Document RJvnm5oJO4pN2oNg23nxLMzv7

292 CHAPTER 24 plications, they might be used if the air must be provided in the immediate vicinity of equipment in the center of an open space. Modifications to elevate the grille face above the floor and provisions for cleanout are desirable. REFERENCES 1 H. P. Schulte et at: Evaluation of laboratory fume hoods {American Industrial Hygiene Association, Quarterly, 15.3, September 1954). 1 James Halitaky: Vent to intake short circuit (Atr Conditionmg. Heating and Ventilating, July 1961, p. SI). BIBLIOGRAPHY J. M. Ruddy: Controlling airborne radioactivity during "hot" clean-up {Air Conditioning, Heating, and VentSatino. February 1960.P.67). * R. J- Hale: laboratory Ventilation (Paper presented at the 1962 Guide And Data Book Proceedings of the Sixth Hot Laboratory and Equipment Con. ferenee at the Nuclear Congress, March 19, 1958). J. M. Ruddy: Designing fume hoods for medium level radioactive conditions (Heating, Piping and Air Conditioning, March, W. li. Harris: Laboratories for handling radioactive material. (Healing and Ventilating, November 1953, p. 75). J. E. York^Ventilatioa and air conditioning for Ulwatorie- (Hailingand ventilating, November 1953, p. 81). J. M. Ruddy: Air conditioning rodent quarters (Heating ami Ventilating, March 1952, p. 95). J. F. Turner: New laboratory fume hoods cut sir conditioning load (Heating, Piping and Air Conditioning, January 195L p. Building Research Advisory Board: Laboratory design for handling radioactive materials (Conference Report No. 3. Novem ber 27 and 28, 1951). . .on- H. B. C3ay: Controlling fume bood exhaust in atomic enenrv Ujhorstories (Heating, Piping and Air Conditioning, July I960, p. CHAPTER 25 PRINTING PLANT AIR CONDITIONING ' Paper Characteristics, Multicolor Offset lithography. Air Conditioning the Multicolor Offset Lithography Plant, Collotype Printing, Sheet-Fed Relief Printing, Sheet-Fed Gravure, Platetnaking, Web Printing, Air Conditioning the Web Press Room, Control of Paper, Air-Conditioning Systems - THIS chapter will outline the air-conditioning require above the comfort zone due to the high motor load in the ments of the various printing operations and discuss the press room. Also, the variation in dry-bulb temperature is application of equipment to obtain the desired results. Hie beyond the limits required for constant control of the process. problem^ in the various printing processes and the behavior For best results the air-conditioning system should provide of paper and other materials due to variable moisture con separate control of the relative humidity and temperature of tent will be discussed to provide a better understanding of the air in the conditioned space during the entire year. This bow the air conditioning system will reduce production prob also includes filtering the air, providing ventilation air, and lems, help maintain uniform production throughout the year, exhausting the air from certain areas. and in certain operations improve quality. Air conditioning of printing plants is a means of solving PAPER CHARACTERISTICS some of their most troublesome problems by providing uni form moisture content and temperature of the air in the working spaces. Paper, the principal raw material used in The moisture content of paper is controlled by the relative humidity of the surrounding air. Fig. 1 indicates how the his tory of the hygroscopic state of lithographic paper determines printing, is hygroscopic and very sensitive to variations in the humidity of the surrounding air, as are some of the other its equilibrium condition at different relative humidities.1 materials and operations. The problems due to the expansion and contraction of paper in the printing process are satisfac torily solved by controlling the moisture content of the paper from the time it leaves the mill until the printing is complete. This requires control of the temperature and moisture con tent of tire air in the plant. The temperature and humidity requirements are not the same for all types of printing and printing operations, and certain printing processes require more exacting control of the moisture content of the ambient air. For this reason, careful consideration of the problems masting in the process is essential in calculating the needs of a specific plant. Symptoms of varying air conditions in the printing plant include: (1) distorted, curled, or buckled paper; (2) static electricity; (3) wrinkling of sheets or web in printing; (4) misregistcr of color prints; (5) failure of ink to dry; and (6) swelling or shrinking of composition rollers. Other indications of changing humidity conditions are changes in the light sen sitivity of the coatings used in preparing the printing surfaces in photolithography, gravure, and photoengraving. The dif ficulties result from reactions of paper and the other hygro scopic materials when their moisture content is not in equi librium with the ambient air. The value of controlling the temperature and humidity of tiie air to correct the preceding problems is not the same for all printing operations. The control of relative humidity is of prime importance where the problem is one of maintaining constant moisture content in the paper during the entire printing operation. Installations have been made with only humidity control and no provision for cooling. This approach Rg. 1 .... Equilibrium Moisture Content of Papers at >s not recommended because the dry-bulb temperature is far Various Relative Humidities 293