NCCCO Tower Crane Operator 2

Question 1

What is the function of the tower crane's out-of-service storm position?

Accepted Answer

A configuration where the jib is free to weathervane (rotate freely) into the wind, minimizing wind load on the structure during storms when the crane is unattended

Answer

The out-of-service (weathervaning) position unlocks the slewing mechanism so the jib can rotate freely into the wind, aligning with wind direction and minimizing the wind force and overturning moment on the crane structure.

Question 2

What is the deceleration distance and why is it important for tower crane load placement accuracy?

Accepted Answer

The distance a load travels after the operator begins stopping crane motion, due to load inertia and hoist/slew braking characteristics

Answer

Deceleration distance is the distance a load continues moving after the operator initiates stopping, due to the load's momentum; understanding this characteristic is essential for accurate load placement without abrupt stops that create shock loads.

Question 3

What is the significance of a tower crane's 'maximum out-of-service wind speed' versus 'maximum in-service wind speed'?

Accepted Answer

In-service wind speed limit is much lower because the crane is actively loaded; out-of-service limit is higher because the jib is free to weathervane without load

Answer

In-service wind limits are lower because the loaded crane cannot weathervane freely and carries additional load-induced stresses; out-of-service limits are higher because the freely weathervaning unloaded jib experiences much lower wind forces.

Question 4

What is the maximum trolley travel capacity variation that can occur on a hammerhead tower crane as the trolley moves from minimum to maximum radius?

Accepted Answer

Rated capacity decreases significantly as the trolley moves to greater radii, with maximum capacity at minimum radius

Answer

Tower crane rated capacity decreases dramatically as the trolley moves to greater radii due to increasing load moment, with maximum capacity at minimum radius and minimum capacity at maximum radius.

Question 5

What is a luffing jib tower crane and how does its operation differ from a hammerhead crane?

Accepted Answer

A luffing jib crane has a jib that can be raised and lowered (luffed) to change the working radius, rather than using a trolley to move the load along a fixed horizontal jib

Answer

A luffing jib tower crane changes working radius by raising or lowering the jib angle (luffing), making it suitable for confined sites where a horizontal jib would swing over adjacent buildings or restricted airspace.

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

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

NCCCO Tower Crane Operator 2