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Glossary of Terms - All Terms

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Glossary Subsets

ABEC

The Annular Bearing Engineering Committee. Also used with a number from 1 - 9 for tolerance grades (precision) of bearings. ABEC1 is standard, ABEC9 is ultra-precision.

Accelerator

A chemical that speeds the curing of an adhesive. It is added in a minor quantity compared with the amounts of the primary reactants. Also referred to as a catalyst.

Acetal

Acetal resins are high performance engineering plastics with superior abrasion resistance and toughness. These resins may require pretreatments to enhance adhesion properties.

Adapter Assembly

An assembly for locking a tapered bore bearing to a shaft. The assembly consists of an adapter sleeve, locknut and lockwasher.

Ampere

A unit of electric current flow. One ampere will flow when one volt is applied across a resistance of one ohm.

Anti-Wear Agent

An additive that minimizes wear caused by metal-to-metal contact.

Aeration

The presence of air in the hydraulic fluid. Excessive aeration causes the fluid to appear milky and also causes components to operate erratically. This is because of compressed air trapped in the fluid.

Accumulator

A container in which fluid is stored under pressure as a source of fluid power. The accumulator also absorbs shocks and smoothes out an operation.

Amperage

The measurement of the flow of the electrical current.

Absolute

A type of measure having its zero point (base point) as being the complete absence of the entity being measured.

Angular Contact Bearing

A bearing in which the design creates a contact angle between the inner race, outer race and rolling element when the bearing is in use. Because of the design, angular contact bearings support both axial and thrust loads.

Absolute Pressure (PSIA)

The pressure above zero absolute, the sum of both atmospheric and gage pressure.

Aqueous

Related to or based on water containing compositions.

ABS

Acrylonitrile Butadiene Styrene. A thermoplastic polymer that has moderate resistance to heat, low temperatures and chemicals. ABS also bonds to many different adhesive materials.

AGMA

American Gear Manufacturers Association. One activity of AGMA is the establishment of standards for gear lubricants.

API

American Petroleum Institute. The society formed to further the interests of the petroleum industry. One of the API's activities has been the development of the API Service Classification for gearcase oils.

Annular Area

A ring shaped area that often refers to the effective area of the rod side of a cylinder piston, that is, the piston area minus the rod area.

Amplitude

The height of a waveform above ground, equivalent to 1/2 peak-peak value.

AFMBA

Anti-Friction Bearing Manufacturers Association. This group sets standards for the bearing industry.

Air Gap

The gap between the rotor and stator in an electric motor.

Anti-Friction Bearing

A term commonly used for a rolling element bearing, such as a ball or roller bearing.

Airframe Bearing

A bearing designed for use in the control systems and surfaces of an aircraft.

Armature

The rotating member of an electric motor. In brush-type DC motors, the armature consists of the main current carrying windings (conductors) in the rotor. The commutator switches the power supply to the armature windings to generate a magnetic field.

Alternating Current (AC)

Electric power supplied in single or three-phase forms. In the United States, 60 Hz is the standard, while overseas, 50 Hz is the standard. AC current cycles or changes its direction of flow.

Aircraft Bearing

A term generally applied to bearings used by the aircraft industry or the Air Force. These bearings usually have to meet some Military Specification for quality and performance.

Additive

A compound that enhances some property of, or adds a new property to the base fluid. Some types of additives include anti-oxidants, anti-wear additives and corrosion inhibitors to list a few.

Amplitude of Sound

The loudness of a sound.

Alignment

A condition where the center lines of two shafts are in line (coaxial).

Actuator

A device used to convert hydraulic energy into mechanical energy. A device to convert rotary motion into thrust or linear motion.

Annular Bearing

A rolling element bearing designed primarily to support a load perpendicular to the shaft axis. Commonly referred to as a radial bearing.

Ambient Temperature

The temperature of the surrounding environment, usually air, in which the system components operate.

Amp Meter

Used to read amperage in individual lines.

Armature Current

The rated armature circuit current when the motor is operating at full load.

ASLE

American Society of Lubrication Engineers. The prior name of an organization involved with friction, wear, and lubrication. They are now known as the Society of Tribologists and Lubrication Engineers (STLE).

Attenuation

The decrease in signal amplitude during its transmission from one point to another.

Atmosphere (ONE)

A pressure measure equal to 14.7 psi.

Atmospheric Pressure

Pressure on all objects in the atmosphere because of the weight of the surrounding air. At sea level, this is about 14.7 pounds per square inch.

ASTM

The American Society for Testing and Materials, an organization devoted to the promotion of knowledge of engineering materials and the standardization of specifications and methods of testing.

Ash Content

The non-combustible residue of a lubricating oil. Since some detergents contain metallic compounds, the percentage of ash has been considered to have a relationship to detergency.

Axial Internal Clearance

Also referred to as end play, it refers to the maximum movement possible of the outer race relative to the inner race.

Back EMF

Refers to the voltage produced across a motor's windings. This is due to the winding turns being cut by the magnetic field during motor operation. Also referred to as counter EMF (CEMF).

Axial Load

A load that is parallel to the axis of the shaft, also referred to as thrust load.

Back Connected

A condition where port connections are on normally unexposed surfaces of hydraulic equipment.

Back Pressure

Usually refers to pressure existing on the discharge side of a load, it adds to the pressure required to move the load.

Backlash

In a mechanical system, backlash is the relative motion between two connected devices, either by a coupling, gear, etc.

Auxiliary Contacts

Contacts of a switching device in addition to the main current contacts. These contacts can be normally open or normally closed and alternate their state when operated.

Baffle

A device, usually a plate, installed in a reservoir to separate the pump inlet from return lines. The baffle also aids in fluid cooling.

Ball Complement

The number of balls used in a ball bearing.

Ball Bearing

A bearing using balls as the rolling elements.

Ball Contact

The area of contact between the raceway and ball.

Axial

In the same direction as the axis of the shaft.

Ball

A spherical rolling element.

Axis

An imaginary line running through the center of a shaft, also referred to as center line.

Ball Diameter

The dimension measured across the ball center.

Ball Pocket

A drilled, stamped, or molded receptacle that holds the ball in a cage.

Bar

A unit of pressure based on 105 Newtons per square meter, equal to 100kPa (kilopascals), approx. equal to 14.5 psig.

Base Speed

The speed a DC motor develops at the rated armature and field voltage with the rated load being applied.

Basic Dynamic Load Rating

Basic dynamic load rating (Cr) is the calculated constant which a group of identical bearings with stationary outer rings can theoretically endure for a rating life of 1 million revolutions of inner ring.

Bearing Seal

A soft washer, usally made of synthetic rubber, which contacts the inner and outer rings to retain lubricant and keep out contamination.

Bearing Shield

A steel washer which helps to retain lubricant and keep out larger particles. Not recommended for applications involving small particulate contamination or washdown applications since the inner race does not come in full contact with the shield.

Beta Rating

The method of comparing filter performance based on efficiency. This is done using the multi-pass test which counts the number of particles of a given size before and after a fluid passes through a filter.

Bernoulli Principle

An increase in velocity causes a decrease in pressure.

Bleed-Off

To divert a specific controllable portion of pump delivery directly to reservoir.

Block Grease

A very firm grease manufactured in block form to be applied to certain large open plain bearings or other system components operating at high temperatures and slow speeds.

Bore

The smallest internal dimension of inner or outer ring or separator. Also, the surface of the inner ring that fits against the shaft.

Boundary Dimensions

Refers to the basic dimensions for bore, width, outside diameter.

Boundary Lubrication

A state of lubrication characterized by partial contact between two metal surfaces. Due to metal-metal contact, severe wear can take place during boundary lubrication. This is countered by additives in certain lubricants, which will minimize wear under

Bridge Rectifier

A section of the DC drive that converts the AC power supply into DC.

Braking Torque

The torque required to stop a running motor. Also may refer to the torque developed by a motor during dynamic braking.

Brush

A carbon or graphite piece which contacts the commutator of a DC motor and conducts current to the armature windings from the power supply.

Brake

An device that stops a running motor and/or holds a load.

Brinelling

Permanent deformation of the bearing surfaces where the rollers or balls contact the races. Brinelling results from excessive load or impact on stationary bearings.

Brookfield Viscosity

The viscosity, in centipoises, as determined on the Brookfield viscometer (ASTM D2983). The operating principle for the Brookfield viscometer is the torque resistance on a spindle rotating in the fluid being tested. Most frequently associated with low

Breakdown Torque

The maximum torque that a motor develops without a significant drop in speed.

Breather

A device which permits air to move in and out of a component to maintain atmospheric pressure.

BSPP

British Stantard Parallel Pipe

BTU

British thermal unit. The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

By-Pass

A secondary passage for fluid flow.

BSPT

British Standard Pipe Thread

Bypass Filtration

A system of filtration in which only a portion of the total flow passes through a filter at any instant.

Cage

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.

Capacitance

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

Calibration

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

Capacitor

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

Cartridge

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.

Case Drain Line

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

Cartridge Bearing

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

Catalyst

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

Cavitation

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).

Chamber

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

Celsius

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

CGSB

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

Channeling

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)

Check Valve

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

Chassis

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

Channel

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

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.

Circuit

• 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.

Closed Circuit

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

Coalescor

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

Closed Loop

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

Cogging

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

Commutator

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

Clutch

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.

Concentric

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

Coil

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.

Common

The potential level serving as ground for the entire circuit.

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.

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.

Compressive Strength

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

Component

A single pneumatic or hydraulic unit.

Composite

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

Compressibility

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

Compressor

A device which converts mechanical force into pneumatic fluid power.

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

Coefficient of Friction

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

Cone

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

Conductor

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

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.

Contacts

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

Cooler

A heat exchanger used to remove heat from hydraulic fluid.

Contactor

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.

Coulomb

• 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.

Core

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.

Control

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

Cracking Pressure

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

Crosstalk

Leakage of signal from one source into another.

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.

Cryogenic

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

Cyanoacrylates

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

Cure

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

The flow of electrons through a circuit.

Cushion

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.

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.

Cycling

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

De-vent

To close the vent connection of a pressure control valve permitting the valve to function at its adjusted pressure setting.

Cylinder

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.

Dehydrator

A separator that removes water from the system fluid.

Deaerator

A separator that removes air from the system.

DC Power (Direct Current)

Electrical flow in only one direction.

Degas

Removing air from a liquid, usually by ultrasonic or vacuum methods.

Delivery

The volume of fluid discharged by a pump in a given time period, usually expressed in gallons per minute (gpm).

Delta Connection

A common three phase connection shaped schematically like the Greek Delta. The end of one phase is connected to the beginning of the next phase, or vice versa.

Delta P

The change in pressure between two points in a system, such as in a passageway or between the inlet and outlet of a componet. Also expressed as DP.

Directional Valve

A valve which selectively directs (or prevents) fluid to specific ports.

Direct Current (DC)

Electrical flow in only one direction.

Double Acting Cylinder

A cylinder in which fluid force can be applied in either direction.

Displacement

The quantity of fluid which can pass through a pump, hydraulic motor, or cylinder in a single revolution or stroke.

Differential Pressure Indicator

An indicator which signals the difference in pressure between any two points of a system or a component.

Diode

Often used as a rectifier, a diode is a two electrode electron tube containing an anode and a cathode.

Dispersant

A term usually used interchangeably with detergent. An additive which keeps fine particles of insoluble materials in an oil. Particles are not permitted to settle or accumulate.

Dielectric Strength

The voltage an insulating material can withstand before breaking down.

Design Horsepower (DHP)

A rating achieved by multiplying horsepower by the service factor.

Demulsify

Separate water from oil.

Detergent

An additive that neutralizes contaminants in oil before they become insoluble.

Double Row Bearing

A bearing with two rows of rolling elements.

Drain

A port or a line from a hydraulic component which returns fluid independently to a reservoir or vented manifold.

Drawn Cup Needle Roller Bearing

A needle roller radial bearing with thin pressed steel outer ring. This design, also referred to as a drawn cup needle bearing, usually has both ends open, but may have one closed end.

Drip Cover

A cover on the top of a motor that protects it from solids and/or liquids that might drop onto it.

Dropping Point

The temperature at which a grease changes from a semi-solid to a liquid state under test conditions. It may be considered an indication of the high temperature limitation for application purposes.

Duplex Bearing

A bearing with controlled axial location of faces of inner and outer rings. This makes it suitable for mounting in various combinations with one or more bearings controlled in the same manner.

Duplex Filter

An assembly of two filters with valving that allows use of either or both filters.

Dynamic Braking

• A quick way to stop a motor by disconnecting the power source. The rotating motor then becomes a generator.
• When connected to a resistor, the energy of rotation is then dissipated as heat in the resistor.

Duty Cycle

The ratio of the lengths of the positive to negative halves of a waveform expressed in percentages.

Dynamic Load

A load exerted on a bearing that is in motion.

Eccentric Collar

A ring having a recess on one side which is eccentric in relation to the bore. The collar fits over an equally eccentric extension of the inner ring of the insert bearing. The collar is turned in the same direction of rotation in relation to inner ring

Eccentric

Not having the same center.

Efficiency

The ratio of output to input. Volumetric efficiency of a pump is the actual output flow divided by the theoretical or design flow. The overall efficiency of a hydraulic system is the output power divided by the input power. Efficiency is usually expressed as a percent.

Elastomer

A material that can be stretched repeatedly to at least twice its original length. When the stress is removed, the material immediately returns to its approximate original length. Elastomeric couplings refer to couplings having an elastomer insert which

Electro-Hydraulic Servo Valve

A directional type valve which receives a variable or controlled electrical signal. This type of valve controls hydraulic flow.

Element

The porous device that performs the actual process of filtration.

Elongation

The fractional increase in length of a material that is stressed in tension.

EMF (Electro-Magnetic Field)

The magnetic field formed any time current flows through a conductor.

Emulsion

A fluid formed by the suspension of one liquid in another.

Enclosure

• In bearings, refers to the rubber seal or metal shield that protects the bearing from contamination.
• Also refers to the cabinet or specially designed box in which electrical controls are housed. It is required by the National Electrica

Encapsulating

Enclosing an article in an envelope of adhesive or epoxy.

Encoder

A feedback device that translates mechanical motion into an electronic signal or pulse. The more pulses per revolution (PPR), the more accurate the feedback device.

End Play

• The axial play of the outer ring in a bearing.
• The measured maximum possible movement of the inner ring in relation to outer ring.

Energy

The ability or capacity to do work, measured in units of work.

EP Agent

An additive that improves the extreme pressure properties of a lubricant.

Epoxy

A versatile group of polymers used for adhesive, sealant, coating, potting/encapsulation, impregnation and coating uses. Generally consists of two components, but can be a one part heat cured composition. Features high physical strengths, superior resis

Explosion Proof Motor

A motor in a specially designed housing that serves two purposes:
• If an explosive vapor or gas should explode inside the motor, the frame of the motor will not be affected.
• The enclosure is designed so that no such explosion will i

Exudation

The migrating of adhesives from the interior to the surface of plastic.

Farad

• A unit of capacity in an electromagnetic system. A condenser is said to have a capacity of one farad if it will absorb one coulomb (one ampere per second) of electricity when subjected to a pressure of one volt.
• The unit of capacitan

Feedback Signal

The output signal from a feedback element. One example would be a motor used in conjuction with an encoder. The encoder supplies a feedback signal to the motor to precisely control motor speed.

Fahrenheit

A temperature scale. 32°F is the freezing point of water, 212°F is the boiling point of water.
• C° = (F° - 32) * (5/9)
• F° = (9/5) * C° + 32

Fillers

Substances added to an adhesive to improve the ease of application or some specific performance property such as strength, hardness or other characteristic.

Fillet Radius

The corner dimension in a bearing housing that the bearings outer race corner radius must clear.

Filling Notch

A slot or notch cut in the shoulder of a ring to allow the loading of more balls into a bearing. This gives the bearing more load carrying capabilities.

Film Strength

A property of a lubricant that helps prevents the scuffing or scoring of metal parts.

Filtration

The process of separating insoluble particulate matter from a fluid, such as air or liquid, by passing the fluid through a filter medium that will not allow the particulates to pass through it.

Filter

? A device whose primary function is the retention of insouluble contaminants from a fluid by a porous media. This keeps the oil free of contamination.
? An electrical device used to suppress electrical noise, or to improve the DC output to a DC motor.

Finish

A term usually applied to the last machining operation on any surface.

Fire Point

The temperature to which a combustible liquid must be heated so that the released vapor will burn continuously when ignited under specified conditions.

Fixed Bearing

A bearing which prohibits shaft axial movement in both directions.

Flash Point

The temperature which a combustible liquid must be heated to give off sufficient vapor to form a flammable mixture with air when a small flame is applied under specified conditions.

Fit

• The amount of internal clearance in a bearing.
• Also used to describe shaft and/or housing size and how they relate to the bore and/or outside diameter.

Flooded

A condition where the pump inlet port is charged by placing the reservoir oil level above the pump inlet port.

Flow Control Valve

A valve which controls the rate of oil flow.

Floating Bearing

A bearing designed or mounted so as to permit axial movement between the shaft and housing.

Flowmeter

A device which measures flow rate, total flow, or a combination of both.

Fluid

• A liquid that is specially compounded for use as a power transmitting medium in a hydraulic system.
• Can refer to a liquid or gas.

Flushing

A process designed to remove contamination from a fluid system.

Four-Way Valve

A directional valve having four flow paths.

Four Quadrant

Refers to a drive's ability to control the velocity and torque of a motor in either direction of rotation. The direction of torque can be in the opposite direction of the velocity for applications requiring braking or deceleration. Single-quadrant drive

Foam Inhibitor

An additive which causes foam to dissipate more rapidly.

Frequency

The number of times an action occurs in a unit of time. Frequency is the basis of all sound. A pump or motor's basic frequency is equal to its speed in revolutions per second multiplied by the number of pumping chambers.

Force

Any push or pull measured in units of weight. In hydraulics, total force is expressed by the product of pressure and the area of the surface on which the pressure acts.
• F = P x A

Front Connected

Piping connections are on exposed surfaces of hydraulic components.

Friction

The resisting force encountered at the common boundary between two bodies when one body moves or tends to move relative to the surface of the other body.

Flow Rate

The volume, mass, or weight of a fluid passing through a conductor per a given unit of time. This is normally expressed in gallons per minute (gpm).

Full Complement Bearing

A rolling bearing without cage in which sum of clearances between rolling elements in each row is less than the diameter of rolling elements and small enough to give satisfactory function of bearing.

Full Flow

In a filter, the condition where all the fluid must pass through the filter element.

Full Load Amps

The current flowing through a line terminal of a winding when rated voltage is applied at rated frequency with rated horsepower.

Full Load Current

The greatest current that a motor or other device is designed to carry under specific conditions. Anything additional is considered an overload.

Fuse

An over-current protective device which consists of a conductor that melts and breaks when current exceeds rated value beyond a predetermined time.

GPM (Gallons Per Minute)

Unit of measure representing volume of liquid flow.

Gauge Pressure (psig)

A pressure scale where atmospheric pressure is ignored, in other words, its zero point is atmospheric pressure (14.7 psia at sea level).

GPH (Gallons Per Hour)

Unit of measure representing volume of liquid flow.

Ground

A connection, either intentional or accidental, between an electric circuit and the earth or some other conducting body.

Ground Fault Interruption (GFI)

A unit which provides protection against ground fault currents below the trip levels of the breakers of a circuit. The GFI system must be capable of sensing the ground fault current and be able to disconnect any faulted circuit from its source voltage.

Generator

A machine for converting mechanical energy into electrical energy or power.

Grounded Neutral

The common neutral conductor of an electrical system which is connected to ground to provide a current carrying path for the line to neutral load devices.

Hall Effect Sensor

A feedback device, commonly used in brushless motors, that provides information for the amplifier to electronically commutate the motor. The sensors generate commutation signals by sensing the position of a magnetized wheel on the rotor.

Head

The height of a column of fluid above a set point. Head is often used to indicate gauge pressure. The pressure is equal to the height times the density of the fluid.

Harmonics

Ripples on the sine wave that can cause vibration or excessive heat to be generated in the lines and panels. Mathematically, any multiple of the fundamental frequency.

Heat Exchanger

A device which transfers heat through a conducting wall from one fluid to another fluid.

Hardening

The process of heating parts to a high temperature and then quenching them, either in oil, water, air, or another solution.

Heat

A form of energy that has the capacity to increase the temperature of a substance. Any energy that is wasted or used to overcome friction is converted to heat. Heat is measured in calories or British Thermal Units (BTUs). One BTU is the amount of heat required to raise one pound of water one degree Fahrenheit.

Hot Melt

An adhesive which is in a molten state when it is applied, and forms a bond when cooled.

Hot Tack

A characteristic of hot melts in that they have holding power even while in the liquid hot state.

Hertz (Hz)

A unit of frequency equal to one cycle per second.

Housing Fit

The amount of interference or clearance between a bearing, seal or components outside diameter and the housing bore.

Horsepower (HP)

The power required to lift 550 pounds one foot in one second or 33,000 pounds one foot in one minute. A horsepower is equal to 746 watts or to 2544 BTU's per hour.

Hydraulic Balance

A condition of equal opposed hydraulic forces acting on a part in a hydraulic component.

Hydraulics

Engineering science pertaining to liquid pressure and flow. Also referred to as hydrodynamics.

Hydraulic Nut

A collar temporarily fixed to a shaft which incorporates a hydraulic piston to transmit axial mounting or dismounting force.

Hydro

Greek word for water.

Hydraulic Control

A control which is actuated by hydraulically induced forces.

Hydrodynamics

Engineering science pertaining to liquid pressure and flow. Also referred to as hydraulics.

Hydrostatics

Engineering science pertaining to the energy of liquids at rest.

Hydrolysis

The decomposition of a substrate by reaction with water.

Impedance

The total apparent opposition a circuit offers to the flow of alternating current in an electrical circuit.

Induction

When an electrical conductor becomes electrified and becomes magnetized.

Impregnation

• The process of imbedding a reactive liquid into a porous substrate in order to change its properties.
• The process of adding oil into the porous cavaties in powdered bronze to assist in lubrication.

Inductive Current

Any current created by a magnetic field.

Insulator

A device for fastening and supporting a conductor.

Inner Ring

The inner part of a bearing that fits on a shaft and contains the external raceway for the rolling elements.

Inhibitor

A substance which is added to slow down the rate of a chemical reaction.

Intensifier

A device which converts low pressure fluid power to higher pressure fluid power.

Inertia

A function of the mass and shape of an object. The inertia represents the property of an object that resists a change in motion.

Internal Race

The ball or roller path on the bore of the outer ring.

Inverter

A device that converts DC power to AC power.

IR Compensation

It varies the mount of voltage to the armature in response to current/load changes.

Jacobi's Law

A law of electric motors which states that the maximum work of a motor is performed when its counter electromotive force is equal to one half the electromotive force expended on the motor.

JIC

Joint Industry Conference

Joule's Law

The law first stated by Joule, that the quantity of heat developed in a conductor by the passage of an electric current is proportional to the resistance of the conductor, to the square of the strength of the current, and to the duration of the flow.

Kilowatt (kW)

1,000 Watts.

Jogging

Momentarily moving the motor at a slower speed than normal operating speed. This function is normally available on many drive controls as a separate control button.

Kinetic Energy

Energy that a substance or body has by virtue of its mass and velocity.

ISO

International organization for standardization. An organization which establishes internationally recognized standards for products and test methods.

Land

Commonly called the OD of the inner ring or the ID of the outer ring.

Laminar (Flow)

A condition where the fluid particles move in continuous parallel paths.

Laminate

A product made by bonding together two or more layers of material with adhesive.

Lapping

An process for refining the surface finish and the geometrical accuracy of a surface. Often a finishing process for many component parts or bearings.

Leverage

A gain in output force over input force by sacrificing the distance moved. Mechanical advantage or force multiplication.

Leakage

The escape of electric current through defects in insulation or other causes.

Lift

The height a body or column of fluid is raised, for instance from the reservoir to the pump inlet. Lift is sometimes used to express a negative pressure or vacuum. The opposite of head.

Life

The number of revolutions (or hours at some given constant speed) which a bearing runs before first evidence of fatigue develops in the material of either ring or any rolling elements.

Line

A tube, pipe or hose which acts as a conductor of hydraulic fluid.

Limits

Maximum and minimum allowable dimensions, resulting from predetermined tolerances to a specified dimension.

Line Current

The measurement of amperage through the line.

Linear Actuator

A device for converting hydraulic energy into linear motion, i.e., a piston or ram.

Locked Rotor

The maximum current drawn by the motor during the starting period.

Lock Nut

A nut used in combination with a lock washer to hold a bearing or component in place on a shaft.

Load Sensing

A type of circuit where the actual pressure or power required by the load is transmitted to the control elements. This typically allows the system to deliver only the pressure or power required, usually saving energy.

Loose Fit

A fit of inner ring, balls, and outer ring which results in larger radial clearance.

Lockout

A mechanical device which may be set to prevent the operation of a push-button or other device.

Magnetic Field (EMF)

The magnetic field formed any time current flows through a conductor.

Loss

Power expended without accomplishing useful work.

Lock Washer

A washer with tongue and prongs to hold a lock nut in place.

Manifold

A fluid conductor which provides multiple connection ports.

Manual Control

• A control actuated by the operator, regardless of the means of actuation.
• A lever or foot pedal control for directional valves.

Manual Override

A means of manually actuating an automatically-controlled device.

Manual Transfer Switch

A switch designed to disconnect a load from one power source and reconnect it to another source.

Meter

To regulate the amount or rate of fluid flow.

Mechanical Control

Any control actuated by linkages, gears, screws, cams or other mechanical elements.

Meter-In

To regulate the amount of fluid flow into an actuator or system.

Maximum Capacity Bearing

A bearing with filling notches to allow the loading of the maximum number of balls. This gives the bearing more load carrying capability.

Meter-Out

To regulate the flow of discharge fluid from an actuator or system.

Methacrylates

A family of high performance thermoplastics having optical clarity, abrasion resistance and good physical strength properties.

Micron Rating

The size of the particles a filter will remove under normal operating conditions.

Molecular Weight

The sum of the atomic weight of all atoms in a molecule.

Motor Circuit Protector

A disconnect switch that is specifically designed for motor circuits, it provides short circuit protection. A motor circuit protector differs from a standard breaker in that it does not have a thermal overload device.

Motor

A rotary motion device which changes hydraulic energy into mechanical energy; a rotary actuator.

NEC

The National Electrical Code (NEC) is the standard of the National Board of Fire Underwriters for electric wiring and apparatus, as recommended by the National Fire Protection Association.

Motor Efficiency

A measure of how effectively a motor converts electrical energy into mechanical energy. While motor efficiency is never 100 percent, many energy efficient motors have efficiencies well above 90 percent. This compares with standard efficient motors where

Micron (µm)

• The size of a particle one millionth of a meter.
• The symbol for a micron is µm.

Misalignment

Lack of parallelism between the axis of the rotating member and the stationary member.

Needle Roller

A cylindrical roller of small diameter, with a large ratio of length to diameter.

NEMA

National Electrical Manufacturers Association. A non-profit trade association supported by the manufacturers of electrical apparatus and supplies. NEMA sets standards to facilitate understanding between the manufacturers and users of electrical products.

NEMA 1 Enclosure

A general purpose electrical enclosure. For indoor use where oil, dust, and water is not a problem.

NEMA 12 Enclosure

An electrical enclosure used for excluding oils, coolants, flying dust etc.

NEMA 2 Enclosure

A driptight electrical enclosure. For indoor use. Excludes falling moisture and dirt.

NEMA 3 Enclosure

A weatherproof electrical enclosure that provides protection against rain, sleet and snow.

NEMA 4 Enclosure

A watertight electrical enclosure required for hose down applications or other applications where water comes from any angle.

NEMA 5 Enclosure

A dust tight electrical enclosure used for excluding non-hazardous dust.

NEMA 9 Enclosure

A dust tight electrical enclosure used for applications where combustible dust is present. Acceptable for Class II Groups E, F and G.

Neutral

The point common to all phases of a circuit. The neutral in most systems is grounded at or near the point of service entrance only and becomes the grounded neutral.

Newton Meter (Nm)

Metric unit of measure representing force.

Noise

Any unwanted voltage or current in an electrical circuit.

NPT

National Pipt Taper (requires pipe sealant)

NPTF

National Pipe Taper Fuel or Dry Seal Pipe Threads (may not require pipe sealant)

Ohm

A unit of electrical resistance. One volt will cause a current of one ampere to flow through a resistance of one ohm.

Open Center

A condition where pump delivery circulates freely to tank in the center or neutral position.

Open Circuit

An electrical circuit whose continuity has been interrupted, as by opening a switch.

Open Loop

A system that does not use feedback information to regulate performance.

Orifice

A restriction, the length of which is small in respect to its cross-sectional dimensions.

Outer Ring

The outer part of a bearing that fits into the housing and contains the internal raceway for the rolling elements.

Overload Relay

A relay that responds to an electric load and operates at a pre-set value of overload. The unit senses the current to the motor.

P.S.I.A.

Pounds per square inch absolute.

Parallel

Not in series but fed from the same sources.

Oxidation

The chemical reaction of elements with oxygen which cause corrosion or deterioration.

Pascal

A unit of pressure in metric system, usually expressed in kPa (kilopascals).
• 1 kPa = 0.01 bar = 0.145 psi.

Passage

A fluid conducting path which lies within or passes through a component.

Peel Strength

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

Penetration

The entering of an adhesive into a substrate.

Pilot Pressure

Auxiliary pressure used to actuate or control hydraulic components.

Pilot Valve

An auxiliary valve to control the operation of another valve.

Plunger

A cylindrically shaped part with only one diameter that is used to transmit thrust. A ram.

Piston

A cylindrically shaped part which fits within a cylinder and transmits or receives motion by means of a connecting rod.

Pi

Often shown as p, it is the ratio of circumference of circle to diameter. Numerically can be expressed as 22/7 or 3.14159265 more accurately.

Poles

The magnetic poles in an electric motor that result from connection and placement of the windings in the motor. 7,200 divided by the number of poles gives the synchronous speed of the motor, i.e., a 4-pole motor is 1,800 rpm (7200/4).

Polymerization

A chemical reaction where two or more small molecules continue to form larger molecules that contain repeating structural units of the original molecules.

Poppet

That part of certain valves which prevents flow when it closes against a seat.

Port

An internal or external passage in a component.

Polymer

A chemical compound or mixture of componds formed by polymerization.

Positive Displacement

A characteristic of a pump or motor which has the inlet positively sealed from the outlet so that fluid cannot re-circulate in the pump or motor.

Pocket

The portion of a cage shaped to hold the ball or roller.

Potential Energy

The energy level change which results when an object is raised to a new height.

Potting

Enclosing an article in an envelope of adhesive.

Potentiometer

A control element in the servo-system which measures and controls electrical potential.

Pour Point

The lowest rated temperature at which a hydraulic fluid will flow.

Pot Life

The period of time an adhesive or potting compound remains useful after adding an accelerator, catalyst or exposure to other curing conditions.

Power Factor

The ratio of real power actually used to the amount of apparent power being supplied to an electrical load.

Power Relay

An electro-mechanical device that allows automatic or remote operation to repeatedly establish or interrupt an electrical power circuit. Sometimes called a contactor.

Power

Work per unit of time, measured in horsepower (hp) or watts.

PPM (Pars Per Million)

Unit of mearsure representing the number of particles in a given body.

Preload

An internal loading characteristic in a bearing which is independent of any external radial and/or axial load carried by the bearing.

Precharge Pressure

The pressure of compressed gas in an accumulator prior to the admission of liquid.

Prelubricated Bearing

A shielded, sealed, or open bearing originally lubricated by the manufacturer.

Pressure

Force per unit area; usually expressed in psi, bar, or kPa.

Pressure Differential

Same as pressure drop. The change in pressure between two points in a system, usually referring to the inlet and outlet ports of a component. Also expressed as DP (Delta P).

Pressure Drop

The change in pressure between two points in a system, usually referring to the inlet and outlet ports of a component. Also expressed as DP (Delta P).

PSIA (Pounds Per Square Inch Absolute)

See Absolute Pressure

Pressure Override

The difference between the cracking pressure and the full flow pressure of a valve.

Pressure Line

The line carrying the fluid from the pump outlet to the pressurized port of the actuator.

Primer

A coating applied to a surface prior to the application of an adhesive in order to enhance the strength of the bond or speed up the cure.

PSIG (Gauge Pressure)

A pressure scale which ignores atmospheric pressure, i.e., its zero point is atmospheric pressure (14.7 psia at sea level).

Pressure Reducing Valve

A valve which limits the maximum pressure at its outlet regardless of the inlet pressure.

Pump

A device which converts mechanical force and motion into hydraulic fluid flow.

Radial Clearance

• The average outer ring race diameter, minus the average inner ring race diameter, minus twice the ball diameter.
• Radial clearance is expressed by C0 (Normal Clearance), C1, C2, C3, C4 and C5. C2 clearance is less than normal (C0), and

Radial Bearing

A rolling element bearing designed primarily to support a load perpendicular to the shaft axis. Also referred to as an annular bearing.

Ram

• A single acting cylinder with a plunger rather than a piston and rod.
• The plunger in a ram type cylinder.

Rating Life

The rating life of a group of identical bearings is the life in millions of revolutions that 90% of the group will complete or exceed. Often referred to as L10 life.

RBEC

Class or degree of precision of anti-friction roller bearings. Similar to ABEC.

Reciprocation

Back and forth straight line motion or oscillation.

Rectifier

A device that converts AC power to DC power.

Regenerative

Regenerative drives refer to the regeneration of energy from the motor and drive back to the power source. A motor generates when the load forces the motor to go faster than the drive has set. A drive is regenerative when it puts the generated energy ba

Relay

An electric device that is designed to read input conditions in a prescribed manner.

Relief Valve

A pressure operated valve which bypasses pump delivery to the reservoir, limiting system pressure to a predetermined maximum value.

Relieved End Roller

A roller with a slight modification of diameter at ends of the outside surface to reduce stress concentration at contacts between rollers and raceways.

Replenish

To add fluid to maintain a full hydraulic system.

Resin

An organic material that has an indefinite and often high molecular weight. Resins tend to flow when subjected to stress, usually have a softening or melting range.

Reservoir

A container for storage of liquid in a fluid power system.

Resistance

The non-reactive opposition which a device or material offers to the flow of direct or alternating current. Usually measured in ohms.

Resistor

One or more units possessing the property of electrical resistance. Resistors are used in electric circuits for the purpose of operation, protection, or control.

Restriction

A reduced cross-sectional area in a line or passage which produces a pressure drop.

Reversing Valve

A four-way directional valve used to reverse a double acting cylinder or reversible motor.

Return Line

A line used to carry exhaust fluid from the actuator back to the tank.

Rotor

The rotating assembly of a motor. Usually includes a shaft, fan and rotor core.

Retainer

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

RTV

An acronym for room-temperature vulcanizing. An RTV adhesive vulcanizes (cures) without the application of heat.

Runout

Displacement of the surface of a bearing relative to a fixed point when one raceway is rotated with respect to other raceway.

Rotary Actuator

• A device for converting hydraulic energy into rotary motion.
• A hydraulic motor.

SAE O-Ring

Refers to a style of threaded connection that employs straight thread to secure the fitting and an o-ring to provide sealing. This style of connection is very poplular for use in hydraulic systems and can be removed and reinstalled numerous times without damaging the sealing ability of the connection. Tapered pipe thread is actually damaged to make a fluid tight seal. Vibration and repeated connection of tapered pipe threaded connections will always resulin in leaks.

SAE

The Society of Automotive Engineers

Safety Switch

A manually-operated disconnecting switch which is horsepower and current rated, it disconnects all power lines simultaneously.

Saybolt Universal Seconds (SUS)

A measure of viscosity, the time required for a given fluid to flow through a standard orifice.

SCFM (Standard Cubic Feet Per Minute)

Unit of measure representing volume of gas flow.

Self-Aligning Bearing

A bearing which can accommodate angular misalignment.

Self-Locking Collar

A ring having a recess on one side which is eccentric in relation to the bore and fits over an equally eccentric extension of the inner ring insert bearing. The collar is turned in relation to inner ring until it locks and then secured to shaft by tight

Separable Bearing

A bearing that may be separated completely or partially into its component parts.

Semiconductor

A name given to substances having only moderate power of transmitting electricity.

Separator

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

Sequence

• The order of a series of operations or movements.
• To divert flow to accomplish a subsequent operation or movement.

Sequence Valve

A pressure operated valve which diverts flow to a secondary actuator while holding pressure on the primary actuator at a predetermined minimum value after the primary actuator completes its travel.

Series

In line with the load.

Servo

A system consisting of an amplifier, actuator, and feedback element. Servos tend to control one or a combination of the following variables: position, velocity and torque.

Service Factor

• A safety factor designed and built into some motors which allows the motor, when necessary, to deliver greater than its rated horsepower.
• Also used as a factor when sizing system components, based on application, to achieve design hors

Servo Mechanism

A mechanism subjected to the action of a controlling device which will operate as if it were directly actuated by the controlling device, but capable of supplying power output many times that of the controlling device, this power being derived from an external and independent source.

Servo Valve

• A valve which controls the direction and quantity of fluid flow in proportion to an input signal.
• A follow valve.

Setting

The hardening or solidification of an initially liquid plastic material by chemical and/or physical action.

Shield

• A metal formed washer attached to the outer ring and set so it rides close to, but not contacting, the inner ring.
• Helps retain lubricant and prevent contamination.
• Does not keep out fine particles like a seal does.

Shaft Fit

Amount of interference or clearance between the bearing inside diameter and shaft bearing seat outside diameter.

Shear Strength

The sliding force required to break a bond, divided by its cross-sectional area.

Short Circuit

A fault in an electric circuit or apparatus due usually to imperfect insulation, such that the current follows a by-path and inflicts damage or is wasted.

Shunt

A device to bypass power away from a line.

Shoulder

• The side of a ball race.
• A surface in a bearing application or shaft which axially positions a bearing and takes the thrust load.

Silicon Controlled Rectifier (SCR)

Converts AC to DC. Used to supply DC power to drive DC motors.

Single Acting Cylinder

• A cylinder in which hydraulic energy can produce thrust or motion in only one direction.
• Can be spring or gravity returned.

Signal

A command or indication of a desired position or velocity.

Single Phase

A circuit that differs in phase by 180 degrees. Single phase circuits have two conductors, one of which may be a neutral, or three conductors, one of which is neutral.

Single Row

A bearing with one row of rolling elements.

Skiving

• To cut, split or pare away outer layer of a flexible hose.
• Also refers to a type of cut for belting or other rubber products.

Slip

Internal leakage of hydraulic fluid.

Spacer

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

Solenoid

A spiral of conducting wire, wound cylindrically so that when an electric current passes through it, its turns are nearly equivalent to a succession of parallel circuits, and it acquires magnetic properties similar to those of a bar magnet.

Snap Ring

• A removable ring used to axially position a bearing or component in a housing.
• May also be used as a means of fastening a shield or seal in a bearing.

Specific Gravity

The density of any material divided by that of water at a standard temperature.

Spherical Roller Bearing

A self-aligning rolling bearing with convex rollers or concave rollers as rolling elements. With convex rollers, the outer ring has spherical raceway. With concave rollers, the inner ring has spherical raceway.

Spike

A large momentary increase in the amount of voltage or amperage supplied to the circuitry.

Spool

A term loosely applied to almost any moving cylindrically shaped part of a hydraulic component which moves to direct flow though the component.

Standard Bearing

A bearing which conforms to the basic plan for boundary dimensions of metric or inch dimensions.

Star Connection

The same as a ""Y"" or ""Wye"" connection. This three-phase connection is so called because, schematically, the joint of the ""Y"" points looks like a star.

Starter

• A device used to control the electrical power to motors.
• Provides overload protection as required by the NEC.
• Can be operated manually, electrically, or by automatic pilot devices.
• A starter has two basic parts -

Starting Amps

The maximum current drawn by the motor during the starting period.

Static Load

A load exerted on a bearing not in motion.

Stator

The stationary part of a motor. A permanent magnet DC motor holds its magnets in the stator.

STLE

The Society of Tribologists and Lubrication Engineers, who are involved with friction, wear, and lubrication. Formerly known as ASLE, the American Society of Lubrication Engineers.

Strainer

A coarse filter for trapping large particles.

Stroke

• The length of travel of a piston or plunger.
• To change the displacement of a variable displacement pump or motor.

Subplate

An auxiliary mounting for a hydraulic component providing a means of connecting piping to the component.

Substrate

The basic surface upon which the adhesive is applied and to which it is expected to adhere.

Sump

A reservoir.

Supercharge

See charge

Suction Line

The hydraulic line connecting the pump inlet port to the reservoir.

Surface Preparation

Physical and/or chemical pretreatments to enhance the adhesive strength of an adhesive to be applied to a specific surface.

Surge

A momentary rise of pressure in a circuit.

SUS

Saybolt Universal Seconds. A measure of viscosity, the time required for a given fluid to flow through a standard orifice.

Surge Suppressor

• A device that suppress voltage transients that can occur on the AC line.
• A metal oxide varistor (MOV).

Swash Plate

A stationary plate in an axial type piston pump or motor which causes the pistons to reciprocate as the cylinder barrel rotates.

Tachometer Feedback

A tachometer (tach) generates a voltage proportional to speed. Tachs provide a closed-loop system with excellent speed regulation.

Tack

• Adhesive ""stickiness"" on an adhesively coated surface that is to yet not completely dried.
• The property of an adhesive that permits it to form a bond of measurable strength immediately.

Tank

The reservoir or sump.

Tensile Strength

The maximum tensile load per unit area required to break a bond, expressed in pounds per square inch.

Terminal Block

An insulating base equipped with terminals for connecting wires.

Thermal Conductivity

The ability of a material to conduct heat.

Thermoplastic

A material capable of being repeatedly softened by heat and hardened by cooling.

Thermal Overload Protector

A device which protects motor windings from excessive temperature by opening a set of contacts. This device may reach its’ pre-set trip point as a result of ambient temperature, current, or both.

Thrust Face

The face of a thrust bearing against which housing or shaft shoulder pushes.

Timken OK Load

This is a measure of the extreme pressure properties of a lubricant. Lubricated by the product under investigation, a standard steel roller rotates against a block. Timken OK load is the heaviest load that can be carried without scoring occurring.

Three Phase

Three lines of power supplied each 120° apart. Most common in heavy industrial applications.

Time Delay Relay (TDR)

A device that performs a timing function upon being energized or receiving a control signal.

Throttle

To permit passing of a restricted flow. May control flow rate or create a deliberate pressure drop.

Torque Converter

A rotary fluid coupling that is capable of multiplying torque.

Torque Limit

This feature permits the operator to adjust the maximum current the motor can draw. This, in effect, limits the maximum torque the motor will produce.

Tolerance

• The amount a given dimension may vary from specifications.
• The range between two limiting sizes as a means of specifying the degree of accuracy.

Track Roller

A radial roller bearing with a heavy section outer ring, intended to roll on track. Also known as a cam follower.

Torque Limiter

A device used to protect a motor or other system components from damage due to overloads or jamming.

Torque

A rotary or twisting force. The output torque of a motor is usually expressed in pound-inches (lb-in) or Newton-Meters (Nm).

Transducer

A device that transforms an analog signal to a specific variable output signal that is proportional to the input signal. Typical inputs include variable pressure, level, voltage or current.

Transformer

A device used to change power into more usable forms. Usually to increase the voltage on the line just before power is supplied to a main entrance.

Transistor

An active semiconductor device with three or more terminals. Transistors turn on instantly. They don't require a warm-up time like a tube does. A transistor will last for years and very little voltage is needed.

Turbine

A rotary device that is actuated by the impact of moving fluid against blades or vanes.

Torque Motor

An electromagnetic device consisting of coils and the proper magnetic circuit to provide actuation of a spring restrained armature, either rotary or translatory.

Two-Way Valve

A directional control valve with two flow paths.

Turbulent Flow

A condition where the fluid particles move in random paths rather than in continuous parallel paths.

UL (Underwriter Laboratories)

An independent lab which certifies not only safety but function of electrical devices used in the U.S.A.

Unload

To release flow to prevent pressure being imposed on the system or a portion of the system.

Uninteruptabile Power Supply (UPS)

• A device to insure a constant power to critical circuits such as computer banks, or hospital lighting.
• Very susceptible to spikes and surges.

Unloading Valve

A valve which bypasses flow to tank when a set pressure is maintained on its pilot port.

Vacuum

• The absence of pressure.
• A perfect vacuum is the total absence of pressure.
• A partial vacuum is some condition less than atmospheric pressure.
• Measured in inches of Mercury (in.Hg) with the zero point equal to atm

Vapor Pressure

The pressure at which the liquid and gaseous phases of a fluid are in equilibrium.

Variable Frequency Drive (VFD)

A device to control the speed and efficiency of electric motors.

Velocity

• The speed of flow through a hydraulic line expressed in feet per second or meters per second.
• The speed of a rotating component measured in revolutions per minute.

Valve

A device which controls fluid flow direction, pressure, or flow rate.

Vent

• To permit opening of a pressure control valve by opening its pilot port to atmospheric pressure.
• An air breathing device on a fluid reservoir.

Viscosity

The measure of the resistance of a fluid to flow, usually expressed in poise or centipoise. The higher the reading, the thicker the material.

Viscosity Index

A measure of the viscosity-temperature characteristics of a fluid as referred to that of two arbitrary reference fluids.

Voltage Drop

The drop of pressure in an electric circuit due to the resistance of the conductor.

Volume

• The size of a space or chamber in cubic units.
• Loosely applied to the output of a pump in gallons per minute (gpm).

Voltage

The measurement of the pressure of the electric power.

Watts

The unit of measurement for power. Amps times voltage is the amount of power that is used.

Wicking

The flow of an adhesive into a tightly restricted opening.

Wide Inner Ring Bearing

A bearing with the inner ring extended on one or both sides in order to achieve greater shaft support and permit addition of locking device or provide additional space for sealing devices.

Withdrawal Sleeve

• An axial slotted sleeve with a cylindrical bore, tapered outside, and male screw thread at the large end.
• Used for mounting and dismounting of a bearing with tapered bore on cylindrical outside surface of shaft.
• Also called

Y Connection

Same as a star connection or wye connection. This three-phase connection is so called because, schematically, the joint of the ""Y"" points looks like a star.

Wye Connection

Same as a star connection. This three-phase connection is so called because, schematically, the joint of the ""Y"" points looks like a star.

Work

Exerting a force through a definite distance. Work is measured in units of force multiplied by distance; for example, pound-feet or joule (1 J = 1 Nm).