Technical Knowledge: Capacity Limits, Components, and Inspection
Technical Knowledge
Technical Knowledge tests the machine itself: how capacity is limited, how components fail, and what inspections and safety devices are required.
Capacity and stability
- A service truck crane is rated by structure (boom, cylinders, wire rope) and stability (tipping). The lower value governs.
- Load moment is load times radius. Increasing radius reduces capacity quickly; counterweight and outrigger footprint resist tipping.
- On-rubber capacities are lower than outrigger capacities and are not a substitute for setting outriggers.
Components and inspection
- Know the boom sections, extension cylinders, holding valves, winch, wire rope, sheaves, hook, and LMI/ATB.
- Inspect wire rope for broken wires, diameter reduction, kinks, birdcaging, corrosion, and heat damage. Remove damaged rope per ASME B30.5.
- Check hooks for latch operation, throat opening, wear, and cracks. Never repair a hook by welding.
- Holding valves and LMI/ATB are safety devices; do not bypass or adjust them outside the manufacturer’s procedure.
Worked example: A rope shows several broken wires in one lay and a sharp kink. Even if the crane still lifts, the rope must be removed from service-broken wires reduce strength, and a kink creates unequal loading. The operator tags the machine out until the rope is replaced.
Traps: assuming the LMI is a load chart, ignoring structural limits at short radius, using a hook with a missing latch, and treating a holding valve as a way to work under an unblocked boom.