Pressure relief valve--pressure control valve used to keep system pressure from exceeding
predetermined limits.
Pressure switch--electrical switch operated by the increase or decrease of fluid pressure.
Priority valve--valve used to route fluid to those components requiring immediate completion of action
when a reduction in normal system flow and pressure occurs.
Pump--device that converts mechanical energy into fluid energy.
Ratchet valve--valve used with double-action actuator cylinders to aid the cylinder in holding a load in
the position selected by the operator.
Reservoir--container that serves primarily as a supply source of the fluid for a hydraulic system.
Selector valve--valve used to control the direction of movement of an actuating unit.
Servo--device used to convert a small movement into a greater movement or force.
Sloppy link--point of interconnection between control linkage, pilot valve, and servo piston rod in a
servo.
Standpipe--pipe located in a reservoir where the main hydraulic system draws its fluid.
Stroke--distance a piston moves in its bore from bottom to top, a single movement of a piston from one
end of its range to the other.
Thermal expansion--increase in volume of a substance due to temperature change.
Variable-delivery pump--type of pump in which the volume of fluid per cycle can be varied.
*U.S. GOVERNMENT PRINTING OFFICE: 2000-528-075/20366
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AL0926
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