CET Roping & Counterweight Systems Flashcards

What type of wire rope construction is most commonly used for elevator hoist ropes?

Answer: 8×19 Seale, independent wire rope core (IWRC)

8×19 Seale construction with IWRC is the most common elevator hoist rope, offering a good balance of flexibility, strength, and fatigue resistance.

What is the purpose of the counterweight guide rails?

Answer: Keep the counterweight traveling in a straight vertical path within the hoistway

Counterweight guide rails constrain the counterweight to a precise vertical path, preventing lateral movement that could cause contact with hoistway walls or the car.

What is 'rope creep' in a traction elevator system?

Answer: Slow slippage of hoist ropes relative to the drive sheave under traction

Rope creep is the slow, controlled slippage of hoist ropes relative to the drive sheave, which occurs due to the difference in tension between the car and counterweight sides.

Which condition would most likely cause loss of traction in a traction elevator?

Answer: Overloaded car creating too large a traction ratio between loaded and unloaded rope sides

An overloaded car creates an extreme tension ratio between the car-side and counterweight-side ropes, exceeding the traction limit and causing the ropes to slip on the sheave.

What is the purpose of 'compensating ropes' or 'compensating chains' in a tall-rise traction elevator?

Answer: Compensate for the weight imbalance caused by hoist rope weight shifting as the car travels

Compensating ropes or chains loop under the car and counterweight to compensate for the changing weight of hoist ropes as the car moves up and down in high-rise applications.

What is the minimum bend ratio (D/d ratio) required for elevator hoist rope sheaves under ASME A17.1?

Answer: 60:1

ASME A17.1 requires a minimum sheave diameter to rope diameter (D/d) ratio of 40:1 for traction elevator drive sheaves to limit rope fatigue from bending.