• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
Pneumatic System
Air cylinder

Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them
Page Navigation
  282    283    284    285    286  287  288    289    290    291    292  
The other type of system in current use has its own compressor and other equipment necessary for maintaining an adequate supply of compressed air during flight. Provision for ground charging this type of system is also provided. In addition to a compressor, the components in this type of system usually include a filter, a pressure regulator, a moisture separator, a relief valve, a chemical drier, and storage cylinder(s). AIR COMPRESSORS.—A typical air com- pressor is shown in figure 7-43. An installation of this type receives its supply of air from the compressor section of the aircraft engine. This air is then compressed further to the required pressure for operating the system.    Compressors of this type are capable of maintaining up to and above 3,000 psi pressure during flight. On some aircraft, the compressor is operated by an electric motor. On others, a hydraulic motor is used to drive the compressor. Compressors must be serviced with oil periodically, as outlined in the aircraft MIM. An oil level sight gauge is provided on the compressor (fig. 7-43). AIR FILTERS.—An air filter is usually located in the line leading into the system compressor. Additional filters may be located at various points in the system lines to remove any foreign matter that may enter the system. Figure 7-43.—Air compressor. Like hydraulic filters, air filters have a removable element and a built-in relief valve. The relief valve is designed to open and bypass the air supply around the filter element should the element become clogged. Some air filters are equipped with the micronic-type element, which must be replaced periodically. Others have the screen mesh type, which requires periodic cleaning. The latter type may be reinstalled after cleaning and drying. AIR PRESSURE REGULATORS.—A pressure regulator is generally located in the line between the engine compressor and the pneumatic system compressor; however, it may be incorporated within the system moisture separator. Its purpose is to regulate the pressure of the supply air before it enters the system compressor. The pressure regulator maintains a stable outlet pressure regardless of the inlet pressure. MOISTURE SEPARATORS.—The moisture separator in a pneumatic system is always located downstream of the compressor. Its purpose is to remove any moisture caused by the compressor. A complete moisture separator consists of a reservoir, a pressure switch, a dump valve, and a check valve, and it may also include a regulator and a relief valve. The dump valve is energized and de-energized by the pressure switch. When de-energized, it completely purges the separator reservoir and lines up to the compressor. The check valve protects the system against pressure loss during the dumping cycle and prevents reverse flow through the separator. RELIEF  VALVES.—A  relief  valve  is incorporated in a pneumatic system to protect the system from overpressurization. Overpressurization is generally caused by thermal expansion (heat). Relief valves are generally adjusted to open and close at pressures slightly above normal system operating pressure. For example, in a system designed to operate at 3,000 psi, the relief valve might be set to open at 3,750 psi and reseat at 3,250 psi. CHEMICAL DRIERS.—Chemical driers are incorporated at various locations in a pneumatic system. Their purpose is to absorb any moisture that may collect in the lines and other parts of the system. Each drier contains a cartridge, which should be blue in color. If otherwise noted, the cartridge is to be considered contaminated with moisture and should be replaced. STORAGE CYLINDERS.—Pneumatic storage cylinders (bottles) are made of steel and maybe either 7-44







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.