NCCCO - National Commission for the Certification of Crane Operators Tower Crane Operator Test 1 — Questions and Answers
Question 1: When a tower crane is climbing (jumping) to gain additional height, who is responsible for supervising and directing the climbing procedure?
- The general contractor's site superintendent
- A qualified and competent person designated by the crane manufacturer or erector (Correct answer)
- Any certified crane operator on site
- The local building inspector
Correct answer: A qualified and competent person designated by the crane manufacturer or erector
Climbing operations must be supervised by a qualified and competent person with specific knowledge of that crane's climbing system, as specified by the manufacturer. This ensures the procedure follows engineered sequences to prevent structural failure.
Question 2: What does the anti-two-block (ATB) device on a tower crane prevent?
- The boom from rotating beyond its rated radius
- The hook block from colliding with the boom tip or head machinery (Correct answer)
- The crane from slewing in high wind conditions
- The counterweight from shifting during hoisting
Correct answer: The hook block from colliding with the boom tip or head machinery
The anti-two-block device detects when the hook block approaches the head machinery (or boom tip) and stops the hoist before a two-block condition occurs, which could part the hoist rope and drop the load.
Question 3: On a hammerhead (top-slewing) tower crane, where is the counterweight located?
- At the base of the mast inside the concrete foundation
- On the opposite end of the jib from the hook, mounted on the counter-jib (Correct answer)
- Directly above the cab on a separate mast section
- Suspended below the slewing ring on the mast
Correct answer: On the opposite end of the jib from the hook, mounted on the counter-jib
The counterweight is mounted on the counter-jib (back mast), which extends in the opposite direction from the load-carrying jib. This balances the crane and reduces the bending moment on the mast.
Question 4: A tower crane operator receives a signal from a signal person to stop and hold a load. The operator notices the load has begun to drift due to wind. What is the correct action?
- Slowly continue the original travel path to the landing zone
- Lower the load immediately to the ground regardless of below-hook clearances
- Hold the load in position and communicate with the signal person before taking further action (Correct answer)
- Increase hoist speed to get the load to its destination faster
Correct answer: Hold the load in position and communicate with the signal person before taking further action
When a stop signal is given, the operator must hold position. Any change in condition — such as wind-induced drift — must be communicated with the signal person so the team can assess the situation and issue appropriate instructions before any further movement.
Question 5: What is the primary purpose of the load moment indicator (LMI) on a tower crane?
- To display the exact weight of the load in kilograms or pounds
- To alert the operator when the combination of load and radius approaches or exceeds the crane's rated capacity (Correct answer)
- To calculate wind speed and automatically reduce capacity in high winds
- To record all lifts in the crane's maintenance log automatically
Correct answer: To alert the operator when the combination of load and radius approaches or exceeds the crane's rated capacity
The LMI monitors the combination of load weight and working radius (the moment) and provides a warning — and in many cases an automatic cutout — before the rated load moment is exceeded, helping prevent structural overload.
Question 6: During a pre-operational inspection, a tower crane operator discovers a visible crack in a structural chord of the tower mast. What is the required action?
- Document the crack in the daily log and monitor it throughout the shift
- Apply a temporary weld repair and continue operations
- Remove the crane from service immediately and notify the competent person and/or manufacturer (Correct answer)
- Reduce the crane's rated capacity by 10% and continue operations
Correct answer: Remove the crane from service immediately and notify the competent person and/or manufacturer
Any crack in load-bearing structural members is a critical defect that must immediately take the crane out of service. Operations must not resume until a qualified engineer or the manufacturer evaluates and approves the repair, per ASME B30.3 and OSHA requirements.
NCCCO - National Commission for the Certification of Crane Operators Tower Crane Operator Test 1
When a tower crane is climbing (jumping) to gain additional height, who is responsible for supervising and directing the climbing procedure?