Pounds per square inch pressure indicated by a pressure gauge
Purge air
The portion of dry, full line pressure, compressed air taken from the drying side tower of a dual
tower desiccant dryer system allowing to expanded to a very low pressure and passed across the
wet desiccant to strip the moisture in the desiccant of the regenerating tower. In the case of an
external blower type dryer, the purge air is atmospheric air compressed by a blower and heated by
an external heater to strip moisture off a wet desiccant bed
Quick coupler
A coupling device that consists of a spring-loaded shutoff valve and a positive locking mechanism
used to connect tools, hoses and other accessories. Also known as Quick Disconnect
Safety relief valve
An automatic pressure-relieving device actuated by the static pressure upstream of the device,
which opens in proportion to the increase in pressure over the opening pressure
Saturated air vapor mixture
Is one in which the space occupied by the mixture is saturated with water vapor at the mixture
temperature
Saturated vapor pressure
Is the pressure existing at a given temperature in a closed vessel containing a liquid and the vapor
from that liquid after equilibrium conditions have been reached. It is dependent only on
temperature and must be determined experimentally
Saturation
Occurs when vapor reaches dew point or saturation temperature corresponding to its partial
pressure as a gas never becomes saturated with a vapor. However, the space occupied jointly by
the gas and vapor may be saturated
SCFM
Standard cubic feet per minute or flow of free air measured at some reference point and converted
to a standard set of reference conditions (e g , 14 4 psia, 80° F, and 60% relative humidity). CFM
means cfm at standard conditions, however, standards vary and some care is necessary. In the
United States, the usual standard is 14.696 psiA and 60°F. Some chemical engineers will use one
ATA and 0°C, but usually will be specific about the reference point. Europeans normally use one
ATA and 0°C. It is not the same to all people; therefore, it is best that the reference pressure and
temperature be definitely specified
Screw compressor
Is a positive displacement rotary compressor
Single stage compressors
Machines in which air or gas is compressed in each cylinder or casing from initial intake pressure
to final discharge pressure
Silica gel
A desiccant most commonly used in heat regenerative type dryers
Standard air
Air at a temperature of 68 °F, a pressure of 14 70 psia and a relative humidity of 36 per cent (0
0750 density) (as per A S M E however in the gas industry the temperature of standard air is
usually given as 60 °F (Unless specifically stated otherwise)
Temperature discharge
Temperature existing at the discharge port of the compressor
Temperature inlet
Temperature at the inlet flange of the compressor
Temperature intake
The total temperature at the intake flange of the compressor
Two stage compressor
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