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Compressed Air Glossary of Terms :: I ::
Glossary Index
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- IBV
- Inlet butterfly valve. These are fitted on the inlet of most
types of compressor and the valve opens and closes to throttle the
air flow. However, the term IBV is usually associated with turbo
compressors.
- ICFM
- CFM flowing through the compressor inlet filter or inlet valve
under rated conditions
- I.D.
- A measurement. Inside diameter.
- Ideal gas
- Is a gas that follows the perfect gas laws without deviation.
There is no such thing, however it is the basis from which
calculations are made and corrections applied.
- Ideal multi
stage compression
- The condition when a perfect gas is isentropically compressed,
and the gas inlet temperature and also the amount of work spent is
the same for each stage.
- IGV
- Inlet guide-vane valve. Valve assembly at the air inlet of a
"blower" (single stage, low pressure, centrifugal air compressor).
Usually advised to be mounted in very close proximity to
the "blower" impeller. Provides "pre-swirl" of air flow in same
rotational direction as "blower" impeller. Proven to improve
efficiency (reduced bhp) during throttled-down modulation
of "blowers". Effectiveness, when used with multi-stage
centrifugal air compressors, degrades rapidly.
- Immiscible
- Incapable of being mixed without separation phases. Water and
petroleum oil are immiscible under most conditions, although they
can be made miscible with the addition of an emulsifier.
- Impeller
- The part of the rotating element of a dynamic compressor that
imparts energy to the flowing medium by means of centrifugal
force. It consists of a number of blades mounted so as to rotate
with the shaft.
- Inches of water
- A measurement of vacuum or pressure that is used to measure
the airflow restriction.
- Indicated power
- Power as calculated from compressor-indicator diagrams.
- Indicator card
- A pressure-volume diagram for a compressor or engine cylinder
produced by direct measurement made by the use of a device called
an indicator.
- Indicator pressure
- An indicator that signals pressure conditions.
- Induced draft
- An air flow caused by a fan that draws air through the heat
exchanger core in a uniform pattern to dissipate the sensible
heat.
- Inducer
- A curved inlet section on an impeller.
- Inert gas
- Is one that does not enter into known chemical combination,
either with itself or another element. There are four known gases
of this type: helium; neon; argon and krypton. or a gas that does
not supply any of the needs of combustion.
- Inertia base
- A concrete foundation with lateral supports which rests upon a
number of steel springs. Designed to deal with disturbing
frequencies in vibration isolation
- Inertia forces
- When reciprocating compressors run, the moving parts such as
pistons, rods, crossheads, connecting rods are repeatedly
accelerated and retarded. These velocity changes set up pulsating
inertia forces. The forces are of the first and second order. The
first order forces have the same frequency as the compressor shaft
speed and the second order forces have a frequency twice the shaft
speed.
- Influent
- The fluid entering a component.
- Ingested
contaminants
- Environmental contaminant that ingresses due to the action of
the system or machine.
- Inlet pressure
- Is the total pressure (static plus velocity) at the inlet
flange of the compressor.
- Inlet temperature
- Is the temperature at the inlet flange of the compressor.
- Inlet throttle
- A compressor control mechanism designed to control performance
output of the compressor to the demands of the plant process.
- Inline filter
- A filter assembly in which the inlet, outlet and filter
element axes are in a straight line.
- Insolubles
- Insoluble material suspended in the lubricating oil. This
material may come from contamination or oil degradation.
- Instrument air
- A quality of compressed air for use with pneumatic instruments
and controls. (usually dry and free from contaminants)
- Intake filter
- A device for separating solids or suspended particles in the
air before they enter the air intake of the compressor.
- Intake filter
silencer
- A device for separating solids or suspended particles in the
air before they enter the air intake of the compressor and reduce
intake noise as on reciprocating compressors through a silencing
chamber in the filter housing.
- Intank check valve
- A valve designed to prevent air volume and pressure from
escaping the compressor tank back into compressor heads while
compressor is not operating.
- Intercooler
- Heat exchangers for removing the heat of compression between
stages of a compressor.
- Intercooling
- The removal of heat from the air or gas between stages.
- Internal energy
- Energy which a substance possesses because of the motion and
configuration of its atoms, molecules, and subatomic particles.
- International
Organization for Standardization
- ISO.
- Irreversible process
- is one in which a portion of the original system energy is
dissipated and cannot be returned to the system through its own
operation. The system and/or surroundings cannot be returned to
their original state.
- Isentrop
- Is a process taking place without any heat exchange with the
surroundings.
- Isentropic
compression
- An adiabatic compression with no increase in entropy; a
reversible-adiabatic compression.
- Isentropic
efficiency
- The ratio of the real gas isentropic power consumption to
shaft input.
- Isentropic power
consumption
- The power which is theoretically required to compress a gas
under constant entropy from a given inlet pressure to a given
discharge pressure. (calculated assuming ideal
conditions).
- ISO
- International Organization for Standardization.
- Isobar
- Is a process taking place under constant pressure. To change
the volume from state 1 to state 2, heat must be removed. The
temperature change is proportional to the change in specific
volume.
- Isochor
- Is a process taking place under constant volume. To raise the
pressure from state 1 to state 2, heat must be added. The pressure
change is proportional to the change in temperature.
- Isotherm
- Is a process taking place under constant temperature. To
compress the gas from state 1 to state 2, heat must be removed to
keep the temperature constant. The pressure change is reciprocal
to the change in specific volume.
- Isothermal
compression
- Is a compression in which the temperature of a gas remains
constant.
- Isothermal
efficiency
- The ratio of the isothermal power consumption to shaft input.
- Isothermal power
consumption
- The power which is theoretically required to compress a gas
under constant temperature, in a compressor free from losses, from
a given inlet pressure to a given discharge
pressure.
Glossary Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Thanks to Impact RM for permission to reprint the glossary.
Compressed Air Glossary © Impact RM
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