Heavy Duty Equipment Technician (421A) — Red Seal

Performs common occupational skills

During an engine repair a technician disconnects the battery but a co-worker later energizes the starter circuit. What lockout practice would have prevented this?

1. Telling the co-worker verbally that the machine was being serviced before walking away
2. Applying a personal lock and tag to the isolation point that only the technician can remove
3. Parking the machine in a quiet corner of the shop away from main traffic
4. Removing the ignition key and keeping it loose in a shared shop key cabinet nearby

Lockout/tagout requires the worker exposed to the energy to apply their own lock and tag at the isolation point, so no one else can re-energize the circuit while that lock is in place. Verbal notice fails the moment a shift changes or someone forgets. Parking away from traffic does not isolate stored or supply energy. A key in a shared cabinet can be taken by anyone, so it provides no personal control of the energy source. Only a personal lock-and-tag controlled solely by the exposed worker guarantees the starter cannot be energized during the repair.

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
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 feeding each side
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