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Glossary of Terms - All Terms

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Glossary Subsets


A device which separates the balls or rollers in a bearing. Also referred to as a separator or retainer.

Cam Follower

A radial roller or plain bearing with a heavy section outer ring, it is normally intended to roll on track. Also known as a track roller.


The process of comparing an instrument or device against a standard to determine instrument accuracy or to make a correction.


The property of a system of conductors which enables the system to store electricity when a voltage is applied between the conductors. Capacitance is expressed as a ratio of the electrical charge stored and the voltage across the conductors. The basic


A device which is used to start single phase motors. It can also be used for three phase power factor correction.


The replaceable element of a fluid filter. The pumping unit from a vane pump, composed of the rotor, ring, vanes and one or both side plates. A removable valve element that fits into a cavity in a hydraulic component, e.g. manifold.

Cartridge Bearing

An extra wide double shielded or sealed bearing designed to increase grease capacity of a bearing.

Case Drain Line

A line conducting fluid from a component housing to the reservoir.


A chemical that hastens the curing of an adhesive. Also referred to as an accelerator.


A Localized gaseous condition within a liquid stream which occurs where the pressure is reduced to the vapor pressure.

Cellulose Media

A filter material made from plant fibers. Because cellulose is a natural material, its fibers are rough in texture and vary in size and shape. Compared to synthetic media, these characteristics create a higher restriction to the flow of fluids.

Centistokes (cSt)

A unit of kinematic viscosity.
• 1 cSt = 10-2 square centimeters per second (cm²/s).


A compartment within a hydraulic unit. May contain elements to aid in operation or control of a unit.


Canadian General Standards Board. An organization which develops standards for products and test methods specifically required in Canada.


A temperature scale. 0° C is the freezing point of water, 100°C is the boiling point of water.
• C° = (F° - 32) * (5/9)
• F° = (9/5) * C° + 32


A fluid passage, the length of which is large with respect to its cross-sectional dimension.


The formation of a groove in the grease path, normally associated with a ball or roller bearing. The amount of channeling can be controlled to a large extent by the consistency of the lubricant. Some degree of channeling is desirable to prevent excessiv

Charge (Supercharge)

• To replenish a hydraulic system above atmospheric pressure.
• To fill an accumulator with fluid under pressure (precharge pressure).

Charge Pressure

The pressure at which replenishing fluid is forced into the hydraulic system (above atmospheric pressure)


Open construction of an electronic drive for mounting within a customer’s enclosure or control console.

Check Valve

A valve which permits the flow of a fluid in one direction only.


• Any path over which electric current may flow, such as motor circuits or lighting circuits.
• The complete path of flow in a hydraulic system including the flow-generating device.

Circuit Breaker

A mechanical switching device. A circuit breaker is capable of breaking current as well as carrying current under normal conditions. Circuit breakers have an ampere trip rating for normal overload protection.

Closed Center

The condition where pump output is not unloaded to tank in the center or neutral operating condition.

Closed Loop

A system that uses feedback information to regulate the output response and adjusts speed accordingly, thus, speed accuracy increases.

Closed Circuit

A piping arrangement in which pump delivery, after passing through other hydraulic components, bypasses the reservoir and returns directly to pump inlet.


A device used for engaging and disengaging a motor or drive component. This is often used when many starts and stops are required in an application.


A separator that divides a mixture of two liquids on a particular porous medium.


Cogging refers to shaft rotation occurring in jerks or increments rather than smooth continuous motion. Cogging is often very apparent at low speeds.


A unit of a winding consisting of one or more insulated conductors connected in series and surrounded by common insulation. A coil links or produces magnetic flux.

Coefficient of Friction

The number obtained by dividing the friction force resisting motion between two components by the normal force pressing both components together.


The potential level serving as ground for the entire circuit.


A device mounted on the armature shaft consisting of a number of copper segments. These segments are insulated from the shaft and from each other. Motor brushes ride on the commutator and electrically connect and switch the armature coils to the power s

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.


A single pneumatic or hydraulic unit.


A material made up of two or more different substances, each having its own properties. This new material has its own specific performance properties. An example might be epoxy or polymer type resins that are combined with glass or graphite fibers to cr


The change in volume of a unit volume of a fluid when it is subjected to a unit change in pressure.

Compounded Oil

A blend of petroleum oil with small amounts of fatty oils is referred to as compounding. Often used in wet applications to prevent washing-off of the lubrication from the metal surfaces. The fatty materials enable the oil to combine with the water inste

Compressive Strength

The crushing force necessary to break a bond, divided by its cross-sectional area.


Parts having the same center are referred to as being concentric.


A device which converts mechanical force into pneumatic fluid power.

Concentric Locking Collar

A ring fitting over an extended inner ring of a bearing and having setscrews which pass through holes in inner ring to make contact with shaft.


A wire, cable or bus bar designed for the passage of electrical current.


The inner ring and roller assembly of a tapered roller bearing.

Conrad Bearing

A standard single row deep-groove bearing named for the inventor of its assembly method, Joseph Conrad.

Contact Angle

The contact angle is formed by a line drawn between the areas of ball and ring contact and a line perpendicular to the bearing axis.


An electro-mechanical device operated by an electric coil allowing automatic or remote operation to repeatedly establish or interrupt an electrical power circuit. A contactor provides no overload protection.


Devices for making and breaking electrical circuits. Contacts are present in all electrical switching devices.


A device used to regulate the function of a unit (see Hydraulic Control, Manual Control, Mechanical Control, and Compensator Control).


A heat exchanger used to remove heat from hydraulic fluid.


The filter media support.

Corrosion Inhibitor

A lubricant additive that protects surfaces against chemical attack from contaminants. The most common types of inhibitors react with the metal surfaces forming an inert film.


• A unit of electrical charge.
• The quantity of electricity passing in one second through a circuit in which the rate of flow is one ampere.

Counter EMF

Also known as back EMF, it is the voltage produced across the motor's windings due to the winding turns being cut by a magnetic field during rotation of the motor.

Counterbalance Valve

A valve which maintains resistance in one direction but permits free flow in the other. Usually connected to the outlet of a vertical double-acting cylinder to support weight or prevent uncontrolled falling or dropping.

Cracking Pressure

The amount of pressure which a pressure actuated valve begins to pass fluid.


Leakage of signal from one source into another.


• Applicable to very low temperature conditions such as liquid nitrogen and below.
• Usually referring to temperatures below 100°K.


To change the physical properties of an adhesive by causing a material reaction. This reaction can be initiated by a chemical process or energy such as ultra-violet light.

Current Limit (Torque Limit)

Ability to adjust the maximum current a motor can draw. In effect, this limits the maximum torque a motor will produce.


The flow of electrons through a circuit.


A device sometimes built into the ends of a hydraulic cylinder which restricts the flow of fluid at the outlet port, thereby slowing the motion of the piston rod.


A family of exceptionally fast curing so called ""instant glue"" adhesives with the capability of quick bonding to a wide range of metallic and nonmetallic surfaces. Special primers are also available for certain difficult-to-bond to substrates such as so


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


Loads being switched in and out of the line, either manually or automatically.