Electric_Software

Glossary

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A

ABRASION
External damage to the hose assembly caused by rubbing on a foreign object, wearing away by friction.

ABSOLUTE
A measure having as its zero point or base the complete absence of the entity being measured

ABSOLUTE PRESSURE
The indicated value of the weight of the earth's atmosphere. At sea level this value is approximately 14.65 psi (pounds per square inch).

ACCUMULATOR
A vessel, normally cylindrical, which is used to store fluid and gas for future release of the energy in the compressed fluid and gas. Normally contains a diaphragm or piston between the fluid (liquid) and gas chambers. Fluid is normally introduced at one end and the gas at the opposite end.

ACCURACY
The ability of the servo system to achieve the desired output.

ACTUATOR
A device for converting hydraulic energy into mechanical energy, i.e., a motor or cylinder.

ADAPTER
A mechanical device used to align the shaft of an electric motor (or other rotary device) with the shaft of a hydraulic pump to maintain radial and parallel shaft alignment. Fittings of various sizes and material used to change an end fitting from one type to another type or one size to another    ( i.e., male JIC to male pipe adapter is often attached to a female JIC to create a male end union fitting)

AERATION
Air trapped in the hydraulic fluid. Excessive aeration causes the fluid to appear milky and components to operate erratically.

AIR BLEEDER AUTOMATIC
A valve that is fit into a hydraulic pipe line to facilitate automatic release of air trapped in the pipeline. See also AIR BLEEDER MANUAL.

AIR BLEEDER MANUAL
A valve that is fit into a hydraulic pipe line to facilitate manually initiated release of air trapped in the pipeline. See also AIR BLEEDER AUTOMATIC.

AIR BREATHER
A mechanical device which contains a fine mesh filter element. Normally attached to the top of a reservoir or tank to allow air to pass in and out of the reservoir or tank.

ALTERNATING CURRENT (AC)
A continuously changing magnitude of current, produced by a power source (e.g., generator, alternator).

AMBIENT
The current condition of temperature, humidity and atmospheric pressure.

AMBIENT NOISE LEVEL (BACKGROUND NOISE)
The noise level in the area surrounding the machine or component to be tested with machine being tested not operating.

AMERICAN WIRE GAUGE
A device used to determine the standard sizes of wire conductors.

AMPLIFIER
An electronic device that receives an input voltage or current signal and modifies the signal into a driving voltage or current at a different level.

AMPLITUDE OF SOUND
The loudness of a sound.

ANALOG DEVICE
An electronic device that requires or produces an infinitely variable signal, usually voltage or current, in response to a state change within the device.

ANALOG SIGNAL
An AC or DC voltage or current signal that represents continuously variable physical quantities (e.g., voltage, current, pressure, temperature, or speed).

ANCHOR

A restraint applied to eliminate motion and restrain forces.

AND LOGIC GATE
A digital circuit in which the output state equals a binary 1 if and only if all of its inputs are a binary 1 at the same time.

ANNULAR AREA
A ring shaped area — often refers to the net effective area of the rod slide of a cylinder piston, i.e. the piston area of the rod.

ANNODIZE
An electrolytic process used to deposit protective or cosmetic coatings in a variety of colors on metal, primarily used on aluminum.

ANSI FLANGE
American National Standards Institute. A mechanical device that is used to connect two pieces of pipe together to form a pressure tight joint. ANSI flanges are round, use through bolts and/or nuts to attach two matched flanges together or to a valve or other mechanical device. See ANSI standards for pressure and temperature ratings.

ASTM
American Society for Testing and Materials

ATMOSPHERE (ONE)
A measure of pressure equal to about 14.7 psi.

ATMOSPHERIC PRESSURE
Pressure exerted by the atmosphere at any specific location. (Sea level pressure is approximately 14.7 pounds per square inch (1.01 bar) (101.34 kPa) absolute).

ATTENUATION
Opposite of gain (see gain).

ATTENUATOR
A variable resistive device used to reduce the value of current or voltage.

AXIAL MOVEMENT
Compression or elongation along the longitudinal axis.
 

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B

BACK CONNECTED
A condition where pipe connections are on normally unexposed surfaces of hydraulic equipment. (Gasket mounted units are back connected.)

BACK PRESSURE
The level of pressure on the return or downstream side of a device or system.

BACKUP BOTTLE
A vessel, normally cylindrical, which is used to store gas for future release of the energy in the compressed gas to an accumulator.

BACK-UP RING
A fabric or plastic device that is used with an o-ring or other gasket to present extrusion of the o-ring or gasket into an adjacent space or crevice.

BAFFLE
A separator found in a reservoir, tank or other chamber to divert fluid flow in specific direction(s) for de-aeration of moving fluid.

BALL VALVE
A valve that may be used to divert the flow of fluid in a passage. Most normally configured in a two way pattern which is either open or closed.

BAR
The measure of pressure in the metric system. One (1) bar = 14.5 psig.

BARB
The portion of a fitting inserted into a hose, usually comprised of two or more radial serrations or ridges designed to form a redundant seal between the hose and fitting.

BEND RADIUS
The radius of the bent section of the hose measured to the innermost surface of the curved portion. Referred as minimum bend radius.

BETA RATIO ( )
The amount, expressed as a ratio, of particles in a fluid stream upstream of a filter, divided by the amount of particles downstream, for a particular size particle. See PARTICLE COUNT.

BILLET
A compressed cylinder of Fluropolymer resin from which raw tubing is extruded. Or a solid piece of material from which a fitting is manufactured.

BINARY NUMBER SYSTEM
A number system used in digital equipment that has a base of 2. The digits 0 and 1 are the only digits used in forming numbers in this system

BLADDER
A separator or diaphragm, usually found in a chamber to facilitate separation of two (2) fluids of gases. See ACCUMULATOR.

BLEEDING
Surface exudation

BLEED-OFF
To divert a specific, controllable portion of pump delivery directly to reservoir.

BLISTER
A raised area on the surface or a separation between the layers of reinforcement creating a void or air-filled space in a vulcanized article.

BOLT KIT
A set of bolts or screws that are selected to suit a particular application, i.e. preselected length, threads and strength to match the mounted component.

BORE
An internal cylindrical passageway, as a tube, hose, or pipe. The internal diameter of a tube, hose, or pipe.

BRAID
The woven portion of a hose used as reinforcement to increase pressure and hoop strength. Materials used can be polyester, cotton, or metal wire. A hose may have one or two braids applied outside or between layers of hose material.

BRAID ANGLE
The angle developed at the intersection of a braid strand and a line parallel to the axis of a hose.

BRAKE VALVE
A device used in the exhaust line of a hydraulic motor to (1) prevent overspeeding when an overrunning load is applied to the motor shaft and (2) prevent excessive pressure buildup when decelerating or stopping a load.

BRAZING
A process of joining metals using a non-ferrous filler metal having a melting point lower than the “parent metals” to be joined, typically over +800° F.

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

BURST PRESSURE
The level of pressure at which a component, pipe, tube, hose or other fluid passage will burst during application of internal pressure. Normally 4.0 times working pressure. See also WORKING PRESSURE and PROOF PRESSURE.

BYPASS
A secondary passage for fluid flow.
 

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C

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 sdtandards, specifications, tests, materials, and/or performance attributes of which the referenced item(s) have or will meet.

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

CARTRIDGE
The replaceable element of a fluid filter. The pumping unit from a vane pump, composed of rotor, ring, vanes and one or both side plates.

CARTRIDGE VALVE
A valve that is inserted into a standard size cavity in a manifold block and is held in place with either self-contained screw threads or a cover secured with bolts. May be slip-in or screw-in types. Perform directional, pressure or flow control functions.

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

CHAMBER
A compartment within a hydraulic unit. May contain elements to aid in operation or control of a unit. E.g., spring chamber, drain chamber, etc.

CHARGE (supercharge)
-To replenish a hydraulic system above atmospheric pressure. -To fill an accumulator with fluid under pressure (see precharge pressure).

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

CHARGING ASSEMBLY
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 VALVE
A valve that allows fluid flow in one direction, yet stops flow in the opposite direction.

CHEMICAL CAPATIBILITY
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 CENTER 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 CENTER 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
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.

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D


DATE CODE
Any combination of numbers, letters, symbols, or other methods used by a manufacturer to identify the time of manufacture of a product.

DEADBAND
The region or band of no response where an error signal will not cause a corresponding actuation of the controlled variable.

DEADTIME
Any definite delay between two related actions. Measured in units of time.

DEBURR
To remove the ragged edges from the inside diameter of a hose end or fitting; an important fabrication step for assembling Teflon® ( PTFE) in order to ensure a good seal.

DECIBEL (dB)
A non-dimensional number used to express sound pressure and sound power. It is logarithmic expression of the ratio of a measure quantity to a reference quantity.

dB (A) & (C)
A sound level reading in decibels made on the A- & C- weighted network, respectively of a sound level meter.

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

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

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

DEVICE
A combination of individual components that are arranged to form a unit with a specific set of operating parameters.

DIAGRAM
A formal drawing showing the arrangement of components or devices.

DIE
A tool used to swage or crimp a fitting onto a hose. Swage dies usually consist of two halves machined to a predetermined diameter, designed for a specific hose type or size. A crimp die set is typically six to eight “fingers” designed for infinite diameter settings within a range or preset to a specific diameter for a given hose type and size.

DIFFERENTIAL CURRENT
The algebraic summation of the current in the torque motor; measures in MA (milliamperes).

DIFFERENTIAL CYLINDER
Any cylinder I which the two opposed pistons are not equal.

DIFFERENTIAL PRESSURE
The value or magnitude of pressure measured as the absolute difference of the inlet pressure and outlet pressure.

DIGITAL
The production of a discrete signal based on a change in state. See ANALOG.

DIGITAL DEVICE
A device or component that responds to or produces a discrete function based on a change in state. See ANALOG.

DIGITAL SIGNAL
A voltage or current that varies between two distinct and fixed levels.

DIODE RECTIFIER
A device used to convert AC voltage into DC pulses.

DIRECT CURRENT (DC)
A steady level of electrical current, produced by a power source (e.g. battery, thermocouple, etc.) that flows in only one direction in a circuit.

DIRECTIONAL VALVE
A valve whose primary function is to direct or prevent flow through selected channels.

DIRT CAPACITY
The measure of volume (or weight) of particles that a filter or strainer will hold at the limit of operation.

DISPLACEMENT
The volume for one revolution or stroke or for one radiant when so stated.

DITHER
A cyclic application of voltage across a solenoid or coil. Most often used to assure that the device driven by the coil or solenoid remains in a state of constant motion, thus reducing breakaway friction.

DOG-LEG ASSEMBLY
Two hose assemblies joined by a common elbow.

DOT
Department of Transportation

DOWNSTREAM
The passage beyond a device, normally at the outlet of direction of flow.

DRAIN
A passage in, or line from a hydraulic component which returns leakage fluid independently to reservoir or to a vented manifold.

DRIFT
The measure of movement of a device after a preset condition is applied. Normally drift is measured with varying temperature, although drift may be plotted against any variable, such as humidity, etc.

DUROMETER
An instrument for measuring the hardness of rubber and plastic compounds.

DUROMETER HARDNESS
A numerical value which indicates the resistance to indentation of the blunt indentor of the durometer.

DYNAMIC BEHAVIOR
Describes how a control system or an individual unit reacts with time when subjected to an input signal.

DYNAMIC ERROR
The error that results during the transient state, that is, the state when the system is moving from one steady state condition to another.

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E

ECCENTRIC WALL
A wall of varying thickness

ECCENTRICITY
The condition resulting from the inside and the outside diameters not having a common center. See eccentric wall.

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

EFFUSION
The escape, usually of gases, through a material. See permeation.

ELASTIC LIMIT
The limiting extent to which a body may be deformed and yet return to its original shape after removal of the deforming force.

ELASTOMER
Any one of a group of polymeric materials, usually designated thermoset, such as natural rubber, or thermoplastic, which will soften with application of heat.

ELECTRIC MOTOR
An electro-mechanical device that converts electrical power into rotary motion. The resultant power output is measured in horsepower

ELECTROHYDRAULIC SERVO-VALVE
A servo-valve which is capable of continuously controlling hydraulic output as a function of an electrical input.

ELECTROMAGNETIC INTERFERENCE (EMI)
A modification of signals contained in circuit wiring (or stored in a microprocessor) caused by a strong magnetic flied radiated from some other electrical or electronic device or conductor.

ELECTROMOTIVE FORCE (EMF)
The force produced by a difference of electrical potential that causes current to flow in circuit. EMF is measured in units called volts.

ELECTROSTATIC DISCHARGE
The sudden discharge of static electricity from an area of buildup to a grounding point.

ELEMENT
See FILTER ELEMENT

ELONGATION
The increase in length expresses numerically as a percentage of the initial length.

ENCLOSURE
A rectangle drawn around a graphical component or components to indicate the limits of an assembly.

ENDURANCE TEST
A service or laboratory test conducted to product failure, usually under normal use conditions

ENERGY
See JOULE.

EPDM
Ethylene Propylene Diene Monomer; an elastomer.

EROSION
Degradation of a surface which is the result of mixtures of fluid and air or fluid and dirt particles passing over the surface at the same time as a change in pressure occurs.

ERROR (SIGNAL)
The signal which is the algebraic summation of an input signal and feedback signal.

EXHAUST LINE
A passage that is open to atmosphere. Normally used in systems using pressurized air or gas which may be dispersed into the atmosphere.

EXTRUDE/EXTRUDED/EXTRUSION
Forced through the shaping die of an extruder; extrusion may have a solid or hollow cross section.

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F


FATIGUE
The weakening or deterioration of a material occurring when a repetitious or continuous application of stress causes strain which can lead to failure.

FERRULE
A metal cylinder placed over a hose end to affix the fitting to the hose.

FEEDBACK
Part of a closed loop system which monitors back information about the condition under control for comparison.

FEEDBACK LOOP
Any closed circuit consisting of one or more forward elements and one or more feedback elements.

FILLER CAP
A mechanical device which provides an access for filling a reservoir or tank. Normally equipped with a fine screen to strain out dirt particles.

FILTER
A mechanical device used to house a filter element. See FILTER ELEMENT.

FILTER ELEMENT
A series of wire or fabric meshes which are bonded together by caps or perforated cylinders and are fitted into hydraulic system passages to strain fine particles and silt from fluid passed through the passage.

FITTING
A mechanical device used to attach two pieces of tubing/piping together or to attach a piece of tubing/pipe to a component.

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

FLAT SPOTS
Flat areas on the surface of cured hose caused by deformation during vulcanization.

FLOW CONTROL VALVE, PRESSURE COMPENSATED
A valve used to cause a variable pressure drop in a fluid passage, thus reducing the amount of fluid that may pass through the passage regardless of the pressure level at the inlet of the valve. Often fitted with a check valve that permits free flow of fluid in the opposite direction.

FLOW CONTROL VALVE, NONPRESSURE COMPENSATED
A valve used to cause a variable pressure drop in a fluid passage, thus potentially reducing the amount of fluid that may pass through the passage regardless of the pressure level at the inlet of the valve. Varying pressures at the inlet of the valve will change the flow capacity. Often fitted with a check valve that permits free flow of fluid in the opposite direction.

FLOW DIVIDER
A mechanical device used to divide the fluid in a passage into two or more separate fluid streams.

FLOW RATE
The volume, mass, or weight of a fluid passing through any conductor per unit of time.

FLOW SWITCH
A digital device that opens or closes a contact when a preset flow passes over the sensing element. Normally mounted in a fluid flow passage with a paddle or want perpendicular to the fluid stream.

FLOWMETER
An analog device which indicates the volume of fluid passing through its interior passage. The output signal may be a visual one or a low level electrical signal.

FLUID
A media used in a fluid power system for transfer of energy (work). See FLUID POWER SYSTEM.

FLUID FRICTION
The measure of the resistance of flow of fluid in a passage, measured in psi (pounds per square inch) or other measures of pressure. Fluid friction results in increased fluid temperature and loss of work potential in the fluid power system.

FLUID MOTOR
A mechanical device that transforms the flow of pressurized fluid into rotary motion.

FLUID POWER SYSTEM
The term used to describe a system of components that use a pressurized fluid to transfer energy (do work).

FLUID VELOCITY
The speed of fluid through a cross section expressed in length divided by time.

FOLLOW VALVE
A control valve which ports oil to an actuator so the resulting output motion is proportional to the input motion to the valve.

FORCE
The measure of the result of pressurized fluid acting upon a chamber in a fluid power system. Normally the measure is in pounds and is most often used to state the force in pounds that will be available at the rod of a cylinder when acted upon by pressurized fluid from a fluid power system. The system of units normally used are square inches, pounds per square inch, and pounds.

FOUR WAY
A term used to describe a valve that has four ports, normally a pressure (inlet) port, a return (tank) port, an `A' (`1') work port and a `B' (`2') work port. Used to change direction of a cylinder or other output device.

FOUR WAY VALVE, MANUALLY & DIRECT OPERATED
A valve having a four way functional capability that may be manually activated to directly control the operating spool. Movement of the spool from extreme end to extreme end reverses the flow paths of the ports. See FOUR WAY.

FOUR WAY VALVE, PROPORTIONAL CONTROL &DIRECT OPERATED
A valve having a four way functional capability that may be proportionately actuated by a solenoid to control the operating spool in infinite resolution. Movement of the spool from extreme end to extreme end completely reverses the flow paths of the ports. See FOUR WAY.

FOUR WAY VALVE, SOLENOID & DIRECT OPERATED
A valve having a four way functional capability that may be solenoid activated to directly control the operating spool. Movement of the spool from extreme end to extreme end reverses the flow paths of the ports. See FOUR WAY.

FOUR WAY VALVE, SOLENOID & PILOT OPERATED
A valve having a four way functional capability that may be solenoid activated to directly control the operating spool which then controls a secondary, larger spool. Movement of the secondary spool from extreme end to extreme end reverses the flow paths of the ports. See FOUR WAY.

FREE LENGTH
The lineal measurement of hose between fittings or couplings.

FREQUENCY
The number of times an action such as vibration or flexure occurs in a unit of time.

FREQUENCY BANDS
A division of the audible range of frequencies into sub-groups for detailed analysis of sound.

FREQUENCY RESPONSE ANALYSIS
A control system analysis which by introducing a varying rhythmic change (like alternating current) into a process or control unit observes what effect these changes have on the output. Since the information determines how a system or control unit will react, it is possible to use this method of analysis to predict what the addition of new equipment will mean to an operation.

FRONT CONNECTED
A condition wherein piping connections are on normally exposed surfaces of hydraulic components.

FULL FLOW
A filter in which all the fluid must pass through the filter element or medium.

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G


GAIN
Ratio of increase in a signal (or measurement) as it passes through a control system or a specific control element. If a signal gets smaller, it is said to be attenuated.

GALVANIC CORROSION
Corrosion that occurs on the less noble of two dissimilar metals in direct contact with each other in an electrolyte, such as water, sodium chloride in solution, sulfuric acid, etc.

GAS BOTTLE
See BACK-UP BOTTLE.

GASKET
A seal, made from rubber or other synthetic material in the shape of a circle and of polygonal cross-section. See O-RING.

GATE VALVE
A two-way valve that may be opened or closed to block the flow of fluid in a passage. Normally manually operated, but may be automated, especially for larger sizes. Normally designed so that when open, the opening of the passage is not restricted, but there will be some small pressure loss. See GLOBE VALVE and NEEDLE VALVE.

GAUGE PRESSURE
A term used to state that any pressure stated is corrected for atmospheric pressure. Normally abbreviated psig (pounds per square inch gauge)

GLAND
A mechanical device that is used to contain a seal, o-ring or gasket in a specified space to result in a leak-proof connection between two or more mechanical components.

GLOBE VALVE
A two-way valve that may be opened or closed to block the flow of fluid in a passage. Normally manually operated, but may be automated, especially for larger sizes. Normally designed so that the flow of fluid must make a non-straight turn inside the valve body which results in a loss of pressure across the valve when open, which is greater than the loss across a gate valve. See GATE VALVE and NEEDLE VALVE.

GROUND
A point of zero reference in electrical circuits to which all circuit voltages are compared. Also, to ground a device means to make connections to an earth ground for safety purposes.

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H


HARDNESS
Resistance to indentation. See durometer hardness.

HEAD
The measure of pressure at the base or other reference point of a column of fluid. Normally measured in feet of water.

HEAT
The form of energy that has the capacity to create warmth or 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 (BTU's). Once BTU is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit. In the metric system one calorie is the amount of heat required to raise the temperature of one gram of water from 3.5 C to 4.5 C (called a small calorie). If the temperature change is from 14.5 C to 15.5 C, the unit is the normal calorie.

HEATER
An electro-mechanical device that converts electricity into heat, normally for use in raising the temperature of fluid stored in a reservoir or tank.

HEAT EXCHANGER
See COOLER.

HEAT RESISTANCE
The property or ability to resist the deteriorating effects of the elevated temperatures.

HELIX
A shape formed by spiraling a wire or other reinforcement around the cylindrical body of a hose; typically used in suction hose.

HORSEPOWER
The measure of energy used in description of the normal power level in a system. 1 horsepower = 550 lb.-ft./ min. of work.

HOSE
A passage used to transport fluid between components in a fluid power system. Normally a flexible conduit consisting of a tube, reinforcement, and usually an outer cover

HUNTING
Tendency for a system to oscillate continuously.

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

HYDRAULIC CONTROL
A control which is actuated by hydraulically induced forces.

HYDRAULIC POWER
See FLUID POWER.

HYDRAULIC MOTOR
See FLUID MOTOR.

HYDRAULICS
Engineering science pertaining to liquid pressure and flow.

HYDRODYNAMICS
Engineering science pertaining to the energy of liquid flow and pressure.

HYDROKINETICS
Engineering science pertaining to the energy of liquids in motion.

HYDROPNEUMATICS
Pertaining to the combination of hydraulic and pneumatic fluid power.

HYDROSTATICS
Engineering science pertaining to the energy of liquids at rest.

HYDROSTATIC TESTING
The use of liquid pressure to test a hose or hose assembly fro leakage, twisting, and/or hose change in length.

HYSTERESIS
The difference between the response of a unit r system to an increasing signal and the response to a decreasing signal.

HZ (HERTZ)
A measure of the number of cycles that occur in a specific period of time. Usually the time base is the second, but the time base may be any acceptable measure of time. Synonymous term for "cycles per second".

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I

IDENTIFICATION YARN
A yarn of single or multiple colors, usually embedded in the hose wall, used to identify the manufacturer.

IMPEDANCE
The combination of AC and DC resistance in a circuit measured in ohms.

IMPRESSION
A design formed during vulcanization in the surface of a hose by a method of transfer, such as fabric impression or molded impression.

IMPULSE
An application of force in a manner to produce sudden strain or motion, such as hydraulic pressure applied in a hose.

IMPULSE SERVICE
An application parameter characterized by continuous cyclical pressure changes from low to high.

INDENTATION
1) The extent of deformation by the indentor point of any one of a number of standard hardness testing instruments. 2) A recess in the surface of a hose.

INDICATOR
A mechanical device with points to a scale to provide a visual perspective of the state of a component. See NEEDLE.

INPUT
Incoming signal to a control unit or system.

INTAKE LINE
A passage at the inlet port of a component, normally at the inlet port of a pump.

INSULATOR
A material that blocks the flow of current which is used for a short circuit and shock prevention.

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J


JACKET
A seamless tubular braided or woven ply generally on the outside of a hose.

JOULE
A unit of work, energy, or heat. 1 J (joule) = 1 Nm (Newton meter).

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K


KINETIC ENERGY
Energy that a substance or body has by virtue of its mass (weight) and velocity.

KINKING
A temporary or permanent distortion of the hose induced by bending beyond the minimum bend radius.

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L


LAG
Preferred engineering term for delay in response (usually in degrees).

LAMINAR FLOW
A condition of flow in a passage that is typified by slow movement of fluid in a relatively straight path along the centerline of a passage. See TURBULENT FLOW.

LEVEL TRANSMITTER
An electro-mechanical device which senses the level of fluid in a chamber and produces an analog signal that corresponds with the change of state in the chamber. See LEVEL SWITCH.

LEVEL SWITCH
An electro-mechanical device which senses the level of fluid in a chamber and opens or closes a digital switch to indicate a change of state. See LEVEL TRANSMITTER.

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

LIFT
The measure of the capability of a pump to raise fluid from a lower to higher level at its inlet port without damage to the pump. Normally expressed in feet of water.

LINE
A connection between components, a passage for fluid or gas transfer. See PIPE, and TUBE and HOSE.

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

LINEAR VARIABLE TRANSFORMER (LVT)
An electro-mechanical linear device that produces an analog signal in proportion to the difference in velocity between a magnet and a separate fixed coil.

LINEAR VARIABLE DIFFERENTIAL TRANSFORMER (LVDT)
An electro-mechanical linear device that produces an analog signal in proportion to the difference in distance between a magnet and separate fixed coil.

LINEARITY (SERVOVALVE)
The degree of straightness of the hysteresis plot.

LIQUID LEVEL GAUGE
Gauge to visually indicate the fluid level in a reservoir or tank.

LITER
A metric measure of volume. One (1) liter = 0.2642 gallons.

LOGIC CIRCUIT
A digital circuit (also called a gate) that has binary inputs and outputs and is capable of performing a decision making function.

LOOP INSTALLATION
The assembly is installed in a loop or “U” shape and is most often used when frequent and/or large amounts of motion are involved.

LUBRICATOR
A mechanical device which is used to inject drops or mist of oil into an air line for lubrication purposes.

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M


MANDREL
1) A form, generally of elongated round section used for size and to support hose during fabrications and/or vulcanization. It may be rigid or flexible. 2) A tapered expanding device, fixed in diameter which is pulled through a shank of a fitting thus expanding the diameter to exert force on the hose between the shank and ferrule.

MANIFOLD
A fabricated system of passages to which various components are attached to form a working assembly or subassembly.

MANUAL CONTROL
A control actuated by the operator.

MANUAL OVERRIDE
A means of manually actuating an automatically-controlled device.

MANUFACTURER’S IDENTIFICATION
A code symbol used on or in some hose to indicate the manufacturer.

MASS FLOW RATE
The mass of fluid per unit of time passing through a given cross-section of a flow passage in a given direction.

MEAN DIAMETER
The mid-point between the inside diameter and the outside diameter of a corrugated/convoluted hose.

MECHANICAL CONTROL
A control actuated by linkages, gears, screws, cams or other mechanical elements.

MENDER
A fitting or device used to join two sections of hose.

METER
39.37 inches. The measure of distances in the metric system.

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

METER-OUT
To regulate the flow of the discharge fluid out of an actuator or system.

MICRON
1/1000th of a millimeter or 0.00003937 inches. The measure used to determine the particle size of contaminants in a fluid system.

MICRON RATING
The size, in microns, of the particles a filter will remove.

MICROPROCESSOR
A digital computer based on a single miniature integrated circuit that offers programmability and computational ability for use in electrohydraulic control applications.

MINIMUM FREE LENGTH
Calculated as four times the hose OD plus half the hose minimum bend radius as a best practice for hydraulic hose assemblies.

MODEM
Modulator / Demodulator. A device used to provide digital data communications between two separate microprocessing units. The modulator converts digital information into tomes that are transmitted over telephone lines and the demodulator changes the received tones back to digital data.

MOTOR
A device which converts hydraulic fluid power into mechanical force and motion. It usually provides rotary mechanical motion.

MULTIMETER
A device (VOM or DMM) used to measure electrical quantities.

MUFFLER
A mechanical device which provides a complex path for exhaust of air from a pressurized chamber, thus reducing the noise level of the exhausting air.
 

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N


NAHAD
The abbreviation for the Association for Hose and Accessories Distribution.
 

NATIONAL ELECTRICAL CODE (NEC)
Standards, recommended practices, specifications and directional for electrical wiring of residential, commercial, industrial and farm buildings. Published by the National Fire Prevention Association.

NECKING DOWN
A localized decrease in the cross-sectional area of a hose resulting in tension.

NEEDLE VALVE
A two-way valve that may be opened or closed to block the flow of fluid in a passage. Normally manually operated, but may be automated, especially for larger sizes. Normally designed so that the flow of fluid must make an non-straight turn inside the valve body which results in a desired loss of pressure across the valve when open which is greater than the loss across a gate valve. See GATE VALVE and GLOBE VALVE.

NEWTON
A unit of force based on the unit of mass, Kg (kilogram), multiplied by the acceleration, m/s2 (meters per second per second) which produces Kgm/s2, called the Newton. 1 N = 1 Kgm/s2 = 0.1225 lbs. (F) — (pounds force).

NIPPLE
The internal member or portion of a hose fitting.

NITRILE RUBBER ( NB/BUNA-N)
A family of acrylonitrile elastomers used extensively for industrial hose.

NITROGEN
An inert gas used to serve as an energy source for accumulators or to be used as a cleaning agent when pure, nonexplosive gases are required.

NOISE (Electrical)
Interference-type problems within electrical circuits and associated wiring that can cause erratic and improper operation of equipment.

NON-CONDUCTIVE
The inability to transfer an electrical charge.

NULL
The position of a device that is its normal or otherwise preset `zero' condition.

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O


OFFSET-LATERAL, PARALLEL
The distance the ends of a hose assembly are displaced in relation to each other as the result of connecting two misaligned terminations in a system or intermittent fixture required in a hose application.

OHM'S LAW
Stated that the current in a circuit is directly proportional to the voltage and indirectly proportional to the resistance. Expressed as a formula: I = E / R.

OPEN CENTER CIRCUIT
One in which pump delivery flows freely through the system and back into the reservoir in neutral.

OPEN CENTER VALVE
One in which all ports are interconnected and open to each other in the center or neutral position.

OPEN CIRCUIT
A circuit in which a complete path for electrical current flow does not exist.

OPEN STEAM CURE
A method of vulcanizing in which steam comes in direct contact with the product being cured.

OPERATIONAL AMPLIFIER (OP AMP)
An integrated circuit amplifier with special characteristics (high gain, high input impedance, low output impedance, differential amplification) that make it especially suitable for electrohydraulic control systems.

OPERATING PRESSURE
The maximum level of pressure at which a component, pipe, tube, hose or other fluid passage will experience during application of maximum expected fluid pressure. See also BURST PRESSURE and PROOF PRESSURE.

O-RING
A seal, made from rubber or other synthetic material in the shape of a circle and of circular or other polygonal cross-section. See GASKET.

OR LOGIC GATE
A seal, made from rubber or other synthetic material in the shape of a circle and of circular or other polygonal cross-section. See GASKET.

ORIFICE
An opening or passageway which can be have tapered edges.

OUTPUT STAGE
A spool or other device that is controlled by a smaller spool or torque motor.

OVERALL LENGTH ( OAL)
The total length of a hose assembly which consists of the free hose length plus the length of the couplings.

OVERLAP
The condition of a spool and body in a servo valve or other spool valve wherein the spool must move a specified amount (the overlap) before exposing two adjacent cavities.

OVERSHOOT
Occurs when the process exceeds the target value as operating conditions change.

OXIDATION
The absorption of oxygen into fluid and the subsequent plating of the oxygen/ fluid mixture onto metal surfaces evidenced by a change in the appearance or feel of the surface or by a change in physical properties.

OZONE CRACKING
The surface cracks, checks, or crazing caused by exposure to the atmosphere containing ozone.

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P


PACKING
A seal or gasket. See SEAL, O-RING and GASKET

PARALLEL DATA TRANSMISSION
A form of digital data transmission in which all of the bits of a binary word are processed or transmitted at the same time. Faster than serial transmission but requires separate circuitry for each bit.

PARTICLE
A piece of debris (sand, dirt, metal, fabric, etc.) Found in a fluid.

PARTICLE COUNT
The visual or electronic summation of the quantity of particles, grouped by size, in a fluid sample of specified size.

PASSAGE
A hole through which fluid is passed in a fluid power system. See TUBE, PIPE, HOSE and MANIFOLD.

PERMEATION
The process of migration of a substance into and through another usually the movement of gas into and through a hose material; the rate of permeation is specific to the substance, temperature, pressure, and the material being permeated.

PETROLEUM FLUID
A hydraulic oil (fluid) that is made from a petroleum base. Normally will support combustion if heated to a specific temperature.

PH (PHASE)
A term used to describe the quantity of cyclic electrical power sources in a high voltage system. Most commonly 1phase or 3-phase.

PHASE SHIFT
A time difference between the input and output signal of a control unit or system, usually measures in degrees.

PHOSPHATE ESTER FLUID
A hydraulic oil (fluid) that is made from an ester base. A synthetic fluid, manufactured to specific characteristics. Normally will not support combustion if heated to a specific temperature.

PILOT LINE
A passage in a fluid power system that is used to transport a fluid at a pressure lower than the normal operating pressure to facilitate controlled shifting of spool valves.

PILOT-OPERATED CHECK VALVE
A special check valve that may be opened against a check load by applying pilot pressure from a secondary source to open the check to free reverse flow.

PILOT PRESSURE
The pressure in the pilot circuit.

PILOT VALVE
A valve applied to operate another valve or control. The controlling stage of a 2stage valve.

PIPE
A passage in a fluid power system that is constructed of metal and conforms dimensionally to standard established by the ANSI. May be acquired by size and schedule, where increase in wall thickness does not increase the outside diameter. See TUBE.

PISTON
A cylindrically shaped part in which fits within a cylinder

PISTON, CYLINDER
A cylinder in which the movable element has a greater cross-sectional area than the piston rod.

PISTON RING
A metal ring that is used to seal high pressure fluid inside a passage to prevent (limit) leakage across the passage. Normally found in cylinders.

PITCH
1) The distance from one point on a helix to the corresponding point on the next turn of the helix, measured parallel to the axis. 2) The distance between the two peaks of adjacent corrugation or convolution.

PLAITS
An individual group of reinforcing braid wires or strands.

PLATING
A material, usually metal applied to another metal by electroplating for the purpose of reducing corrosion; typically a more noble metal such as zinc is applied to steel.

PLUNGER, CYLINDER
A cylinder in which the movable element has the same cross-sectional area as the piston rod.

POLYMER
A macromolecular material formed by the chemical combination of monomers, having either the same or different chemical compositions.

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

PORT
An internal or external terminus of a passage in a component.

POSITIVE DISPLACEMENT
A characteristic of a pump or motor when a constant volume is delivered for each revolution or stroke.

POTENTIOMETER
An electrical device that changes its internal resistance when moved to a specified point. Most commonly found in electronic control panels. Used to change the voltage in a control system for required control changes (position, speed, pressure, etc.)

POUNDS PER SQ. INCH, GAUGE (PSIG) & ABSOLUTE (PSIA)
The measure of pressure, corrected for atmospheric pressure, that is `zero' psig= 14.65 psia. `Zero' psia = absolute zero vacuum.

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

POWER PACK
An integral power supply unit usually containing a pump, reservoir, relief valve and directional control.

POWER SUPPLY
Term used to describe a fluid power source. A hydraulic power unit.

PRE-FILL VALVE
A valve that is arranged so its inlet port is connected to a reservoir or tank and so that fluid will flow from the inlet of the valve into a cylinder or ram when opened. When closed, the valve must close off the ram or cylinder from the reservoir or tank to permit application of high pressure from another source on the cylinder side of the valve. Most commonly used to fill large rams on presses to take up non-operating stroke.

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

PRESSURE
Force per unit area. Usually expressed in pounds per square inch (psi), bar or kilopascal (kPa).

PRESSURE COMPENSATOR
A hydro-mechanical device fitted to a pump or other flow producing/controlling device that reduces flow when pressure rises and increases flow as pressure decreases, to preset limits.

PRESSURE DIFFERENTIAL (Drop)
The difference in pressure between any two points in a system or a component.

PRESSURE DIFFERENTIAL SWITCH
A digital device that opens or closes a switch when the internal pressure differential changes state. Most commonly used to sense clogging of filter elements.

PRESSURE DROP
See Pressure, Differential.

PRESSURE 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 atmospheric pressure. See VACUUM GAUGE and COMPOUND GAUGE.

PRESSURE LINE
A passage that carries fluid from the source of flow to various operating elements of a fluid power system.  Rated for operating pressure at the maximum expected pressure of the system.

PRESSURE OVERRIDE
The measure of pressure increase over the nominal setting of a device when additional fluid flow is passed over the device after it initially opens.

PRESSURE PLATE
A side plate in a vane pump or motor cartridge on the pressure port side.

PRESSURE, PROOF TEST
A non-destructive pressure test applied to hose assemblies.

PRESSURE REDUCING VALVE
A pressure control valve whose primary function is to limit outlet pressure.

PRESSURE, SHOCK/SPIKE
The peak value of a sudden increase of pressure in a hydraulic or pneumatic system producing a shock wave.

PRESSURE SWITCH
A digital device that opens or closes a switch when the internal pressure changes state.

PRESSURE TRANSDUCER
An analog device that produces a change in voltage or current when the internal pressure changes state. Normally a fast response device for use in servo control systems. See PRESSURE TRANSMITTER.

PRESSURE TRANSMITTER
An analog device that produces a change in voltage or current when the internal pressure changes state. Normally a slow acting device for use in display systems where update time is not crucial. See PRESSURE REDUCER.

PROGRAMMABLE LOGIC CONTROLLER (PLC)
A valve which controls and varies pressure, flow, direction, acceleration and deceleration from a remote position. They are adjusted electrically and are actuated by proportional solenoids rather than by a force or torque motor. The output flow is proportional to the input signal. They provide moderately accurate control of hydraulic fluid.

PROOF PRESSURE
A non-destructive level of pressure at which a component, pipe, tube, hose or other fluid passage will not yield during testing of internal pressure. Normally 2 times working pressure. See WORKING PRESSURE and BURST PRESSURE.

PROPORTIONAL FLOW
In a filter, the condition where part of the flow passes through the filter element in proportional to pressure drop.

PROPORTIONAL VALVE
A valve which controls and varies pressure, flow, direction, acceleration and deceleration from a remote position. They are adjusted electrically and are actuated by proportional solenoids rather to the input signal. They provide moderately accurate control of hydraulic fluid.

PTFE
Polytetrafluoroethylene, a high molecular weight fluoroplastic polymer with carbon atoms shielded by fluorine atoms having very strong interatomic bonds, giving it chemical inertness.

PULSE WIDTH MODULATION
An electronic signal of constant frequency and amplitude that has varying pulse width to control the level of power to the solenoid.

PUMP, AIR-OIL
A mechanical device containing two sets of isolated pistons and control valving that are used to intensify fluid pressure by use of a multiplication effect across the two sets of pistons. The air piston being larger than the fluid piston.

PUMP, FIXED DISPLACEMENT
A mechanical device that creates a flow of fluid when its shaft is rotated in the proper direction and when its inlet is connected to a chamber filled with fluid (a reservoir or tank). The outlet port may be connected to a passage leading to a fluid power system or exhausted into another chamber that is at a higher pressure. The higher pressure chamber must be equipped with a pressure limiting device. The output flow rate is fixed by the pump displacement per revolution.

PUMP, VACUUM
A mechanical device that creates a pressure that is lower than atmospheric at its inlet when the shaft is rotated. The outlet port is normally connected to a higher pressure chamber or atmosphere.

PUMP, VARIABLE DISPLACEMENT
A mechanical device that creates a flow of fluid when its shaft is rotated in the proper direction and when its inlet is connected to a chamber filled with fluid (a reservoir or tank). The outlet port may be connected to a passage leading to a fluid power system or exhausted into another chamber that is at a higher pressure. The higher pressure chamber must be equipped with a pressure limiting device. The output flow rate is fixed by the pump displacement per revolution but variable by the operator in a manual or servo controlled system, depending on the design.

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Q


QUICK DISCONNECT
A mechanical device that may be engaged or Dis-engaged to attach two fluid passages. Typically, Disengagement is possible by manual means.

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R


RAM
A cylinder that has an extend port only. Usually accompanied by auxiliary cylinders that are mechanically linked to the ram to facilitate retraction action.

RAMP
The rate of change of a specific output, such as the ramp of a pressure compensator.

RAMP MODULE
An electronic device that controls the rate of rise of a servo or proportional valve by using capacitors to limit the rate of voltage or current change to the servo or proportional valve.

RATED FLOW
The maximum flow that a manufacturer assigns to a specific component as the maximum desirable flow at which the device will function properly. Also the flow that a designer assigns to a system as the nominal maximum flow. See WORKING PRESSURE.

RATED PRESSURE
The maximum pressure that a manufacturer assigns to a specific component as the maximum desirable pressure at which the device will function properly. See WORKING PRESSURE.

RECIPROCATION
Back-and-forth straight line motion or oscillation.

REDUCING VALVE
A valve that decreases the downstream pressure (at the valve outlet) in order to control the flow and therefore the outlet pressure to some preset level. Normally accomplished by balancing the outlet pressure against a precision spring.

REGENERATIVE CIRCUIT
A piping arrangement for a differential type cylinder in which discharge fluid from the rod end combines with pump delivery to be directed into the head end.

REGULATOR
A term used to describe a valve or device that limits the pressure in a passage.

REINFORCEMENT
The strengthening members, consisting of fabric, cord, and/or metal, of a hose.

RELAY
An electromagnetic device that allows one circuit to control another without a direct electrical connection between the two circuits.

RELAY LOGIC
A system for controlling a machine or process based on the status of various interconnected relays.

RELIEF VALVE
A valve that limits the pressure at its inlet port by exhausting flow present at its inlet port to another chamber of lower pressure potential through its outlet port.

REPLENISH
To add fluid to maintain a full hydraulic system.

RESERVOIR
A chamber used to store fluid.

RESISTANCE
The opposition to current flow offered by the components of an electrical circuit.

RESPONSE TIME
The elapsed time that occurs after the beginning of a function until its completion. For example, the time elapsed between application of electrical power to a solenoid and its full excursion or stroke.

RESTRICTION
A reduced cross-sectional area in a line of passage producing a pressure drop.

RESTRICTOR
See ORIFICE.

RETURN LINE
A passage that is used to route fluid to a reservoir or tank after use in some function. Normally limited to low pressures of 0-150 psig, but may be higher in special applications if so designed.

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

RMA
The Rubber Manufacturers Association, Inc.

ROTARY ACTUATOR
A hydro-mechanical device that converts fluid flow into incremental rotary motion as compared to a fluid motor which produces infinite numbers of turns. See FLUID MOTOR.

ROTARY JOINT
A connector or fitting that is equipped with seals or o-rings that allow it to rotate while passing one or more fluid paths through sealed internal passages.

ROTARY VARIABLE DIFFERENTIAL TRANSFORMER (RVDT)
An electro-mechanical rotary device that produces an analog signal in proportion to the difference in distance between a magnet and a separate fixed coil.

ROTARY VARIABLE TRANSFORMER (RVT)
An electro-mechanical rotary device that produces an analog signal in proportion to the difference in velocity between a magnet and a separate fixed coil.

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S

SAE
Society of Automotive Engineers

SAE 4 BOLT PORT, CODE 61
A system for flange and surface mounting configurations that are used to attach pipes, tubes or hoses to a component or manifold. Normally rated at 3000 psig. See SAE 4 BOLT PORT, CODE 62.

SAE 4 BOLT PORT, CODE 62
A system of flange and surface mounting configurations that are used to attach pipes, tubes or hoses to a component or manifold. Nominally rated at 6000 psig, although larger sizes are only See SAE 4 BOLT PORT, CODE 61.

SAE PORT
A threaded hole and stud system that may be used to attach fittings to a component or manifold. Sealed with an o-ring or gasket.

SAFETY FACTOR
The ratio of burst pressure to rated pressure under specific static pressure and temperature conditions. See BURST PRESSURE.

SCRAPER RING
A metal or synthetic ring that is fitted to the shaft of a cylinder to remove particles from the shaft so to prevent them from entering the cylinder seal chamber.

SEAL
See O-RING and GASKET.

SENSITIVITY
The minimum input signal required to produce a specified output signal.

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

SEQUENCE VALVE
A valve that is normally closed or normally open and changes to the opposite state when pilot pressure is applied to its spring chamber at a preset pressure level. Normally used to initiate a secondary set of operations in a system, based on application of the pilot signal.

SERIAL DATA TRANSMISSION
A form of digital data transmission in which the data bits of a binary word are processed or transmitted one at a time. Slower than parallel data transmission, but does not require separate circuitry for each bit.

SERRATIONS
Bumps, barbs, corrugations, or other features increasing the holding power of the device.

SERVO CONTROL
A term used to describe the type of electronic system used for finite, analog control of a function. See SOLENOID CONTROL.

SERVO VALVE
A valve that uses a torque motor type coil to control a small stream of fluid. Direction of the fluid stream is used to position a large spool. Therefore a low level power signal may provide precise spool position. Normally, the spool had mechanical feedback of spool position to the torque motor, creating a closed loop spool position system.

SHANK
The portion of a fitting inserted into the bore of a hose.

SHUTTLE VALVE
A valve that has three ports and a common ball or spool check valve. When flow is applied at either of the two inlet ports, the third or output port receives flow from the higher pressure inlet port.

SKIVE
The removal of a short length of cover and/or tube to permit the attachment of a fitting directly over the hose reinforcement.

SILENCER
See MUFFLER.

SILT
Fine particles of debris. Normally found in chambers with little or no circulation, such as at the bottom of a reservoir or tank. See SLUDGE.

SLIP
Internal leakage of hydraulic fluid.

SLUDGE
Partially hardened silt. See SILT.

SOCKET
The external member or portion of a hose fitting, commonly used in describing screw-together reusable fittings.

SOLENOID
A coil of metallic wire, usually copper, wound around a bobbin. Used to magnetize the bobbin and produce linear motion of a companion spool when electricity is applied.

SPIRAL
A method of applying reinforcement in which there is no interlacing between individual strands of reinforcement; coiling around an axis in a series of planes, helical.

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

SPRING GUARD
A helically wound component applied internally or externally to a hose assembly, used to strain relief, abrasion resistance, or collapse resistance.

STABILITY
Ability of a system to maintain control when subject to severe outside disturbances.

STANDARD
A document, or an object for physical comparison, for defining product characteristics, products, or processes, prepared by a consensus of a properly constituted group of those substantially affected and having the qualifications to prepare the standard for use.

STATIC BEHAVIOR
Describes how a control system, or an individual unit, carries on under fixed conditions (As contrasted to dynamic behavior which refers to behavior under changing conditions).

STATIC CONDUCTIVE
Having the capability of furnishing a path for a flow of static electricity.

STEP CHANGE
The change from one value to another in a single step.

STATIC HEAD
A measurement of pressure that is present when no fluid flow exists in a passage. The static head is normally expressed in feet of water.

STRAINER
A series of wire or fabric meshes which are bonded together by caps or perforated cylinders and are fitted into hydraulic system passages to strain particles from fluid passed through the passage.

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

SUBPLATE
A metal base to which a specific valve may be attached using a specified bolt kit.

SUCTION LINE
A passage that leads from a reservoir or tank to the inlet port of a pump.

SUPERCHARGE
To replenish a hydraulic system above atmospheric pressure.

SUMP
A reservoir.

SURGE
An increase in pressure that occurs for a specified short period of time over the normal expected working pressure.

SWAGE
The method of fitting attachment incorporating a set of die halves designed to progressively reduce the collar or ferrule diameter to the required finish dimension by mechanically forcing the fitting into the mating die.

SWASH PLATE
A stationary canted plate in an axial type-piston pump which causes the pistons to reciprocate as the cylinder barrel rotates.

SWELLING
An increase in the volume or linear dimension of a specimen immersed in liquid or exposed to a vapor.

SWITCH
A digital device which closes or opens a discrete set of contacts at a pre-set condition.

SWIVEL JOINT
A connector or fitting that is equipped with seals or o-rings allowing partial rotation while passing a fluid path through a sealed internal passage.

SYNCHRO
A rotary electromagnetic device generally used as an AC feedback signal generator which indicates position. It can also be used as a reference signal generator.

SYNTHETIC FLUID
A hydraulic oil (fluid) that is made from a synthetic base. A fluid, manufactured to specified characteristics. Normally will not support combustion if heated to a specific temperature.

SYSTEM PRESSURE
See OPERATING PRESSURE.

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T

TACHOMETER
A digital or analog device that produces a pulse train of electrical signals that is proportional to its rotational speed.

TANK
See RESERVOIR.

TEMPERATURE SWITCH
A digital device that opens or closes a switch when the internal temperature changes state to a preset temperature limit.

THERMOCOUPLE
A precision resistive element that changes resistance in proportion to the temperature of the element. May be used, therefore, with proper DC electrical voltage to indicate temperature on a voltmeter style indicator.

THREE WAY
A term used to describe a valve that has three ports, normally a pressure (inlet) port, a normally closed (n.c.) port and a normally open (n.o.) port. Used to block or open a common flow passage.

THREE WAY VALVE, PROPORTIONAL CONTROL AND DIRECT OPERATED
A valve having a three way functional capability that may be proportionately actuated by a solenoid to control the operating spool in infinite resolution. Movement of the spool from extreme end to extreme rod completely reverses the flow paths of the ports. See THREE WAY.

THREE WAY VALVE, MANUALLY AND DIRECTOPERATED
A valve having a three way functional capability that may be manually activated to directly control the operating spool. Movement of the spool from extreme end to extreme end reverses the flow paths of the ports. See THREE WAY.

THREE WAY VALVE, SOLENOID AND PILOT OPERATED
A valve having a three way functional capability that may be solenoid activated to directly control the operating spool which then controls a secondary, larger spool. Movement of the secondary spool from extreme end to extreme end reverses the flow paths of ports. See THREE WAY.

THREE WAY VALVE, SOLENOID AND DIRECTOPERATED
A valve having a three way functional capability that may be solenoid activated to directly control the operating spool. Movement of the spool from extreme end to extreme end reverses the flow paths of the ports. See THREE WAY.

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

TIE ROD
A metal rod that is used to prevent two or more components from separating. Normally used to restrain the end plates of cylinders against the cylinder tube.

TORQUE
The measure of force applied to a lever arm. Normally expressed in lb.-ft. (pound-feet) or lb.-in. (pound-inch).

TORQUE CONVERTER
A rotary fluid coupling that is capable of multiplying torque.

TORQUE MOTOR
A coil of wire and bobbin assembly used in a servo valve that causes the internal mechanism of the servo valve to be offset when current passes through the coil.

TRANSDUCER
An analog device which produces a change in signal level during state changes. Normally used for high speed control systems.

TRANSFER FUNCTION
A mathematical expression of the relationship between the outgoing and incoming signals of a process or control element.

TRANSFORMER
A device that transfers AC energy from one circuit to another without electrical contact between the two circuits.

TRANSMITTER
An analog device which produces a change in signal level during state changes. Normally used for indication systems.

TUBE
A term used to describe a passage for fluid in a hydraulic system. Normally specified by outside diameter, wall thickness, material type and material strength.

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

TURBULENT FLOW
A condition of flow in a passage that is typified by rapid movement of fluid in a passage, where the fluid is churning and bouncing off the passage walls. See LAMINAR FLOW.

TWIST
1) The turns about the axis, per unit of length of a fiber, roving yarn, cord, etc. Twist is usually expressed as turns per inch. 2) The turn about the axis of a hose subjected to internal pressure.

TWO WAY
A term used to describe a valve that has two ports, normally a pressure (inlet) port and an outlet port. Used to open or close a flow passage. May be configured as normally closed (n.c.) Or normally open (n.o.).

TWO WAY VALVE, SOLENOID AND PILOT OPERATED
A valve having a two way functional capability that may be solenoid activated to directly control the operating spool which then controls a secondary, larger spool. Movement of the secondary spool from extreme end to extreme end opens or closes the flow paths of the ports. See TWO WAY.

TWO WAY VALVE, SOLENOID AND DIRECT OPERATED
A valve having a two way functional capability that may be solenoid activated to directly control the operating spool. Movement of the spool from extreme end to extreme end opens or closed the flow paths of the ports. See TWO WAY.

TWO WAY VALVE, MANUALLY AND DIRECTOPERATED
A valve having two way functional capability that may be manually activated to directly control the operating spool. Movement of the spool from extreme end to extreme end opens or closed the flow paths of the ports. See TWO WAY.

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U

UNDERLAP
The condition of a spool and body in a servo valve or other spool valve wherein the spool is displaced a specified amount (the underlap) to expose two adjacent cavities to each other.

UNLOAD
To release flow (usually directly to the reservoir), to prevent pressure being imposed on the system or portion of the system.

UNLOADING VALVE
A valve that is normally closed and opens from a separate fluid source on rising pressure that is balanced against a precision spring. Re-set point is normally fixed.

UPSTREAM
The passage ahead of a device, normally at the inlet of direction of flow.

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V

VACUUM
Pressure less than atmospheric pressure. It is usually expressed in inches of mercury (Hg) as referred to the existing atmospheric pressure.

VACUUM 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 below atmospheric pressure.

VALVE
A mechanical device that is used in a fluid power system, which is used to provide some change of state of the fluid.

VAPOR PRESSURE
The measure of pressure at which a specific fluid will change to a gas.

VARIABLE
A factor or condition which can be measured, altered or controlled, i.e., temperature, pressure, flow, liquid level, humidity, weight, chemical composition, color, etc.

VELOCITY
The speed of fluid flow through a hydraulic line. Expressed in feet per second (fps), inches per second (ips), or meters per second (mps). Also, the speed or a rotating component measure in resolutions per minute (rpm).

VENT
-To permit opening of a pressure control valve by opening its pilot port (vent connection) to atmospheric pressure.An air breathing device on a fluid reservoir.-To remove trapped air from a component.

VENT VALVE
A valve that may be manually opened to allow air or fluid or a combination of both to be exhausted into a lower pressure chamber or to the atmosphere.

VIBRATION
Amplitude motion occurring at a given frequency

VISCOSITY
The measure of resistance to flow of a fluid against an established standard. See SUS and SSU.

VISCOSITY INDEX
A measure of the viscosity-temperature characteristics of a fluid as referred to that of two arbitrary reference fluids (ASTM Designation D2270-64).

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

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

VOLUMETRIC EXPANSION
The volume increase of hose when subjected to internal pressure.

VULCANIZATION
A process during which a rubber compound, through a change in its chemical structure improves or extends elastic properties over a greater range of tempertures.

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W

WAFER VALVE
A two way valve that may be opened or closed to block the flow of fluid in a passage. Normally manually operated, but may be automated, especially for larger sizes. Normally designed so that when open, the opening of the passage is only restricted by the thickness of the wafer. There will be some pressure loss. See GATE VALVE, GLOBE VALVE and NEEDLE VALVE.

WATER GLYCOL FLUID
A hydraulic fluid that is comprised of a mix of distilled or other pure water and glycol to form a fluid that has enough lubricity to function as a fluid power fluid, but is relatively fire-resistant, i.e., will not support combustion.

WATT'S LAW
States that when one amp. of current flow through a device with one volt voltage drop, one watt of power is dissipated in the form of heat(P = I x E).

WEATHERING
The surface deterioration of a hose cover during outdoor exposure, as shown by checking, cracking, crazing, and chalking.

WIPER RING
A rubber or other synthetic seal that is fitted around a moving shaft to form a low pressure seal. Normally used to prevent fluid from entering the sealed volume.

WIRE REINFORCED
A hose containing wires to give added strength, increased dimensional stability; crush resitance. See reinforcement.
 
WORK
The transfer of power from one state to another. The movement of weight over a specified distance.

WORKING PRESSURE
The maximum pressure to which a hose will be subjected, including momentary surges in pressure, which can occur during service.

WRAPPED CURE
A vulcanizing process using a tensioned wrapper, usually of fabric, to apply external pressure.