NCCCO Maintenance and Troubleshooting 4 — Questions and Answers
Question 1: When inspecting wire rope, what condition requires immediate removal from service?
- Six randomly distributed broken wires in one rope lay (Correct answer)
- Slight surface rust on outer wires
- Minor kinking that can be straightened by hand
- Lubrication that appears discolored
Correct answer: Six randomly distributed broken wires in one rope lay
Six or more randomly distributed broken wires in one rope lay is a disqualifying condition per ASME B30.2 standards.
Question 2: A crane's load line sheave shows excessive groove wear. What is the primary risk if it continues in service?
- Increased rope wear and potential wire damage (Correct answer)
- Reduced block weight
- Slower line speed
- Higher load capacity
Correct answer: Increased rope wear and potential wire damage
Worn sheave grooves cause accelerated wire rope wear by creating high contact stress on individual wires.
Question 3: What does a milky or foamy appearance in hydraulic fluid indicate?
- Water contamination (Correct answer)
- Normal aeration during operation
- Overheating of the pump
- Low fluid level
Correct answer: Water contamination
Milky or foamy hydraulic fluid indicates water contamination, which reduces lubrication and can cause cavitation.
Question 4: During a functional test after maintenance, the crane's swing brake does not hold on a slope. What is the most likely cause?
- Worn or improperly adjusted brake linings (Correct answer)
- Low engine RPM
- Overloaded hook block
- Loose boom pendant
Correct answer: Worn or improperly adjusted brake linings
Worn or maladjusted brake linings reduce clamping force, preventing the swing brake from holding the superstructure on a grade.
Question 5: Which lubrication point on a lattice boom crane requires grease at the most frequent interval?
- Boom pin connections (Correct answer)
- Counterweight attachment pins
- Carbody roller path
- Engine air filter housing
Correct answer: Boom pin connections
Boom pin connections experience continuous dynamic loading and must be greased most frequently to prevent galling and wear.
Question 6: A hoist drum shows spiral grooving damage. What operational condition most likely caused this?
- Rope wrap-on under load without fleet angle control (Correct answer)
- Operating in cold temperatures
- Exceeding maximum line speed
- Using undersized wire rope
Correct answer: Rope wrap-on under load without fleet angle control
Improper fleet angle during spooling causes the rope to cross-wind and dig into previously wound layers, creating spiral groove damage.
Question 7: A load moment indicator (LMI) gives an erratic reading. Which step should be performed first during troubleshooting?
- Check all sensor connections and cable integrity (Correct answer)
- Replace the display unit
- Recalibrate the system at full rated load
- Bypass the LMI and continue operations
Correct answer: Check all sensor connections and cable integrity
Loose or damaged sensor connections are the most common cause of erratic LMI readings and must be checked before replacing components.
NCCCO Maintenance and Troubleshooting 4
When inspecting wire rope, what condition requires immediate removal from service?