LINES, FITTINGS, AND SEALS:Hose Connection Side of Hose Fittings.

Hose Connection Side of Hose Fittings

Hose fittings are attached to the hose by several methods. Each method is determined by the fitting manufacturer and takes into consideration such things as size, construc­ tion, wall thickness, and pressure rating. Hose used for flexible connections requires one of the following methods for attachment of the fittings to the hose.

One-piece reusable sockets. The socket component of the fitting is fabricated as a single piece. One-piece reusable sockets are screwed or rocked onto the hose OD, followed by insertion of the nipple component.

Segmented bolted sockets. The segmented bolted socket consists of two or more segments that are bolted together on the hose after insertion of the nip­ple component.

Segmented ring-and-band sockets. The segmented ring-and-band attachment socket consists of three or more segments. As with the bolted segments, the segments, ring, and band are put on the hose after insertion of the nipple. A special tool is required to compress the segments.

Segmented ring-and-bolt. The segmented ring-and-bolt attachment consists of three or more components and is assembled in the same way as the preceding fittings.

QUICK-DISCONNECT COUPLINGS

Self-sealing, quick-disconnect couplings (Figure 8-15) are used at various points in many fluid power systems. These couplings are installed at locations where frequent uncoupling of the lines is required for inspection, test, and maintenance. Quick-disconnect couplings are also commonly used in pneumatic systems to connect sections of air hose and to connect tools to the air pressure lines. This provides a convenient method of attaching and detaching tools and sections of lines without losing pressure.

Quick-disconnect couplings provide a means for quickly disconnecting a line without the loss of fluid from the system or the entrance of foreign matter into the system.

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Several types of quick-disconnect couplings have been designed for use in fluid power systems. Figure 8-15 illustrates a coupling that is used with portable pneumatic tools. The male section is connected to the tool or to the line leading from the tool. The female section, which contains the shutoff valve, is installed in the pneumatic line leading from the pressure source. These connectors can be separated or connected by very little effort on the part of the operator.

The most common quick-disconnect coupling for hydraulic systems consists of two parts, held together by a union nut. Each part contains a valve which is held open when the coupling is connected, allowing fluid to flow in either direction. When the coupling is disconnected, a spring in each part closes the valves, preventing the loss of fluid and entrance of foreign matter.

MANIFOLDS

Some fluid power systems are equipped with manifolds in the pressure supply and /or return lines. A manifold is a fluid conductor that provides multiple connection ports. Manifolds eliminate piping, reduce joints, which are often a source of leakage, and conserve space. For example, manifolds may be used in systems that contain several subsystems. One common line connects the pump to the manifold.

There are outlet ports in the manifold to provide connections to each subsystem. A similar manifold may be used in the return system. Lines from the control valves of the subsystem connect to the inlet ports of the manifold, where the fluid combines into one outlet line to the reservoir. Some manifolds are equipped with check valves, relief valves, filters, and so on, that are required for the system. In some cases, the control valves are mounted on the manifold in such a manner that ports of the valves are connected directly to the manifold.

Manifolds are usually one of three types: sandwich, cast, or drilled. The sandwich type is constructed of three or more flat plates. The center plate, or plates, is machined for passages, and the required inlet and outlet ports are drilled into the outer plates. The plates are then bonded together to provide a leakproof assembly. The cast type of manifold is designed with cast passages and drilled ports. The casting may be iron, steel, bronze, or aluminum, depending on the type of system and fluid medium. In the drilled-type manifold, all ports and passages are drilled in a block of metal.

A simple manifold is illustrated in Figure 8-16. This manifold contains one pressure inlet port and several pressure outlet ports that can be blocked off with threaded plugs. This type of manifold can be adapted to systems containing various numbers of sub­ systems. A thermal relief valve may be incorporated in this manifold. In this case, the port labeled T is connected to the return line to provide a passage for the relieved fluid to flow to the reservoir.

Figure 8-17 shows a flow diagram in a manifold that provides both pressure and return passages. One common line provides pressurized fluid to the manifold, which

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distributes the fluid to any one of five outlet ports. The return side of the manifold is similar in design. This manifold is provided with a relief valve, which is connected to the pressure and return passages. In the event of excessive pressure, the relief valve opens and allows the fluid to flow from the pressure side of the manifold to the return side.

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