Document b57nyDqDbQxG2VgVjpbn0B8vD

704 CHAPTER 27 1958 Guide .X Table 1. Thermal Conductivity (k) op Industrial and Pipe Insulations (For Mean Temperatures Indicated) Expressed in Btu per (hour) (square foot) (Fahrenheit degree temperature difference per in.) Material (Composition) Accepted Mat. DEN Temp. SITY Lb/Cu FOB Use* F Typical Conductivity jfc at Mean Temp. Fahb. .40 70 100 200 300 500 700 900 MINERAL WOOL (Rock, Slag, or Glass) Metal Reinforced Felt-Flexible Type Felt-Semi-Rigia Type VEGETABLE A ANIMAL FIBER Hair Felt or Hair Felt plus Jute 1200 450 . 450 180 ASBESTOS Molded Amoeite A Binder laminated Asbestos Paper Q Corrugated A Laminated Asbestos Paper 4 ply 6 ply 8 ply On CALCIUM SILICATE CELLULAR GLASS a- CORKBOARD (Without Added Binder) 2 < DIATOMACEOUS SILICA 03 85% MAGNESIA . W Mag. Carb. A Asbestos oo nJ MINERAL WOOL (Rock, Slag or Glass) Low Temp. (Asphalt or Resin Bonded) High Temp. (Resin Bonded) (With Inorganio Binder) PLASTICS (Foamed) RUBBER (Foamed) 1200 700 300 300 300 1200 800 200 1500 1900 600 200 600 1600 176 150 ASBESTOS Molded Amoeite A Binder laminated Asbestos Paper Corrugated A laminated Asbestos Paper 4 Ply per in. 6 Ply per in. 8 Ply per in. CALCIUM SILICATE O' 2 Calc. Sil. A Asbestos CELLULAR GLASS H<J CORK (Without Added Binder) DIATOMACEOUS SILICA 85% MAGNESIA Mag. Carb. A Asbestos MINERAL WOOL (Rock, Slag or Glass) Low Temp. (Asphalt or Resin Bonded) Low Temp. (Fine Fiber Resin Bonded) High Temp. Blanket-Type (Metal Rein forced) PLASTICS (Foamed) RUBBER (Foamed) VEGETABLE A ANIMAL FIBER Wool Felt Hair Felt or Hair Felt plus Jute 1200 700 300 300 300 1200 800 200 1500 1900 600 200 450 1200 175 150 180 180 (2 85% MAGNESIA Mag. Carb. A Asbestos Shs MINERAL WOOL (Rock, Slag or Glass) Sjo With Colloidal Clay Binder 600 1800 6-15 0.29 0.35 0.42 9.56 0.5-3 0.2<) 0.25 0.26 0.34 0.45 2-8 0.24 0.25 0.27 0.35 0.44 10 0.27 0.28 0.30 18 0.37 0.40 0.47 9.56 D.66 9.76 30 0.40 0.45 0.50 9.60 11-13 0.54 0.57 0.68 0.80 15-17 (MS 0.51 O.fifl 0.69 18-20 0.41 0.45 0.57 0,65 11 0.32 0.32 0.43 9.53 9.64 9.75 9 0.37 0.35 0.41 0.48 0.55 6.5-8 0.2fl 0.27 0.2$ 22 9.60 9.64 9.68 25 9.70 9.75 9.80 11-14 0.35 0.38 0.42 9.46 6-18 0.28 0.29 0.3(1 6-10 0.28 0.35 0.43 16-24 0.34 0.39 0.44 9.54 0.64 1.6 0.26 0.28 0.30 5 0.23 0.24 0.25 16 0.33 0.38 0.43 9.53 30 0.40 0.45 0.50 0.60 11-13 15-17 18-20 0.54 0.57 0.62 0.80 9.49 0.51 0.59 9.69 0.47 0.49 0.57 0.65 11 9 7-10 22 25 - 0.36 0.40 0.44 0.55 9.37 9.39 9.41 9.48 9.55 9.27 9.28 9.29 0.30 ).64 >.66 >.71 0.70 9.75 >.80 11-14 0.39 0.42 0.45 0.51 15 0.28 0.30 0.33 0.39 3 9.22 9.23 0.24 9.27 9.31 6-15 0.29 0.36 0.42 0.56 1.6 0.26 0.28 0.31 5 0.23 0.24 0.25 20 0.29 0.31 0.33 10 0.27 0.28 0.30 18 0.46 0.52 0.58 24-30 0.49 0.61 0.73 0.83 * These temperatures are generally accepted as maximum. When operating temperature approaches these .limits the Manufacturer's recommendations should be followed. insulation the user should consult the manufacturer or obtain the results of unbiased tests. . Other properties of thermal insulations that are of more or less im-portanpe, depending upon the use, are strength, hardness, density, com pressibility, specific heat, resistance to high or low temperature, and thermal coefficient of expansion. The final choice of an insulating material for a given purpose usually involves a compromise with regard to several Pipe and Industrial Insulation 705 desirable properties. Tor example, an insulating firebrick must have considerable strength and must be resistant to the temperature to which it is to be exposed. The desirable properties of low conductivity and light weight must be sacrificed to some extent to achieve these necessary proper ties of strength and temperature resistance. TEMPERATURE RANGE OF USE OF INDUSTRIAL INSULATION Since thermal insulation reduces the exchange of heat energy between an insulated surface and its surroundings, it can be useful at any temperature from the lowest to the highest. Actually insulation is used in industrial processes operating at temperatures from minus 400 F to 3000 F and higher. At the low end of the scale are processes involving liquefied gases, usually in vessels or piping, at temperatures from the lowest up to about minus 40 F. From minus 40 F to normal atmospheric temperatures large amounts of low temperature insulation are used for enclosing freezing tun nels, cold-storage rooms, and a great variety of food and industrial processes requiring low temperatures. At normal and near-normal temperatures insulation in building struc tures is required for economical operation of heating and air conditioning systems. Insulation for heating and cooling equipment and for the dis tribution ducts, piping, etc., is, however, usually considered as industrial. The range of temperatures is from that of chilled water or about 32 F up to steam at 100-125 psig (about 350 F). Drying and baking ovens, boilers small and large, distillation equipment in oU refineries, high-pressure and superheated-steam piping call for insulation suitable up to 1200 F. Petroleum cracking units, heat treating furnaces, ceramic kilns may reach 2200-2400 F. Still higher temperatures with surfaces to be insulated up to 3000 F are found on melting furnaces for glass, iron, steel, and metals of all kinds as well as furnace enclosures for . combustion spaces for many kinds of heating units. Above 3000 F the variety of materials physically suited for walls and structural parts rapidly decreases with increasing temperature. Insulation for conservation of heat energy must, therefore, often be applied so. as to permit enough heat to escape to retain mechanical strength. TEMPERATURE LIMITATIONS OF INSULATIONS Probably the greatest volume of low temperature insulations is used for temperatures from minus 100 F to atmospheric. The effect of temperature alone on physical integrity is not ordinarily very important for most types in the low-temperature field. There are more definite limitations for materials in the high-temperature field where decomposition, excessive linear shrinkage, softening or some other effect of temperature alone will put a maximum limit on the temperature for which a material is suited. As extremes in temperature are approached, both high and low, the selec tion of a material for a specific service becomes more and more critical and must be based on experience and factual performance data. FORMS OF INSULATION ....^he physical form of industrial insulations varies from powders and loose nUs which might be called formless, through materials with varying degrees to comPressibility and flexibility, to completely rigid shapes often referred as preformed insulation. After deciding that a material has the neces"jy insulating value, physical properties, and temperature resistance, the ice of the form desired will usually be governed by considerations of