Operators control and monitor centrifuge operation through a touch screen interface.
Monitoring these parameters enables operators to judge how well the material is being de-watered, and to monitor the solids loading of the machine. This constant monitoring is critical as the solids concentration can change throughout the day and week. Operations staff makes flow rate adjustments to the material fed to the centrifuge based on solids concentration to maintain optimal final biosolids quality.
The control system allows the operator to change the feed material flow rate, and the flow rate of the supplemental lime used to aid in de-watering. The operator enters flow-rate percentages via the HMI touch panel. The PAC adjusts the signal to the variable frequency drives (VFDs) to control pump speeds according to the flow rate values.
An RTD inserted through the bearing retainer and in contact with the stationary bearing race measures the centrifuge bearing temperature. A converter translates the RTD signal into a 4-20 mA signal. The bearings are pressure-lubricated by a lubrication unit. If the temperature rises to a preset level, an alarm sounds. If the temperature continues to increase, the centrifuge is shut down to prevent bearing damage.
A magnetic flowmeter monitors flow of sludge into the centrifuge. The HMI displays this flow rate, and the PAC totalizes the flow to provide per-shift production metrics. The operator adjusts the flow at the HMI touch screen, and the PAC in turn controls the pump speed via the VFD.
The PAC also monitors vibration. The Solids Operations supervisor and the maintenance staff review these data to determine when the centrifuge requires repair, extensive cleaning or overhaul. PAC alarm functions include bearing temperature, lube oil temperature, drive motor current, conveyor system status and lime addition.
