Document vyVbMEpBMk6XVBo2K58Bg7QZq

510 CHAPTER 26 ,1948 . Guide A modification of this type of humidifier is the combination of spray nozzle and heater type in which the water is sprayed over a hot surface and evaporated. It has the disadvantage of. accumulating scale on. the surfaces of the vessel or heating surface. ' For a discussion of various methods of humidification see Chapter 37. . . REFERENCES ^"See National Fan Manufacturers Association standard definitions in Chapter 32. : *-Standard Code for Testing and Rating Steam Unit Heaters (A.S.H.V.E. Transactions, Voi; 36,1930, p.; 165), prepared by a Joint Code Committee of the American Society op Heating and Ventilating Engineers and the Industrial Unit Healer Association and adopted .1930, * Standard Code for Testing Hot Water Unit Heaters prepared by Engineering Committee of Industrial Unit Heater Association. Adopted by Industrial Unit Heater Association. August 1942 and published September 1942. 4"A-S.H.V.E. Research Report No. 958--Temperature Gradient Observations in a Large Heated Space, by G. L. Larson, D. W. Nelson and O. C. Cromer (A.-S.HiV.E. Transactions, Vol. 39.1933, p. 243). A.S.H.V.E. Research Report No. 1011--Tests of Three Heating Systems in an Industrial Type of Build ing by G. L. Larson. D. W. Nelson and John James (A.S.H.V.E. Transactions, Vol. 41, 1935, p. 185). .8--A.S.H.V.E. Standard Code for Testing and Rating SteamXJnit Ventilators (A.S.H.VIE. Transac tions, Vol. 38, 1932, p. 25). --A.S.H.V.E. Research Report No. 936--Investigation of Air Outlets in Class Room Ventilation, by G. L..Larson, D. W. Nelson and R. W. Kubasta (A.S.H.V.E. Transactions, .Vol. 38, 1932, p.-463). A.S.H.V.E.-Research Report No. 1017--Air Supply to Classrooms in Relation to Vent Flue Openings, by F. C. Houghteh, Carl Gutberlet arid M. F. Lichtenfels (A.S.H.V.E. Transactions, Vol. 41.1935, p. 279). T--Estimating the Humidification Requirements of -Residences; by W. H: Severns (Papers Presented at the First-Annual Conference on Air Conditioning, Universityof Illinois. Engineering Exteriment Station Circular. No. 6. October, 19361. . .. Chapter 27 PIPE, FITTINGS, WELDING Pipe Materials, Types of Pipe, Commercial Pipe Dimensions, Expansion and Flexibility of Pipe, Pipe Threads and Hangers, Types of Fittings, Flange Facings and Gaskets, Welding in Erection of Piping*.. '. Valves, Corrosion , IMPORTANT considerations in the selection and installation of pipe and fittings- for heating, ventilating, and air conditioning are dealt with in this chapter; - .................... PIPE MATERIALS Use of corrosion-resistant materials for pipe, including special alloy steels and irons, wrought-iron, copper, and brass, has increased con siderably during the past few years. The recent development of copper, brass, and bronze fittings which can be assembled by soldering or sweating permits the use of thin-wall pipe and thereby has reduced the initial cost of such installations. The following brief discussion indicates the variety of pipe materials and the types of pipe available. Wrought-Sted Pipe. Because of its low price, the great bulk of wrought pipe used for heating and ventilating work at the present time is of wrought steel. The material used for steel pipe is a mild steel made by the add-bessemer, the open-hearth, or the electric-furnace! process. Ordinary wrought-steel pipe is made either by shaping sheets of metal into cylindrical form and welding the edges together, or by forming or drawing from a solid billet. The former is known as welded pipe, the latter as. seamless pipe. Many types of welded pipe are available, although the smaller sizes most frequently used in heating and ventilating work are made by the lap-weld, resistance-weld, or butt-weld process. While the lap-wela and resistance-weld processes produce a better weld than the butt type, lap-weld and resistance-weld pipe are seldom manufactured in nominal pipe sizes less than 2 in. Seamless pipe can be obtained in the small sizes at a somewhat higher cost. Seamless steel pipe is frequently used for high pressure work or where pipe is desired for- close coiling, cold bending, or other forming operation. Its advantages are its somewhat greater strength which permits use.of a thinner wall and, in the small sizes, its freedom from the occasional tendency of welded pipe to split at the weld when bent. Wrought-iron. Pipe. Wrought-iron pipe is claimed ' to. be more corro sion-resisting than ordinary steer pipe and therefore its somewhat higher first cost is said to be justified on the basis of longer life expectancy. Wrought-iron pipe may be identified by the spiral line marked into each length, either knurled into the metal or painted on it in red or other bright color. Otherwise, there is little difference in the appearance of wrought, iron and steel pipe, although microscopic examination of polished and etched specimens will readily disclose the difference. ., Cast-Ferrous Pipe. There are now available several types of castferrous metal pipe made of a good grade of cast-iron with or without additions of nickel, chromium, or other alloy. This pipe is available in sizes from 1in. to 6 in., and in standard lengths of 5 or 6 ft with external and internal diameters closely approximating those of extra strong 511