Document evLJEJ0kd4rzeovJxqrZxb5Kq

326 Chapter 17 1945 Guide I' -' - Table 3.. Heat Loss erom Bright Copper Pipe Given One Thin Coat of Clear Lacquer Expressed in Blu per {hour) {linear foot) {degree Fahrenheit difference between the pipe and surrounding still air at 70 F) Nominal ' Pith pm ' (Inches) K K l IK m 2 2H 3 3K 4 4K 5 6 : s' Hot Water {Type K Copper Tube) 120 F 150 F 180 F 210 F Steam (Standard Pipe Size Pipe) 227.1 F ' 297.7 F (5 Lb) (50 Lb) d3o37o.9m Temperatube Difference 50F 0.240 0.320 0.390 0.470 0.540 0.690 0.840 0.960' 1.100 1.241 1.480 1.700 2.200 80 F, . no F. 0.265 0.356 0.437 0.537 0.612 0.762 0.937 1.025 . 1.250 1.400 0.282 0.373 0.463 0.554 0.645 0.818 0.991 1.135 1.318 1.480 1.685 1.936 2.500 1.790 .2.052 2.630 1*0 F 0.307 0.414 0.507 0.614 0.714 0.892 1.085 1.270 1.442 1.556 1.965 2.272 2.854 157.1 F 0.401. 0.477 0.598 0.700 <0.830 1.005 1.178 1.400 1.580 1.750 1.910 2.130 2.450 . 3.120 227.7 F 0.461 0.571. 0.681 0.812 0.966 1.164 1.361 1.625 1.845 2.040 2.240. 2.415 2.810 3.425 267.9 f 0.478 0:578 01710 0.840 0.990 1.201 1.420 1.700 1.905 2.130 2.350 2.610 2.990 3.730 jacket. Blanket insulations are sometimes used for wrapping large pipes particularly where removal for frequent servicing 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 Table 4. Heat Loss from Horizontal Tarnished Copter Pipe Expressed in Btu per (hour) (linear foot) (degree Fahrenheit difference between the pipe and surrounding still air at 70 F) Nominal Pipe &EE- (Ikcbes) Hot Water (Type K Copper Tube) Steam (Standard Pipe Sise Pipe) * 120 F 150F .-| 180 F . 210 F 1. 227.1 F ($ Lb) 1 297.7 F ! \(50 Lb) 337.9 F (100 Lb) Temperature Difference KVi. 1 IK ik 2 2M 3 3H 4 . 4K 5 6 8 50 F 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 ` 80 F 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 1*0? 0.321 0.429 0.536 0.622 0.750 0.957 1.143 1.343 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 0.500 0.543 0.746 0.878 1.053 1.273 1.490 1.800 2.020 2.240 2.465 2.770 3.210 4.050 : 241.9 F 0.530 0.654 0.803 0.934 1.120 1.364 1.605 1.940 2.170 2.430 2.650 2.990 3.440 4.370 -- Pipe Insulation 327: Table 5. External Surface per Linear Foot of Pipe /Nominal 7Pipe Size (Inches) K K l IK IK Surface Area (So Ft) 0.22 0.275 ' 0.344 0.435 0.498 Nominal Pipe Size (Inches) 2 2H 3 3K * . 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 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 manm 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 8. 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 eli minated. Individual manufacturer's materials will, of course, vary in conductivity to some extent from these values. The heat losses through 1, 1J4, and 2-in. thick 85 per cent Magnesia type of insulation for temperature differences between the pipe and the . surrounding atmosphere up to. 280 F are shown in Figs. 1, 2, and 3. -standard thicknesses of 85 per cent Magnesia pipe covering are not exactly 1 in. However, the loss through any given thickness of insulation can be obtained by interpolation. Also, the losses through any of the Table 6. External Surface per Linear Foot of Copper Tubing Outside diameter K in. greater than nominal size i use Size i.lNCBES) lA. Vi 1 Surface Area (Sq Ft) 0.164 0.229 0.295 0.360 0.426 Tube Sice (Inches) 2 2K 3 3K 4 Surface Area (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