Emerson VSG & VSSG Software Manual page 44

2.0 Control Action
2.1 The ball valve can rotate through a full 360° arc.
2.2 The actuator restricts the ball to a 90° arc of travel.
2.3 The actuator is powered (120V or 24V) all the time.
2.4 The position target signal from the compressor controller is a 4-20mA analog value.
2.5 There is no feedback position from the actuator.
3.0 Initial Position
3.1 With the electrical power to the valve de-energized, the valve is set to its initial position
by ensuring that the ball is in the closed position and that the actuator indicator
displays CLOSED.
3.2 When the electrical power to the valve is energized, the valve should rotate to fully
OPEN.
4.0 Operation
4.1 When initially installed, the ball must be in the closed position.
4.2 When electrically energized, if the compressor is not running, the compressor
controller will turn the valve fully open (100%).
4.3 When the compressor starts, the valve remains fully open (100%) until the oil injection
temperature rises above the control setpoint.
4.4 When the oil injection temperature rises above the control setpoint, the oil
temperature control valve will begin to close.
4.5 The hot oil from the oil separator begins to divert to the oil cooler, mixing the hot and
cooled oil flow streams together downstream of the oil temperature control valve. The
valve can fully close (0%) diverting the entire oil flow stream to the oil cooler.
4.6 As the oil injection temperature drops below the setpoint, the oil temperature control
valve begins to open so that the oil injection temperature does not become too cold.
4.7 When the compressor stops, the valve returns to fully open (100%).
5.0 Fail Position
The actuator remains in its last position when power is removed.
6.0 Screen Display
The oil temperature control valve, identified as "OIL MIX" on the main HMI display screen,
shows a numerical value with "%" as units. This is to be understood as "% OPEN." It is a direct
indication of the position of the ball valve.
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