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| Mind the Gap:
Monitoring Conveyance Systems
Jim Sinopoli PE, LEED BD+C, RCCD
Smart Buildings LLC
Elevators, escalators and moving walkways are key equipment that
facilitates the movement of large numbers of people for public transit,
airports, theme parks, large buildings and other venues. Without such
equipment, people traffic and the related building and business
operations are significantly slowed.
An example of the critical role that conveyance equipment plays in the operation of these types of facilities is the London Underground, where the famous “Tube” transports over 1.1 billion passengers per year. The conveyance equipment used by the London Underground includes 426 escalators (one with a 90 foot vertical rise) and 164 lifts or elevators. This equipment runs 20 hours a day and is able to handle over 13,000 passengers per hour. With that kind of volume and traffic, extremely high reliability of the conveyance equipment is a requirement.
Counting on complaints from the pubic to notify management of an outage in conveyance equipment will not provide high availability of the systems. It requires that the equipment be monitored and managed in real time; it’s the only way of optimizing the performance and reliability of the conveyance machinery. Such monitoring can provide facility management with the current status of the equipment, as well as the capability to analyze data to discover and predict its performance, use and the need for maintenance. If a facility has hundreds of conveyance systems, it’s going to be impossible to keep 100% of them operational at any given time; a smart monitoring system can get you in the high 90% range though.
There are a few key indicators of equipment performance that help in managing the conveyance systems. The following are basic metrics, required data and applications to keep things running smoothly.
Wait Time for Elevators – People hate to wait. If there are long wait
times for passengers, there’s probably a problem with the elevators
related to the condition of the equipment or legacy controls such as
the use of relays. You need to measure wait times during peak and
off-peak times and adjust equipment use as needed. Theresa Christy, a
mathematician at Otis Elevator says that people get impatient and
agitated around 20 seconds of waiting; yes, just 20 seconds and we
start to get irritated. Studies show that people overestimate how long
they've waited in a line by 36%. Remarkably, some building owners that
have had complaints about long wait times have determined the
complaints are the result of boredom and have responded by making the
lobbies more “interesting”.
Elevator Speed - Elevator speed is important. One needs to periodically
monitor the time it takes to go from the bottom to the top floor. This
is a good metric to trend and observe whether the speed is
deteriorating, indicating issues with the equipment.
The speed of an elevator is related to the different type of elevators (hydraulic, geared-traction, gearless-traction) and how tall the building is. A three-story building using a hydraulic system elevator has a speed around 100 feet per minute; a geared-traction elevator in a 25 story building may be 700 feet per minute; real high rise buildings have speeds over 1,000 feet per minute. During the recent renovation of the Empire State Building, the speed of the elevators was increased to 20 feet per second to get more people up to the observation deck. Passengers now rise 80 floors in about 48 seconds (without seatbelts).
Temperature and Humidity in The Machine Room – This is not related to the use of the equipment but the conditions that the controller of the equipment is experiencing. Many machine rooms have inadequate ventilation; they’re too hot, too humid and the outside air is not filtered. You don’t want the elevator drive and control system to overheat, fatigue the electronic controls and possibly increase breakdowns. Even if you don’t have breakdowns you’ll shorten the life of the control equipment. These rooms need to be treated similarly to a telecommunication room with adequate cooling and air quality, and sensors for environmental and security aspects being remotely monitored.
Energy Consumption - On the initial industry push for building energy conversation and sustainability, conveyance equipment was pretty much disregarded by the “green” certifications. Generally elevator energy consumption is about 5-10% of total energy consumption for a “typical” five to 30 floor building, modest compared to HVAC and lighting systems but still significant. In transit organizations and airports where you have hundreds of individual conveyance units, one would expect that percentage to be considerably higher. Organizations need to sub meter the power provided to the conveyance equipment; this allows for visibility not only into the energy consumption of the equipment but also its performance. The energy data can be rolled up into an enterprise energy management system and will provide some granularity to overall energy consumption of the organization.
Use Video Cameras – It may seem odd to use video cameras to capture
activity of conveyance equipment but their use has two benefits. One is
that large transit organizations or airports may be liable for
accidents involving passengers using the conveyance equipment. Video
provides a record of what exactly happened to cause the accident and
helps in determining any liability. The second benefit is that video
can also help in managing the performance of the equipment. If the
equipment stops or has a fault, video before and after the event can be
used to help diagnose the problem.
Relevant Conveyance Data - The data that can be acquired will be
limited by the configuration of the controller. Controllers for
conveyance equipment are Programmable Logic Controllers (PLCs) and are
configured using modules for different aspects of the equipment. Alarms
would of course be a top monitoring priority. Here’s some basic
(non-exhaustive) data that should also be collected:
Acquiring relevant data from the conveyance equipment is one thing. Transforming the data into useful information is another. It involves identifying individuals or groups within the organization that would be interested in the information, what their key performance indicators are, and displaying the information in a way that a user can perceive the information, comprehend its importance, and project what needs to be done based on the information. Typical monitoring applications include:
Once you appreciate the role of conveyance equipment in building
operations, the monitoring of the equipment will be critical in
improving building performance.
For more information, write us at firstname.lastname@example.org
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