Book - School of Science and Technology

172 Indirect heating systems0.080.07Thermal conductivity, W/mK0.060.050.040.03Mineral woolCalcium silicate3(64kg/m )Glass fibreStill air0.02Microtherm0.010 20 40 60 80 100 120 140 160 180 200Mean temperature, ºCFigure 6.21 Thermal conductivity of pipe insulating materials. Arrange that piping be run overground, with particular care as to topography and anybuilding features which may assist.. Arrange that piping be routed through basements or, if none exist, through purposebuilt walk-in subways.. Provide for excavation and either formation of underground ducts or direct undergroundburial of piping enclosures.The last of these approaches will most probably be thought of as being the only practicalsolution in terms of first cost. The margin of advantage, however, will be less than firstimagined if the whole of the site preparation and subsequent building constructionmethods are of the necessary quality. If they are not of that quality, excavation for andreplacement of the pipework is not only inevitable in the long term but likely to berequired within five years of installation.Overground arrangementsOn industrial and semi-industrial sites, such as dispersed hospitals, etc., where appearanceis not a first-order priority, pipework may be run externally and be supported either atwaist level on road verges or from gantries where vehicular traffic must have passage. Thethermal insulation must be provided with a finish which is weatherproof and reasonablyresistant to vandalism:supports, etc., must be arranged so that the finish is not punctured.Use of the roofing felt and wire netting combination so often seen is inadequate since it isnot fully weatherproof with the result that the insulation material absorbs water andcorrosion follows. Sheet metal cladding or a proprietary finish are to be preferred.In some recent city centre and housing developments, there has been a tendency toseparate pedestrian and vehicular traffic by use of bridges and overhead walkways. These