East Airfield Lighting Control Vault

Firm: Globetrotters Engineering Corporation

Other Consultants: Milhouse Engineering & Construction, Inc., SPAAN Tech, Inc., RS&H, Inc.

Owner:City of Chicago Department of Aviation

Description:Globetrotters Engineering Corporation provided design services to the O’Hare International Airport East Airfield Lighting Control Vault (EALCV) which contains the electrical regulators that control the intensity (brightness) of the runway and taxi lights associated with the new runway 9C. The regulators are, effectively, dimmer switches for each runway or taxiway circuit and are manipulated in the control tower.

The power to the EALCV is provided through two completely independent feeds from the local electrical utility. There is also a standby diesel-powered generator sized to power the entire EALVC contained within the vault. When the airport is alerted to the possibility of an impending storm (tornado, rain, snow, or high winds) the control tower operators energize the generator and disconnect the utility feeds. This ensures that if the utilities would stop while a plane is landing, the pilots will still be able to see the runway since the generators are already feeding power to the lights.

Airfield Operations personnel conducted an interview session to discuss the problems with the existing vaults including the louvers and dampers for the generator combustion air located at the ground level on one side of the building.

During snowstorms, snow entered the building through the louvers bringing fresh air to the generator. To fix this issue, an electrified snow melting screen was installed upstream of the generator within the building. This limited the amount of snow entering the building; however this created a second problem. When there was heavy snowfall, snow drifts would buildup on the outside of the inlet louvers which blocked airflow to the generators. To remove the snow, operations personnel were required to physically shovel the snow to prevent the generator from shutting down.

The design team at GEC developed a “belt, suspenders, and Velcro” solution to the problems that included the following:
“Belt” - The air intake was located to an elevated location, 14 to 18 feet above grade. This prevented snow drifts from restricting generator air flow.
“Suspenders” - Air inlet, exhaust, and by-pass dampers (identified as the snow-melt dampers) were arranged to use the hot exhaust air to melt any snow entrained in the inlet air
“Velcro” - A nonelectrified snow screen was installed in the inlet plenum. This filtered out large droplets without using electrical energy to melt the snow.

In addition, the floor of the air inlet plenum was sloped to allow rain or melted snow to drain to floor drains and the inlet air is required to follow a path designed to centrifugally remove liquid upstream of the air filter. These design elements effectively ventilate the space given the environmental constraints.

City of Chicago Department of Aviation

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