Document OEoOg16ReZp2OeKNEyB0Km84K

American Society of Heating and Ventilating Engineers Guide, 1929 &25, The Temperature of Evaporation, W. H. Carrier; p. 352, Bibliograph on Food Tying and Dryers; Vol. 26, p. 651, Commercial Dehydration, J. E. Whiteley; Vol. 27, p. 251, Drying as an Air Conditioning Problem, A. W. Lissauer; Journal American Society of Heating and Ventilating Engineers, October, 1921, p. 715, A Chrono logical Survey of Drying and Dryers, J. E. Bolling; Modern Drying Machinery, H. B. Crenshaw, London, 1926; The Kiln Drying of Lumber, A. .Koehler and R. Thelen, New York, 1926; Drying, W. H. Carrier, Marks' Mechanical Engineers Handbookt 2nd Ed., New York, 1924, p. 1444; Drying, Kent's Mechanical Engineers Handbook, 10th Ed., New York, 1923, p. 619; Calculations for Drying Design, Grosvenor, Trans. A. I. Chem. Eng. 1908, p. 184; The Rate of Drying Solid Materials, J. Lewis, Ind. Eng. Chem., 1921, p. 427. Chapter xxxii DUST, EXHAUST AND COLLECTING SYSTEMS Types of Systems, Air Velocity, Sire of Connections, Suction at Hoods, Resistance of Conveyor Pipes, Fan Selection, Collectors. PNEUMATIC exhaust and collecting systems may be classified in various ways. They may be classified by the economic purpose to be accomplished by the industries served, or by the type of system used. Classifying exhaust systems by industries served, they fall in sub divisions such as, metal working, woodworking, leather and shoe manu facturing, rubber industry, flint grinding, pottery works, pulverizing works, celluloid manufacturing, printing establishments, felt hatting and fur manufacturing, textile mills, grain and cereal industry, etc. TYPES OF SYSTEMS The type of exhaust system to be used is determined by the industry served, kind of material handled, and the work to be accomplished. There are two general arrangements; the central and the group systems. In the central system a single or double fan is located near the center of the shop with a piping system radiating to the various machines to be served. In the group system, which is sometimes employed where the machines to be served are widely scattered, small individual exhaust fans are located at the center of the machine groups. The group arrangement has the advantage of flexibility. Exhaust systems are'also classified, by the means employed to collect dust or other material handled. The dust or refuse.may be collected and controlled by enclosing hoods, open hoods, inward air leakage or general room exhaustion. With some classes of machinery it is not feasible, to closely hood the machines and in these cases open hoods over or adjacent to the machines are provided to collect as much of dust and fumes arising as .possible. In this class come such machines as rubber mills, package filling ma chinery, sand blast, crushers, forges, pickling tanks, melting furnaces, and the unloading points of various types of conveyors. The open hoods should be placed as close to the source of dust or fumes as possible with due regard to the movements of the operator. When the hood has to be placed at some distance above the machine it should be large enough to encompass an area of considerable extent as diffusion is usually quite rapid. Consideration must also be given to the natural movement of the fumes. For those that are lighter than air the hood should be over or Material for this Chapter originally prepared lor The Guide by H. M. Nichols, revised by R. E. Shaw, and W. A. Rowe. 461