Traction Elevator Mechanics Flashcards
7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Traction Elevator Mechanics flashcards as text
What is the role of the machine brake in a traction elevator during normal stopping?
Answer: It holds the car stationary after the motor has stopped and the car has leveled
The machine brake is a holding brake that engages after the motor decelerates the car; it maintains position at the landing, not the primary deceleration device.
What is meant by 'contract speed' of a traction elevator?
Answer: The rated speed at which the elevator is designed and certified to operate under full load
Contract speed is the rated speed specified in the elevator contract and approved by the authority having jurisdiction, used for all safety device settings.
Why are guide rails lubricated in a traction elevator system?
Answer: To reduce friction and wear on the car and counterweight guide shoes
Lubrication of guide rails minimizes friction and wear between the guide shoes and rails, reducing noise and extending component life.
In a traction elevator, what component prevents the counterweight from rebounding excessively after a buffer impact?
Answer: Oil buffers with a controlled return stroke
Oil (hydraulic) buffers absorb impact energy and have a controlled return stroke to prevent violent rebound of the car or counterweight.
What is the purpose of the slack rope device in a traction elevator?
Answer: To stop the elevator if hoist ropes lose tension, indicating a serious fault
A slack rope switch detects loss of rope tension, which could indicate rope failure or car sitting on a buffer, and removes power from the machine.
Which factor most directly determines the sheave groove diameter's effect on rope fatigue life?
Answer: The ratio of sheave pitch diameter to rope diameter (D/d ratio)
The D/d ratio determines the bending radius the rope experiences each cycle; a higher D/d ratio means less bending stress and longer rope fatigue life.
What is the consequence of operating a traction elevator with unequal rope tensions?
Answer: Overloading of some ropes and premature wear, reducing the overall safety margin
Unequal tensions concentrate load on fewer ropes, reducing the effective safety factor and accelerating fatigue failure of the overloaded ropes.