HEAD

Vertical distance measured between two stages in a liquid.

HEAT EXCHANGER

A device which transfers heat through a conducting wall from one fluid to another. (Typically to cool a system.) Hydraulic components that help relieve the excessive heat that builds up in a hydraulic system.

HORSEPOWER

The horsepower required to drive a hydraulic pump is dependent on both pressure and output in GPM. The higher the pressure, or greater the volume, the more Horsepower (HP) required. As a rule of thumb, a 1000 PSI (pounds per square inch) pump will require 1 Horsepower (HP), for the first gallon per minute and 3/4 HP each gallon per minute after that. Doubling the pressure or output volume will require 4 time the input HP. The maths: Input HP= GPM x PSI / 1714

HOSE

A type of hydraulic fluid conductor that joins other hydraulic components usually in a non-linear fashion. Hose bends and flexes and is the most versatile hydraulic conductor.

HYDRAULIC ACTUATOR

The piece of machinery that receives pressure from the energized fluid and then converts it to motion and mechanical force.

HYDRAULIC CYLINDERS

Hydraulic cylinders transform the pressure and oil flow in a hydraulic system into work or mechanical force. They are used where linear motion is required to move something. Hydraulic cylinders are usually double-acting, that is, oil under pressure can be applied to either side of the piston to provide movement in either direction. Single acting hydraulic cylinders are sometimes used where the weight of the load is used to return the hydraulic cylinder to the closed position.

HYDRAULIC FLUID

A liquid such as oil or water that is used to generate power in a hydraulic system.

HYDRAULIC INTENSIFIER

A hydraulic component that converts low pressure from a large linear actuator into high pressure in a small linear actuator. Also called boosters, intensifiers are usually two different-sized hydraulic cylinders connected by a common piston.

HYDRAULIC MOTOR

A device which converts the energy from liquid flow into mechanical motion. However, instead of a hydraulic cylinder (force moving linear) the hydraulic motor uses hydraulic pressure to rotate. In terms of how it's built, a motor is like a pump. But, when it's operated oil enters the hydraulic motor and turns the shaft. The speed of a hydraulic motor is dependent on the amount of oil supplied by the hydraulic pump and the torque is dependent on the amount of pressure supplied.

HYDRAULIC POWER

Power derived from the motion and pressure of a liquid, such as water or oil.

HYDRAULIC POWER UNIT

Any device used to create kinetic energy within a hydraulic system. Motors and manual energy are both sources of power in hydraulic power units.

HYDRAULIC PUMP

A device that converts mechanical force and motion into fluid power; used to move liquids in a hydraulic system.

HYDRAULIC TESTER

A device used to troubleshoot and check hydraulic powered system components.

HYDRAULIC VALVE

A device used to regulate water distribution in hydraulic applications.

HYDRAULICS

The science dealing with the transmission of force through the medium of a contained fluid.

HYDROSTATIC TRANSMISSION

Combination of one or more hydraulic pumps and motors forming a unit.

IMMISCIBLE

Incapable of being mixed without separation of phases.

INHIBITOR

An additive that improves the performance of a petroleum product through the control of undesirable chemical reactions.

INTENSIFIER

Hydraulic components that convert the low pressure from a large linear actuator into high pressure in a small linear actuator. Intensifiers are usually two different-sized hydraulic cylinders connected by a common piston. Also called a booster.

INTERCHANGE

The ability of a quick-action coupling half from one hydraulic manufacturer to fit and function with a mating half from another hydraulic manufacturer without assurance of equal pressure containment rating or performance.

INTERFACE

That portion of the male tip (nipple) half that establishes and controls interchangeability.

KINEMATIC VISCOSITY

Absolute viscosity of a fluid divided by its density at the same temperature of measurement.

LINEAR ACTUATOR

An actuator that directs force in a straight line. A hydraulic cylinder is a linear actuator.

LOAD

The amount of force or pressure placed on a hydraulic system.

LOCKING BALLS

Other nomenclature "detent balls". Normally found in the female half of the quick-action coupling, they align with the shoulder groove on the mating male half providing a durable locking mechanism while allowing both coupling halves to swivel and align easily.

LUBRICATOR

A device that adds controlled or entered amounts of lubricant into an air system.

LUBRICITY

Ability of an oil or grease to lubricate. The property that diminishes friction and increases smoothness and slipperiness.

MANIFOLD

A conductor that provides multiple connection ports.

MECHANICAL ACCUMULATOR

A hydraulic component that transfers mechanical energy to trapped fluids. Mechanical accumulators include dead-weight and spring-loaded accumulators.

MECHANICAL POWER

Energy created by the physical interaction of instruments or tools.

MISCIBLE

Capable of being mixed in any concentration without separation of phases.

MOTOR

A device which converts hydraulic energy into rotary motion, either fixed or variable.

MUFFLER

A device for reducing gas flow noise.

NEEDLE VALVE

A valve that adjusts the flow of hydraulic fluid between and including fully on and fully off. The needle valve consists of a sharp conical obstruction that is extended or retracted to block or allow flow.

NEWTONIAN FLUID

Fluid whose viscosity does not change with rate of flow.

NON-NEWTONIAN FLUID

A fluid in which shear stress is not proportional to shear rate.

NON-PETROLEUM BASED OIL

A hydraulic fluid that contains no petroleum. Non-petroleum based oils are ideal for hydraulic systems that are used near a fire hazard.

OPEN-CENTRE SYSTEM

A hydraulic system in which the yield of the pump has a free-flow passageway back to the reservoir, while in the neutral condition.

OPEN-CENTRE VALVES

Open centre hydraulic valves are the same as the tandem centre, except that in the neutral position all lines are connected back to the reservoir. The primary use of this system is to prevent "shock" loading when the valve is placed in neutral. This takes pressure off the hydraulic motor. This system is used in situations where the operating device needs to be moved by hand.

OPERATING PRESSURE

The maximum pressure at which a system is operated.

OUTPUT

The Output of a hydraulic pump (gallons per minute, or GPM) is related directly to its operating speed. The pressure of a hydraulic pump is determined by its manufactured capabilities.

OXIDATION INHIBITOR

Substance added in small quantities to petroleum products to increase its oxidation resistance.

PACKING

A sealing device consisting of bulk deformable material or one or more mating deformable elements, reshaped by manually adjustable compression to obtain and maintain effectiveness.

PETROLEUM-BASED OIL

A hydraulic fluid developed from petroleum. Petroleum-based oils are the most common hydraulic fluids.

PIPING

A type of hydraulic fluid conductor that joins other hydraulic components usually in a straight line and on a permanent basis. When you are connecting up a hydraulic system, use the tubing or pipe that is capable of handling heavy pressures and loads required by the hydraulic system. Pipes should have a minimum number of bends and fittings, should be securely fastened and clean. Iron pipes are not recommended because they have particles that will flake off and contaminate a hydraulic system.

PISTON

A device used for converting hydraulic power to mechanical energy. A rod inside a hydraulic cylinder that is moved by hydraulic pressure. In hydraulic pumps, the piston is responsible for pushing down and pulling up the ram.

PISTON BARREL

A rotating cylindrical mechanism that houses the pistons in a hydraulic piston pump.

PISTON PUMP

A hydraulic pump that uses pistons driven by a rotating swash plate or cam to move fluid through a hydraulic system.

PISTON SHOE

The swivelling end portion of a piston that maintains contact with the swash plate in a piston pump.

POLAR COMPOUND

A chemical compound whose molecules exhibit electrically positive characteristic at one extremity and negative characteristics at the other.

POPPET VALVE

Machined, self aligning valve that incorporates an elastomer to provide a positive seal upon disconnection, no low pressure leakage, and generally provides higher flow that a ball valve.

PORT

The internal or external terminus of a passage. The point where the fitting is attached.

PORT BLEED

A port that provides a passage for the purging of gas from a hydraulic system or hydraulic component.

PORT, CYLINDER

A port that provides a passage to or from an actuator.

PORT, EXHAUST

A port that provides a passage to the atmosphere.

POSITIVE DISPLACEMENT PUMP

A hydraulic pump that continues to discharge fluid as long as it is powered.

POUNDS PER SQUARE INCH (PSI)

A unit of pressure that measures the amount of load pressure per inch. Pounds per square inch is abbreviated "psi".

POUR POINT

Lowest temperature at which an oil or distillate fuel is observed to flow.

POWER UNIT

A combination of hydraulic pump, pump drive, reservoir, controls and conditioning components to supply hydraulic power to a hydraulic system

PRESSURE

The force per unit area, usually expressed in pounds per square inch (psi), bars, or atmospheres.

PRESSURE; BACK

The pressure encountered on the downstream or return side of a component.

PRESSURE, BURST

The pressure that creates loss of fluid through the component envelope, resulting from failure.

PRESSURE; CRACKING

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

PRESSURE; MAXIMUM RATED

The maximum pressure at which a hydraulic component should be operated on a continuous basis, usually the relief valve setting at maximum flow rate.

PRESSURE, OPERATING

The pressure at which a hydraulic system is operated.

PRESSURE, PEAK

The maximum pressure encountered in the operation of a hydraulic component.

PRESSURE, RATED

The qualified operating pressure which the hydraulic manufacturer recommends for a component or a system.

PRESSURE CONTROL VALVE

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

PRESSURE RELIEF VALVE

A non-adjustable control valve that regulates pressure in a hydraulic system. A pressure relief valve is a safety device and is required on all hydraulic systems. Once adjusted, the pressure relief valve opens whenever the pressure goes beyond the value set and allows oil to flow back to the reservoir.

PRESSURE, SHOCK

The pressure existing in a wave moving at sonic velocity.

PRESSURE, STATIC

The pressure in a fluid at rest.

PRESSURE, WORKING

The pressure at which the working device normally operates.

PRESSURE VESSEL

A container that holds fluid under pressure.

PRIME MOVER

The component of a hydraulic system that powers the main pump.

PUMP

A mechanical device used to move liquids and gases; The building block of any hydraulic system. The four most common designs are the vane pump, gear pump, gerotor pump and piston pump. All are well suited to common hydraulic uses with the piston design best suited for higher pressures. The variable displacement type is particularly well suited in circuits using hydraulic motors where variable speeds and the ability to reverse is needed.