Pollan Dam is designed to treat and supply 13.5 MLD to the regional scheme network. The PLC upgrade is designed to work in conjunction with the existing treatment processes including:
- Screening of raw water at the abstraction point;
- Powdered Activated Carbon (PAC) dosing skid to address occasional taste and odour issues;
- Pre-treatment alkalinity adjustment;
- Tapered flocculation streams;
- Dissolved air flotation (DAF) streams;
- Post-clarification pH adjustment;
- Cross flow Rapid Gravity Filters;
- Oxidation of iron and manganese using chlorine produced by OSEC system;
- Disinfection using sodium hypochlorite produced by OSEC system;
- Sludge storage, pumping and dewatering.
The project scope undertaken by TES was to upgrade the current TSX57 Premium PLCs and TSX37 micro PLCs with new Scheider M580 PLC and Remote I/O units communicating across a new fibre redundant network to a new Wonderware Scada package.
The Scada package was installed in the site control room with 3 number local IPC Screens installed with individual runtime licences across the site at key operating points.
TES constructed all PLC, remote I/O and Scada systems on a test rack at our HQ to provide the client with a complete simulation test (FAT) of the automatic process. Due to the site being operational throughout the upgrade the simulation of the process is critical at the FAT stage to allow full testing to be completed prior to installing on site to limit the down time of the water works during the installation phase.
A wide range of site operational efficiencies have been achieved through:
- Replacement of the existing control and automation system to resolve ongoing operational deficiencies;
- Upgrade of individual premium PLC UPS’s;
- Minor process upgrade works;
- All associated mechanical, electrical & civil engineering works;
- Optimise Coagulation and efficiency savings.
In addition each supervisory PLC has a 2.2KVA UPS installed, fitted with a monitoring SMART card connected to the PLC for status information. The UPS will;
- Provide short term power to keep the PLC and associated hardware powered up during the automatic switching from ESB supply to generator supply;
- Allow for a controlled shutdown of all PLC and associated hardware across the plant in the event that there is a failure with the automatic change over from mains to generator supply;
- Maintain a stable supply to the PLC and associated hardware for a period of 30 mins.