What is the purpose of the dead wraps requirement on a crane hoist drum?

Accepted Answer

To maintain anchor friction on the drum so the rope does not slip off when the hook is at its lowest point

Answer

To ensure the ATB device has enough rope to trigger before the block reaches the tip

Answer

To provide extra rope for emergency lowering beyond normal travel

Answer

To prevent the hoist drum from rotating backward under load

Question 6

Under ASME B30.5, how often must anti-two-block devices be tested?

Accepted Answer

Before each shift in which the crane will be used

Answer

Once per year during the annual inspection

Answer

Every 500 operating hours

Answer

Only after maintenance or repair