Elevator

Acceleration and Velocity

The total amount of time it takes for a traction elevator car to start, move, and stop a given amount of distance at different elevator speeds can be generalized from the table below.

A typical traction elevator accelerates at <3.5fps for <= 400fps, and >4.5fps for > 500fpm.

Speed (ft/m) vs. Height (ft)	9	10	11	12	13	14	15	20	30	10ft+
100ft/m	7.6	8.2	8.8	9.4	10.0	10.6	11.2	14.2	20.2	6.0
150ft/m	6.7	7.1	7.5	7.9	8.3	8.7	9.1	11.1	15.1	4.0
200ft/m	5.8	6.1	6.4	6.7	7.0	7.3	7.6	9.1	12.1	3.0
300ft/m	5.2	5.4	5.6	5.8	6.0	6.2	6.4	7.4	9.4	2.0
400ft/m	4.8	5.0	5.1	5.2	5.4	5.6	5.7	6.5	7.0	1.5
500ft/m			4.3	4.4	4.5	4.6	4.7	5.2	6.4	1.2
700ft/m			4.3	4.4	4.5	4.6	4.7	5.2	6.1	0.86
1000ft/m			4.3	4.4	4.5	4.6	4.7	5.2	5.8	0.6

Examples:

1. For a 300ft/m elevator to move 15 ft, it will take 6.4 seconds.
2. For 400ft/m elevator to move 150 ft, it will take 25.0 seconds.
   • The first 30 ft takes 7.0 seconds
   • The remaining 120 ft takes 18 seconds, calculated by: 120ft / 1.5 seconds/10ft = 18 seconds

Hydraulic elevators operate at a top speed of 200fpm

Basic Considerations

Definitions

Light traffic occurs when the number of people riding or requiring elevator service at one time does not exceed the number of elevators in the group. Traffic is light, for example, if there are four cars in a group and no more than four calls, either car or landing, are expected to be registered at one time.

Moderate traffic occurs when the number of people riding or seeking elevator service at a given time is such that the available elevators in a group must be shared by more than one person, and the average loading is not expected to fill any elevator beyond 50% of its capacity.

Heavy traffic occurs when the demands on the elevator system are such that the available capacity must be equalized among many passengers, and priority of service may have to be given to passengers riding in one direction over those seeking to travel in the opposite direction.

Operations

Light incoming traffic periods require at least one elevator parked at the loading lobby to receive passengers. Operation should be to respond to the highest required call and immediately return to the lobby if no other elevator is at the lobby to receive passengers.

Moderate incoming traffic periods require that all the elevators should be at the loading lobby or returning to the lobby to receive passengers. The elevator travels to the highest required call and returns immediately to the lobby. More than one elevator should be able to be loaded at the same time, and any filled car should be dispatched.

Heavy incoming traffic periods require all the aforementioned operations plus a system to give priority to lobby traffic during designated periods of working days. Service to upper-floor up and down landing calls can be temporarily denied if no car is available at the lobby for loading.

Two-way Traffic. Light two-way traffic periods require the elevators to be available throughout the building, either at rest or in motion, so that a car is either at or traveling toward the next expected call. One approach is to station elevators at various zones of the floors served and to operate them as individual units during periods of minimum demand.

Moderate two-way traffic periods require operation of all elevators in a predetermined regulated manner to minimize the waiting time for landing calls and to provide concentrated elevator service in the direction of heaviest traffic.

Heavy two-way traffic periods require that, in addition to the predetermined operation to minimize landing call waiting time, priority operations for longer waits and for potentially long-wait calls should be instituted. Means should be provided to move elevators from areas of light demand into areas of heavy directional demand. For intense situations a system that bypasses some calls to deploy elevators to floors with potential long-wait landing time should be employed.

Interfloor traffic operations include all the actions required for two-way traffic with the elevators concentrating on floors of heaviest demand. Trips to terminal floors should be restricted unless definite demands are registered for travel to those floors.

Outgoing Traffic. Light outgoing traffic periods should reduce time spent by any elevator at the unloading terminal. This is true for any outgoing situation. Elevators should return up into the building to serve down demand with travel no higher than necessary.

Moderate outgoing traffic periods require elevators to minimize time spent at the unloading landing, and bypass landing calls if the elevators are filled up to or beyond a predetermined loading.

Heavy outgoing traffic periods require all of the foregoing plus a system to restrict service to up landing calls if down landing calls are being bypassed during a predetermined time each day. In addition, some means should be provided to divide the available elevator service to minimize the possibility of lower floors being bypassed by cars filling at upper floors.

Priority should be given to outgoing traffic limited to a predesignated time at the end of a working day. A system to automatically restrict up landing call service when passengers only wishing to go down operate both up and down landing calls is often required.

Nighttime and Traffic Lulls (Off-Peak). With any Group Automatic operating system, it should be decided how the elevators will be stationed during nighttime and periods of traffic lulls, which can occur at any time during the day. As previously mentioned, this may be done by parking the elevators in zones or at other strategic locations.

Floor Zones

The Otis Elevator Company used the zone parking approach to provide the starting point for the operation of elevators during various traffic patterns. Both Otis and Westinghouse, now Schindler, as well as most manufacturers, use load-sensing devices in the cars and landing call button information to change the operation of the elevator group during certain distinct traffic patterns. For example, an absence of substantial landing call demand and filled elevators leaving the lobby are definite indications of incoming traffic activity. Conversely, a heavy down landing call demand and filled cars traveling in the down direction indicate heavy outgoing traffic.

Continued down traffic, with elevators bypassing down landing calls and down landing calls waiting beyond a predetermined time, was a signal that Westinghouse used to cause elevators to travel directly, without intermediate stopping, to down landing zones (predesignated zones consisting of two or three floors) with down landing call or calls exceeding a predetermined time. Otis formerly employed a similar strategy of distributing the elevators among the various zones or concentrating service in the zone with the heaviest demand.

Initiating the proper operations of the elevators at the proper time is a task that must be accomplished automatically. In earlier systems an attendant was required to change the mode of operation, or program, as it was known. Too often the system was set for one operation and not changed, so that when it was time to go home, the passengers had to fight elevators that had been left on “up-peak” operation. Modern systems should be completely responsive to the traffic situation. Sophisticated systems that utilize programmable microprocessors to determine where elevators can be directed to best serve the prevailing traffic are available and offer immeasurable opportunity. (pg 171)