Heavy Duty Equipment Technician (Red Seal)

Performs common occupational skills

A technician will work under a raised excavator boom to replace a hydraulic line. Which action keeps the work area safe during the repair?

1. Rely on the hydraulic hold valves alone to keep the heavy boom raised in place
2. Leave the engine running the whole time so full hydraulic pressure stays available
3. Place a single plastic warning cone beside the open hydraulic line on the floor
4. Install a mechanical boom support or lower the boom to the ground first

A raised boom held only by hydraulics can drop if a line, seal, or valve fails, so a positive mechanical support or lowering the boom fully removes the crushing hazard before anyone works beneath it. Trusting hold valves leaves the load supported by the very system being opened. Leaving the engine running maintains pressure but does nothing to protect against a sudden loss of that pressure and adds running hazards. A cone marks an area but provides no physical protection against a falling boom. Mechanical support or grounding the boom is the recognized safe practice.

RSOS 2023 | A-1.02 Maintains safe work environment

Services, diagnoses and repairs engines and supporting systems

A cylinder compression test reads low, but when a small amount of oil is added through the injector bore and the test is repeated the reading rises noticeably. What does this wet test result point to?

1. Worn rings or cylinder bore allowing combustion gas past the piston
2. A leaking head gasket carrying compression between two adjacent cylinders in the block
3. A stuck-open exhaust valve leaking compression past the seat in that one cylinder
4. A cracked cylinder head leaking compression above the combustion chamber on that cylinder

Adding oil temporarily seals the gap between the rings and the bore. If compression jumps after the oil is added, the leak path is past the piston, pointing to worn rings or a worn bore. A leaking head gasket between cylinders would not be sealed by oil on the piston, so the reading would stay low. A stuck-open valve leaks at the valve seat, which oil on the piston cannot block. A cracked head also leaks above the piston, so the wet test would show little change, making ring or bore wear the clear conclusion.

RSOS 2023 | B-5.02 Diagnoses base engines

Services, diagnoses and repairs steering, suspension, brake and undercarriage systems, and wheel assemblies

A skid-steer with separate left and right travel controls pulls hard to one side under load even though both tracks turn at equal commanded speed. Steering is achieved by varying drive output to each side. What should the technician check first?

1. The steering column universal joint for excessive play and worn needle bearings that the operator's manual lists as a service item
2. The engine power-steering belt for correct tension and signs of glazing or slip
3. Relative output of the two drive pumps or motors that feed each side of the machine
4. The front-axle tie-rod end clearance and the toe setting of the steered wheels

A skid-steer turns by sending different drive output to the left and right sides, so a pull under load points to one side delivering less power than the other, typically a weak drive pump or motor. Checking and comparing the output of each side isolates the imbalance. A skid-steer has no steering column, tie rods, or steered front axle, so those components do not exist to cause the pull. There is no separate power-steering belt because steering comes from the hydrostatic drive itself.

RSOS 2023 | C-13.02 Diagnoses steering systems