Download Pneumatic Dictionary

Pneumatic Dictionary
Bernoulli's Law As a fluid begins to flow it begins to lose pressure. The faster it flows, the lower the
pressure will drop.
Boyle’s Law The absolute pressure of a confined body of gas varies inversely with its volume, provided its
temperature remains constant.
Check Valve
A directional control valve which permits fluid flow in only one direction.
Condensation The process of changing water from a vapor into a liquid by the extraction of heat.
Cv Factor The flow rating of an air valve, expressed in the quantity of water, in gallons per minute, which
will flow through the valve with a one psi pressure drop.
Cylinder, Double-acting A cylinder in which a fluid force can be applied to the moveable element in
either direction.
Cylinder, Single-acting A cylinder in which a fluid force can be applied to the moveable element in only
one direction.
Dew point The temperature at which water vapor condenses into a liquid. For practical purposes, it must
refer to a stated pressure.
Differential Pressure Indicator An indicator which signals a difference in pressure between two points
in a pneumatic system.
Double Rod Cylinder Double-rod cylinders have a common rod, driven by a single piston, extending from
both cylinder end caps. When one end retracts, the other extends. They are excellent for providing an
adjustable stroke and providing additional rigidity.
Filter, Air line A device made of a porous medium whose primary function is to remove insoluble
contaminants from compressed air.
Filter, Coalescing An airline filter used to remove oil aerosols by the use of a filter medium such as
borosilicate glass fibers or activated charcoal. This type of filter should always be located downstream of a
general purpose air filter.
Flow The movement of a fluid generated by pressure differences.
Flow Control Valve A valve that allows free flow in one direction and adjustable or restricted flow in the
other direction. Typically used to control the speed of a cylinder in one direction by restricting the flow of
exhaust air out of the cylinder.
Flow Rate Amount of a fluid that passes a given point in a given period of time, measured in SCFM.
Force in Fluid Power Force equals pressure of a fluid (typically measured in PSI) multiplied by the area of
the surface against which it is applied (typically the piston of a cylinder)
Lubricator, Air line A device which adds controlled or metered amounts of lubricants into a pneumatic
system.
Manifold A conductor which provides multiple connection ports.
Normally Open Valve A valve that allows air to pass through it in the at-rest or unactuated condition.
Normally Closed Valve A valve that prevents the flow of air through it in the at-rest or unactuated
condition.
NPT National Pipe Thread. A standard for specifying pipe thread used in the U.S.
Paschal’s Law Pressure in a closed container is equal at all points throughout the fluid.
PSIA
Pounds per square inch absolute. Pressure reference to a vacuum.
PSID
Pounds per square inch differential. Pressure difference between two points in a pneumatic circuit.
PSIG
Pounds per square inch gauge. Pressure references to ambient air pressure.
Pneumatics An engineering science pertaining to gaseous pressure and flow.
Poppet An internal element of a valve that opens or closes flow paths by seating and removing a seal
against an orifice.
Pressure Force per unit area, usually expressed in pounds per square inch (psi).
Pressure, Atmospheric Pressure exerted by the atmosphere at any specific location. (Sea level is approx.
14.7 psia; 1 bar = 14.5 psia).
Pressure, Burst The pressure which causes failure of, and consequential loss of compressed air through,
a container wall.
Regulator, Air line Pressure A valve which transforms a fluctuating air pressure supply into a constant,
lower pressure output.
SCFM Standard Cubic Feet per Minute a unit of flow of non-compressed air.
Shuttle Valve A valve that will direct air coming from either of two sources to a single destination.
Solenoid Valve A valve that is opened or closed by an electromagnet. This action is achieved by the
movement of a magnetic plunger to seal off or open a port when voltage is applied.
Solenoid Valve, Pilot-operated A directional control valve whose internal element is shifted by air
pressure controlled by a solenoid pilot valve.
Spool An internal element of a valve that opens or closes flow paths by sliding back and forth in the bore
of the valve.
Torque Rotary force transmitted by the driving shaft of a motor or rotary actuator.
Torr A unit of pressure equal to 1/760 of an atmosphere. A perfect vacuum is -29.92 inHg or 760 mmHg.
Trunnion A mounting device consisting of a pair of opposite projecting cylindrical pivots. The cylindrical
pivot pins are at right angle to the piston rod centerline to permit the cylinder to swing in a plane.
Vacuum Any pressure less than ambient atmospheric pressure. A perfect vacuum is 0.0 psia or -29.92
inHg.
Valve actuator An external mechanism used to shift a valve's internal flow-direction element, such as a
spool or poppet.
Valve, 2-way A valve that has a single flow path which may be normally passing or normally non-passing.
Valve, 3-way A directional control valve whose primary function is to alternately pressurize and exhaust a
single port.
Valve, 4-way A directional control valve whose primary function is to alternately pressurize and exhaust
two ports.