Copyright Goodheart-Willcox Co., Inc. Chapter 8 Fluid Storage and Distribution 195 The connection styles can be generally grouped into one of four categories: • Category 1. Straight threads and a shoulder sealed with an O-ring or a metal compression washer. • Category 2. Tapered pipe threads for both attachment and seal. • Category 3. Flanged connection with the seal provided by an O-ring held in a groove. • Category 4. Flared connections for the seal. Adapter fi ttings Adapter fi ttings are connectors used to eliminate twist- ing or excessively bending a conductor during instal- lation. They also assist in disassembly and reassembly of the system during service. Adapter fi ttings are often used between pipe, tube fi ttings, or hose-end fi ttings and the component. A variety of connection styles are available for the ends of these adapters based on both American and international standards. See Figure 8-25. B A System connection Insert nipple Two clamp pieces Hose Disassembled Unit Assembled Unit System connection Insert nipple Nipple-to-shell thread Outer shell Hose Disassembled Unit Assembled Unit Goodheart-Willcox Publisher Figure 8-24. Reusable hose-end fittings are either screw-together or clamp type. A—Screw together. B—Clamp.