Describes an investigation of the performance of fibrous glass pipe insulation used in district heating and cooling subject to underground water attack. The insulation was tested at pipe fluid temperatures from 35degF (1.6degC) to 450degF (232.2degC). The surrounding water was maintained at temperatures from 46degF (7.7degC) to 100degF (37.7degC) to simulate the possible conduit water temperatures when the system fails. Presents results for the effective thermal conductivity, time required for moisture absorption, the drying rate and the extent to which the insulation can be dried out once the source of moisture is removed. Finds that the effective thermal conductivity of the wet fibreglass insulation can be from 52 to 185 time higher than that of the dry insulation. After drying, the thermal conductivity of the fibreglass insulation reverted to the value before submersion.

KEYWORDS: year 1997, District heating, pipelines, glass fibre, thermal insulation, performance, thermal conductivity, water, underground, ground water