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Fig. 10. Arrangement of an Impingement Drier Cabinet for Drying Fine Grain Release Positive Film at 300 fpm.
to be used for drying Fine Grain Release Positive Safety Film at 300 fpm with 200 F air at a velocity of 4,000 fpm. From Fig. 5, the required drying time for this film for these conditions is 10 sec. To this must be added 10% to compensate for the low initial moisture content of the experiment, making the actual required drying time 11 sec. This means the film path in the drier must be 11/60 X 300 = 55 ft. This is approximately 15.4 times as large as the pilot-plant machine. Therefore, the total air requirement is 900 cfm and the heat required is 1800 Btu/min. The pressure required to deliver air at this velocity through the orifices is 2.7 in. of water. Any fan similar to a
Glarage size 1£ type W single-width fan running at about 1800 rpm and powered with a 1-hp motor would be suitable for this service.
Figure 10 is a sketch to illustrate the approximate size of the drier cabinet and showing some of the features which would be desirable in such an installation.
In this arrangement the machine would have a single rack of film 5 ft high with 6 strands on it. Three-inch diameter film spools could be used. Backing rollers would be required so that the maximum unsupported film length would be 20 in. The air would be supplied from a large duct at the rear of the film cabinet. The three sections of the center plenum chamber would be rigidly attached to this duct and open into it. The two outside plenum chambers impinging on the emulsion surface would also open into the duct; however, they could be hinged on the duct so that they could be swung aside to facilitate inspection of the film or threading up. Inside the air duct at the openings to the side plenums, flaptype dampers could be provided which would automatically close off the air flow to the plenum chambers when they were swung aside.
Attached to the outside plenums, across the vertical edges, glass panels are shown and these together with the metal flaps attached to the bottoms would form a cabinet when the plenums were in their operating position. The top of the cabinet would be formed by the fixed exhaust duct which should be piped outside the building.
It would probably be desirable to install an automatic damper in the main air supply to shut off the air to the plenums in case of accidental stops while film is in the cabinet. The space occupied by the machine would be approximately 1 X 2 ft without fan or heaters.
Since this sketch and description are not intended to be a finished design,
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February 1953 Journal of the SMPTE Vol. 60