PACE Zenith Awards 2014: Best Fieldbus Implementation
sponsored by Beckhoff
WINNER: UGL
Project: Eastern Tertiary Alliance
Built in 1975, the Eastern Treatment Plant (ETP) in Bangholme, south-east of Melbourne is the largest activated sludge wastewater treatment plant in the southern hemisphere, and processes over 40% (700 Mega litres per day) of Melbourne’s sewage in the service of approximately 1.6 million people.
Effluent from the plant was historically treated to Class C recycled water quality (secondary effluent with chloramine disinfection). The Class C water serviced a range of re-use customers and the remaining flows were pumped to a near-shore ocean discharge point at Boags Rocks on the southern Mornington Peninsula.
With the upgrade of the tertiary treatment, Melbourne Water has been able to significantly improve the quality of water discharged to the marine environment and at the same time produce high quality Class A recycled water.
The treatment process includes Ozone dosing, Biological Media Filters plus UV and Chlorine for disinfection. The project included the design, construction and commissioning of the ATTP. In March 2010 Melbourne Water entered into an alliance agreement with four private sector partners which formed the Eastern Tertiary Alliance.
UV reactors in operation at Melbourne's Eastern Treatment Plant
The organisations were UGL, Melbourne Water, Baulderstone, Black & Veatch and KBR.
The objective was to provide Melbourne Water with a control system that combines robustness and high availability to be able to operate under demanding conditions in a 24/7 environment.
For seamless integration with the existing plant, the Siemens PCS7TM platform was selected for the new plant. The plant required a reliable control system for high availability and to deal with the enormous amount of data communicated over the plant networks.
Several fieldbus/network technologies are utilized around the plant, including Ethernet, Profibus and HART.
Two fibre optic ring networks are installed for Ethernet communications:
- PCS Data LAN. All the Operator Workstations, Engineering Workstation, Historian Server, Backup Server, Printers and two HMI Servers, operating as a redundant system, are connected to this network. It also provides the interface to the servers at the existing plant thus enabling viewing and control of both plants from all locations.
- Control LAN. This network is the backbone for the control system and allow for high speed communication between the plant PLCs and vendor equipment like the Ozone Master Control Panel, UV Master Control Panel and VPSA Control Systems. The two HMI Servers mentioned previously collect data and relay control signals to and from the control systems. The managed Ethernet switches in the Server Rooms provide connections to the existing system.
The managed Ethernet Switches in each network are operating at 1000Mbps.
Plant inlet and tertiary supply pump station
With an already high level of redundancy provided by utilizing ring networks for Ethernet, the control system needed an extra level of redundancy to cater for high availability of the plant.
Therefore each plant PLC was designed to have redundant processors with Ethernet and Profibus interfaces. Each plant PLC Profibus Card (configured as master) is linked to a fibre optic network through OLMs (Optical Link Modules). Connected to the OLMs are DMKs (Distributed Marshalling Kiosk), installed in each plant area to house remote I/O racks.
Field instruments, valves, level switches etc are connected to the IO modules in the DMKs. Each remote rack is equipped with dual Profibus (configured as slave) cards for communications to the Profibus master. All VSDs are controlled over the Profibus network and utilise a Y-Link for connection to each of the Profibus networks in the PLC.
Size and complexity of the plant were a major challenge for the Alliance team in every step of the way. Starting with the design, the control system architecture was thoroughly reviewed and checked by both the design team and the client to ensure nothing was left out.
[Pictured alongside is BMF overflow]
Timing of the project was crucial in terms of meeting the deadlines for commissioning.
The UGL Specialist System Integration team consisted of six (6) engineers working on site to allow for easy and early involvement in design decisions, interaction with the client and the design team and access to all available resources.
A divide and conquer strategy was used to tackle the complex implementation of the control system. For the control system for example, several teams were formed to test and commission certain areas of the plant.
For a successful implementation of any fieldbus technology and more specific Profibus, it is critical to have the right skills.
It all started with the design of the Profibus networks and consideration was given to the number of nodes per network, the speed of the bus, number of repeaters, amount of data to be exchanged and the cable runs. The Profibus networks were designed by certified Profibus Engineers.
Individual Profibus networks are linked back to the PLCs through optic fibre cables. The success of a fibre optic installation depends on the skills and equipment used by the installer.
A licensed fibre optic installer was called to the site for splicing of the fibres and testing of the network to ensure all fibre connection losses were within limits.
A full test report was issued to detail the optical losses for each fibre.
Once all the Profibus cabling was completed and power was available, certified Profibus Engineers carried out the commissioning of the networks. With the use of Profitrace (oscilloscope for Profibus) they were able to quickly commission the network and iron out any issues such as the lack of termination.
Because of the high quality craftsmanship on site, only minor problems with Profibus connectors were found which were easily rectified.
Aerial view of the ETP
The ETP Tertiary Upgrade Project has delivered a world class treatment facility producing Class A water fully complying with the requirements of the Department of Health. The design and method of control system delivery has considerably contributed to this success.
As well as meeting the quality objectives, the project also achieved successful operational outcomes, fully automating and integrating the Eastern Tertiary Treatment Plant.