NCCCO Maintenance and Troubleshooting 1 — Questions and Answers
Question 1: When inspecting wire rope on a lattice boom crane, what condition requires immediate removal from service per ASME B30.5?
- Six randomly distributed broken wires in one rope lay, or three broken wires in one strand in one lay (Correct answer)
- Any single broken wire regardless of location
- More than 12 broken wires in any 10-foot section
- Surface corrosion affecting more than 50% of the rope diameter
Correct answer: Six randomly distributed broken wires in one rope lay, or three broken wires in one strand in one lay
ASME B30.5-5.4.3 specifies that wire rope must be replaced if it has six or more randomly distributed broken wires in one rope lay, or three or more broken wires in one strand in one lay.
ASME B30.5 removal-from-service criteria for wire rope include: (1) six randomly distributed broken wires in one lay length, (2) three broken wires in any one strand within one lay, (3) kinking, crushing, bird-caging or any other damage distorting the rope structure, (4) evidence of heat damage, (5) significant corrosion, or (6) reduction in diameter exceeding specified limits.
Question 2: A hydraulic mobile crane's boom drifts down slowly when holding a suspended load with no commands given. What is the most likely cause?
- Internal leakage in the boom cylinder or holding valve (Correct answer)
- Excessive counterweight
- Overloaded hoist drum brakes
- A faulty anti-two-block switch
Correct answer: Internal leakage in the boom cylinder or holding valve
Slow boom drift under load with no operator input indicates hydraulic fluid bypassing internally through a worn cylinder seal or a holding valve (load-holding valve/counterbalance valve) that is not seating properly.
Boom drift is a serious condition under ASME B30.5 maintenance criteria. The holding valve (counterbalance or load-holding valve) is designed to prevent boom movement without active hydraulic command. Internal cylinder seal wear or a damaged holding valve allows fluid to bypass, causing drift. The crane must be taken out of service until the hydraulic circuit is repaired and tested.
Question 3: Which lubrication point on a mobile crane requires consistent attention during maintenance?
- Wire rope and sheaves, which require lubrication per manufacturer intervals or at minimum monthly under ASME B30.5 (Correct answer)
- Engine air filter housing O-rings
- Cab door hinges and window seals
- Outrigger pad rubber surfaces
Correct answer: Wire rope and sheaves, which require lubrication per manufacturer intervals or at minimum monthly under ASME B30.5
Wire rope and sheave lubrication is critical to prevent internal corrosion and wear. ASME B30.5 and manufacturer requirements specify regular re-lubrication of running ropes and sheave bearings.
Wire rope loses internal lubricant through use and weathering. ASME B30.5-5.4.2 requires that wire rope be lubricated at intervals recommended by the rope manufacturer. Sheave bearings must also be greased per crane manufacturer schedules. Dry wire rope experiences accelerated fatigue wire breaks and corrosion, reducing its rated capacity prematurely.
Question 4: During troubleshooting, an operator notices the crane's load moment indicator (LMI) is reading significantly less than the actual calculated load. What hazard does this create?
- The operator may believe there is more remaining capacity than actually exists, leading to overloading (Correct answer)
- The LMI alarm will activate too early, unnecessarily stopping lifts
- The anti-two-block device will be disabled automatically
- Swing speed will increase beyond design limits
Correct answer: The operator may believe there is more remaining capacity than actually exists, leading to overloading
If the LMI under-reads actual load, the system will not alarm at the true capacity limit. The operator may continue to add load beyond safe limits without warning, creating an overload and tip-over risk.
LMI systems compare measured load to rated capacity and alarm before the limit is reached. An under-reading LMI is more dangerous than an over-reading one because it fails to warn the operator at the true capacity threshold. Per OSHA 1926.1416(d)(1), cranes with malfunctioning safety devices must be taken out of service or the device repaired before operations continue.
Question 5: A crane's swing brake is not holding the load from rotating when power is removed. According to ASME B30.5, what is the correct action?
- Remove the crane from service immediately — a failed swing brake requires repair before further use (Correct answer)
- Continue operations but limit swing to 180 degrees maximum
- Manually hold the swing lever in neutral at all times
- Reduce all lifts to 50% of rated capacity
Correct answer: Remove the crane from service immediately — a failed swing brake requires repair before further use
A swing brake that fails to hold is a deficiency under ASME B30.5 frequent inspection criteria. The crane must be removed from service until the brake is repaired and properly tested.
ASME B30.5-5.2.2 requires that all brakes hold properly. The swing brake prevents uncontrolled rotation of the upper works, which could cause the load to swing into workers or structures. A failed swing brake is categorized as a condition that requires removing the crane from service and notifying the designated person responsible for equipment.
Question 6: What is the purpose of a periodic inspection on a mobile crane, and how often must it occur per ASME B30.5?
- A thorough examination of structural and mechanical components performed at 1-to-12 month intervals based on usage severity (Correct answer)
- A quick walkaround performed at the start of each shift
- A government-required inspection conducted every 5 years by a licensed inspector
- An operator self-certification submitted to OSHA annually
Correct answer: A thorough examination of structural and mechanical components performed at 1-to-12 month intervals based on usage severity
ASME B30.5-5.2.3 defines periodic inspections as covering structural members, fasteners, sheaves, drums, bearings, hooks, and all safety devices at intervals of 1 to 12 months, or as recommended by a qualified person based on usage.
Per ASME B30.5-5.2.3, periodic inspections examine components not easily visible during daily checks: boom sections for cracks and deformation, wire rope end connections, sheave and drum groove wear, holding brakes, outrigger cylinders, and all safety devices. Intervals range from 1 month (severe service) to 12 months (infrequent use), determined by a qualified person.
NCCCO Maintenance and Troubleshooting 1
When inspecting wire rope on a lattice boom crane, what condition requires immediate removal from service per ASME B30.5?