Document LwLpyGnD54O5EOazoED6Zom7

American Society of Heating and Ventilating Engineers Guide, 1924-25 welding. This scale is strongly electro-negative to iron, like copper, and should therefore be removed. For a number of years efforts have been directed to accomplish this object and a scale removing process has finally been worked out, which is in effect a further application of the process of laterally working the steel above mentioned, but in this process the work is applied to the hot pipe in the finishing operations at a temperature below the welding heat. When the skelp has reached the proper tempera ture for welding, it is drawn through the customary type of welding bell forming an unfinished pipe of larger size than is usual. The pipe is then held on a cooling table until the temperature is reduced to about 1800 deg. fahr. ft then passes through a series of rolls where it is reduced in size and elongated. These rolls reduce the pipe to its correct finished size. The reduction in the size of the pipe which it receives in passing through the series of rolls cracks the hardened welding-scale from both the interior and exterior surfaces of the pipe,, leaving them clean and smooth. After a pass through a set of cross rolls, to take care of any straightening that may remain to be done and to give the exterior a smooth, clean finish, the pipe is taken to a tank of water where it is dipped, lifted to a slanting position and the water allowed to rush out, carrying with it the loose scale from the pipe. Certain sizes have the loose scale blown out by a blast of compressed air instead of being dipped in the water. The advantages of scale-free pipe are, its clean, smooth surfaces present and ideal base for the adherence of a galvanizing coating--full working capacity is assured^ the interior being free from any obstructions tending to reduce the flow. This is important in. heating and other piping work. Troubles caused by the deposit of scale in valves and strainers, and other apparatus, are practically eliminated, while pitting by corrosion is materially reduced. These improvements narurally give rise to the thought that a longer life might reasonably be expected from the pipe under certain conditions, and while this has been the object of most of the research, experiments and perfection of processes, considerable improvement has been attained in this respect, the fact still remains that the life of pipe is governed largely by installation conditions, and no matter how well made or uniform the pipe may be, the life of pipe, particularly under severe cor rosion conditions; such as, hot water supply lines, boiler feed and return lines, is limited, and some protective measures are necessary to secure a longer life. For some years past considerable research and experimental work has been carried on to determine the causes of failure in pipe lines, and to ameliorate the effects of corrosion; to investigate unusual conditions of service, and to determine a practical means of corrosion prevention. The electrolytic theory of corrosion as formulated in 1903 by Dr. Whitney has led to the development of certain protective systems which are based on the removal of dissolved oxygen from water. Careful ex periments in various research laboratories have demonstrated that the amount of corrosion found is almost directly proportional to the amount of oxygen in solution, and varies directly as the temperature. The 152 American Society of Heating and Ventilating Engineers Guide, 1924-25 predominating influence of free oxygen in water was suspected before this, as a result of the early study of pipe corrosion, for the most striking fact in practical pipe experience is that hot-water-heating systems in variably showed no corrosion to speak of after 35 or 40 years' use; where as, frequently, hot-water-supply systems operating at the same average temperature with the same water lasted less, than half this time. That this was independent of whether the material was iron or steel was fully demonstrated by many service tests which were conducted for a period of more than ten years, in which representative pipes of each class were installed alternately in hot-water lines. Size Internal T h ic k n e s s Threads and couplings T hreaps PER INCH Diameter Butt TABLE 88. STANDARD PIPE--BLACK AND, GALVANIZED* All Weights and Dimensions are Nominal Diameters 1 RV. m Weight per Foot c8 e 'a Couplings si M C .2 1 Test Pres sure in Pounds a 3 3 0.405 0.675 H ^.840 H 1.050 ii? . 1.900 2.375 2.875 3.500 3H 4.000 4.500 5.000 5.563 6 6.625 7.625 8.625 8.625 9 9.625 10.750 10 10.750 10.750 11 11.750 12 15 O. D. 12.750 12.750 14.000 15.000 16 O. D. 17 O. D. 18 O. D. 20 0. D. 16.000 17.000 18.000 20.000 0.269 0.068 0.364 0.088 0.493 0.091 0.622 0.109 0.824 0.113 1.049 0.133 1.380 0.140 1.610 0.145 2.067 0.154 2.469 0.203 3.068 0.216 3.548 0.226 4.026 0.237 4.506 0.247 5.047 0.258 6.065 0.280 7.023 8.071 7.981 8.941 0.301 0.277 0.322 0.342 10.192 0.279 10.136 0.307 10.020 0.365 11.000 0.375 12.090 0.330 12.000 0.375 13.250 0.375 14.250 0.375 15.250 0.375 16.214 0.393 17.182 0.409 19.182 0.409 0.244 0.424 0.567 0.850 1.130 1.678 2.272 2.717 3.662 5.793 7.575 9.109 10.790 12.538 14.617 18.974 23.544 24.696 28.554 33.907 31.201 34.240 40.483 45.557 43.773 49.562 54.568 58.573 62.579 69.704 76.840 85.577 0.245 0.425 0.568 0.852 1.134 1.684 2.281 2.731 3.678 5.819 7.616 9.202 10.889 12.642 14.810 19.185 23.769 25.000 28.809 34.188 32.000 35.000 41.132 46.247 45.000 50.706 55.824 60.375 64.500 72.602 80.482 89.617 27 0.562 18 0.685) 18 0.848 14 1.024 14 ubi 11V? UH 1.281 1.576 1.950 2.218 2.760 8 3.276 8 3.948 8 4.591 8 5.091 8 5 591 8 6.296 8 7.358 8 8, 8. 8 8.358 9.358 9;358 10.358 8 11.721 8 11.721 8 11.721 8 12.721 8 13.958 8 13.958 8 15.208 8 16.446 8 17.446 8 18.683 8 19.921 8 21.921 X 1 m lH m in 2H 2X 22 nX 3*i 3X 4H m 4W 5X QH 6H 6H 6X 6H 6M 6V? ax avxx 7H VJi 0.029 700 0.043 ____ 0.070 700 -- 0.116 700 -- 0.209 700 ____ 0.343 700 ........ 0.535 700 1000 0*743 700 1000 1.208 1,720 2.498 4.241 700 800 800 -- 1000 1000 1000 4.741 5.241 8.091 9.554 ____ -- 1000 1000 1000 10.932 13.905 ...___ 13.905 17.236 1000 800 900 29.877 29.877 29.877 32.550 _____ _____ _____ ---- 43.098 43.098 _____ 47452 59.493 -- 600 vuu 600 700 63.294 _____ 90.941 108.672 120487 -- 600 600 5UU The permissible variation in weight is 5 per cent above and 5 per cent below. Furnished with threads and couplings and in random lengths unless otherwise ordered. Taper of threads is #*in. diameter per foot length for all sizes. The weight per foot of pipe with threads and couplings is based on a length of 20 ft., including the coupling, but shipping lengths of small sizes will usually,average less than 20 ft. ' All weights given in pounds. All dimensions given in inches. On sizes made in more than one weight, weight desired must be specified. From National Tube Co.'s " Book of Standards." ' 153