Document 19gEamBXmYqDMy4eKYbEpZyK

576 CHAPTER 27 1950 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 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) X K 1 IK IX 2 2H 3 3H 4 5 .6 8 10 .12 . .. :. 120 F Hot -Water 150 F 180 F . 210 F, 227.1 F (5 Lb) Steam 299.7 F 337.9 F (50 Lb) (100 Lb)": , Temperature Difference 50 F 0.455. 0.555 0.684 0.847 0.058 1.180 1.400 L6801.900 . 2.118 2.580 . 3.036 3.880 4.760 5.590 . 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 . 110 F 0.546 0.666 0.819 1.014 P.148 1.412 .1.683 2.010 2.221 2.534 3.084 3.626 4.638 5.680 6.670 140 F 0.584 0.715 0.877 1.086 a 1.230 1.612 1.796 2.153 . 2.433 - 2.717 3.303 3.886 4.960 . 6.090 7.145 157.1 F 227.7 p ' 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 8:800 267.9 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 Size */ (Inches) . Hot Water (Type K Copper Tube) 120 F 150 F 180 F 210 F Steam (Standard Pipe Size Pipe) 227.1 F (5 Lb) 297.7 F (50 Lb) 337.9 F (100 Lb)t Temperature Difference if. 1. ;' ' ih 1M 2 2H 3 ' 3H 4 4H 5 '; 6 -8 . 50 F . 80 F 110 F . 140F 157.1 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 0.287 0.300 0.381 0 409 0.475 0.509 '0.559 0.618 0.656 - 0.710 0.825 0.890 . 1.000 . 1.091 1.175 1.272- . 1.350 1.454 1.500 - 1.635 r V ' 1.812 1 :|.980 . 2.125- 2.270 2.685 .. 2.910 0.321 v .0.433 0.429 0.533 0.536 . 0.636 0.622 0.764 0.750 ' 0.904 0.957 .1.101 1.143 1.305 1.343 * 1.560 1.535 . 1.750 1.715 1.941 2.131 2.071 2.387 2.430 2.740 3.110 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 4.050 267.9 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 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 Ripe Insulation 577 Tablev3.! External-Surface per Linear. Foot of Pipe Nominal Pipe Sim: (Inches) X '. X i IX IX Surface Area (Sq Ft) 0.22 0.275 0.344 0.435 0.498 Nominal Pipe Size (Inches) 2 2H 3 3K 4 Surface Area (Sq Ft) 0.622 0.753 0.917 1.047 1.178 Nominal Pipe Si?e (Inches) 5 6 8 10 12 Surface Area (Sq Ft) 1.456 1.734 2.257 2.817 3.33S 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 manu facturers should be consulted in. regard-to the selection , of insulation which is to meet specific requirements. j 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 they1 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, vary in conductivity to some extent from these values. The heat losses through 1, If, 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. Table 4. : External Surface per Linear Foot of (Topper Tubing ,............... .' Outside diameter \ in. greater than nominal size Tube Size (inches) Surface Area (SqFt) X 0.164 H -T . 0.229 0.295 - - .AX............... .. . --0.360........... iX 0.426 Tube Size (Inches) 2 2M .3 ...3X 4 - Surface Area (Sq Ft) 0.556 0.687 0.S18 .. 0.949............ 1.080 Tube Size (Inches) 5 6. `8 -- Surface Area (Sq Ft) 1.342 1.604 - 2.128 - -.