The Auto Clean System is designed to eliminate the high cost of labor associated with continuously removing and cleaning of a pH sensor in coating processes. As a sensor becomes coated the ionic exchange between the reference cell and the liquid being measured becomes compromised. As the ionic exchange diminishes, pH offsets start to develop. If left unattended, the offset will increase significantly resulting in inaccurate pH readings. The sensor’s reference impedance diagnostic is a real time measurement that detects surface coating on a sensor. The Auto Clean System uses this diagnostic to trigger a cleaning cycle. A predetermined impedance value is programmed to activate a relay when the set-point has been breached. The sensor is then automatically retracted to the service position isolating the sensor from the process without disrupting the process flow or causing any pressure drops. Once the sensor is in the service position the rinse cycle will begin. The rinse cycle continues until the minimum impedance set-point is reestablished. The now clean sensor is re-inserted into the process automatically. Maintenance personnel no longer need to spend time doing tedious sensor cleaning to keep the pH measurement working properly. This modular system gives the end user the freedom to integrate any HART® capable Rosemount Analytical transmitter with either type of retraction mechanism, pneumatic or electronic.

The HART® system: The HART® system uses a HART® Interface Module (HIM) to activate the retraction of the sensor once a reference diagnostic set-point has been breached. The HART® Interface Module (HIM) not only supplies power to the transmitter, but monitors the reference impedance diagnostic of the sensor. The HART® communication protocol transmits the primary variables and all diagnostic variables to the bus. The HIM can then monitor the reference impedance from the bus. Once the predetermined reference impedance set-point has been breached a relay activates, applying the proper signal to remove the sensor from the process. Once in the retracted position, the flushing of the sensor begins. The flushing cycle stops once the reference impedance drops back below the pre-configured diagnostic set-point. At that point the signal is reversed and the sensor is then automatically re-inserted into the process.

The FOUNDATION™ fieldbus system: The FOUNDATION™ fieldbus system uses a Rosemount 848L Logic Transmitter to activate the retraction of the sensor once a reference impedance diagnostic setpoint has been breached. The 848L is programmed to monitor the reference impedance of the pH sensor and activate a relay to start the cleaning cycle. Once the Pasve valve has rotated the sensor into the service position the cleaning cycle will commence. The flushing cycle stops once the reference impedance drops back below the pre-configured diagnostic set-point. At that point the sensor is then automatically re-inserted into the process.

Pasve Valve - Pneumatic Actuation: The Pasve rotary valve provides safe extraction of the pH sensor from the process without the need to shut down the process or cause pressure or flow disruptions. The Pasve valve rotates the sensor into the service position and completely seals the sensor from the process preventing any cross contamination. The actuators of the Pasve valve are either electric or pneumatic.

GENERAL SPECIFICATIONS

Wetted Materials:	316LSS, PTFE, graphite (optional)
Maximum Temperature:	100°C (212°F)
Maximum Pressure:	232psig (16bar)
Cleaning Ports:	¼" NPSF
Compatible pH Sensors:	396PVP, 396P, 3300HT & 3300HTVP
Process Temperature:	-10 to 140°C
Inputs:	100 TO 240 VAC 50 W
Output:	24VDC 2.1A