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Heating Ventilating Air Conditioning Guide 1939 tinued turning in the threaded joint may in time result in a leak, par ticularly when the pressure is high. The amount of elongation which a rth when hot from the length when cold shall not disarrange the normal and orderly provisions for drainage of the branches. swivel joint can take up is controlled by the length of the swing employed and by the lateral displacement which is permissible in the long pipe runs. It is especially necessary with light-weight radiators so to anchor the icing and so to give it freedom for expansion that no strain therefrom *hall be allowed to distort the radiators. When expansion strains from Probably the most economical method of providing for expansion of piping in a long run is to take advantage of the directional changes which the pipes, are permitted to reach these light metal heaters they usually emit sounds of distress which are exceedingly troublesome. : must necessarily occur in the piping and proportion the offsets so that sufficient flexibility is secured. Ninety-degree bends with long, straight Table 6. Thermal Expansion of Pipe in Inches per 100 Ft* tangents in either a horizontal or a vertical plane are an excellent means {For superheated steam and other fluids refer to temperature column's for securing adequate flexibility with larger sizes of pipe. When flexibility cannot be obtained in this manner, it is necessary to make use of SiTUBlTSD SrBAM Elongation in Inches per 100 FT FRO m - 20 F cp Saturated Steam Elongation in Inches per 100 FT FROM --20 F UP some type of expansion 'bend. The exact calculation of the size of ex pansion bends required to take up a given amount of thermal expansion ygftnrm lodttf of Hg- Pressure Pounds Tem perature Square Inch Gage Degrees Fahren heit CastIron Pipe Steel Pipe Wrought Iron Pipe Copper Pipe Pressure Pounds ,, per Square Inch Gage Tem perature Degrees Fahren heit CastIron Pipe Steel Pipe Wrought Iron Pipe Copper Pipe -20 0 0 0 0 664.3 500 3.847 4.296 4.477 6.110 0 0.127 0.145 0.152 0.204 795.3 520 4.020 4.487 4.677 6.352 20 0.255 0.293 0.306 0.442 945.3 540 4.190 4.670 4.866 6.614 40 0.390 0.430 0.465 0.655 1115.3 560 4.365 4.860 5.057 6.850 29.39 60 0.518 0.593 0.620 0.888 1308.3 580 4.541 5.051 5.268 7.123 Offset U bend 28.89 27.99 80 0.649 0.725 0.780 1.100 1525.3 600 4.725 5.247 5.455 7.388 100 0.787 0.898 0.939 1.338 1768.3 620 4.896 5.437 5.660 7.636 Fig. 1. LMeasurement of on Various Pipe Bends 26.48 24.04 20.27 14.63 ___ .... __ 120 140 160 180 0.926 1.055 1.110 1.570 2041.3 1.051 1.209 1.265 1.794 2346.3 1.200 1.368 1.427 2.008 2705 1.345 1.528 1.597 2.255 3080 640 5.082 5.627 5.850 7.893 660 5.260 5.831 6.067 8.153 680 5.442 6.020 6.260 8.400 700 5.629 6.229 6.481 8.676 ] is relatively complicated1. The following approximate method, however, 'j has been found to give reasonably good results and is deemed to be 6.45 200 1.495 1.691 1.778 2.500 2.5 220 1.634 1.852 1.936 2.720 10.3 240 1.780 2.020 2.110 2.960 720' 5.808 6.425 6.673 8.912 740 6.006 6.635 6.899 9.203 760 6.200 6.833 7.100 9.460 ii sufficiently accurate for most heating work. ij Fig. 1 shows several types of expansion bends commonly used for 20.7 260 34.5 280 52.3 300 1.931 2.183 2.279 3.189 2.085 2.350 2.465 3.422 2.233 2.519 2.630 3.665 780 6.389 7.046 7.314 9.736 800 6.587 7.250 7.508 9.992 820 6.779 7.464 7.757 10.272 taking up thermal expansion. The amount of pipe, L, required in each of iJ these bends may be computed from the following formula: Jj 74.9 320 103.3 340 138.3 360 2.395 2.690 2.800 3.900 2.543 2.862 2.988 4.145 2.700 3.029 3.175 4.380 840 6.970 7.662 7.952 10.512 860 7.176 7.888 8.195 10.814 880 7.375 8.098 8.400 11.175 180.9 380 2.859 3.211 3.350 4.628 900 7.579 8.313 8.639 11.360 L = 6.16 ^ D A (2) | 232.4 400 3.008 3.375 3.521 4.870 920 7.795 8.545 8.867 11.625 293.7 420 3.182 3.566 3.720 5.118 940 7.989 8.755 9.089 11.911 where _ 366.1 440 3.345 3.740 3.900 5.358 451.3 460 3.511 3.929 4.096 5.612 960 8.200 8.975 9.300 12.180 980 8.406 9.196 9.S47 12.473 L = length of pipe, feet. ' )' ; j, ^ 550.3 480 3.683 4.100 4.280 5.855 1000 8.617 9.421 9.776 12.747 D = outside diameter ofthe pipe used,inches. A = the amount of expansiontobe takenup, inches. ^ ^ "From Piping Handbook, by Walker and Crocker. This table gives the expansion from -20 F to the v^ j temperature m question. To obtain the amount of expansion between any two temperatures take the r attterence between the figures in the table for those temperatures. For example, if a steel pipe is installed at a temperature of 60 F and is to operate at 300 F. the expansion would be 2.519 -- 0.593 = 1,926 in. This formula, based on the use of mild-steel pipe with wall thicknesses not heavier than extra-strong, assumes a maximum safe value of fiber PIPE THREADS stress of 16,000 lb per square inch. When square type bends are used, the width of the bend should not exceed about two times the height. It is All threaded pipe for heating and ventilating installations uses the further assumed that the corners are made with screwed or flanged elbows American Standard taper pipe thread which is made with a taper of l.in or with arcs of circles having radii five to six times the pipe diameter. Tv,mejSUret^ -n tlie diameter of the pipe so. as to secure a tight joint. 1 nreads of fittings are tapped to the same taper. The number of threads ru All risers must be anchored and safeguarded so that the difference in Per'nch varies with the different pipe sizes. All threaded pipe should be made up with a thread paste suitable for the service under which the; Piping Handbook', by Walker and Crocker, and A Manual for the Design of Piping for Flexibility, by the Use 01 Graphs, by E. A. Wert, S. Smith, and E. T. Cope; published by The Detroit Edison Company- pipe is to be used. 368 369