Document Lp6O6OJzDd4mnZeQ0bm6GR9vd

514 CHAPTER 28 1946 Guide ' '' PIPE INSULATIONS Pipe insulations are of several general' forms and are made of various . types of material. The most common form is the rigid sectional covering either split longitudinally into halves or cut through" bn one side and scored on the other, to facilitate assembling on pipes. Preformed materials are supplied in segments for assembly on large pipes. The . sectional coverings are generally supplied with a pasted on canvas .Table 1. Heat Losses from Horizontal Bare Steel Pipes , Expressed in Btu per {hour) {linear foot) {Fahrenheit degree difference between the pipe and surrounding still air at 70 F) Nominal - Pipe Size (Inches) y % i iK i)4 2 2H 3 ' 3H 4 5 6 8 10 12 . . 120 F 50 F 0.455. 0.555 0.684 0.847 0.958 1.180 1.400 1.680 . 1.900 2.118 2.580 3.036 3.880 4.760 5.590 Hot Water 150 F 180 F 210 F 227.1 F (5 Lb) 80 F . 0.495 0.605 0.743 0.919 1.041 1.281 1.532 1.825 2.064 2.302 2.804 3.294 4.215 5.180 6.070 Temperature Difference 110 F 140 F 157.1 F 0.546 0.666 0.819 1.014 1.148 1.412 1.683 2.010 2.221 2.534 3.084 3.626 4.638 5.680 6.670 0.584 0.715 0.877 1.086 1.230 1.512 1.796 2.153 2.433 2.717 3.303 3.886 4.960 6.090 7.145 0.612 0.748 0.919 1.138 1.288 1.578 1.883 2.260. 2.552* 2.850 3.470 4.074 5.210 6.410' 7.500 Steam . 299.7 F (50 Lb) 337.9 F (100 Lb) 227.7 F .0.706 0.866 1.065 1.324 1.492 1.840 2.190 2.630 2.974 3.320 4.050 4.765 6.100 7.490 8.800 ' 267.9 F 0.760 0.933 1.147 1.425 1.633 1.987 2.363 2.840 3.215 3.590 . 4.385 5.160 6.610 8.115 ~ 9.530 Table 2. Heat Loss from Horizontal Tarnished Copper Pipe Expressed in Btu per {hour) {linear foot) {Fahrenheit degree difference between the pipe and surrounding still air at 70 F) Nominal Pipe Sues (Inches) Hot Water (Type K Copper Tube) Steam (Standard Pipe Si*e Pipe) - , 120 P 150 F 180 F 210 F 227.1 P (5 Lb) 297.7 P (50 Lb) 337.9 (100 Lb) Temperature Difference w %. imm 2 2)4 . 3 'm 4 4M -5 6-. .8 50 P 0.250 0:340 0.440 0.500 0.580 0.730 0.880 1.040 1.180 1.460 1.600 1.840 2.400 0F 0.287. 0.381 . 0.475 0.559 0.656 0.825 1.000 1.175 1.350 1.500 1.812 2.125 2.685 110 F 0.300 0.409 0.509 0.618 0.710 0.890 1.091 1.272 1.454 1.635. 1.980 2.270 2:910 140 F 0.321 0.429 0.536 0.622 0.750 0.957. 1.1431.343 1.535 1.715 2.071 2.430" .3.110 157.1 F 0.433 .0.533 0.636 0.764 0.904 1.101 1.305 1.560 1.750 1.941 2.131 2.387 2.740 3.310 227.7 F 267.9 F 0.500 0.530 0.543 0.654 0.746 0.803 0.878 0.934 , 1.053. 1.120 1.273 1.364 1.490 1.605 1.800 . 1.940 2.020 2.170 2.240 2.430 2.465 2.650 .2.770 . 2.990 3.210 3:440 4.050 4.370 Pipe Insulation 515 Table 3. External Surface per Linear Foot of Pipe Nominal 'Pipe Size (Inches) )4 % l 1 Ya. 1)4 Surface Area (Sq Ft) 0.22 0.275 0.344 0.435 0.498 Nominal Pipe Size (Inches) 2 2)4 3 3)4 4 Surface Area (Sq Ft) 0.622 , 0.753 0.917 1.047 1.178 Nominal Pipe Size (Inches) 5 6 8 10 12 Surface Area (Sq Ft) 1.456 1.734 2.257 2.817 3.338 jacket. Blanket insulations aresometimes used for wrapping large pipes, particularly where removal for frequent servicing of the pipe is necessary. Fittings and bends are commonly covered with portions of standard pre formed insulation or, when irregular in contour, with plastic materials known as insulating Cements. ' < Insulation is secured to pipes with staples which are used to bridge the joint between half sections, and with metal pipe covering bands or rings of wire which secure individual sections and effect a junction between abutting sections. A number of surface finishes are used over pipe insulation depending upon the service encountered and appearance desired. Canvas jackets are most common although asbestos paper or asbestos finishing cements are sometimes employed. Insulation outdoors should be waterproof and is generally protected with an asphalt felt for piping and asphaltic cements for fittings. Insulation On lines carrying cold water, brine, or other cold fluids is carefully finished to obtain adequate sealing against the penetration of water vapor. .The selection of pipe insulation for a particular service condition must be made with full consideration of a number of properties in addition to thermal conductivity: Factors which may be of more importance than the thermal conductivity, are: ease of application, fire resistance, heat stability, weathering stability, resistance to damage by physical abuse, . and others which may apply to a particular installation. A complete 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. 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 Table 4. External Surface per Linear Foot of Copper Tubing Outside diameter Y% in. greater than nominal size Tube Size (Inches) H U 1 .m Surface Area (Sq Ft) 0.164 0.229 0:295 0.360 0.426 Tube 8bs (Inches) 2 m 3 3)4 4 Surface Abba (Sq Ft) 0.556 0.687 .0.818 0.949 1.080 Tube Size (Inches) 5 6 8 Surface Area (Sq Ft). ; 1.342 1.604 , 2.128