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Glossary and index of fluid power principles and components

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C

Cartridge : A replaceable part of a component such as a filter or pump vane set.

Cartridge valve (slip in) : A valve that is inserted (slipped) into a standard sized cavity in a manifold eliminating the need for a seperate body.

Cartridge valve (screw in) : A valve that is screwed into a standard sized cavity in a manifold eliminating the need for a seperate body.

Carcass : The fabric, cord, and/or metal reinforcing section of a hose as distinguished from the hose tube or cover.

Case drain line : The line or passage from the internal cavity of a pump or other component that will carry fluid leakage from the device to a low pressure reservoir or tank.

Cavitation : A localised gaseous condition within a liquid stream which occurs where the pressure reduces to the vapour pressure, where demand exceeds fluid availability.

Chamber : A compartment within a hydraulic valve housing a component part.

Charge pressure : The pressure at which replenishing fluid is forced into the the hydraulic system above atmospheric pressure.

C of C : Certificate of conformance or certificate of compliance; a document typically signed and dated pertaining to a particular lot or purchase order of item(s) describing any standards, specifications, tests, materials, and/or performance attributes of which the referenced item(s) have or will meet.

Charging kit : A system of valves and passages that allow addition or deletion of gas to the gas chamber of an accumulator without discharging any existing gas.

Check valveA valve that allows fluid flow in one direction, yet stops flow in the opposite direction.

Chemical compatibility : The relative degree to which a material may contact another without corrosion, degradation, or adverse change of properties.

Chemical resistance : The ability of a particular polymer, rubber compound, or metal to exhibit minimal physical and/or chemical property changes when in contact with one of more chemicals for a specified length of time, at specific concentrations, pressure, and temperature.

Choke : A restriction, the length of which is large with respect to its cross sectional dimension.

Circuit : A combination of passages, components and devices that form a working set of logic for a particular application.

Clean out : A hole in a reservoir or tank that is normally covered with a plate that may be removed to allow cleaning of the interior of the reservoir or tank.

Closed centre circuit : One is which flow through the system is blocked in neutral and pressure at the pump outlet is maintained at the maximum pressure control setting.

Closed centre valve : A condition where pump output is not unloaded to pump when the valve is in its center or neutral operating position.

Closed circuit : A piping arrangement in which pump output, after passing through other hydraulic components, returns directly to pump inlet.

Closed loop control : In a control system, a type of control that has an input signal and a feedback of the result of the input signal which is used to modulate the input signal automatically. See OPEN LOOP.

COEFFICIENT OF FRICTION
A relative measure of the surface lubricity

COLLAR
The portion of a fitting compressed by swaging or crimping to seal the hose onto the fitting to create a permanent attachment. Also known as a ferrule.

COMBUSTIBLE LIQUID
A combustible liquid is one having a flash point at or above +100° F ( 37.8° C).

COMMAND SIGNAL
An external signal to which the servo must respond.

COMPENSATOR CONTROL
A displacement control for variable pumps and motors which alters displacement in response to pressure changes in the system as related to its adjusted pressure setting.

COMPONENT
A single hydraulic or electrical unit.

COMPOUND
The mixture of rubber or plastic with other materials combined to give the desired properties when used in the manufacture of a product.

COMPOUND GAUGE
A visual indicator of pressure that is set for `zero' psi at atmospheric pressure and includes a dial which will continue to indicate the level of pressure above or below atmospheric pressure.

COMPRESSIBILITY
The change in volume of a unit of fluid when it is subjected to a unit change in pressure (in2/lb).

COMPRESSION
The name used to describe the change in pressure in a hydraulic system from low pressure to an elevated pressure. Normally the change in pressure is made in a controlled amount of time to cause an even application of energy into the system. See DECOMPRESSION.

COMPRESSION SET
The deformation remains in rubber after it has been subjected to and released from a specific compressive stress for a definite period of time at a prescribed temperature.

CONCENTRICITY
The uniformity of hose wall thickness as measured in a plane normal to the axis of the hose.

CONDITIONING
The exposure of a specimen under specified conditions, e.g., temperature, humidity, for a specified period of time before testing.

CONDUCTIVE
The ability to transfer electrical potential.

CONDUCTOR AMPACITY
The maximum number of amperes that an electrical conductor can safely carry continuously.

CONNECTOR
A mechanical device used to attach two pieces of tubing together or to attach a piece of tubing to a component.

CONTAMINATION
Any material foreign to a hydraulic fluid that has a harmful effect on its performance in a system. Contaminants may be solid particles, liquids or gases.

CONTROL
1) A device used to regulate the function of a unit. 2) A product of known characteristics which is included in a series of tests to provide a basis for evaluation of other products.

CONTROLLABILITY
The finest adjustable increment of a system.

CONTROLLED FLEXING
Occurs when the hose is being flexed regularly as in the case of connections to moving components (e.g. platen presses, thermal growth in pipe work).

CONVOLUTED
Description of hose or innercore having an annular or helical ridges

COOLER
A mechanical device used to transfer heat from a fluid to air or another fluid. Normally constructed of finned tubes with one fluid on the inside and the other fluid or air on the outside of the tubes. See HEAT EXCHANGER.

CORE
The inner portion of a hose, usually referring to the material in contact with the medium.

CORROSION
The process of material degradation by chemical or electrochemical means.

CORRION RESISTANCE
The ability of metal components to resist oxidation.

COUNTERBALANCE VALVE
A valve used to balance the weight of a machine or dead load by causing a back pressure in the system cylinders of sufficient magnitude to support the weight. Normally closed, opened by internal pressure in the counterbalance valve or from a separate source of fluid, that is connected to the opposite end of the balanced cylinder.

COUPLING
1) A mechanical device used to attached the shaft of an electric motor or other motive power device to a hydraulic pump. 2) A frequently used alternative term for fitting.

COVER
The outer component usually intended to protect the reinforcement of a hose product.

CPE
Chlorinated polyethylene; a rubber elastomer.

CRACKING
A sharp break or fissure in the surface, generally caused by strain and environmental issues.

CRACKING PRESSURE
The pressure at which a pressure operated valve begins to pass fluid.

CRIMP DIAMETER
The outside diameter of a crimp collar or socket measuring the opposite flats after crimping.

CRIMPING
A fitting attachment method utilizing a number of fingers or dies mounted in a radial configuration. The dies close perpendicular to the hose and fitting axis; compressing the collar, ferrule, or sleeve around the hose.

CURE
The act of vulcanization. See vulcanization.

CURRENT
The directed flow of electrical charges from one point to another around a closed electrical circuit. Current is measures in units called amperes or amps.

CUSHION
A mechanical device fitted into a hydraulic cylinder that closes off the flow path of fluid to effect a smooth deceleration and stop of the cylinder at the end of the stroke.

CUT OFF FACTOR
The hose length to be subtracted from the overall assembly length which allows the hose coupling end connection extension beyond the end of the hose.

CYCLE
The time of activation of a device or system that is one complete movement from the start position to an extreme position and back to the original position.

CYCLE-MOTION
Movement from normal to extreme position and return.

CYCLING
A rhythmic change of the factor under control.

CYLINDER, DOUBLE ACTING
A hydro-mechanical device, usually a cylindrical chamber with one closed end and a movable shaft at the other end. When fluid flow is applied to a port in the closed end, the shaft extends until the collar or piston reaches the shat end. When fluid is applied to the shaft end port, the shaft will retract into the chamber until the piston or collar reaches the closed end. The cylinder will produce an output force at the shaft end in proportion to its internal area multiplied times the pressure potential of the fluid power system.

CYLINDER, SINGLE ACTING
A hydro-mechanical device, usually a cylindrical chamber with one closed end and a movable shaft at the other end. When fluid flow is applied to a port in the closed end, the shaft extends until the collar or piston reaches the shaft end. When an external weight or load is placed on the shaft, the shaft will retract into the chamber until the piston or collar reaches the closed end. The cylinder will produce an output force at the shaft end in proportion to its internal closed end area multiplied times the pressure potential of the fluid power system.

CYLINDER, TELESCOPINGSINGLE ACTING
A hydro-mechanical device, usually a cylindrical chamber with one closed end and a telescoping movable shaft at the other end. When fluid flow is applied to a port in the closed end, the telescoping shaft extends until all collars or pistons reach their limit. When an external weight is applied to the shaft end, the shaft will retract into the chamber until all the pistons or collars reach their closed end limits. The cylinder will produce an output force at the shaft end in proportion to its internal closed end area multiplied times the pressure potential of the fluid power system.

CYLINDER, DOUBLE ROD
A hydro-mechanical device, usually a cylindrical chamber with movable shafts at the both ends. When fluid flow is applied to a port in either end, the shaft extends until the collar or piston reaches the shaft end. When fluid is applied to the other port, the shaft will retract into the chamber until the piston or collar reaches the opposite end. The cylinder will produce an output force at the shaft end in proportion to its internal area multiplied times the pressure potential of the fluid power system.

CYLINDER, TELESCOPING, DOUBLE ACTING
A hydro-mechanical device, usually a cylindrical chamber with one closed end and a telescoping movable shaft at the other end. When fluid flow is applied to a port in the closed end, the telescoping shaft extends until all collars or pistons reach their limit. When fluid is applied to the shaft end port, the shaft will retract into the chamber until all the pistons or collars reach their closed end limits. The cylinder will produce an output force at the shaft end in proportion to its internal area multiplied times the pressure potential of the fluid power system.