NCCCO Load Moment Indicators and Safety Devices 4 — Questions and Answers
Question 1: During a lift, the LMI alarm sounds and crane motion stops. The operator believes the load is within the chart. What is the MOST likely cause?
- The load chart data is wrong
- The boom configuration entered does not match actual rigging (Correct answer)
- The LMI computer has overheated
- The load is lighter than estimated
Correct answer: The boom configuration entered does not match actual rigging
A mismatch between the boom length or jib configuration entered into the LMI and the actual crane setup is the most common cause of unexpected capacity limit alarms.
Question 2: Which ASME B30 standard directly governs the use of rated capacity limiters on mobile cranes?
- ASME B30.2
- ASME B30.5 (Correct answer)
- ASME B30.22
- ASME B30.9
Correct answer: ASME B30.5
ASME B30.5 covers mobile and locomotive cranes and includes requirements for rated capacity limiters and load moment indicators.
Question 3: A load line pull indicator shows 18,000 lb with two parts of line reeved. What is the approximate gross load on the hook?
- 9,000 lb
- 18,000 lb
- 36,000 lb (Correct answer)
- 72,000 lb
Correct answer: 36,000 lb
With two parts of line, the gross load equals the line pull multiplied by the number of parts, so 18,000 lb × 2 = 36,000 lb.
Question 4: Why must the operator deduct the weight of the hook block and rigging when using an LMI to assess available net load capacity?
- The LMI adds hook block weight automatically in some models
- Hook block and rigging are part of the gross load but not the net payload (Correct answer)
- Regulations require separate tracking of rigging costs
- The LMI sensor cannot detect the hook block
Correct answer: Hook block and rigging are part of the gross load but not the net payload
The LMI measures gross load including the hook block and all rigging; the net payload capacity is reduced by those weights, so they must be subtracted to know how much actual cargo can be lifted.
Question 5: When operating a crane with a luffing jib, which additional LMI input is critical compared to a fixed-angle jib?
- Jib temperature reading
- Luffing jib angle (Correct answer)
- Counterweight position only
- Swing speed
Correct answer: Luffing jib angle
A luffing jib changes the working radius as its angle changes, so the LMI must receive the current jib angle to calculate the correct load moment and rated capacity.
Question 6: An operator notices the LMI display shows dashes or an error code. The SAFEST immediate action is to:
- Estimate the load and continue operating carefully
- Suspend all lifting operations until the fault is resolved (Correct answer)
- Reset the unit by cycling crane power and continue
- Reduce all loads by 10% and continue
Correct answer: Suspend all lifting operations until the fault is resolved
When the LMI displays a fault or is non-functional, lifting operations must be suspended because the system cannot verify that loads are within rated capacity.
Question 7: Which of the following best describes the purpose of a load chart in relation to an LMI?
- The load chart replaces the need for an LMI on modern cranes
- The LMI uses load chart data programmed into its computer to determine rated capacity for current conditions (Correct answer)
- The load chart is only used when the LMI is malfunctioning
- Load charts and LMIs are independent systems with no connection
Correct answer: The LMI uses load chart data programmed into its computer to determine rated capacity for current conditions
The LMI's computer is programmed with the crane's load chart data and uses current sensor inputs (radius, boom length, angle) to look up the rated capacity applicable to those conditions.
NCCCO Load Moment Indicators and Safety Devices 4
During a lift, the LMI alarm sounds and crane motion stops.
The operator believes the load is within the chart.
What is the MOST likely cause?