The solution involved the development of a comprehensive control system for the Settler and Clarifier, which are key components of the sludge dewatering and effluent treatment process. The control system was designed to operate both locally and remotely, incorporating necessary interlocks and safety functions.

Electrical, Control, and Instrumentation (EC&I) Aspects

1. Control System Architecture:
   • The control system is based on a Rockwell (Allen Bradley) CompactLogix L3 PLC system, which manages all operations, interlocking, and event alarming related to the Settler and Clarifier equipment.
   • Operator interfaces are provided via Rockwell PanelView Plus 7 HMIs, located at various control panels for local and remote operation.
2. Electrical Service Requirements:
   • The system requires a 400V 3-phase supply, with various control panels (CP/13501, CP/13502, CP/13701, CP/13801) housing the necessary power distribution and control equipment.
   • Power supplies to motors are protected by circuit breakers with overload protection, and all electrical equipment meets IP55 requirements.
3. Local and Remote Control Panels:
   • Local Control Panel (CP/13501): Houses the main PLC, power supplies, and motor control equipment. It includes a 15” HMI for local operation.
   • Remote Control Panel (CP/13502): Located in the control room, it features a 15” HMI for remote operation.
   • ESST Local Control Panel (CP/13701): Manages the ESST skid with a 6.5” HMI.
   • Dosing Local Control Panel (CP/13801): Controls the dosing skid with a 6.5” HMI.
4. PLC and I/O Configuration:
   • The PLC system includes various input/output modules to handle analog and digital signals from field devices.
   • Point I/O modules are used for remote I/O connections, ensuring efficient data communication and control.
5. Network and Communication:
   • The control system network is based on EtherNet/IP technology, utilising Rockwell Stratix 5700 managed network switches for reliable communication.
   • The network design ensures seamless data flow between the PLC, HMIs, and other control devices.
6. Human Machine Interface (HMI):
   • HMIs provide intuitive control and monitoring of the system, with screens for manual operation, semi-automatic sequences, interlock status, alarms, and system management.
   • Security levels are implemented to restrict access based on user roles, ensuring safe and controlled operations.
7. Safety and Interlocks:
   • The system incorporates a master emergency stop system, with dual-channel inputs and safety relays to ensure safe shutdown in case of emergencies.
   • Interlocks are implemented to prevent unsafe operations and ensure the system operates within defined safety parameters.