NCCCO - National Commission for the Certification of Crane Operators Load Moment Indicators and Safety Devices 1

Question 1

What is the primary function of an anti-two-block (ATB) device, and which crane movements does it typically arrest when activated?

Accepted Answer

It prevents the hook block from contacting the boom tip sheaves by automatically stopping hoist-up and boom-down movements

Answer

It prevents the load from swinging freely by engaging the swing brake when the load exceeds 90% capacity

Answer

It prevents crane travel while a load is suspended by locking the drive motors

Answer

It prevents the outriggers from retracting during a lift by sensing downward pressure on the pads

Question 2

How does operating a crane on an out-of-level surface most directly affect the accuracy of an LMI system?

Accepted Answer

It shifts the crane's center of gravity, increasing actual radius and causing the LMI to underestimate the load moment

Answer

It causes the LMI display screen to flicker, making readings unreliable

Answer

It trips the anti-two-block circuit prematurely because the boom angle sensor references level ground

Answer

It overloads the slew ring sensors, causing the LMI to shut down automatically

Question 3

When an LMI's audible alarm and warning light activate while a lift is in progress, the operator's FIRST required action is to:

Accepted Answer

Stop all crane motion immediately and assess the situation before any further movement

Answer

Reduce hoist speed to creep mode and continue the lift while monitoring the display

Answer

Lower the load directly to the ground without any lateral movement

Answer

Radio the rigger to attach an additional sling to redistribute the load weight

Question 4

In the load moment formula used by LMI systems, the load moment is the product of:

Accepted Answer

The gross load weight multiplied by the horizontal radius from the crane centerline to the load

Answer

The gross load weight divided by the boom length in feet

Answer

The boom angle in degrees multiplied by the rated line pull

Answer

The hoist line tension multiplied by the number of parts of line

Question 5

When calculating the total suspended load for comparison against an LMI reading, the operator must include:

Accepted Answer

The cargo weight plus the combined weight of the hook block, ball, shackles, slings, and all other below-the-hook hardware

Answer

Only the weight of the cargo being lifted, as the crane's hook block is pre-zeroed by the manufacturer

Answer

The cargo weight plus the hook block weight only, since slings are considered part of the crane's rigging system

Answer

The cargo weight multiplied by a dynamic factor of 1.25 to account for hook and rigging hardware

Question 6

If an LMI system becomes inoperative or gives clearly erroneous readings during crane operations, the operator must:

Accepted Answer

Cease operations until the LMI is repaired, or until a qualified person authorizes continuation using manual load chart procedures with appropriate precautions

Answer

Continue operations at no more than 75% of the rated capacity shown on the load chart, using personal judgment

Answer

Continue operations only for lifts in which the load weight is known exactly from certified scale tickets

Answer

Notify the employer in writing and then continue normal operations until the end of the shift