Document bBrpr1nVO84N5Edgbmo63mBX3

656 CHAPTER 28 1956 Guide suiation. The manufacturer's recommendations should be followed. Pipe insulation is usually fastened with staples across' the joints between sections and with metal bands or wire rings to hold individual sections and keep all joints tight. Surface finishes used over insulations depends upon the exposure, whether indoor or outdoor, the temperature of the insulated surface, and the ap pearance desired. The insulations over flat or large curved surfaces, operating at temperatures above the ambient, are usually coated with a finishing cement when exposed to indoor conditions and by a finishing cement plus a weatherproof finish when used outdoors., The insulation over pipes operating above ambient temperature is usually coated with a canvas cover for indoor exposure and an asphalt impregnated felt for outdoor exposure. Sectional pipe covering is available with a wide variety Of surface finishes and jackets. Insulation over surfaces operating at temperatures below the ambient must be protected from water vapor penetration, whether used indoors or outdoors. The selection of an insulation for a particular service condition should be made with full consideration of a number of properties in addition to thermal conductivity. Factors which may, under certain circumstances, be of more importance than thermal conductivity are ease of application, fire resistance, heat stability, weathering stability, and resistance to damage by physical abuse. Other factors may apply to a particular in stallation. A complete evaluation of all insulations cannot be included here. Insulation manufacturers should be consulted with regard to the selection of insulation to meet specific requirements. In general, the use of skilled and experienced applicators will go a long way toward insuring a satisfactory installation. Elbows and fittings should be covered with an insulation of equal thick ness and material which is similar to the pipe covering. Pre-fabricated fittings are available for many types of insulation, such as cork and rock cork. Where asbestos cement or magnesia cement is used to build up the fittings, the material should be applied in layers not exceeding a thickness of Y% in- The final coat should be mixed with 10 percent Portland cement and troweled smooth. After the final coat has thoroughly dried, it is recom mended that canvas of the same weight as that used on the pipe covering be pasted over the surface. This procedure will prevent the built-up portions of the covering from falling off due to a slight bump or other minor damage. On permanent installations of high quality, it is recommended that all coverings and fittings be further encased in 8-oz. canvas, drawn tight over rosin-sized paper and sewed in place, using not less than four stitches per inch. All pipe covering which has a high differential temperature between the pipe surface and the ambient air should be provided with metal pipe sleeves around the covering to support the pipe by means of hangers on the out side of the covering, thus preventing the conduction of heat through the hangers. HEAT LOSSES FROM INSULATED PIPES Table 6 lists a number of typical thermal conductivities for various insulating materials. These conductivities have been selected as average design values for engineering calculations and must not be confused with Pipe and Industrial Insulation 657 Table 6. Thermal Conductivity (fc) of Industrial and Fife Insulations {For Mean Temperatures Indicated) Expressed in Btu per {hour) {square foot) {Fahrenheit degree temperature difference. ' per in.) Form Material (Composition) Accepted Max. Den Temp. sity 1 for Lb^Cu Use* F Typical Conductivity h at Mean Temp. Fahb. 40 70 100 j 200 1 300 I 6001700) 900 MINERAL WOOL (Rock{ Slag, or Glass) Metal Reinforced Feit-FIexibie Type Felt-Semi-Rigid Type VEGETABLE A ANIMAL FIBER Hair Felt ox Hair Felt plus Jute 1200 450 450 ASBESTOS Q Molded Amosite A Binder Laminated Asbestos Paper Corrugated A Laminated Asbestos Paper! 4 ply 1200 700 Pi 6 ply 3 8 ply CALCIUM SILICATE CELLULAR GLASS 300 1200 pz < CORKBOARD {Without Added Binder) DIATOMACEOUS SILICA 02 K O O 85% MAGNESIA Mag. Carb. A Asbestos MINERAL WOOL {Rock, Slag or Glass) 800 200 1500 1900 600 h-3 Low Temp. (Asphalt or Resin Bonded) High Temp. (Resin Bonded) 200 (With Inorganic Binder) PLASTICS (Foamed) 600 1600 RUBBER (Foamed) 175 150 ASBESTOS Molded Amosite & Binder Laminated Asbestos Paper Corrugated A Laminated Asbestos Paper 1200 700 4 Ply per in. 6 Ply per in. 8 Ply per in. oZ S CALCIUM SILICATE Calc. Sil. A Asbestos CELLULAR GLASS CORK {Without Added Binder) DIATOMACEOUS SILICA 300 300 300 200 1500 85% MAGNESIA 1900 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 ,%z 85% MAGNESIA 4 Asbestos 531 With Co1ll!oidal Cla<yRBxitn- dSelar ^ <?!) 200 450 1200 175 150 180 180 600 1800 6-15 0.5-3 2-8 0.23 0.29 0.35 0.2510.2610.34 0.42 0.45 j0.56; 0.24.0.25, 0.27,0.35 0.44i 0.30 (0.37 0.40 O.f1l7 JO'..861 0.66 0.40 0.45 0.50 10.601 76 I 11-13 15-17 18-20 11 9 6.5-8 0.54 0.57 0.68 0.80 0.49 0.51 0.59 0.69 0.47 0.49 0.57 0.65 f0.37|' 0.39 0.26 0.27 0.33 0.41 0.28 0.38 0.43 0.48 10.55 Mi(0.75 22 25 ft7*0K[*0)...7554l 0.68 0.80 11-14 0.35| 10.42 (0.46 6-18 0.28 0.29 0.31 6-10 0.28i 0.351 16-24 1.6 5 0.34 ;0.39 o! 4410.54(0.64 o0:28100..2248 0.30 0.25 11-13 15-17 18-20 0.371 7-10 0.27 22 25 11-14 15 0.28 3 '0.22 6-15 1.6 0.261 5 0.23 20 0.29| 10 0.271 18 24-30 0.33 0.381 0.43 0.53 0.40 0.45 0.50 0.60 0.57 0.62|0.80 0.51 0.59 0.69 0.49 0.57'(0.65 0.36 0.40|10.44 0.55 0.41 0.48 0.55 0.29 0.30 .64 0.66 0.71 .70 0.75 0.80 0.4510.51 0.39 0.27 0.36 0.58 0.73 operating texture approach actual test data. The conductivity of any particular insulation or pipe covering can only be obtained from unbiased tests, or from data guaran teed by the manufacturer. The terms standard and double standard thickness of magnesia and diatomaceous silica pipe covering have been declared obsolete by the