23
Glossary
Becoming familiar with these terms will help you understand
and operate most air compressors:
Air Delivery
– A combination of psi and CFM. The air
delivery required by a tool or accessory is stated as
“’number’ (S)CFM at ‘number’ psi”. For example “9.0 CFM at
90 psi”. The combination of these values dictates the
required air compressor capacity.
Air Tank Capacity
– The volume of air stored in the tank and
available for immediate use.
Alternating Current
(AC) - Voltage that increases to a
maximum positive value (+) and falls back to zero and then
continues to a maximum negative value (-) and back to zero.
This cycle is repeated 60 times each second for 60 hertz AC
power.
ASME Certified
- Indicates that the pressure vessel (air tank)
and related components are manufactured, tested, and
inspected to the specifications set by the American Society
of Mechanical Engineers.
ASME Safety Valve
- A protection device that automatically
releases tank air if the air contained within exceeds a preset
maximum rating.
Cast Iron Sleeve
- A thin iron cylinder cast into the cylinder
head, producing a harder surface between the aluminum
cylinder walls and steel piston rings, thus extending the life
of the compressor.
CFM
or
SCFM
(Standard Cubic Feet per Minute). SCFM is
the volume of air, in cubic feet, that the compressor can
pump in one minute at a specific working pressure. The term
CFM is used in this manual.
Circuit Breaker
- A thermal switch that opens a circuit if too
much current is passing through it. The air compressor
motor is protected by this resettable device.
Cut-In Pressure
– As air is taken from the air tank, the tank
air pressure drops. At a certain low level, the Pressure
Switch senses this low pressure and turns-on the
compressor motor, thus refilling the air tank. The level at
which the motor switches ON is called the Cut-In Pressure.
Cut-Out Pressure
– While the compressor is running, air is
being produced and stored in the air tank. If no air is being
used, air pressure will build in the tank. The Pressure Switch
senses this high pressure and at a certain high level, it turns
the compressor motor off. The level at which the motor
switches OFF is called the Cut-Out Pressure.
Duplex Receptacle
- Two 120 volt AC receptacles that are
tied together. Similar to common household outlets.
GFCI
- Ground fault current interrupter. A device that will
sense current flow in the milliamp range in a power circuit to
ground conductor and activate a relay to open both line
conductors.
Ground
- A connection, either intentional or accidental,
between an electric circuit and the earth or some conducting
body serving in place of the earth.
Pressure Control
– Often called a regulator, this device is
used to adjust the air compressor’s pressure output. The
Pressure Control is adjusted to supply the psi value required
by certain air tools, as monitored on the regulated pressure
gauge.
psi
- pounds per square inch. The measure of air pressure
delivered by the air compressor system.
Single Stage
- Single stage refers to an air compressor with
one or more cylinders that take air in each cylinder at the
down stroke and compresses the air into the air tank on the
up stroke.
Tank Pressure Gauge
– A device used to indicate the air
pressure contained in the air tank, in psi
Two Stage
- A two-stage compressor always has a minimum
of two cylinders - a low pressure (LP) cylinder (largest) and
an high pressure (HP) cylinder (smallest). As the LP piston
goes downward, air is taken in at atmospheric pressure; on
the upward stroke the LP piston discharges the air through
an intercooler and into the HP cylinder on its downward
stroke. On the upward stroke of the HP piston the air is
discharged into the air tank. Two-stage compressors are
recommended when tool usage is continuous.
Vibration Isolators
– When installed, are designed to
minimize vibrations produced by the air compressor.
