Until now the only options for measuring filter bed expansion during backwash were homemade devices or expensive fixed mount, echo-time measuring systems. The new Raven m edia expansion system offers an affordable solution. Th esimple, two-part system includes Raven's infrared interface detector coupled with the expansion measurement arm. Lightweight and rugged, the system can easily be transported throughout the plant.
The measurement arm is mounted to the filter railing (round or square) with a non-marring clamp. The pully at the top of the arm allows for easy deployment and retrieval of the sensor. The sensor drop point can be extended up to 3' from the rail. A pivot point allows the operator to rotate the probe in a semi-circle to verify uniformity of expension at multiple point.
Prior to backwash, the flat bottom sensor is lowered to rest on the top of the media bed. With the cable taut, it is fastened to the slidng marker block. The sliding ruler is positioned so the marker block is on zero determining the reference point. When backwash begins, the sensor will react to the turbidity and debris escaping the bed with illumination of all 20 LEDs on the face of the meter. After the turbidity has been evaculated, the operator slides the marker block with sensor cable away from the filter to raise the sensor to just above the fuildized media - all LEDs on the meter will go out determining the top of the expanding media bed. The operator can lock the sliding marker at this point allowing the expanding media bed to catch up to the sensor. This repeated until the media has fully expanded allowing determination of the top within 1/4 of an inch.
Upon settling, the filter bed should be at a lower level than before the backwash. The probe can be lowered back to the top of the bed while moving the marker block toward the filter chamber. A negative reading on the scale verifies the bed has settled to a lower point.
The media interfacte detector includes a 30' cable and sensor assembly. Other lengths are available. Order the measurement arm with clamps for 2-1/4" round or 3" square rails. 1-year warranty.