Maintenance and Troubleshooting Flashcards

During a routine inspection, you discover that the load line wire rope shows 6 broken wires in one rope lay AND 4 broken wires in one strand within one rope lay. Per ASME B30.2 discard criteria, what is the correct action?

Answer: Remove the rope from service immediately — both thresholds are independently met

ASME B30.2 specifies rope must be removed from service if EITHER discard criterion is met independently: 6 or more broken wires in one rope lay, OR 3 or more broken wires in one strand within one rope lay. Here, both thresholds are exceeded (6 in a lay and 4 in a strand), so immediate removal is mandatory regardless of any averaging.

A lattice boom crane's boom hoist drum is experiencing 'creep' — the drum slowly rotates when the holding brake is applied and the hoist is stationary under load. Which component failure MOST specifically explains this symptom?

Answer: A worn or oil-contaminated boom hoist brake lining

Brake creep under static load is a direct symptom of the holding brake failing to maintain full torque — caused by worn friction lining or oil/grease contamination of the brake surface. A gearbox output shaft with play would cause backlash during movement, not static creep. The angle indicator and backstop cylinder are unrelated to drum holding capability.

A crane operator notices that the anti-two-block (ATB) device activates prematurely — the load line stops even though the hook block is still 8 feet below the sheave. After resetting, it triggers again at the same point. What is the MOST likely root cause?

Answer: The ATB weight or bail has shifted or is hanging at an angle, contacting the switch body

Premature and repeatable ATB activation at a consistent position — well before the hook actually reaches the sheave — indicates a mechanical issue with the ATB assembly itself, most commonly the weight/bail physically resting on or contacting the switch due to a bent bail, twisted mounting, or debris. An overload would trigger the load moment indicator, not the ATB. Boom radius errors affect capacity charts, not the two-block sensor. Hoist drum limit switches are a separate system.

While lubricating the slewing ring (swing bearing) on a mobile crane, you notice that the grease purging from the old fittings is grey and watery with metallic particles visible. What does this condition indicate and what is the appropriate response?

Answer: Contamination of the grease with water and metal wear debris; the bearing requires immediate inspection for raceway damage and possible replacement

Grey, watery grease with metallic particles is not a normal purge condition. Water infiltration into the bearing cavity causes rust and accelerated wear of the hardened raceways and rolling elements, producing metallic debris. This is a critical finding: the bearing must be taken out of service for detailed inspection (including rotation checks, backlash measurement, and raceway surface examination) to determine if replacement is required. Continuing operation risks catastrophic slewing ring failure.

A telescoping boom crane's boom extension fails to lock into the fully extended position. The boom extends but the locking pin indicator light never illuminates. The hydraulic system pressure is normal. Which diagnostic step should be performed FIRST?

Answer: Verify that the boom section is fully extended to the pin-hole alignment position before assuming a pin or sensor fault

Before condemning any component, first confirm that the boom section has fully stroked to the point where the locking pin holes are aligned — incomplete extension is the most common cause of pin non-engagement and a dark indicator light. Sensors and pins can only be properly evaluated after confirming correct physical alignment. Increasing hydraulic pressure beyond spec to force a pin risks structural damage, and bleeding cylinders is irrelevant if the boom simply hasn't reached full extension.

During a load test following boom structural repairs, a lattice boom crane exhibits a 'bounce' or oscillating vertical movement of the load when the hoist is stopped abruptly under a near-capacity lift. Boom angle and load weight are within rated parameters. What is the MOST likely contributing factor unique to lattice boom cranes in this scenario?

Answer: Insufficient pendant rope tension or loose lacings allowing boom elastic deflection and rebound

Lattice boom cranes rely on pendant ropes and chord lacings to maintain boom rigidity. If pendants are under-tensioned or lacings are loose following repair, the boom can deflect elastically under dynamic loading and spring back, producing vertical load oscillation (bounce) when the hoist stops suddenly. This is a structural compliance issue specific to lattice booms. Hydraulic overpressure affects speed, not post-stop bounce. The LMI does not control hoist dynamics. Wire rope modulus affects bounce but is secondary to boom structural compliance under near-capacity loads.