| 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. |