uses hydraulic or pneumatic medium. The basic components are as follows:

Reservoir

Strainers and filters

Pumps

Control valves (directional and relief)

Actuating devices (cylinders)

Accumulators

Motors

Lines (pipe, tubing, or flexible hose)

Connectors and fittings

Sealing materials and devices

Several applications of fluid power require only a simple system; that is, a system which uses only a few components in addition to the basic components.

Reservoir

A properly constructed reservoir (fig. 3-6) is more than just a tank to hold oil until the system demands fluid. Is should also be capable of the following:

1. Dissipating heat from the fluid,

2. Separating air from the oil, and

3. Settling out contamination in the oil.

Ideally, the reservoir should be high and narrow, rather than shallow and broad. The oil level should be as high as possible above the opening to the pump suction line. This condition prevents the vacuum at the line opening from causing a vortex or whirlpool effect. Anytime you see a whirlpool at the suction line opening, the system is taking in air.

As a rule of thumb, the reservoir level should be two to three times the pump output per minute. By this rule which works well for stationary machinery, a 20- gpm system would require a 40- or 60-gpm reservoir. However, this is not possible for mobile equipment. You are more likely to find a 20- or 30-gallon tank to support a 100-gpm system. This is possible because mobile systems operate intermittently, rather than all the time. The largest reservoirs are on mobile equipment. These reservoirs may have a 40- or 50- gallon capacity, capable of handling more than 200-gpm output.

The reservoir must be sized to ensure there is a reserve of oil with all the cylinders in the system fully extended. The reserve must be high enough to prevent a whirlpool at the suction line opening. Also, there

Figure 3-6. - Typical hydraulic reservoir.