QUICK-ACTION COUPLING

Quick-Action Coupling A device to join or separate fluid lines without the use of tools or special devices.

QUICK-ACTION COUPLING, BALL LOCKING TYPE

A quick-action coupling which is connected and disconnected by applying an axial force to move an external sleeve. This sleeve motion allows detent balls in the female half to engage or disengage into a groove in the mating male tip (nipple) half.

QUICK-ACTION COUPLING, DOUBLE SHUT OFF

A quick-action coupling with a shut-off valves in both mating halves.

QUICK-ACTION COUPLING, NON-VALVED

Other nomenclature "straight-through". A quick-action coupling without a shut-off valve in either half.

QUICK-ACTION COUPLING, SINGLE SHUT OFF

A quick-action coupling with a shut-off valves in one half only.

QUICK-ACTION COUPLING, THREADED TYPE

A quick-action coupling that has threads on both mating halves and is connected or disconnected by the rotation of the sleeve on the body half with respect to the male tip.

RACK-AND-PINION ACTUATOR

A hydraulic rotary actuator that directs energy in a circular motion through the use of a toothed piston that turns a toothed gear.

RAM

A hydraulic mechanism that uses the kinetic energy of a flowing liquid to force a small amount of the liquid to a reservoir contained at a higher level.

RATED PRESSURE

The maximum pressure at which a device is designed to operate.

RATIO-OF-AREAS PRINCIPLE

A physical law governing hydraulic intensifiers stating that a given pressure in a larger hydraulic cylinder can be intensified by the same pressure exerted in a smaller hydraulic cylinder. In general, the ratio of areas is inversely proportioned to the ratio of pressures, meaning the larger area has a smaller pressure and the smaller area has a larger pressure.

RECIPROCATING MOTION

Movement characterized by repeatable back-and-forth action.

REDUCING VALVE

An adjustable hydraulic control valve that regulates pressure in a particular zone of a hydraulic system.

RELIEF VALVE

A non-adjustable hydraulic control valve that regulates pressure in a hydraulic system. When a critical pressure is exceeded, the hydraulic relief valve releases.

RESERVOIR

A container for the storage of liquid in a hydraulic system. The size of a reservoir will depend on the capacity of the hydraulic system, as well as what is required by the hydraulic system. The reservoir should contain a large volume of oil and should provide ample oil to the hydraulic pump.

RESISTANCE

In hydraulics, the condition created by an obstruction or restriction in the flow path.

RESTRICTOR

A device that reduces the cross-sectional flow area.

REVOLUTIONS PER MINUTE (RPM) RPM.

A unit of measurement that indicates the number of revolutions a hydraulic pump component makes in one minute.

REYN

The standard unit of absolute viscosity in the English system. It is expressed in pounds-seconds per square inch.

ROTARY ACTUATOR

An actuator that directs force in a circular motion.

SEAL

A device which prevents or controls the escape or passage of hydraulic fluid.

SEQUENCE VALVE

A hydraulic control valve that allows hydraulic fluid to flow into another area of the hydraulic system once a critical pressure has been achieved.

SERVO VALVE

A hydraulic valve that modulates output as a function of an input command.

SHEAR RATE

The rate at which adjacent layers of fluid move with respect to each other, usually expressed as reciprocal seconds.

SHEAR STRESS

The frictional force overcome by sliding one layer of fluid along another, as in any fluid flow.

SHIELDED RETAINER

Other nomenclature "valve shield". Protects valving from high velocity flow, preventing flow checking. Used primarily on agricultural interchange quick-action couplings.

SHOCK LOAD

Sudden extreme pressure increases within a hydraulic system.

SILENCER

A device for reducing gas flow noise. Noise is decreased by tuned resonant control of gas expansion.

SINGLE-ACTING CYLINDER

A hydraulic actuator that directs energy in one direction.

SINGLE-ACTING SLEEVE

Other nomenclature "one-way sleeve". Making a connection requires manually pushing the sleeve backward or pulling the body forward when mounted in a breakaway clamp, inserting the male tip, then allowing the sleeve to return to its original position. Allows pull-to-disconnect convenience when the coupling is mounted in a breakaway clamp. Sleeve Lock Prevents accidental disconnection. An arrangement which provides an additional lock which must be actuated prior to the retraction of the locking sleeve.

SPILLAGE

Occurs upon disconnection of the quick-action coupling. This is the fluid trapped between the mating seal and the valve seal of the mating halves.

SPOOL VALVE

A hydraulic valve that controls the direction of hydraulic fluid flow. A spool valve consists of cylindrical spools that alternately block and open channels in the hydraulic system.

SPRING-LOADED ACCUMULATOR

A hydraulic component used to store hydraulic fluid. The spring-loaded hydraulic accumulator increases and relieves pressure through the use of a spring-loaded piston.

SUBPLATE

An auxiliary ported plate for mounting hydraulic components.

SURFACTANT

Surface-active agent that reduces interfacial tension of a liquid.

SURGE FLOW/PRESSURE

A transient rise of flow or pressure.

SWASH PLATE

A flat, angled component of a hydraulic piston pump that moves the pistons when rotated.

TANDEM-CENTRE VALVES

Using tandem centre valves when in a neutral position bypasses the flow of hydraulic oil to the return line. This is used to hold the hydraulic cylinder/piston in position with no load on the pumps. With this system the hydraulic pump is running constantly to keep a ready supply of hydraulic oil, but as long as the hydraulic cylinder/piston is not in operation the hydraulic pump is working under no pressure or load. This system keeps wear and tear on the hydraulic pump down to a minimum.

THERMAL BUILD-UP

Hydraulic pressure caused by expansion of the fluid due to heat from an external source such as sunlight.

THREE-WAY SPOOL VALVE

A spool valve with three ports.

TIP HALF

Other nomenclature "male tip", "nipple", "plug", "male half".

TORQUE

The force exerted in rotation.

TRAPPED PRESSURE

Pressurized fluid trapped behind closed valving in one of the quick-action coupling mating halves.

TUBE

A type of hydraulic fluid conductor that joins other hydraulic components usually in a non-linear fashion. Despite being stronger than pipe, tubing is easily bent. Tube is available in varied wall thicknesses and is measured by its outside diameter.

UNBALANCED VANE PUMP

A hydraulic pump that consists of a rotor mounted off-centre in a circular cavity. As the rotor spins, vanes trap and move hydraulic fluid.

UNLOADING VALVE

The Unloading valve is installed in hydraulic systems using accumulators (below). The function of this hydraulic valve is to "unload" the pump of pressure until such time as a device on the hydraulic system, such as a hydraulic cylinder, actually begins operation. In this way, the hydraulic pump is allowed to operate without load (pressure) until it is needed. The unloading valve is not intended to replace the pressure relief valve. In fact, the pressure setting of the unloading valve is much lower than the setting on the pressure relief valve.

VACUUM

The state of negative pressure. A hydraulic pump works by creating a vacuum in the closed hydraulic system.

VALVE

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

VALVE, CLOSED CENTRE TYPE

Has the inlet port blocked from the outlet and works in neutral.

VALVE, DIRECTIONAL CONTROL

A valve whose primary function is to direct or prevent flow through selected passages.

VALVE, FOUR-WAY

A 4 port valve (in, out and 2 work) used with double acting hydraulic cylinders, bi-directional hydraulic motors.

VALVE, FLOW CONTROL

A valve whose primary function is to control flow rate

VALVE, FLOW DIVIDING

A valve which divides the flow from a single source into two or more branches.

VALVE, LOAD CHECK (LIFT CHECK)

A device which prevents a load from dropping when a valve is shifted, until ample pressure and flow is available to hold or move the load.

VALVE, OPEN CENTRE

Has the inlet port connected to the outlet (tank) port in neutral.

VALVE, PARALLEL TYPE

A multiple spool valve in which the inlet oil is connected to all spools simultaneously. If more than one spool is actuated, the function requiring the lowest pressure will operate first.

VALVE POSITION, DETENT

A predetermined position maintained by a holding device acting on the flow-directing elements of a directional control valve.

VALVE POSITION, NORMAL

The valve position when signal or actuating force is not being applied.

VALVE, POWER BEYOND (HIGH PRESSURE CARRYOVER)

A sleeve attachment which permits the oil flow from one valve (when in neutral) to be used by another valve downstream. Hence, a 3-spool valve could be connected to a 2-spool valve to create a 5-spool valve, The first valve takes priority and must have a separate outlet port to return oil from an activator back to the reservoir.

VALVE RETAINER

Provides the valve stop. It's precise location allows maximum flow when mating quick-action halves are connected.

VALVE, SERIES PARALLEL TYPE

A multiple spool valve which has all spools connected to the open centre passage in neutral. However, when actuated, the upstream valve takes full priority. The return oil is directed to downstream spools as in a series type valve.

VALVE, THREE-WAY

A 3 port valve (in, out ~r,d work) normally used with a single acting hydraulic cylinder or uni-directional motor.

VALVE, TWO-WAY

A 2 port valve with inlet and outlet ports.

VALVE; TWO, THREE, FOUR POSITION

The number of positions in which a hydraulic valve can be positioned.

VALVE, SERIES TYPE

A multiple spool valve in which the return oil from the first spool is directed to the inlet of the second spool (and from the second to the third, etc.). This type of valve permits simultaneous operation of two or more functions with the same oil flow. However, the total pressure requirements of all functions are accumulative.

VALVE, SEQUENCE

A valve whose primary function is to direct flow in a predetermined sequence.

VALVE SEAT

That area of the quick-action coupling that comes in contact with either the ball or poppet valve, allowing a positive sealing surface. Shape and surface varies with valve style.

VANE

A retractable spring-loaded mechanism that extends radially from the centre of a hydraulic pump rotor.

VANE ACTUATOR

A hydraulic rotary actuator that directs energy in a circular motion through the use of a pivoting mechanism.

VANE PUMP

A hydraulic pump that uses a flat protrusion to trap and move liquid through a hydraulic system.

VAPOR PRESSURE

Pressure of a confined vapor in equilibrium with its liquid at a specified temperature, i.e. a measure of a liquid's volatility.

VARIABLE-DISPLACEMENT PUMP

A hydraulic pump that can be adjusted to increase or decreases the amount of liquid that is moved in one pump cycle.

VELOCITY PRESSURE

Pressure in a hydraulic system caused by kinetic energy.

VISCOSITY

A measure of internal friction or the hydraulic fluid's resistance to flow. As temperature increases, viscosity decreases.

WATER-COOLED HEAT EXCHANGER

A component in a hydraulic system that relieves excessive heat with cold water.