Ammonia flow system

Engineering Aid 3 - Beginning Structural engineering guide book
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Figure 3-64.-Ammonia flow system. tank through a gravity-feed system (fig. 3-64). This feed system permits a smooth, even flow of ammonia, thus minimizing the possibility of air or vapor locking of the feed tubing. The amount of ammonia fed into the developer is controlled by a feed regulator at a rate of approximately 50 to 60 drops per minute. The ammonia is directed into evaporating drip trays that are suspended in the developer tank. Fastened to these trays are electric heater rods. These rods, in conjunction with a second thermo-switch controlled heater in the developing tank, serve to heat the ammonia and thereby accelerate the formation of ammonia vapors. These vapors activate the image on the print as they escape through the holes in the upper part of the developer tank. Thus, a semi- permanent image of those areas that were NOT desensitized in the printing section is developed on the print as it passes across the vapors. To protect the machine from flooding with ammonia when the machine is secured, an automatic shutoff valve is located in the ammonia feedline. This value shuts automatically when the machine is secured and opens automatically when the machine is turned on, thereby remitting ammonia to the feed tray. A second ammonia supply system being used in some machines is called the anhydrous ammonia system. Cylinders filled with anhydrous ammonia supply the developing section with an ammonia vapor. This vapor is directed into the developer tank where it is distributed with the aid of distilled water that is fed into the drip trays. For safety reasons, cylinders should be stored away from heat and sunlight. Do not allow the temperature of the cylinders to reach a temperature above 125°F. Position the cylinders upright, and firmly attach them with a chain or strap to a rigid supporting member, such as a wall. Cylinders are attached to the developing tank through a system of piping and fittings, When changing a cylinder, close the valve on the expended cylinder tightly by turning it clockwise. Bleed off all pressure remaining in the feed line by turning on the ammonia flow in the machine. Disconnect the fitting or yoke cylinder connection. Replace the cylinder and remove the protecting valve cap. Ensure that a Teflon washer is in place. Connect the fitting or yoke cylinder connection. Make sure all connections are tight. Open the cylinder valve. Check for possible leaks on all connections by holding a piece of unexposed and undeveloped diazo paper close to the connections. If the diazo paper discolors, retighten the connections. A uniform flow of ammonia is maintained by a pressure gauge located between the cylinder and the developing section. In addition, the pressure gauge indicates the amount of available ammonia left in the cylinder. A new cylinder will have a gauge reading of 150, while an empty cylinder will indicate a reading of 50. 3-48

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