Copyright Goodheart-Willcox Co., Inc. Chapter 16 Conditioning and Distribution of Compressed Air 409 the station as long as the pressure in the distribution system does not drop below that selected pressure. Several different regulator designs and features are available. These designs include: • Direct operated. • Basic, diaphragm chamber. • Relieving. • Balanced-poppet valve. • Pilot operated. A number of variations and combinations of these designs are available. The type of regulator selected for a particular system depends on the accuracy and con- trol needed in the system. Direct-operated regulators Figure 16-18 shows the internal structure of a direct- operated regulator. This is the most basic of the units. The unit consists of a cast body with inlet and outlet ports, spring-loaded poppet valve, fl exible diaphragm, transfer pin (located between the poppet valve and the diaphragm), control spring, and threaded screw (for adjusting the tension of the control spring). Information and specifi cation sheets available from the manufacturer supply these details for the various fi l- ter units it produces. 16.3.2 Pressure Regulation at the Workstation The pressure regulator is the second of the compo- nents in the FRL unit. The regulator maintains a uni- form air pressure at the workstation. This promotes consistent actuator operation for tools and circuits powered by the station. A regulator is necessary as the air pressure in the distribution system is higher than that normally used for workstation operation. Also, the air pressure in the distribution line varies because of the characteris- tics inherent to compressor-capacity control systems. Regulators maintain the desired output pressure for Body Louver Center position Element Sight glass Collected condensate Drain Bowl Baffle IMI Norgren, Inc. Figure 16-16. Many air filters used in the final preparation of air at the workstation use both centrifugal force and filter elements to remove dirt and water from the air distributed by the system. Draincock Goodheart-Willcox Publisher Figure 16-17. Accumulated dirt and water need to be regularly removed from the filter bowl. A manual draincock or automatically operated valve is found on most filter units.