DRYER COMPONENTS

as adsorption There is a difference between absorption and adsorption. Absorption takes place in the telltale oil filter when it removes oil by soaking it up as a liquid (the same way that a sponge absorbs liquid water into its interior pores). Adsorption is a surface and a molecular phenomenon. Mobile gaseous and liquid atoms or molecules are attracted to the surface of any solid because of unbalanced forces existing at the surface. Good absorbents are those that present large surfaces per unit and have high attractive forces. One cubic inch of the adsorbent material used in this dryer has an adsorbent area greater than the area of two football fields. The wet air passes through chambers filled with a molecular sieve type of desiccant, or adsorbing material. Vapor molecules are left behind on the desiccant and the air emerges clean and dry. The dehydrator has two such chambers through which the air passes alternately. While one chamber is removing vapor from the air, a small portion of the dried air is routed through the second chamber to purge it of all collected vapors and to prepare it to do the drying during the next half cycle. The reactivation of the desiccant is completely automatic, and unless slugs of entrained water or oil are permitted to enter the desiccant chambers, the material should not be replaced except at major overhaul. The fluid separator and the telltale oil filter, located upstream, prevent slugs of liquid from reaching the desiccant if they are kept in good operating condition. The dust filter, located downstream from the dehydrator, removes any desiccant or other dust particles that might otherwise be carried along in the dry airstream. At the outlet of the drier unit, a flow limiter is used to prevent the electronic equipment from exceeding the capacity of the dryer. In normal operation, the flowmeter has no effect. However, should an air line or waveguide downstream from the dryer be opened, the flow limiter would prevent an excessive airflow beyond the capability of the dryer. DRYER COMPONENTS In figure 2-1, the placement of the individual components is shown for a typical dryer. This is the order that you should expect to see them. The air dryer is a very reliable piece of equipment and with proper PM can give you years of service. The operation of the dryer can be bypassed by changing the selector valve. With the selector valve in the position as shown, all air is routed through the dryer. Starting at the inlet, the individual operation of each major component will be discussed in depth. Let’s begin with the fluid separator and its dump trap. Fluid Separator and Dump Trap The fluid separator and dump trap consist of two interconnected assemblies, the separator and the automatic trap, connected together as shown in figure 2-2. The separator itself is a welded metal tank within Figure 2-2.—Fluid separator. 2-4