Document jyao47EYoGw429g1Y9R4wZZwZ

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 Table 5. Thermal Expansion of Pipe in Inches per 100 ft3 Sai*urated Steam Vacuum Inches of Hg. rressur Pounds ,,! Square Inch Gage Tem perature Degrees Fahren heit Elongation in Inches per 100 FT FROM -- 20 F UP CastIron Pipe Steel Pipe Wrought Iron Pipe Copper Pipe Saturated Steam Weasurc Pounds ,, Per Square Inch Gage Tcm- perature Degrees Fahren heit Elongation in Inches per 100 it prom -- 20 F OP Cast-. Iron Pipe Steel rSP 05- Pipe Pipe 29.39 28.89 27.99 26.48 24.04 20.27 14.63 6.45 -20 0 20 40 ................... 60 -- 80 ----------- 100 -- 120 -- 140 -- 160 -- 180 -- 200 2.5 220 10.3 240 20.7 260 34.5 280 52.3 300 74.9 320 103.3 340 138.3 360 180.9 380 232.4 400 293.7 420 366.1 440 451.3 460 550.3 480 000 0.127 0.145 0.152 0.255 0.293 0.306 0.390 0.430 0.465 0.518 0.593 0.620 0.649 0.725 0.780 0.787 0.898 0.939 0.926 1.055 1.110 1.051 1.209 1.265 1.200 1.368 1.427 1.345 1.528 1.597 1.495 1.691 1.778 1.634 1.852 1.936 1.780 2.020 2.110 1.931 2.183 2.279 2.085 2.350 2.465 2.233 2.519 2.630 2.395 2.690 2.800 2.543 2.862 2.988 2.700 3.029 3.175 2.859 3.211 3.350 3.008 3.375 3.521 3.182 3.566 3.720 3.345 3.740 3.900 3.511 3.929 4.096 3.683 4.100 4.280 0 664.3 500 .0.204 795.3 520 0.442 945.3 540 0.653 1115.3 560 0.888 1308.3 580 1.100 1525.3 600 1.338 1768.3 620 1.570 2041.3 640 1.794 2346.3 660 2.008 2705 680 2.255 3080 700 2.500 720 2.720 740 2.960 760 3.189 780 3.422 800 3.665 820 3.900 840 4.145 860 4.380 880 4.628 900 4.870 920 5.118 940 5.358 960 51612 980 5.855 1000 3.847 4.296 4.477 6.110 4.020 4.487 4.677 6.352 4.190 4.670 4.866 6.614 4.365 4.860 5.057 6.850 4.541 5.051 5.268 7.123 4.725 5.247 5.455 7.388 4.896 5.437 5.660 7.636 5.082 5.627 5.850. 7.893 5.260 5.831 6.067 8.153 5.442 6.020 6.260 8.400 5.629 6.229 6.481 8.676 5.808 6.425 6.673 8.912 6.006 6.635 6.899 9.203 6.200 6.833 7.100 9.460 7.046 7.314 9.736 7.250 7.508 9.992 7.464 7.757 10.272 7.662 7.952 10.512 7.888 8.195 10.814 8.098 8.400 11.175 8.313 8.639 11.360 .795 8.545 8.867 11.625 8.755 9.089 11.911 8.975 9.300 12.180 i 9.196 9.547 12.473 9.421 9.776 12.747 rruw r-tpmg acnaooo/t, oy waUcer and Crocker. This table gives the expansion from --20Fto the temperature in question. To obtain the amount of expansion between any two temperatures take the difference 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. has been found to give reasonably good results and is deemed to be sufficiently accurate for most heating work. Fig. 1. shows several types of expansion bends commonly used for taking up thermal expansion. The amount of pipe, L; required.in each of these bends may be computed from Equation 2. L = 6.16 y D A where ' L = length of pipe, feet. D = outside diameter of the pipe used, inches. A = the amount of expansion to be taken up, inches. (2) This formula, based on the use of mild-steel pipe with wall thicknesses hot heavier than extra-strong, assumes a maximum safe value of fiber 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 352 CHAPTER 18. PIPE, FITTINGS, WELDING further assumed that the corners are made with screwed or flanged elbows or with arcs of circles having radii five to six times the pipe diameter. Use of welding elbows with radii of 1% times the pipe diameter will decrease the end thrusts somewhat but will raise the fiber stress correspondingly. All risers must be anchored and safeguarded so that the difference in length when hot from the length when cold shall not disarrange the normal and orderly provisions for drainage of the branches. Proper anchoring of piping is especially necessary with light-weight radiators, to allow for freedom of expansion in order that no pipe strain will distort the radiators. When expansion strains from the pipes are Offset U bend Fig. 1. Measurement of L on Various Pipe Bends permitted to reach these light metal heaters they usually emit sounds of distress which are exceedingly troublesome. PIPE THREADS All threaded pipe for heating and ventilating installations uses the American Standard taper pipe thread which is made with a taper of 1 in 16 measured on the diameter of the pipe so as to secure a tight joint. Threads of fittings are tapped to the same taper. The number of threads per inch varies with the different pipe sizes. All threaded pipe should be made up with a thread paste suitable for the service under which the pipe is to be used. HANGERS AND SUPPORTS Heating system piping requires careful and substantial support. Where changes in temperature of the line are not large, such simple methods of support may be utilized as hanging the line by means of rods or perforated strip from the building structure, or supporting it by brackets or on piers. When fluids are conveyed at temperatures of 150 F or above, however, hangers or supporting equipment must be fabricated and assembled to permit free expansion or contraction of the piping. This can be accom plished by the use of long rod hangers, spring hangers, chains, hangers or supports fitted with rollers, machined blocks, elliptical or circular rings of larger diameter than the pipe giving contact only at the bottom, or trolley hangers. In all cases, allowance should be made for rod clearance to permit swinging without setting up severe bending action' in the rods. For pipes of small size, perforated metal strip is often used. For horizontal mains, the rod or strip usually is attached to the joists or steel work of the floor above. For long runs of vertical pipe subject to con siderable thermal expansion, either the hangers should be designed- to 353 X