Document 3Jjd6eQkVanbw52eOxZ8JmE3D

590 CHAPTER 27 1951 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 on one side and scored on the other, to facilitate assembling on pipes. Preformed ma- Table 1. Heat Losses prom Horizontal Bare Steel Pipes Expressed in Btu per (hour) (linearfoot) (Fahrenheit degree difference between the pipe and surrounding still air at 70 F) Nominal Size (Inches) 120 F Hot Water Steam 1 150 F | 180 F 210 F 227.1 F I 299.7 F (5 Lb) (50 Lb) * Temperature Difference 337.9 F (100 Lb) 50 F 80 F 110 F ' 140 F | 157.1 F 227.7 F* 267.9 F g 1 IK \* 34 H 5 6 8 10 12 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 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 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 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 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 prom 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 Size ... (Inches). Hot Water (Type K Copper Tube) j Steam (Standard Pipe Size Pipe) i 120 F - 150 F 180 F o21tn0 FP IJI 2(257L1bF)' 297.7 F (50 Lb) 337.9 F (100 Lb) - Temperature Difference 8. .k 2 !* 43H. !* 6 8 : 50 F , 0.250 0.340 0.440 0.500 . 0.580 0.730 0.880 1.040 1.180 1.460 T.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 TSl2 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 1X80 2.270 2.910 140 F 157.1 F 0.321 N 0.429 0.536 0.622 0.750 0.957 1.143 1.343 1.535 1.715 I 2X71 I 2.430 3.110 0.433 0.533 0.636 0.764 01..910014 1.305 1.560 1.750 1.941 2.131 2.387 2.740 3.310 227.7 F 0.500 0.543 Q.746 0.878 1.053 1.273 1.490 21..082000 2.240 2.465 2.770 3.210 4.050 267.9 F 0.530 0.654 0.803 01..913240 . 1.364 ` 1.605 1.940 2.170 2.430 2.650 2.990 3.440 4.370 terials are supplied in segments for assembly on large pipes. The sectional coverings are generally supplied with a pasted-on canvas jacket. Blanket insulations. are sometimes 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 preformed Pipe Insulation 591 Table 3. . External Surface per Linear Foot of Pipe Nominal Pipe Size (Inches) . 1 IK IK Surface Area | pJ?E Size 0.22 0.275 0.344 0.435 0.498 ,| (INCHES) S2 0 2K R3 fl zy. I4 Surface Area I r(5cQn cFvt) 1J P(l1NPCEHSEizs)e 0.622 I 5 0.753 0.917 1 | 6 8 1.047 I 10 1.178 1 12 Surface Area (Sq Ft) ^ . 1.456 1.734 2.257 2.817 3.338 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 junc tion between abutting sections. Surface finishes used over pipe insulation depend 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 water proof, 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 manufacturers 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 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. Individual manufacturer's materials will, of course, vaiy in conductivity to some extent from these values. The heat losses through 1, I5, and 2-in.' thick, 85 percent 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. Table 4. External Surface peb Linear Foot of Copper Tubing Outside diameter J in. greater than nominal size Tube Size (inches) X 1K 1K IK Surface Area (Sq Ft) 0.164 0.229 0.255 0.360 0.426 Tube Size (Inches) 2 32X 3 4 ISurface Area (Sq Ft) fl 0.556 * 0.687 0.S18 0.949 1.080 J I j 1 Tube Size (Inches). 5 6 -8 - SuRFAce Area . (Sq Fi) . 1.342 1.604 2.128 --