Introduction to Fluid Systems 101

actuators

A component in a fluid system that converts hydraulic or pneumatic energy into mechanical energy through linear motion. Actuators are also known as effectors.

actuators

A component in a fluid system that converts hydraulic or pneumatic energy into mechanical energy. Actuators work to produce high forces.

aftercooler

A device that cools discharged air from an air compressor. An aftercooler also removes moisture and helps minimize vapor lock.

air compressor

The power source of a pneumatic system that pressurizes ambient air. An air compressor directs pressurized air into the system in order to produce mechanical power.

air receiver

An air storage tank used with pneumatic systems that balances air compressor capacity and airflow demand. An air receiver maintains a constant supply of compressed gas for the system.

ambient atmosphere

The air immediately surrounding a pneumatic system's intake filter. Air from the ambient atmosphere is pressurized by a compressor for use in a pneumatic system.

American National Standards Institute

ANSI. A private, non-profit organization that administers and coordinates voluntary standards and systems. The American National Standards Institute writes nationally approved standards for the manufacturing industry.

check valve

A directional control valve that allows fluid to flow in only one direction. A check valve prevents back flow.

closed-loop systems

A type of fluid power system in which the fluids flow continuously between the pump and the actuators. Closed-loop systems typically do not have a reservoir, allowing fluid to flow directly into the pump inlet.

compressibility

The ability to be condensed by pressure. Gases have high compressibility, while liquids do not.

conductors

A component that conveys liquids or gases throughout a fluid system. Conductors include pipe, tube, and hose.

control valves

A mechanism that regulates fluid in a pneumatic or hydraulic system. Control valves direct fluid movement and regulate the amount of pressure exerted in the system.

cylinders

A type of linear actuator that uses a piston to produce motion. Cylinders apply force in a straight line.

demulsibility

The ability to release water. Demulsibility in a fluid means that the fluid will separate from water.

displacement

A movement of fluid that indicates how much fluid is moved in one cycle. Displacement is measured in cubic inches per revolution or cubic centimeters per revolution.

drive shaft

A long, cylindrical component that transfers power from a motor to other machine components. A drive shaft is used in a piston pump to transfer motion to the pistons.

electrical systems

A power transmission system that uses the force of flowing electrons to transmit power. Electrical systems use a network of components, including generators, power lines, and transformers.

energy

The ability to do work. Energy may be potential or kinetic and may appear as electrical, mechanical, fluid, thermal, or chemical energy, among other forms.

filter regulator lubricator

FRL. A device that conditions air for use in pneumatic systems. A filter regulator lubricator unit removes particles, adjusts pressure, and adds a small amount of oil to the air.

fittings

A component that connects, redirects, extends, or terminates the run of a fluid conductor. Fittings on hoses are designed to disconnect quickly.

fixed displacement pump

A hydraulic pump that moves the same volume of fluid per pump cycle. Fixed displacement pumps are often used in applications with low hydraulic horsepower ratings.

flanges

Bent edges that add stiffness. Flanges are used to connect pipes to other components in fluid systems.

fluid motors

A device that converts the energy from fluid flow into mechanical motion through rotary motion. Fluid motors are a type of rotary actuator.

fluid systems

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

fluids

A state of matter that has the ability to flow. Fluids can be liquids or gases.

force

An influence, like a push or a pull, that produces a change in an object's motion or state of rest. Force results from an object's interaction with another object.

force multiplication

An exponential increase in available power created by tools or power transmission systems. Force multiplication is a major advantage of hydraulic and pneumatic systems.

gas

An airlike fluid that expands freely to fill any space available, regardless of its quantity. Gas differs from liquid in that there are no forces keeping gas molecules together.

gases

An airlike fluid that expands freely to fill any space available, regardless of its quantity. Gas differs from liquids in that there are no forces keeping gas molecules together.

gate valve

A valve that either allows or prohibits the flow of a fluid. A gate valve consists of a plate-like obstruction that is raised and lowered into place to control the flow of fluid.

gear pump

A hydraulic pump that uses meshing gears to move liquid through the pump. Gear pumps are relatively inexpensive and are compact in size.

gears

A wheel shaped device with teeth around the perimeter that is used to transmit power. Gears are designed to mesh with one another in order to alter mechanical energy.

hose

A versatile and flexible fluid conductor made of reinforced rubber. Hose is the preferred fluid conductor for non-linear routes.

hoses

A versatile and flexible fluid conductor made of reinforced rubber. Hose is the preferred fluid conductor for non-linear routes.

hydraulic pump

A mechanical power source that creates fluid flow and moves liquid through a hydraulic system. Hydraulic pumps receive energy from a prime mover, such as a motor or engine.

hydraulic pumps

A mechanical power source that creates fluid flow and moves liquid through a hydraulic system. Hydraulic pumps receive energy from a prime mover, such as a motor or engine.

hydraulic systems

A power transmission system that uses the force of flowing liquids to transmit power. Hydraulic systems use oils and water-based liquids to transmit power.

inlet port

A one-way valve where fluid enters a power source, such as a pump or compressor. The inlet port is the valve through which fluid is drawn into the power source.

International Fluid Power Society

IFPS. An organization that provides technical training and certification for fluid power systems. The International Fluid Power Society works to promote the advancement of fluid power professionals.

International Organization for Standardization

ISO. An organization based in Switzerland that develops and publishes standards for various aspects of manufacturing and industry. The International Organization for Standardization is responsible for establishing standards for fluid systems.

kinetic energy

Power that exists because of an object's motion. Kinetic energy is often harnessed, converted to other types of usable energy, or transferred to other objects.

linear actuators

A device that directs force in a straight line. Linear actuators include double- and single-acting cylinders.

liquids

A fluid that has the ability to flow and take the shape of its container. A liquid's volume remains close to constant despite changes in pressure.

liquids

A fluid that has the ability to flow and take the shape of its container. A liquid's volume remains close to constant despite changes in pressure.

lubricants

A fluid designed to reduce the friction between components. Lubricants often include oil and grease.

lubricity

The ability to reduce friction and provide lubrication. High lubricity in a hydraulic fluid indicates an effective lubricant.

manifold

A fluid conductor that consists of a metal block with multiple integrated channels. Manifolds are designed for use with multiple control valves or to conduct fluid in confined spaces.

matter

A substance that has mass and exists as a solid, liquid, or gas. Matter can change states based on temperature and pressure.

mechanical energy

Power that is produced by a force of motion. Mechanical energy results from the physical interaction of instruments or tools.

mechanical systems

A power transmission system that uses forces created by the physical interaction of machines or mechanisms to transmit power. Mechanical systems use a wide range of mechanisms, including belts, gears, and chains.

molecules

A group of atoms bonded together. Molecules represent the smallest physical unit of an element.

National Fluid Power Association

NFPA. An organization consisting of manufacturers, distributors, customers, vendors, and educators who work together to administer and maintain fluid power industry standards. The National Fluid Power Association works to advance fluid power technology.

newtons per square meter

N/m². A unit of pressure that measures the number of newtons per square meter. A newton per square meter is also known as a pascal, which is derived from the International System of Units (SI).

non-petroleum-based oils

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

open-loop systems

A type of fluid power system in which the fluid enters a reservoir. Open-loop systems include a reservoir between an actuator and pump.

outlet port

A one-way valve where fluid exits a power source, such as a pump or compressor. The outlet port is the valve through which fluid is expelled from the power source.

Pascal’s Law

A physical law stating that pressure applied to a confined fluid at rest is transmitted equally throughout the fluid. Pascal's Law describes the relationship between force, pressure, and area.

pascals

Pa. A unit of pressure that measures the number of newtons per square meter. A pascal unit is also known as a newton per square meter, which is derived from the International System of Units (SI).

petroleum-based oils

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

pipe

A fluid conductor made of metal or plastic that is used for linear and permanent routes. Pipe is usually made of steel.

pipes

A fluid conductor made of metal or plastic that is used for linear and permanent routes. Pipe is usually made of steel.

piston compressor

A pneumatic component that uses a piston driven by a rotating crankshaft to pressurize air. A piston compressor traps air as the piston moves back-and-forth.

piston pump

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

pneumatic systems

A power transmission system that uses the force of flowing gases to transmit power. Pneumatic systems most commonly use air to transmit power.

positive displacement

A component that moves a fixed amount of fluid. Positive displacement compressors move a fixed amount of air during each cycle.

positive displacement pumps

A hydraulic pump with a fixed fluid displacement per cycle or revolution that can be adjusted. Positive displacement pumps are used with a pressure relief valve on the outlet side.

potential energy

Stored power in an object. Potential energy is converted to kinetic energy by a component called an actuator.

pounds per square inch

psi. A unit of pressure that measures the number of pounds per square inch. Pounds per square inch is derived from the English system.

power transmission

The transfer of energy from a source to a specific location. Power transmission systems include mechanical, electrical, and fluid power systems.

pressure

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

pressure relief valves

An adjustable control valve that regulates pressure in a fluid system. Pressure relief valves release when the fluid system exceeds a critical pressure.

prime movers

The component in a fluid power system that provides mechanical energy for the power source. Prime movers for fluid power systems include electric motors and internal combustion engines.

psi

Pounds per square inch. A unit of English measurement used to measure pressure. Psi units are used to measure pressure requirements for fluid systems.

rack-and-pinion actuators

A rotary actuator with a round pinion gear that rotates against a linear toothed rack. A rack-and-pinion actuator can rotate up to 360 degrees in either direction.

regulators

A device that monitors the pressure level of the air sent to downstream components. Regulators control the flow of compressed air and liquid in fluid systems.

rotary actuators

A device that directs force in a circular motion. Rotary actuators provide rotational motion of less than 360 degrees.

rotary screw compressor

A pneumatic compressor that uses two interlocking threaded cylinders to pressurize and move air. A rotary screw compressor traps air as the threaded cylinders rotate.

rotor

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

sealants

A material or liquid that provides an airtight or watertight barrier. Sealants protect moving components in a fluid system from leaks and contamination.

separator

A component that removes water from cooled air. A separator keeps water from accumulating and damaging the pneumatic system.

solenoid valve

An output device that uses a coil to convert electrical energy into linear mechanical motion. Solenoids are often used to control valves in fluid power systems.

surface area

The total area of an exposed surface of a solid object. Surface area is expressed in square units.

threads

Long, spiraling grooves on workpieces that are made by a single-point tool. Threads are used to connect pipes to other components in fluid systems.

tubing

A fluid conductor made of metal or plastic that is usually used for non-linear routes. Tubing is easy to bend and eliminates the need for fittings and connection points.

vacuum

The state of negative pressure. A vacuum that forms in the inlet port of a hydraulic pump allows fluid to enter the pump.

vane actuators

A type of rotary actuator that directs energy in a circular motion through a series of flat protrusions. Vane actuators use a vanes to direct fluid.

vane compressor

A pneumatic compressor that uses vanes held in a rotor mounted off-center in a circular cavity to trap and pressurize air. A vane compressor traps air as the rotor spins and the vanes extend.

vane pump

A hydraulic pump that uses a series of flat protrusions that extend within a rotor to trap and move liquid. A vane pump is efficient at fast operating speeds.

vanes

A retractable spring-loaded mechanism that extends radially from the center of a compressor rotor. Vanes trap and move fluid to an outlet port.

variable displacement pump

A hydraulic pump that can be adjusted to increase or decrease the volume of fluid that is displaced during one pump cycle. Variable displacement pumps are generally more expensive than fixed displacement pumps.

viscosity

A fluid's resistance to flow. The higher the viscosity, the greater a liquid's flow.

volume

The amount of space that a material or substance occupies. Volume describes both the quantity of fluid and the capacity of a component in a fluid system.

welds

The area where two metal pieces are joined together by heating the surfaces until they melt. Welds are used to connect pipes to other components in fluid systems.

work

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

workholding

The process of securely supporting, locating, and clamping a workpiece for a manufacturing operation. Workholding helps to ensure that parts are created accurately and with good repeatability.