U.S. Coast Guard - LORAN-C high-power transmitter stations

Project Summary

The U.S. Coast Guard selected Hanson to complete engineering, architectural design, electrical and mechanical services for new transmitter buildings, power plants and renovations located at remote LORAN-C stations at Attu, St. Paul, and Port Clarence, Alaska.  (LORAN-C stations provide the U.S. Coast Guard with radio-navigation services for U.S. coastal waters and beyond.)

This project entailed developing new facilities to house high-power solid-state transmitters while maintaining operations for the existing transmitters. To reduce potential station outages, Hanson also assisted with detailed project phasing and a systematic changeover plan to decommission existing equipment and commission new equipment without interrupting operations.

With special considerations for extreme weather conditions, Hanson provided architectural design with precast elements, reducing concrete placement at the remote cold-weather locations. Facilities included a transmitter building with a main transmitter equipment room; a primary and secondary heat exchanger/mechanical equipment room; and an electrical power transformer/equipment room. Renovations to the existing power plant provided additional maintenance workshop space.  The project also included renovations of other existing spaces and facilities.

For the new primary power plants, Hanson designed a power generation system consisting of three 350-kilowatt engine generator sets for continuous operation, including a heat recovery system to reclaim heat generated by engines for distribution to adjacent buildings.  The design also included a special ventilation system to withstand the extreme cold and high winds characteristic of the area.

Taking into account environmental protection considerations, Hanson designed a new fuel delivery system. Key features were integration with an existing fuel farm and day tank-level switches that automatically operate fuel transfer pumps to meet engine fuel demand.

The fire protection system included a 30,000-gallon underground water supply tank, fire pump, pre-action valve system, and water-piping system. This system operates in conjunction with a cross-zoned ionization and heat-detection system.

Additionally, Hanson provided a system to air condition the transmitter building and cool high-power radio transmitters. The building air-conditioning system consisted of two 20-ton cooling capacity units — one unit was on continuous operation and another unit was on standby. The transmitter cooling system consisted of primary and secondary heat exchangers to evacuate heat generated by transmitters. The team used a cross-zoned fire-protection system for the internal transmitter cabinets with a halon-extinguishing agent.

The electrical system portion of the project consisted of replacing the entire existing power plant with a new power plant, including three new engine generator units with automatic switchgear. The generation system provided 480-volt, three-phase distribution to the transmitter building and 20-volt, secondary feeds to other buildings. The Hanson team enhanced the critical systems with redundant feeders and transformation. Other features of the electrical system included lighting, distribution, heat tracing of piping, fire alarm and security systems.

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