Topic 3 Lift And Escalators

Question 1

What is Round Trip Time (RTT)?

Answer 1

RTT is the time taken by the lift in seconds to go from the first storey to the highest floor including the probable number of stops and back down to the first storey

Question 2

Factors affecting RTT

Answer 2

1. Car speed - The speed of the lift car in m/s, the higher the speed the shorter the RTT
2. Speed of door operation - The lower the speed of the lift door, the longer the RTT.
3. Travel distance - The higher the building, the longer the travel distance for the car, the longer the RTT
4. Number of stops - Lift with express floors have shorter RTT
5. Plan shape of car - Rectangular car shape with the door on the longer side result in shorter RTT

Question 3

What is zoning of lifts

Answer 3

It means that there is different groups of lifts serving certain floors only

Question 4

Advantages of zoning

Answer 4

1. Reduce the time taken to reach a destination
2. Reduce power consumption
3. Reduction in hardware
4. Improve handling capacity

Question 5

Disadvantages of zoning

Answer 5

1. Increases waiting time
2. With fewer lifts in a group, the reliability of the system is affected

Question 6

Safety features of lifts

Answer 6

1. Overspeed governor - When the speed of the lift exceeds the desired level, the governor opens a safety switch that cuts off the power and operates the brake. Safety jaws are released to grip the car to the rails, stopping the car in its downward motion
2. Over travel protection - Limit switches are located at the upper and lower ends of the guide rails. When a car moves past the top of the bottom landing, it will trip the limit switches that cut off the power, applying the brakes
3. Lift homing device - In the event of an activated fire alarm system, all lifts will automatically be brought down to the designated floor

Question 7

Safety features of escalators

Answer 7

1. Vertical deflector plate installed at intersection of criss-cross escalators
2. Emergency stop button
3. Yellow line marker

Question 8

Components of an escalator

Answer 8

1. Bottom section houses the step return idler sprockets, step chain, safety switches, and curve section of the track
2. Centre section carries the straight sections of the track which connect the upper and lower curved sections
3. Top section contains the motor, driving sprockets, electrical controller and emergency brake