Document 6wD892V0OrQNyYQMDzmqwG8J9

628 CHAPTER 28 1954 Guide Table 6. Thermal Conductivity (k) of Various Type Pipe Insulations for Medium and High Temperature Pipe* Expressed in Btu per {hour) (square foot) {Fahrenheit degree temperature difference per inch) Types op Insulating Materials Density Temp. Range Use Mean Temperature, F Deo 100 200 300 400 500 Corrugated Asbestos--Type Laminated Asbestos--Type Diatomaceous Silica--Type.......................... 11-14 11-13 15-17 18-20 30-35 10-15 25-30 13-15 Up to 300 E Up to 300 F Up to 700 F Up to'800 F Up to 1800 F Up to 1200 F 0.39 0.45 0.51 0.57 0.68 0.80 0.51 0.59 0.69 0.49 0.67 0.65 0.39 0.44 0.49 0.54 0.40 0.45 0.50 0.55 0.63 0.66 0.69 0.72 0.75 0.34 0.39 0.44 0.49 0.54 * Average values from laboratories for insulating materials of various manufacturers. evaluation of pipe insulation cannot be included here. Insulation manu facturers should be consulted in regard to the selection of insulation which is to meet specific requirements. . 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 % 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. HEAT LOSSES FROM INSULATED PIPES The conductivities of various materials used for insulating steam and hot water systems are given in Table 6. They are given as functions of the mean temperatures or the arithmetic mean of the inner and outer surface temperatures of the insulations. It should be emphasized that they are the average values obtained from a number of tests made on each type of material; also, that in the use of conductivity all variables due to differences in thickness, pipe sizes, and air conditions, are eliminated. Table 7. Pipe Covering Factors Types of Insulating Materials Temperature Difference, Pipe to Aib f 100 200 300 400 500 Corrugated Asbestos--Type 4 Ply per 1 is........................ 6 Ply per 1 in....................... 8 Ply per 1 in........................ Laminated Asbestos--Type.. Mineral Wool--Type.............. Diatomaceous Silica--Type.. Brown Asbestos Fiber--Type 1.30 1.19 1.15 0.96 0.98 1.37 0.86 1.36 1.23 1.19 0.98 1.00 1.36 0.88 1.42 1.27 1.23 1.00 1.02 1.35 0.91 i *02 1.05 1.35 0.93 1.0j 1.07 1.3J 0.66 Pipe 'Insulation