Emerson Vilter PLC, Operation Manual

Page: 26 / 118

2 – 8
Section 2 • Operational Descriptions
Blower Package PLC Operation Manual •Vilter/Emerson • 35391BLP
WATER COOLED GAS AFTERCOOLER
If installed, the water-cooled gas aftercooler is a heat ex-
changer that uses a modulating valve to control cooling
water
fl ow to remove heat from the gas discharged by
the blowers. The valve position is adjusted to control the
amount of cooling done by the aftercooler.
A PID controller adjusts the opening degree of the
modulating valve to maintain a desired temperature at
the outlet of the gas aftercooler. When the aftercooler
outlet temperature exceeds the desired pressure plus a
deadband, the valve will open further to add more cool-
ing. When aftercooler outlet temperature drops below
the desired temperature minus a deadband, the valve
will begin to close.
• When the blower package is stopped, the valve will
be commanded to 0% open (full close).
• When the blower package is running and the af-
tercooler out temperature rises above the “Open
Valve At” setpoint in the “Water Cooled Aftercooler
Setpoints” screen, the valve will open to a settable
minimum position.
• When the blower is running and the aftercooler out-
let temperature is above the deadband, the PID con-
troller will increase the valve opening degree.
• When the blower is running and the aftercooler out-
let temperature is below the deadband, the PID con-
troller will decrease the valve opening degree.
Figure 2-5. Operational Diagram - Water Cooled Gas Aftercooler