AOpen DE7200 Series Betriebsanleitung PDF herunterladen (Seite 49)

OPERATING INSTRUCTIONS

30 Sep 13 4-11

DE-7200VFDCentrifuge

To adjust pond depth, proceed as follows:

WARNING! DO NOT OPEN COVER OR ATTEMPT ANY ADJUSTMENT OR

MAINTENANCE ON THE CENTRIFUGE UNLESS THE BOWL IS AT A

COMPLETE STANDSTILL.

1. Shut down, lock out, and tag out the centrifuge using the Normal Shutdown procedure

described later in this section.

2. Remove access plate from the inlet side of the case cover.

3. Loosen screws securing the weir plates (Figure 4-4), move the weir plates to the required weir

opening size, and re-tighten screws to torque specified in Section 5.

4. Set all six weir plates to the same diameter.

5. Re-install access plate on case cover.

Figure 4-4. Weir Plate Adjustment

Differential Speed/Conveyor Torque

Generally, a faster conveyor speed results in lower conveyor torque, as solids are discharged

faster and usually wetter. Reducing conveyor speed must be done slowly and cautiously, allowing

steady-state to be reached before further reduction. Slower conveyor speeds permit solids to

remain in the bowl longer, which can permit solids to accumulate in the bowl if the input rate

exceeds the discharge rate. Therefore, the torque must be monitored to prevent overload.

Operator settings for maximum flow and torque limit determine operating limits for the centrifuge.

In flow priority mode, if feed conditions cause the flow rate setting to result in a higher torque than

the Input Torque % Limit setting, the control system will automatically switch from flow priority to

torque priority mode. The centrifuge will then continue operating in torque priority mode until the

operator resets to flow priority mode by clicking on the Input Max GPM cell of the Operation

screen and changing the flow rate.

At certain conveyor speeds the drive motor must reverse direction to accommodate the

differential speed relationship with the bowl. If this occurs, the centrifuge control system

automatically assumes control of the feed pump to reduce its flow rate. The message, Automatic

Flowrate, appears on the Operation screen to alert personnel that the feed pump is under

automatic control. When the reduced feed rate is reached, a 20-second timer is started. This

delay protects the conveyor drive from overload as the motor changes direction. Upon expiration

of the timed interval, the new conveyor differential speed is applied. The pump feed rate returns to

the previous rate when the new differential speed is reached. Manual control of the feed pump is

then restored. This action releases the feed pump from automatic control and clears the

Automatic Flowrate message from the screen.

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AOpen DE7200 Series Betriebsanleitung Seite 49