Mechanical and Electrical Systems Installation and Maintenance
Traction versus hydraulic fundamentals
Traction systems use a sheave, ropes, and counterweight; hydraulic systems use a plunger, cylinder, and power unit. Know the components and their failure modes: rope wear and equalization, sheave grooving, brake adjustment, and traction loss on the traction side; valve adjustment, oil level and temperature, packing, and jack alignment on the hydraulic side. Trap questions mix subsystems, such as asking about a rupture valve on a traction elevator.
Electrical power and control
Understand mainline disconnect location and labeling, branch-circuit protection, motor overload protection, and the difference between the power circuit and the low-voltage control circuit. Know that the disconnect must be lockable and within sight of the machine, and that control wiring is protected separately. Traps include confusing the mainline disconnect with a light-and-receptacle circuit, or assuming a GFCI requirement applies inside the hoistway where code instead requires specific protection.
Ropes, brakes, and governors
Rope safety factors, minimum number of ropes, and retirement criteria are frequent topics. Brakes must be capable of holding rated load; the governor and safeties must be matched to rated speed. A governor set for the wrong tripping speed is a classic maintenance error. Remember that safeties are speed- or direction-actuated and that their type must suit the application.
Worked example
A car is leveling poorly and the machine room is warm. Rule of thumb: check the brake first for drag and adjustment, then verify rope tension equalization, then review drive parameters. Thermal drift in the controller is a plausible cause but should be confirmed, not assumed.
Maintenance practice
Follow the manufacturer's instructions and a documented maintenance control program. Record lubrication, rope inspection, and safety-device testing. The trap is treating a maintenance control program as optional paperwork; it is a code requirement and an inspection item.