13-18-601 Page 44
The AirSmart controller includes an algorithm that determines, in real time, and on the basis of the intake
temperature and the programmed target discharge pressure, the minimum discharge temperature the
compressor must attain in order to keep water vapor from condensing in the oil system. Signals from the
controller command the 3-way ball valve servo to rotate and mix hot and cold oil streams until the desired
compressor discharge temperature is achieved. Refer to Figure 5-4 for the dew point trends of the
compressed air at four typical pressure levels.
At startup, the mixing valve is on full bypass mode. As system heat load increases with ambient
temperature or load, the mixing valve sends more oil flow to the cooler to maintain adequate compressor
discharge temperature.
While the mixing valve is in its modulating range (between extremes of valve position), a compressor
discharge temperature deviation exc/- 10
°
F from the calculated value will trigger an alarm display
to caution that a system malfunction is taking place. Note that the alarm is not triggered once the valve
has reached either end-of-travel position, as oil mixing no longer controls the compressor discharge
temperature.
Pressure Dew Point Trend
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
30
40
50
60
70
80
90
100
110
120
130
Am bient Tem p - °F
D
ischarge PD
P -°F
100psig
125psig
150psig
175psig
Figure 5-4 – PRESSURE DEW POINT OF COMPRESSED AIR
OIL SEPARATION RESERVOIR
/
COALESCING ELEMENT
- This device serves multiple functions in
the compressor package:
•
Air/oil centrifugal separation
- The bulk of the liquid oil is separated, by change of direction,
impingement and additional centrifugal effects, away from the compressed air and aerosol streams,
and is then gravity-collected at the bottom of the sump.
•
Oil degassing and holding
- The sump has sufficient holding capacity to degas the oil mass before
it is drained off on its way to cooling, filtering and re-injection. It also serves as a storage volume for
the oil mass migrating from higher elevations (e.g., oil cooler, compressor casings, and piping).
