Investigation of Preapproved Underground Heat Distribution Systems.
CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL
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The Department of Defense maintains and operates approximately 6,000 mi of steam and hot water heat distribution system piping, mostly underground. Even a small decrease in heat transmission efficiency could waste large amounts of energy, natural resources, and lead to increased greenhouse gas production. USACERL investigated and evaluated the physical condition and general performance of drainable-dryable heat distribution systems installed since 1981. Inspections covered 35 heat distribution systems at 15 locations. Manhole inspections were performed and air pressure tests were successfully conducted on 5.18 mi of conduits. Many systems were not installed in accordance with criteria. Drains and vents were generally found to be dry however, water or evidence of water in the manholes was common. Using a stringent standard of no more than a 1.0 psi drop in pressure after 30 min, 59 percent of the steel conduits passed while only 7 percent of the fiberglass reinforced plastic FRP conduits passed. With a more lenient standard of no more than a 5.0 psi drop in pressure after 30 min, 73 percent of the steel conduits passed while only 24 percent of the FRP conduits passed. In the more lenient case, normalizing to length, the failure rate of FRP-cased conduits was 4.82 times that of steel conduits.
- Air Conditioning, Heating, Lighting and Ventilating