actual flow rate

The flow rate that a pump delivers during operation. Actual flow rate is used when calculating volumetric efficiency.

actual operating torque

The amount of torque required to power a hydraulic pump. Actual operating torque is used to calculate mechanical efficiency.

actuator

A hydraulic system component such as a cylinder or motor. Actuators convert hydraulic energy from the pump into mechanical energy.

adhesives

A glue or similar substance that joins two materials together. Adhesives can be pumped through some hydraulic pumps, such as crescent pumps.

atmospheric pressure

The amount of pressure exerted by the air. Atmospheric pressure in the reservoir forces fluid into the inlet port of the hydraulic pump.

automatic transmissions

A power transmission system with gears that shift to change the speed and torque of mechanical energy. Automatic transmission systems do not require an operator to shift gears.

axial piston pump

A hydraulic pump that has pistons arranged in a circle and parallel to the drive shaft centerline. An axial piston pump uses an angled swashplate in contact with the piston shoes to reciprocate pistons.

balanced vane pump

A hydraulic pump that consists of a rotor mounted in the center of an elliptical cam ring. A balanced vane pump is a fixed-displacement pump.

battery

A device that converts chemical energy into electrical energy. Battery-powered motors can be prime movers for some mobile hydraulic applications.

bearings

A device that minimizes friction between moving parts. Bearings allow for linear or rotational movement, and may also prevent movement by controlling forces that act on moving parts.

bent axis piston pump

A hydraulic pump with a circular arrangement of pistons in a cylinder block that is mounted at an angle to the drive shaft. A bent axis piston pump uses the angle of the cylinder block and drive shaft to cause the pistons to reciprocate.

booster

A component of a hydraulic system that converts low-pressure fluid power into high-pressure fluid power. Boosters, also referred to as hydraulic intensifiers, typically receive pressure from oil.

cam ring

An external rotor casing. The cam ring in a vane pump remains stationary as the rotor turns.

centerline

An imaginary line that defines the theoretical center of an object. The centerline of an object is equidistant from the sides of the object.

constant

A number in an equation that does not change. The constant number 1714 is used when calculating the required horsepower for a hydraulic system.

crescent pump

An internal gear pump that consists of an internal gear that is separated from an external gear by a crescent-shaped seal. Crescent pumps are fixed-displacement pumps.

crescent seal

The stationary component in a crescent pump that separates the internal gear from the external gear. A crescent seal is machined into the pump where there is maximum clearance between the gears.

cubic centimeters

cm³. A metric unit of measurement used to measure the fluid displacement of a hydraulic pump. Cubic centimeters are used to measure volume.

cubic inches

in.³ A unit of measurement used to measure the fluid displacement of a hydraulic pump. Cubic inches are used to measure volume.

cylinder block

A solid unit that houses the pistons in a piston pump. The cylinder block in an axial piston pump rotates and the pistons maintain contact with the angled swashplate in order to reciprocate.

double-acting intensifier

A hydraulic intensifier that provides a continuous supply of high pressure fluid. A double-acting intensifier applies pressure during upward and downward strokes of the piston.

drive gear

The gear that transmits power to an idler gear in a hydraulic pump to move fluid. The drive gear is attached to a drive shaft, which is driven by the prime mover.

drive shaft

A driving mechanism that rotates to transfer motion. A drive shaft is connected to a prime mover, such as an electric motor.

driving mechanism

A component that rotates to transfer motion. The driving mechanism in a positive-displacement pump is typically a drive shaft.

efficiency

The system's work output compared to the pump's energy input. Efficiency ratings are used to determine the condition of a pump.

electric motor

A machine that converts electricity into mechanical energy or motion. An electric motor is a type of prime mover for a hydraulic system.

external gear pump

A fixed-displacement hydraulic pump that has two meshing gears that rotate to move fluid. An external gear pump is available in single or multiple configurations.

fixed-displacement pump

A hydraulic pump with a fluid displacement value that stays the same from cycle to cycle. Fixed-displacement pumps are often used in applications with low horsepower settings.

flow capacity

The total volume of fluid that a pump puts into the hydraulic system in a given period of time. Flow capacity is also known as flow rate.

flow meter

An instrument that measures the flow rate or quantity of a fluid moving through a pipe. Flow meters are used to measure the actual flow rate of a pump.

flow rate

The total volume of fluid that a pump puts into the hydraulic system in a given period of time. Flow rate is also known as flow capacity.

fluid displacement

A pump rating that indicates the total volume of fluid a hydraulic pump moves in one reciprocating or rotating cycle of the pump. Fluid displacement is measured in cubic inches or cubic centimeters.

fluid flow

The motion of a fluid, usually a liquid or a gas, subjected to unbalanced forces or stresses. Fluid flow in a hydraulic system is subjected to resistance, which develops pressure.

fluid systems

A power transmission system that uses the force of flowing liquids or gas to transmit power. Fluid systems include hydraulic systems and pneumatic systems.

friction

A force that resists motion between two components that are in contact with each other. Friction generates heat and increases wear between components.

gallons per minute

gpm. A unit of measurement that is used to measure the flow capacity or flow rate of a hydraulic pump. Gallons per minute is a unit of volumetric flow rate.

gear pump

A fixed-displacement hydraulic pump that has two meshing gears that rotate to move fluid. Gear pumps are relatively inexpensive and compact.

gpm

gallons per minute.A unit of measurement that is used to measure the flow capacity or flow rate of a hydraulic pump. Gpm is a unit of volumetric flow rate.

helical gears

A gear with slanted teeth used in gear pumps. Helical gears are quieter than spur gears.

horsepower

hp. A unit of power. One horsepower is equivalent to 33,000 foot-pounds per minute.

hp

horsepower. A unit of power. One hp is equivalent to 33,000 foot-pounds per minute.

hydraulic fluid

A liquid, typically oil, that transfers the power in a hydraulic system. Hydraulic fluid is generally very thick.

hydraulic intensifier

A component of a hydraulic system that converts low-pressure fluid power into high-pressure fluid power. Hydraulic intensifiers, also referred to as boosters, typically receive pressure from oil.

hydraulic press

A device that uses hydraulic power to generate compressive forces. Hydraulic presses often use hydraulic intensifiers for increased pressure.

hydraulic pump

A mechanical power source that generates fluid flow in order to move fluid through a hydraulic system. Hydraulic pumps receive power from a prime mover, such as a motor or engine.

hydraulic system

A type of fluid system that uses oil or another liquid under pressure to transmit power. A hydraulic system can transmit large amounts of power within a small space.

idler gear

A gear that is driven by the drive gear in a hydraulic pump as the two gears mesh. The idler gear in an internal gear pump is typically smaller than the drive gear.

induction motor

A type of electric motor used for high-duty hydraulic applications. Induction motors can operate for long periods but require an uninterrupted power source.

inlet port

The opening on the side of a hydraulic pump through which fluid enters the pump. Multiple inlet ports can be included in one pump.

internal combustion engine

A type of engine that produces heat energy and mechanical energy internally. Internal combustion engines used for hydraulic systems commonly run on gasoline or diesel.

internal gear pump

A fixed-displacement hydraulic pump with an internal gear that is smaller than the external gear. An internal gear pump is available in single or multiple configurations.

kilopascals

kPa. An SI unit used to measure pressure. Kilopascals may be used to measure the pressure requirements for a hydraulic system.

kPa

kilopascals. An SI unit used to measure pressure. kPa may be used to measure the pressure requirements for a hydraulic system.

leakage

The movement of fluid out of a hydraulic system or from one hydraulic system component to another. Leakage decreases pump efficiency and can lead to system failure.

liters per minute

lpm. A metric unit of measurement that is used to measure the flow capacity or flow rate of a hydraulic pump. Liters per minute is a unit of volumetric flow rate.

load

The force that acts on an object and provides resistance. The load in a hydraulic pump is pressurized fluid.

lpm

liters per minute. A metric unit of measurement that is used to measure the flow capacity or flow rate of a hydraulic pump. Lpm is a unit of volumetric flow rate.

manual pumps

A type of hydraulic pump that uses human power and mechanical advantage to move fluids or air through the pump. Manual pumps use human power as the energy source.

maximum output pressure

A specification for hydraulic intensifiers that describes the amount of pressure the intensifier can exert. Maximum output pressure is measured in pounds per square inch (psi) or kilopascals (kPa).

mechanical efficiency

An efficiency rating that describes the amount of energy loss in a hydraulic pump. Mechanical efficiency can decrease due to friction between mechanical and fluid components.

meshing gears

A pair of discs or wheels that contain evenly spaced teeth around their perimeters. Meshing gears in a gear pump rotate to cause pumping action.

nonpositive displacement

A type of hydraulic pump that delivers a continuous flow and an output that changes with output pressure. Nonpositive displacement pumps are not common in industrial settings.

outlet port

The opening on the side of a hydraulic pump through which fluid is expelled into the hydraulic system. Multiple outlet ports can be included in one hydraulic pump.

outlet pressure

The pressure of the fluid at the pump's outlet port. Outlet pressure is measured in pounds per square inch (psi) or kilopascals (kPa)..

overall efficiency

A pump rating that compares the total horsepower output to the total horsepower input. Overall efficiency is determined by multiplying volumetric efficiency and mechanical efficiency.

parallel

Two lines or components that are equidistant from one another and do not intersect. Parallelism between the pistons and the drive shaft centerline is necessary in an axial piston pump.

perpendicular

Two lines or axes that meet at right angles. A perpendicular arrangement is required in a radial piston pump between the pistons and the drive shaft centerline.

pintle

An upright pin or bolt. A stationary pintle in a radial piston pump allows the cylinder block to turn inside the rotor.

piston

A rod inside a cylinder that is moved by hydraulic or pneumatic pressure. Pistons in piston pumps can be used with high pressures.

piston pump

A hydraulic pump that uses the reciprocal motion of pistons to move fluid through the pump. Piston pumps can have a fixed or variable displacement.

piston pumps

A hydraulic pump that uses the reciprocal motion of pistons to move fluid through the pump. Piston pumps can have a fixed or variable displacement.

piston rod

A movable, cylindrical component attached perpendicularly to a piston. A piston rod is housed in a cylinder.

piston shoes

The swiveling end portion of a piston that contains ball and socket joints. The piston shoes in an axial piston pump maintain contact with the angled swashplate to reciprocate the pistons.

pneumatics

Power created by the motion and control of gas or air under pressure. Pneumatic systems are a type of fluid system.

positive displacement

A hydraulic pump with a given fluid displacement per cycle or revolution. Positive displacement pumps are used with a pressure relief valve on the outlet side.

pounds per square inch

psi. A measurement of pressure. Pounds per square inch is used to measure the pressure requirements for a hydraulic system.

power

The rate of work performed by a system. Power is expressed in units of horsepower.

power source

A device that generates the energy needed to power a tool or system. The power source in a hydraulic system is a hydraulic pump.

power transmission systems

A grouping of components that work together to move energy from a source to an output device in order to perform work. Power transmission systems include fluid, mechanical, and electrical systems.

pressure

The exertion of force upon a fluid or object per unit area. Pressure is expressed in pounds per square inch (psi) or pascals (Pa).

pressure intensification ratio

A specification that indicates how much pressure a hydraulic intensifier can deliver to the hydraulic system. The pressure intensification ratio is inversely proportioned to the area ratio.

pressure relief valve

An adjustable control valve that regulates pressure in a hydraulic system with a positive displacement pump. The pressure relief valve releases when the hydraulic system exceeds a critical pressure.

prime mover

The component in a hydraulic system that provides mechanical energy to the hydraulic pump. Prime movers for hydraulic systems include electric motors and internal combustion engines.

psi

Pounds per square inch. A measurement of pressure. Psi is used to measure the pressure requirements for a hydraulic system.

pumping chambers

A compartment in a hydraulic pump that forms between pump components. Pumping chambers trap fluid and carry it to the outlet port.

radial piston pump

A type of piston pump with a radial arrangement of pistons within a cylinder block. In a radial piston pump, the pistons are perpendicular to the drive shaft centerline.

radially

Having parts arranged in straight lines coming from the center of a circle. The radial arrangement of vanes in a vane pump facilitates fluid movement through the pump.

ratio of areas

A physical law stating that a given pressure exerted in a larger cylinder can be intensified when transferred to a smaller cylinder. The ratio of areas is the area of one piston compared to the area of a second piston.

reciprocating motion

Movement characterized by the repeated back-and-forth action of a component. The reciprocating motion of linear components in some hydraulic pumps moves fluid through the pump.

reservoir

The main storage container for fluid in a hydraulic system. The reservoir holds fluid under atmospheric pressure.

revolutions per minute

rpm. A unit of measurement that indicates the number of rotations a cylindrical component completes in one minute. Revolutions per minute is a measurement of speed.

rotary motion

Spinning or turning movement that takes place around an axis, without a change in linear position. Rotary motion is a type of mechanical energy.

rotor

A rotating part of an electrical or mechanical device. A rotor is the driven component of most hydraulic pumps.

rpm

revolutions per minute. A unit of measurement that indicates the number of rotations a cylindrical component completes in one minute. Rpm is a measurement of speed.

single-acting intensifier

A type of hydraulic intensifier that provides high pressure fluid during downward strokes only. A single-acting intensifier does not provide a continuous supply of pressurized fluid.

spur gears

A gear with straight, flat-topped teeth set parallel to the shaft. Spur gears are often used in gear pumps.

stroke

The length of travel of a piston when it moves in or out. The stroke of a piston determines a piston pump's displacement.

swashplate

A flat, angled component of an axial piston pump that maintains contact with the piston shoes to cause the pistons to reciprocate. The swashplate angle determines an axial piston pump's displacement.

theoretical flow rate

A pump's rated operating flow rate. Theoretical flow rate is different from a pump's actual flow rate.

theoretical operating torque

The amount of torque a hydraulic component is capable of delivering. Theoretical operating torque is used when calculating mechanical efficiency.

throttle

A control used to vary the speed of a mechanical device. A throttle on an internal combustion engine allows operators to control the speed of a hydraulic pump.

unbalanced vane pump

A hydraulic pump that consists of a rotor mounted off-center in a circular cam ring. An unbalanced vane pump can have fixed or variable displacement.

vane pump

A hydraulic pump that uses a series of flat protrusions that extend within a rotor to trap and move fluid. Vane pumps are efficient at fast operating speeds.

vanes

A retractable mechanism that extends radially from the center of a rotor in a vane pump. Vanes trap and move fluid through the pump.

variable-displacement pump

A hydraulic pump that can be adjusted to change the amount of fluid that is moved in one pump cycle. Variable-displacement pumps are generally more expensive than fixed-displacement pumps.

viscosity

A fluid property that describes a fluid's resistance to flow. The viscosity of a fluid decreases as temperature increases.

volume

The amount of space that a substance or object occupies within a container. Volume is measured in cubic inches or cubic centimeters.

volumetric efficiency

An efficiency rating that describes the amount of leakage in a hydraulic pump. Volumetric efficiency is the most commonly used efficiency rating when determining the condition of a hydraulic pump.

work

The result of force applied to an object and the distance through which the force is applied. Work is calculated as force multiplied by distance.