Selection of Lift

Table of Contents

Classification of Lifts

The lifts are classifies based on usage, speed and motor drive as below:

  • USAGE:

    1. Goods Lift.
    2. Passenger Lift.
    3. Service Lift.
    4. Hospital Lift.

  • SPEED:

    1. Slow speed, v < 1.0 m/s.
    2. High speed, v > 1.0 m/s.

  • MOTOR DRIVE:

    1. Geared.
    2. Gearless.

Selection of Lifts

For selection of a Passenger lift, following factors are considered:

  1. Quantity of service: It is a measure of passenger carrying capacity during 5 minutes peak period of day and is also known as passenger handling capacity (H). Following is the criterion followed:

    • 10 - 15 % for diversified tenancy buildings.
    • 15 - 20 % for single purpose occupancy.
    • 7.5 % for residential building.

  • Quality of service: Generally measured by passenger waiting time during peak period, and is classified as follows:

    Waiting TimeQualityNo of floorSpeed
    20 - 25 sExcellent  
    30 - 35 sGood4 - 50.5 to 0.75 m/s
    35 - 40 sFair6 - 120.75 to 1.5 m/s
    45 sPoor13 - 20More than 1.5 m/s
    More than 45 sUnsatisfactory  

    Note

    For residential buildings, longer intervals upto 90 seconds are permissible.

  • Determination of no. & capacity: The capacity calculation is done as in the procedure and example outlined below. The various terms associated with the Lift operation are:

    1. Total travel of lift: Total travel of lift from ground to last floor.

    2. Round trip time: Total time taken by the lift to pick up the passenger to the capacity from ground floor, unloading them at various floors and come back to ground floor. It includes:

      1. Time required for passengers to enter at ground floor (i) - 3 seconds.
      2. Exit of passengers at each discharge (ii) - (F-1) × 2 sec.
      3. Door closing time (iii) - F × 2 seconds.
      4. Door opening time (iv) - F × 2 seconds.
      5. Stopping and leveling time (v) - F × 2 seconds.
      6. Acceleration period (vi) - 10% of (i + ii + iii + iv).
      7. Total travel time (vii) - (2 × maximum distance traveled in one direction) / speed of lift.

      Then Round Trip Time : (i) + (ii) + (iii) + (iv) + (v) + (vi) + (vii).

      Note

      F is the number of floors including ground.

    3. Handling Capacity (H): It is a measure of how many number of passenger in percentage can be handled within 5 minutes of the peak hours.

                  H  = (300 × Pc × 100) / (T × Q).
          Where,
          Pc  =  Average no. of passengers carried in a car = 80 % of P.
          P = Capacity of lift e.g. 10, 13 etc.
          T  = Waiting interval = RTT / n.
          n = number of lifts.
          Q = Total number of passengers to whom service of lift is provided.
          

      Design Criterion:
          Residential Building : 5/6 persons per flat.
          Office Building : 100 ft²/person.
          Technical Building : 400 ft²/person.
          Note: Weight of a person is considered to be 68 kg.

      Example:
          G + 3 technical building, floor height 5 m.
          4th to 8th floor for administrative purpose, floor height 4 m.
          Area of each floor = 1500 m² ≈ 15,000 ft².

          Let lift capacity is 10 persons (P = 10) and speed is 1.5 m/s (v).
          Total travel of lift = 4 × 5 + 5 × 4 = 40 m.
          Number of persons (Q) = 4 × 15 000 / 400 + 5 × 15 000 / 100 = 900.
          RTT = 3 + 8 × 2 + (9 × 2) × 3 + 0.1 (3 + 16 + 36) + 2 × 40 / 1.5 = 145 seconds.
          
          So far n = 4, T = 36 seconds and H = 7.40 %.
          

  • Comparison of lifts: Comparison of lifts is given in the table below:

    Comparison of Lifts
    Single Speed LiftTwo Speed LiftVariable Voltage LiftGearless Lift
    Residential BuildingsOffice and Telephone ExchangesOffice and Telephone ExchangesHigh Rise Buildings
    Up to 5 floors5 to 12 floors5 to 15 floorsAbove 15 floors
    0.3 to 0.65 m/s0.75 to 1.0 m/s1.0 to 1.5 m/s1.5 to 2.5 m/s
    Power door not advisablePower door recommendedPower door recommendedPower door recommended
    Single call control or semi-dual push button controlSelective and collectiveSelective and collectiveSelective and collective
    Automatic rescue device is not possibleAutomatic rescue device is possibleAutomatic rescue device is possibleAutomatic rescue device is possible
    Fireman switch can be providedFireman switch can be providedFireman switch can be providedFireman switch can be provided

  • Typical Dimensions of Lift: Dimension of lift in mm for speed upto 1.5 m/s. (All dimensions are with reference to plan of machine room given below)

    Typical Dimensions of Lift
    CapacityCapacity (kg)ABCDE
    04-1100780 19001300800
    064081100100019001600800
    085441300110019001900800
    106801350130019002100800
    138852000110025001900900
    16108820001300250021001000
    20136020001550250024001000
    Goods (Telephone Exchange)300015004000250045001500 vertical bi-parting door

    Trap Door : 1500 × 750 / 1500 × 1000 with a hook of 1500 kg capacity in center for passenger lift and 1950 × 1150mm with a hook of 3000 kg for goods lift.

     Clearance between machine room and last floor served:
          = 4800 mm for speed upto 1.5 m/s.
           = 5600 mm for speed more than 1.5 m/s.

     Lift pit height:
           = 1600 mm for speeds upto 1.5 m/s.
           = 2600 mm for speeds more than 1.5 m/s.
    Width and depth same as lift well.

    • Relevant IS

    IS 3534 : 1976 - Dimensions of Lift.

    IS 4666 : 1968 - Specifications for passenger and goods Lift.

    IS 1860 : 1968 - Operation, Installation and Maintenance.

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