Safety Devices: Traction Elevator Requirements — Elevator Mechanic (pre-apprentice)

Objective. Students will locate, identify, and describe the code-mandated function and trip conditions of every primary safety device on a traction elevator—governor, car safety, counterweight safety, buffers, and terminal stopping devices—citing the applicable A17.1 rule for each.

Overview: Why Safety Devices Matter

A traction elevator suspends a loaded car on steel ropes driven by an electric machine. If any part of that system fails—rope, brake, controller—the car can move uncontrolled at dangerous speed. ASME A17.1, Safety Code for Elevators and Escalators, is the foundation document that specifies every device required to prevent injury in that event. As a pre-apprentice, you must be able to locate, name, and explain the required function of each primary safety device before you ever touch an elevator in service.

Before any hands-on lab work, the elevator must be placed under full lockout/tagout (LOTO) in accordance with OSHA energy-control procedures. Each student applies a personal lock to the hasp at the main disconnect; no lock is removed until that student is clear of all pinch points, pit, and overhead. Wear required PPE—hard hat, safety glasses, and steel-toed footwear—throughout.

The Governor

The governor is a centrifugal speed-sensing device mounted in the machine room or overhead. As the governor sheave spins with the car, weighted flyweights respond to rotational speed. A17.1 requires the governor to perform two distinct actions as car speed rises above rated speed. First, at a set overspeed threshold, it must activate an electrical safety switch that cuts power to the driving machine and applies the brake. If the car continues to accelerate, the governor reaches its tripping speed, mechanically grips the governor rope, and initiates the car safety. The code specifies maximum permissible tripping speeds based on rated car speed; these limits ensure the car safety can stop the car within an acceptable distance. The governor must be sealed after adjustment so that the trip speed cannot be changed without breaking the seal.

Car Safety

The car safety (also called the car safeties or safety gear) is mounted on the car frame. When the governor trips, it pulls the governor rope taut, which lifts the governor rope gripper or actuating linkage, driving the safety jaws into the guide rails. The wedging or roller action clamps the car to the rails and brings it to a controlled stop. A17.1 distinguishes between instantaneous safeties (acceptable only at low rated speeds) and progressive or flexible-guide-clamp safeties, which apply stopping force gradually and are required above certain rated speeds. The distinction matters because instantaneous safeties can produce deceleration forces that injure passengers at higher speeds. The car safety must be capable of stopping and holding the car with rated load at governor tripping speed.

Counterweight Safety

When ropes fail, the counterweight can fall into the pit just as the car would. A17.1 requires a counterweight safety when the space below the runway is occupied by areas accessible to persons. The counterweight safety works on the same principle as the car safety—a governor (sometimes the same unit, sometimes a separate one) trips and drives jaws into the guide rails to stop the descending counterweight. Students should confirm whether the training elevator has a counterweight governor and where it is mounted.

Buffers

Buffers are energy-absorbing devices installed in the pit under the car and under the counterweight. They are the last line of defense if the car or counterweight travels past the terminal landings. A17.1 recognizes two types:

Spring buffers store and release energy. They are permitted only up to a limited rated speed.
Oil (hydraulic) buffers dissipate energy through fluid restriction. They are required above the speed threshold where spring buffers are no longer permitted.

The code specifies the minimum stroke of oil buffers based on rated speed, ensuring enough travel to decelerate the car within acceptable g-forces. In the lab, you will check that each buffer is fully extended (not compressed or leaking) and that the oil-buffer return switch is in the normal position—a compressed oil buffer must prevent normal elevator operation until it has fully returned.

Terminal Stopping Devices

A17.1 requires multiple layers of protection against overtravel at the terminal floors:

1. Normal terminal stopping devices (often called final travel limit or terminal slowdown switches) slow the car as it approaches the top or bottom landing under normal operation.

2. Final limit switches cut power to the driving machine and brake if the car travels past the normal stopping point. These are not part of normal operation—their activation indicates a malfunction. The elevator must not resume operation until the cause is investigated.

3. Slack-rope devices (on drum machines or where applicable) detect loss of rope tension and remove power, preventing the drum from winding rope over itself or allowing the car to free-fall.

Final limit switches must be positioned so they are triggered before the car or counterweight strikes a buffer, giving the buffer work to do only after electrical means have already attempted to stop travel.

Lockout/Tagout and Tag Identification

During the Component Identification Drill, you will physically locate each device and attach a color-coded tag. The rule is simple: if the LOTO is not complete, no tag goes on any device. Verify zero energy state—no movement, no electrical potential at the controller—before entering the pit or working overhead. Each tag you attach must include the device name, its location, and the A17.1 rule that requires it. Recording the rule is not busywork; the NEIEP curriculum and NAEC CET both test whether technicians can connect a physical component to its code basis.

Putting It Together: Overspeed Sequence

Understand the cascade: (1) Car accelerates past rated speed → (2) Governor electrical switch opens, machine power cut, brake sets → (3) If car continues, governor reaches trip speed, rope gripped → (4) Car safety jaws engage rails, car stops → (5) If all else fails, car or counterweight contacts buffer. Each step has a corresponding A17.1 rule. Knowing that sequence means you can read a malfunction scenario and immediately identify which layer of protection failed and which rule was violated.

Key terms9

GovernorA centrifugal speed-sensing device that activates an electrical switch at a set overspeed and mechanically grips the governor rope at a higher trip speed to initiate the car safety.

Car Safety (Safety Gear)A mechanical device on the car frame that, when actuated by the governor, clamps the car guide rails to stop and hold the car.

Governor Tripping SpeedThe specific overspeed at which the governor mechanically grips the rope and initiates the safety; ASME A17.1 sets maximum permissible values based on rated car speed.

Progressive SafetyA car or counterweight safety that applies stopping force gradually, required at higher rated speeds to limit deceleration forces on passengers.

Oil (Hydraulic) BufferAn energy-dissipating pit device that uses fluid restriction to absorb the kinetic energy of an overspeeding car or counterweight; required above the speed limit for spring buffers.

Final Limit SwitchA terminal stopping device that removes power from the driving machine and brake if the car travels beyond the normal terminal stopping point; its activation always indicates a malfunction.

Slack-Rope DeviceA device that detects loss of tension in the hoisting ropes and removes power to prevent unsafe rope conditions or free-fall of the car.

Counterweight SafetySafety gear mounted on the counterweight frame that stops and holds the counterweight on its guide rails if the hoisting ropes fail, required when the space below the runway is accessible to persons.

Lockout/Tagout (LOTO)An OSHA-required energy-control procedure in which each worker applies a personal lock to the energy-isolating device, ensuring the elevator cannot be energized while anyone is in a hazardous position.

In class: Component identification drill: with the training elevator under lockout/tagout, students attach color-coded tags to the governor, rope gripper, car safety jaws, pit buffer, final limit switches, and slack-rope device, then record the rule that requires each component on a matching worksheet. · Function-and-failure lecture-discussion: instructor explains how each safety device activates in sequence during an overspeed or free-fall scenario; students trace the sequence on a schematic diagram and annotate which code rule establishes each device's required response speed or stopping distance. · Group scenario analysis: instructor presents three written malfunction scenarios (for example, governor rope breaks, buffer missing, final limit bypassed); student groups identify which code rules are violated, what the physical consequence would be, and what corrective action is required before the elevator may return to service.
Materials: ASME A17.1, lockout/tagout kit (personal locks, hasp, tags), color-coded identification tags, traction elevator schematic diagram, safety-device worksheet, dry-erase markers for schematic annotations
Check: Each student correctly labels and cites code rules for all six device categories on the worksheet without assistance — pass mark requires accurate identification and citation of at least five of six devices.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.