Cavitation - A localized gaseous condition within a liquid stream which occurs where the pressure is reduced to the liquid's vapor pressure, often as a result of a solid body, such as a rapidly moving piston moving through the liquid. Also, the pitting or wearing away of a solid surface as a result of low fluid levels that draw air into the system, producing tiny bubbles that expand explosively at the pump outlet, causing metal erosion and eventual pump destruction.

Charles' Law - The volume of a fixed mass of gas varies directly with absolute temperature, provided the pressure remains constant.

Circuit - An arrangement of interconnected components and parts.

Cold Flexibility - Flexibility following exposure to a predetermined time.

Cold Flow - Continued deformation under stress.

Compatibility, Seal - Ability of an elastomer to resist the action of a fluid on its dimensional and mechanical properties.

Compressibility - The change in volume of a unit volume of a fluid when subjected to a unit change in pressure.

Compression Modulus - The ratio of the compressive stress to the resulting compressive strain (the latter expressed as a fraction of the original height or thickness in the direction of the force). Compression modulus may be either static or dynamic.

Compression Set - The amount by which a rubber specimen fails to return to original shape after release of the compressive load.

Compressor - A device which converts mechanical force and motion into pneumatic fluid power.

Condensation - The process of changing a vapor into a liquid condensate by the extraction of heat.

F-R-L Unit - An assembly comprising an air filter, pressure regulator, and a lubricator.

Conductor - A component whose primary function is to contain and direct fluid.

Contaminant - Any material or substance which is unwanted or adversely affects the fluid power system or components, or both.

Control - A device used to regulate the function of a component or system.

Controller - A device which senses a change of fluid state and automatically makes adjustments to maintain the state of the fluid between predetermined limits, e.g., pressures, temperatures, etc.

Copolymer - A polymer consisting of two different monomers chemically combined.

Creep - The progressive relaxation of a given rubber material while it is under stress. This relaxation eventually results in permanent deformation or "set."

Cushion - A device which provides controlled resistance to motion.

Cylinder - A device which converts fluid power into linear mechanical force and motion. It usually consists of a movable elements such as a piston and piston rod, plunger or ram, operating within a cylindrical bore.

Cylinder cap - A cylinder end closure which completely covers the bore area.

Cylinder capacity, extending - Volume required for one full extension of a cylinder.

Cylinder capacity, retracting - Volume (annular) absorbed by one full retraction of the cylinder.

Cylinder capacity - The volume of a theoretically incompressible fluid that would be displaced by the piston during a complete stroke. (For double acting cylinders it must be given for both directions of stroke.)

Cylinder force, theoretical - The pressure multiplied by the effective piston area, ignoring friction. For double acting cylinders, the value must be given for both directions of stroke.

Cylinder, adjustable stroke - A cylinder equipped with adjustable stops at one or both ends to limit piston travel.

Cylinder area, piston rod - Cross-sectional area of the piston rod.

Cylinder area, piston, effective - Area upon which fluid pressure acts to provide a mechanical force.

Cylinder bore - The internal diameter of the cylinder body.

Cylinder, cushioned - A cylinder with a piston-assembly deceleration device at one or both ends of the stroke.

Cylinder, differential - A double acting cylinder in which the ratio of the area of the bore to the annular area between the bore and the piston rod is significant in circuit function.

Cylinder, double acting - A cylinder in which fluid force can be applied to the moveable element in either direction.

Cylinder, double rod - A cylinder with a single piston and a piston rod extending from each end.

Cylinder, dual stroke - A cylinder combination which provides two working strokes.

Cylinder, duplex - A unit comprised of two cylinders with independent control, mechanically connected on a common axis to provide three or four positions depending on the method of application.

Cylinder, piston type - A cylinder in which the piston has a greater cross-sectional area than the piston rod.

Cylinder, plunger (ram) - A cylinder in which the piston has the same cross-sectional area as the piston rod.

Cylinder, rotary actuator - A cylinder which translates piston reciprocation into oscillation of an output shaft.

Cylinder, rotating - A cylinder in which the piston and piston rod, plunger or ram, is permitted to rotate with reference to the cylinder housing.

Cylinder, single acting - A cylinder in which the fluid force can be applied to the movable element in only one direction.

Cylinder, tandem - Arrangement of at least two pistons on the same rod moving in separate

chambers on the same cylinder body allowing the compounding of force on the piston rod.

Cylinder, telescoping - Cylinder with two or more stages or extensions, achieved by hollow piston rods sliding one within the other (may be single or double acting).

Cylinder, tie rod - A cylinder with head and cap end closures that are secured by tie rods.