There are approximately 22,000 elevators and moving conveyances in the city of Chicago—and that number almost doubles when you add in the surrounding communities in Illinois. A great number of these elevators are in condominiums and it’s vital that those in charge understand the codes and maintenance that is required to keep them running smoothly.
Understanding the Differences
There are two basic kinds of passenger elevators used throughout Chicago’s residential buildings: traction and hydraulic. The latter is operated by means of a hydraulic ram, consisting of a piston mounted below the elevator inside a hollow cylinder and adjoined to an electric pump motor. The elevator rises when a liquid substance—usually oil—is pumped into the cylinder. To lower the elevator, the liquid is released from the cylinder by way of a valve.
The more expensive traction elevators are hoisted by a set of four to eight cables that are threaded over a grooved pulley known as the sheave at the top of the shaft and affixed to a counterweight that rises when the elevator descends, and vice versa. The sheave is turned by an electric motor; in gearless traction elevators, the motor is directly attached to the sheave, and in geared traction models, the motor is engaged to a gear train that turns the sheave. Since the counterweight weighs about as much as the elevator when filled to about 40 percent capacity, a traction elevator takes relatively little energy to operate.
“As technology goes, elevator improvements go at sort of a slow to medium pace,” says Rob Bailey, president of Mid-American Elevator, Inc. in Chicago. “There’s been changes in the computers and the motor drives that run elevators in the last 10 to 15 years, and an influx of foreign-made equipment that people need to stay on top of.”
Codes and Requirements
The American Society of Mechanical Engineers (ASME), with input from the Elevator Manufacturers Association of the United States, published the first safety codes for elevators and escalators in 1921.