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glossary
Glossary of Terms
 
A
 
Absolute pressure - total pressure measured from absolute zero, equals gauge pressure + 14.7 PSIA (atmospheric pressure)
 
ACFM - actual cubic feet per minute, measure of the volume of gas at actual temperature, pressure, and humidity conditions, independent of density
 
AC Ionizer - a static eliminator which uses alternating current to produce both positive and negative ions to reduce or neutralize electrostatic fields
 
Air compressor - mechanical device that increases the pressure of air by reducing its volume
 
Air consumption - the total volume of air that a pneumatically operated product draws from a compressed air source
 
Air ionizer - a source of charged air molecules, typically used for the purpose of static elimination
 
Airflow pattern - the airflow shape created by the combined flow of the air exiting the compressed air product and the entrained surrounding air
 
Alloy - a homogenous substance composed of two or more metals, or of a metal or metals with a nonmetal
 
Ambient air - air in the surrounding environment
 
Amplification ratio - the ratio of the total output flow to the volume of air consumed
 
Arc - a luminous bridge of electricity formed across a gap in a circuit or between two electrodes
 
Atmospheric pressure - the measured ambient pressure for a specific location and altitude
 
Axial-flow compressor - uses a series of fan-like rotating rotor blades to progressively compress the gasflow, stationary stator vanes located downstream of each rotor redirect the flow onto the next set of rotor blades, the working fluid principally flows parallel to the axis of rotation
 
 
B
 
Back pressure - a resistant pressure exerted by liquid or gas against the forward motion or flow of an exhaust or pipe system
 
Bar - metric unit used to measure pressure, 1 BARG = 14.5 PSIG
 
Bellows - corrugated, accordion-folded, flexible design which expands or contracts axially
 
Bimetal - a material made by the bonding of two sheets or strips of different metals, each metal having a different coefficient of thermal expansion
 
British Thermal Unit (BTU) - a unit of heat equal to the amount of heat required to raise 1 pound of water by 1° Fahrenheit at 1 atmosphere of pressure
 
BSP - British Standard Pipe, standard screw thread type that has been adopted internationally for interconnecting and sealing pipe ends by mating a tapered external (male) thread with either a parallel or tapered internal (female) thread
 
 
C
 
CE mark - a mandatory European marking for certain product groups to indicate conformity with the essential health and safety requirements set out in European Directives, and that the applicable conformity assesment procedures have been applied
 
Centrifugal compressor - uses a vaned rotating disc or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas, a diffuser (divergent duct) section converts teh velocity energy to pressure energy
 
CFM - cubic feet per minute, the units of measure for air consumption and air flow delivered under specific conditions (see SCFM)
 
Charged device model (CDM) - A specified circuit characterizing an electrostatic discharge which results when a device isolated from ground is first charged and then subsequently grounded
 
Closed-top drum - drum in which the top is fixed and the inside contents are only accessible through screw plugs or bung holes in the top of the drum
 
Coalescing filter - used to seprarate liquid oil from compressed air using a coalescing effect, where the oil droplets merge together on a fine pitch screen filter and drop out of the air stream
 
Coanda profile - surface curved such that a high-velocity fluid that moves across it will exhibit the Coanda effect, the tendency of a fluid to stay attached to a convex surface rather than follow a straight line, as long as the curvature is not too sharp; the net result is a low pressure area into which ambient air can be pulled in to enhance the volumetric flow by way of air amplification
 
Cold fraction - the percentage of cold air flow relative to the total volume of air consumed by a Vortex Tube
 
Common wire - also called the neutral wire, used to complete the connection between an electrical device and a power source
 
Compressed air - air compressed, especially by mechanical means, to a pressure higher than the surrounding atmospheric pressure
 
Compressed air ionizer - ionization device used to simultaneously neutralize charged surface and remove surface particles with high force air
 
Condensate - product of condensation, as a liquid reduced from a gas or vapor
 
Conductive - able to carry an electric current/charge
 
Conical - having a shape like that of a cone, tapered
 
Convection - the transfer of heat by the circulation or movement of the heated parts of a liquid or gas
 
Conveying rate - mass of material conveyed over a specific time period, usually expressed in tons per hour or pounds per minute, also called material mass flow rate
 
Corona ionization/treatment - the production of positive and negative ions by a very localized high electric field, normally established by applying a high voltage to a conductor in the shape of a sharp point or wire, typically used as a surface treatment to increase surface tension, often mistaken for static elimination
 
Cryogenic - of or pertaining to the production or use of very low temperatures
 
Current - measurement of the flow of electricity, measured in amperes (or amps)
 
Cv (C-sub-V) - flow coefficient, flow capacity rating of a valve, defined as the volume (in US gallons) of water at 60F that will flow per minute through a valve with a pressure drop of 1psi across the valve
 
Cyclonic - having a spiral or rotating pattern
 
 
D
 
DC Ionizer - uses direct current to produce either positive or negative ions
 
Dead ended pressure - static pressure at the main orifice when dynamic flow is completely blocked, must be below 30psi to comply with OSHA standards
 
Decibel (dB/dBA) - the unit of measure of sound
 
Demand - flow of air at specific conditions required at a point or by the overall facility
 
Dew point - temperature at which moisture in the air will begin to condense if the air is cooled at constant pressure, at this point the relative humidity is 100%
 
Diagonal flow compressor - also called a mixed-flow compressor, effectively a cross between a centrifugal and axial-flow compressor, has a radial and axial velocity component at the exit from the rotor, has a lower diameter diffuser than the equivalent centrifugal compressor
 
Diaphragm compressor - variant of conventional reciprocating compressor, compression of gas occurs by the movement of a flexible membrane instead of an intake element, the back and forth movement of the membrane is driven by a rod and a crankshaft mechanism
 
Diffuse reflective - reflectino of light from an uneven or granular surface such that an incident ray is reflected at a number of angles
 
Discharge pressure - the actual pressure of the air the outlet or discharge point of a compressed air product
 
Drilled pipe - method of delivering mostly unrestricted compressed air to a point of use, with air exiting through a series of holes drilled along a length of pipe or tube in a manifold arrangement, can be quite wasteful use of air
 
Dynamic compressor - compressor in which air or gas is compressed by the mechanical action of rotating impellers imparting velocity and pressure to a continuously flowing medium
 
 
E
 
Eductor - another name for an ejector
 
Ejector - a device using the pressure of a jet of water, air, or steam to create a partial vacuum in order to withdraw a fluid or gas from a space
 
Electric charge - absence or excess of electrons
 
Electric field - space or region in the vicinity of a stationary charged particle
 
Electronic Flow Control (EFC) - EXAIR product that helps to minimize compressed air consumption by using a photoelectric eye to send signals to a user-programmed control box, which then sends signals to open and close a solenoid valve according to the control box timer settings
 
Electronic Temperature Control (ETC) - EXAIR product that provides a digital display of internal temperature inside a control panel, allows the user to dial the thermostat set point, and activates a solenoid valve based on internal temperature reading
 
Electrostatic charge - electric charge at rest
 
Electrostatic discharge (ESD) - the rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field, usually flows through a spark between two bodies at different electrostatic potentials as they approach one another
 
Electrostatic field - an attractive or repulsive force in space due to the presence of electric charge
 
Electrostatic field meter (Static Meter) - instrument that measures the magnitude and polarity of the electric field produced by a charged object
 
Electrostatic potential - the voltage difference between a point and a specified reference point
 
Electrostatic shielding - presence of a barrier or enclosure that limits the penetration of an electrostatic field
 
Emitter - a conducting sharp object, usually a needle or wire, which will cause a corona discharge when kept at a high potential
 
Energy - the ability to do work over a period of time, usually measured in kilowatt hours (kWh)
 
Entrain - to pull or draw along after itself
 
 
F
 
Field induced model (FIM) - ESD circuit characterizing the electrostatic discharge from a device to ground as a result of that device entering an electric field which causes a separation of the charges on the device surface
 
Free air - air at atmospheric conditions at any specified location, unaffected by the compressor
 
Free air delivered - air delivered to a certain point at a certain condition, converted back to ambient conditions
 
 
G
 
Gauge pressure - pressure as determined by most instruments and gauges, usually expressed in PSIG
 
Generator - Vortex Tube component made of plastic, with a fixed orifice and angled external vanes, responsible for creating the internal vortex and controlling the overall flow of the Vortex Tube
 
Global thread - male pipe thread that can thread into either NPT or BSP female threads
 
Ground - a conducting connection, whether intentional or accidental between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of earth; the position or portion of an electrical circuit at zero potential with respect to the earth; a conducting body such as the earth, used as a return path for electric currents and as an arbitrary zero reference point
 
Grounded - connected to earth or some other conducting body that serves in place of the earth
 
 
H
 
Hard ground - a connection to ground through a wire or other conductor that has very little or nearly no resistance to ground
 
Hose - sized by inside diameter (ID), typically made of rubber or plastic
 
Hot wire - carries voltage from the power source to the electrical device
 
Human body model (HBM) - an ESD circuit characterizing the electrostatic discharge from a person to or through a device to ground
 
 
I
 
ICFM - inlet cubic feet per minute, the volume of air drawn in by the compressor through the inlet filter
 
Inlet pressure - the actual pressure of the air that is supplied at the inlet to a compressed air product
 
Insulative - inhibits the flow of electrical current
 
Ion - a positively or negatively charged particle
 
Ionization - the process by which a neutral atom or molecule (or surface) acquires a positive or negative charge
 
Ionizer - a device which is designed to generate positive and/or negative air ions
 
IP rating - International Protection rating, classifies the level of protection that electrical appliances provide against the intrusion of solid objects or dust, accidental contact, and water, consists of the letters "IP" followed by two digits and an optional letter
 
 
J
 
 
K
 
kCal - Kilocalorie, metric unit of energy used to measure the cooling capacity of a Vortex Tube
 
 
L
 
Laminar flow - non-turbulent, straight air/gas flow, also called directional or streamline flow
 
Loose bulk density - the unit weight per unit volume, usually pounds per cubic foot, measured when the sample is in a loose non-compacted condtion
 
LPM - liters per minute, the metric unit of measurement of air consumption and air flow (see SLPM)
 
 
M
 
Machine model (MM) - an ESD circuit characterizing the electrostatic discharge from a machine to or through a device to ground
 
Magnetic field - space or region in the vicinity of a moving charged particle
 
Material mass flow rate - mass of material conveyed over a specific time period, usually expressed in tons per hour or pounds per minute, also called conveying rate
 
Maximum particle size - the maximum lump dimension in inches for a lumpy bulk material, for a bulk powder or granule it is the maximum sieve size of the largest lump or particle
 
Minimum conveying velocity - the lowest gas velocity that can be used to ensure stable pneumatic conveying conditions for the material, also known as the pickup velocity
 
Minimum practical pressure - the lowest pressure at which the product can operate effectively and efficiently and still achieve the desired result
 
Muffler - device which decreases the audible sound level produced by a product
 
Multi-stage vacuum generator - two or more vacuum generators piped in series to produce greater vacuum flow without using more compressed air, the exhaust from the first unit serves as input for a second stage and the exhaust from the second unit serves as input for a third stage, allowing faster evacuation time of a given volume
 
 
N
 
NEMA rating - National Electrical Manufacturers Association standard defining the protection level of an enclosure
 
NEMA 12 rating - enclosures constructed (without knockouts) for indoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and circulating dust, lint, fibers, and flyings), and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing)
 
NEMA 4 rating - enclosures constructed for either indoor our outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure agains ingress of solid foreign objects (falling dirt and windblown dust), to provide a degree of protection with respect to harmful effects on the equipment due to the ingres of water (rain, sleet, snow, splashing water, and hose-directed water), and that will be undamaged by the external formation of ice on the enclosure 
 
NEMA 4X rating - enclosures constructed for either indoor our outdoor use to provide a degree of protection to personnel against access to hazardous parts, to provide a degree of protection of the equipment inside the enclosure agains ingress of solid foreign objects (falling dirt and windblown dust), to provide a degree of protection with respect to harmful effects on the equipment due to the ingres of water (rain, sleet, snow, splashing water, and hose-directed water), that provides an additional level of protection against corrosion, and that will be undamaged by the external formation of ice on the enclosure 
 
Neutralization - eliminating an electrostatic field by recombining positive and negative charges, either by conducting the charge to ground or by introducing an equal opposite charge
 
NHP - non-hazardous purge, continuous flow of a small amount of air into a sealed enclosure even when primary airflow inlet and exhaust system is turned off
 
Nm3/H - normal meters cubed per hour, flow of free air measured at some reference point and converted to a standard set of reference conditions, typically 1.01 BARA, 20C, and 0% relative humidity
 
Non-porous - having no pores, not penetrable
 
NPT - National Pipe Taper, US standard for tapered threads used to join pipes and fittings, the taper allows the threads to form a seal when torqued as the flanks of the threads compress against eachother, however there is a clearance between the crests and roots of the threads which can be made leak-free with the use of thread seal tape or a thread sealant compound
 
 
O
 
Open pipe/tube - method of delivering nearly completely unrestricted flow of compressed air, where the supply air line is simply left open and aimed directly at the point of use, can be quite dangerous and is a wasteful use of air
 
Open-top drum - drum in which the top is removable, and is secured to the drum body with a ring that has a nut and bolt or lever-lock mechanism
 
Operating pressure - the pressure being supplied to the compressed air product while in operation, also called supply pressure
 
OSHA - Occupational Safety and Health Administration, main federal agency charged with the enforcement of safety and health legislation, whose mission is to prevent work-related injuries, illnesses, and deaths by issuing and enforcing rules (called standards) for workplace safety and health
 
 
P
 
Particulate - a small discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid
 
Pipe - sized by inside diameter (ID), can be metal or plastic
 
Plenum chamber - a space in which a gas, usually air, is contained at a pressure greater than atmospheric pressure
 
Porous - full of tiny pores that allow fluids or gasses to pass through
 
Positive displacement compressor - compressor in which successive volumes of air or gas are confined within a closed space and the space mechanically reduced, resulting in compression
 
Power - the rate at which work is done or energy is transferred, commonly measured in kilowatts and horsepower (kW and hp)
 
Predictive maintenance - involves monitoring compressor condition and trends, including operating parameters such as power requirements, pressure drops, operating temperatures, and vibration levels
 
Pressure - force per unit area, measured in pounds per square inch (PSI)
 
Pressure drop - loss of pressure in a compressed air system or component due to friction or restriction
 
Preventive maintenance - includes regularly scheduled monitoring of operating conditions, replacement of air and lubricant filters, lubricant sampling and replacement, minor repairs and adjustments, and an overview of compressor and accessory equipment operation
 
Proactive maintenance - involves looking for the cause and determining how to prevent a recurrence, if a defect is detected
 
PSI/PSIG/PSIA - pounds per square inch, the English unit of measurement of pressure
 
 
Q
 
 
R
 
Ranque Vortex Tube/Hilsch Tube/Ranque-Hilsch Tube/Maxwell's Demon - various other names by which the Vortex Tube is also known
 
Reciprocating compressor - compressor in which the compressing element is a piston having a reciprocating motion in a cylinder
 
Receiver tank - a vessel designed to store compressed air that is utilized to meet peak demand events where short duration, large air requirements exceed compressor capacity
 
Reclassifying muffler - silencing muffler typically used on pneumatic cylinders and valves that also separates oil from the exhausted air so that it is not released back into the environment
 
Refrigeration - the act or process of cooling a substance
 
Relative humidity (of a gas/vapor or air/vapor mixture) - the ratio of the partial pressure of the vapor to the vapor saturation pressure at the dry bulb temperature of the mixture
 
RoHS - Removal of Hazardous Substances, directive that stands for the restriction of the use of certain hazardous substances in electrical and electronic equipment, bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybromenated biphenyl (PBB), and polybromenated diphenyl ether (PBDE) flame retardants
 
Rotary screw compressor - type of air compressor which uses a rotary type positive displacement mechanism, utilizes either a single screw element or two counter rotating intermeshed helical screw elements housed within a specially shaped chamber
 
 
S
 
SCFM - standard cubic feet per minute, flow of free air measured at some reference point (ACFM) and converted to a standard set of reference conditions, typically 14.5 PSIA, 68F, and 0% relative humidity (see CFM)
 
Scroll compressor - uses two interleaved spiral-like vanes to pump or compress fluids such as liquids and gases, the vane geometry may be involute, archimedian spiral or hybrid curves, often one of the scrolls is fixed while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of fluids between the scrolls
 
Shim - a thin piece of material used to fill gaps, make something level, or adjust something to fit properly
 
Shockless - produces no electrical discharge when touched by a person
 
Short-out - accidental low-resistance connection between two nodes of an electric circuit that are meant to be at different voltages, resulting in excessive current flow, potentially damaging the circuit
 
Single-stage vacuum generator - venturi-style vacuum pump where compressed air flows through the inlet, a single directed nozzle causes the air stream to expand and increase in velocity, which creates a vacuum inside and pulls in ambient air through a tangential vacuum inlet, then the combined air stream is exhausted to atmosphere
 
Sliding vane compressor - a rotary-element gas compressor in which spring-loaded sliding vanes (evenly spaced around a cylinder off-center in a surrounding chamber) pick up, compress, and discharge gas as the cylinder revolves
 
SLPM - standard liters per minute, flow of free air measured at some reference point and converted to a standard set of reference conditions, typically 1.01 BARA, 0C, and 0% relative humidity (see LPM)
 
Standard air - free air measured and converted to a standard set of reference conditions, 14.5psia, 68F, and 0% relative humidity, as defined by ISO
 
Static charge - presence of positive or negative ions at rest
 
Static decay/discharge rate - the decrease of charge or voltage per unit time
 
Static dissipative (range) - surface characteristic of materials that can provide a safe resistive discharge in less than 1 second
 
Static electricity - see electrostatic charge
 
Supply pressure - the pressure being supplied to the compressed air product while in operation, also called operating pressure
 
 
T
 
Thermoswitch - mechanical thermostat that activates when a bimetal material expands to complete the electrical circuit connection across two internal leads, the activation point is determined by the preset distance of the leads and the rate at which the bimetal material expands or contracts relative to a change in temperature
 
Throat diameter - smallest inner diameter through which a fluid or material can flow
 
Total output flow - the total volume of airflow produced by a unit, calculated by multiplying air consumption by amplification ratio
 
Transient - a sudden brief change of voltage or current
 
Triboelectrification - the generation of electrostatic charges when two materials make contact or are rubbed together, then separated
 
Tube - sized by outside diameter (OD), typically made of stainless steel, copper, or other metals
 
 
U
 
UL - Underwriters Laboratory, a US not-for-profit, privately owned and operated product safety testing and certification organization, does not approve products, rather, evaluates products, components, materials, and systems for compliance to specific requirements, its own Standards for Safety
 
Ultrasonic - having a frequency above that which is audible by the unassisted human ear
 
 
V
 
Vacuum level - amount of suction power produced by a product, typically measured in inches of water column (in H2O), or inches of mercury (in Hg)
 
Vacuum pump - a device that removes gas molecules from a sealed volume in order to leave behind a partial vaccum
 
Venturi - a tube of varying diameter through which fluid flows, faster if flowing from larger diameter to smaller diameter, and slower if flowing from smaller diameter to larger diameter, often used in vacuum applications such as suction cups
 
Voltage - measurement of the difference in electrical potential between two points in a circuit, measured in volts
 
Vortex - spinning, often turbulent flow, with closed streamlines
 
Vortex spin chamber - the area inside a vortex tube where the heat transfer occurs, to create two streams of hot and cold air spinning in vortices, one within the other
 
Vortex tube - mechanical device with no moving parts that separates a compressed gas into hot and cold streams
 
 
W
 
 
X
 
 
Y
 
 
Z
 
 
Sources:
 
CAGI Glossary - Compressed Air and Gas Institute
Compressed Air Challenge - Best Practices for Compressed Air Systems
ESD Association Advisory for Electrostatic Discharge Terminology - Glossary
Hydraulicspneumatics.com - Vacuum Generation information
NEMA - National Electrical Manufacturers Association
 
 

 

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Last modified at 11/24/2008 5:17 PM by emilymortimer@exair.com
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