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Compressed Air Glossary of Terms :: C ::

Glossary Index

Can velocity
The velocity of the gas in the passages between the filter units in the filter house of a gas filter.
The pressure screw cover and/or lever housing on a valve. May be screwed, bolted. packed, or plain lever.

Capacity of a compressor is the full rated volume of flow of gas compressed and delivered at certain set conditions.

Capacity filtration
The amount of air that a filter can handle. Expressed in CFM.

Capacity gauge
A gauge that measures air flow as a percentage of capacity, used in rotary screw compressors as an estimator during modulation controls.

Capillary tube
A restrictive tube used in a refrigeration system which restricts the flow of freon and allows pressure to build on one side and suction on the other. It is located between the condenser and the evaporator.

Cap tube
A restrictive tube used in a refrigeration system which restricts the flow of freon and allows pressure to build on one side and suction on the other. It is located between the condenser and the evaporator.

A salt or ester of carbonic acid.

Carbon dioxide
A heavy colorless gas that does not support combustion but is formed by the combustion and decomposition of organic substances. Found in some ambient air conditions.

Carbon monoxide
A colorless odorless very poisonous gas formed by the incomplete burning of carbon. Found in some ambient air conditions.

Carbon residue
The carbon left after evaporating an oil under controlled conditions.

The pressure containing stationary element that encloses the rotor and associated internal components of a compressor, including integral inlet and discharge connections.

°C The international temperature scale where water freezes at 0 (degrees) and boils at 100 (degrees). Also known as the centigrade scale.

Center tube
The internal duct and filter medium support

Centrifugal compressor
A dynamic compressor. A machine in which air or gas is compressed by the mechanical action of rotating vanes or impellers imparting velocity and pressure to the air or gas. In a centrifugal compressor, flow is in a radial direction. Air enters the compressor through the machine mounted inlet control valve and flows to the first stage where the impeller imparts velocity energy to the air. The air then proceeds through a diffuser section which converts the velocity energy to pressure energy. A multistage centrifugal compressor is a machine having two or more of these stages.

ACRONYM - Cubic feet per minute. An airflow measurement of volume.

Charle's law
States that the volume of a gas, at constant pressure, varies directly with the absolute temperature.

Abnormal, rapid reciprocating movement of the disc on the seat of a pressure relief valve.

Chip control
a filter intended to prevent only large particles from entering a component immediately downstream.

Chipping hammer
A hand held pneumatic tool. Designed to chip masonry, plaster, concrete etc.

Check valve
A valve that permits flow in one direction only.

A chemical element that is a heavy strong smelling greenish yellow imitating gas used as a bleach, oxidizing agent and disinfectant. Found in some ambient air conditions.

Chlorofluorocarbons (CFCs)
Compounds containing chlorine, fluorine or bromine, used as aerosol propellants, refrigerants, foaming agents and solvents and which, on decomposition by sunlight, produce oxides of chlorine responsible for the removal of ozone from the stratosphere.
This term is used for turbo compressors and represents the maximum flow condition. It is sometimes also referred to as stonewalling.
A filter element which, when loaded, can be restored by a suitable process, to an acceptable percentage of its original dirt capacity.

Cleanliness level
a measure of relative freedom from contaminants.

Clean room
A facility or enclosure in which air content and other conditions (such as temperature, humidity, and pressure) are controlled and maintained at a specific level by special facilities and operating processes and by trained personnel.

Clean pressure drop
The pressure loss across the filter element determined under steady state flow conditions using a clean test fluid across a clean filter element.

The maximum cylinder volume on a working side of the piston, minus the piston displacement volume per stroke. It is usually expressed as a percentage of the displace volume.

Clearance pocket
An auxiliary volume that may be opened to the clearance space for increasing the clearance, usually temporarily, to reduce the volumetric efficiency of the compressor.

A device for mounting cylinders.

An inward structural failure of a filter element which can occur due to abnormally high pressure drop (differential pressure) or resistance to flow.

Collapse pressure
The minimum differential pressure that an element is designed to withstand without permanent deformation.
ACRONYM - Compressed natural gas, primarily methane.

Closed loop system
A system in which distilled water, antifreeze, and/or corrosion inhibitors are circulated through a collector and storage tank in a closed loop. Heat picked up from the collector by the circulating fluid is transferred to the storage tank through the closed loop or other heat exchangers.

Coalescing filter
A filter unit that combines three principles to filter out oil aerosols: 1) Direct interception - A sieving action, 2) Inertial impaction - Collision with filter media fibers, 3) Diffusion -Particles travel in a spiral motion, presenting an effective frontal area thus capturing particles within the filter medium.

The A.S.M.E. Boiler and Pressure Vessel Code.

Coefficient of discharge
The ratio of the measured relieving capacity to the theoretical relieving capacity.

Cold differential test procedure
Actual gage pressure on the test stand that includes correction factors for temperature, pulsation, vibration, constant back pressure, etc.

Cold start
Starting a compressor from a state of total shutdown. Usually done with "local" control at the compressor. May be done with "remote" control, but only advised with "heavy" instrumentation and monitoring accessories.

An expansion joint designed to take up thermal expansion.

Composition of air
A colorless, odorless, tasteless gas. A mixture of individual gases. The gaseous mixture surrounding the earth..

To reduce the volume of, by or as if by pressure.

Compressed air
Air under pressure greater than that of the atmosphere.

Compressed air challenge
A public/private initiative to promote the efficiency of compressed air in the US.

A factor expressing the deviation of gas from the laws of hydraulics.

Compressibility factor Z
Is the ratio of the actual volume of the gas to the volume determined according to the perfect gas law.

Compression adiabatic
Compression in which no heat is transferred to or from the gas during the compression process.

Compression efficiency
Is the ratio of the theoretical work requirement to the actual work required to be performed on the gas for compression and delivery.

Compression Isothermal
Is a compression in which the temperature of a gas remains constant.

Compression ratio
The ratio of the absolute discharge pressure to the absolute inlet pressure.

A machine that compresses air, gases.

Computer control
May be "local" using a micro-processor or "remote" using a PC (Personal Computer) or "larger" computer. Only recommended where large "swings" in system (process) demand amplitude may occur. Very effective where "load shaping" is an important consideration. "Heavy" monitoring and instrumentation accessories required for it to be efficient and effective. Usually not necessary where system demand is predominantly constant.

the liquid that separates from a vapor during condensation.

A device that changes a vapor into a liquid. Accomplished by exposing a tube containing vapor to air or by passing the tube through a water jacket.

The transfer of heat energy through a material (solid, liquid, or gas) by the motion of adjacent atoms and molecules without gross displacement of the particles.

The mating device that is inserted into the coupler of a quick coupler and locked to complete the connection. Also referred to as plug or nipple.

Constant speed control
The unit that runs continuously and matches air supply to demand, by loading and unloading the compressor.

Foreign matter carried in the air, gas or fluid to be filtered out. Includes air borne dirt, metallic particles produced by wear of moving parts of the air compressor, rust from metal pipelines.

Contaminant capacity
the weight of a specified artificial contaminant that must be added to the influent to produce a given differential pressure across a filter at specified conditions. Used as an indication of relative service life.

Contaminant failure
any loss of performance due to the presence of contamination. Two basic types of contamination failure are: Perceptible -- gradual loss of efficiency or performance, and Catastrophic -- dramatic, unexpected failure.

Control valve
A valve that controls the flow in air lines.

Is a means of transferring heat through mass flow. Also the transfer of heat within a fluid by movements within the fluid.

On a bellow type air actuator, that part of the flexible member forming an annular protrusion larger than the O.D. of the end retainers or bead rings.

Fluid cooling agent.

Cooling tower
A cooling water supply system. There are two different types - Open and closed loop systems.

ACRONYM - Cycles per minute - a unit of measure of the frequency of any vibration.

To subject petroleum oil to heat for breaking down into lighter products.

Critical pressure
Is the saturation pressure at the critical temperature. It is the highest vapor pressure that the liquid can exert.

Critical speed
Rotative speeds at which rotating machinery-axial or screw lobe-pass through unbalanced operation.

Critical temperature
The highest temperature at which well-defined liquid and vapor states exist.

Crosshead assembly
The assembly connecting the crankcase and connecting rod to the cylinder head and piston rod for translating circular to linear motion.

Crosshead compressor
A compressor belonging to the group of displacement reciprocating compressors.

Crosshead loading
The tensile or compressive loading on the crosshead assembly with compressive piston rod loading on the outward stroke and tensile piston rod loading on the inward stroke.

ACRONYM - Canadian Standards Association

ACRONYM - Approach temperature. Usually the difference between cooling water temperature in to compressed air temperature out of an inter-cooler or after-cooler. Sometimes used to define oil cooler efficiency (cooling water temperature in to oil temperature out)

Cubic feet per minute (CFM)
CFM. An airflow measurement of volume.

cu m/sec
A volume. Cubic meters per second.

Cut in cut out pressure
The settings on a pressure switch used to either load or unload the air compressor on a constant speed application, or start or stop the compressor on a start/stop application. The cut out pressure is also known as the maximum pressure, or the point at which there is no air being delivered. The cut in pressure is referred to as the minimum pressure, or the pressure that the system is allowed to fall to before air volume is required.

A single complete operation consisting of progressive phases starting and ending at the neutral position.

Cycle time
Amount of time for a compressor to complete one cycle.

The piston chamber in a compressor or actuator.
a type of separator for removal of larger particles from an exhaust gas stream. Gas laden with particulates enters the cyclone and is directed to flow in a spiral causing the entrained particulates to fall out and collect at the bottom. The gas exits near the top of the cyclone.
Cyclone separator
A means of purifying an air stream by using both gravitational and centrifugal forces.

Glossary Index

Thanks to Impact RM for permission to reprint the glossary.

Impact RM

Compressed Air Glossary Impact RM

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