The Background.

The Scottish Water site at Prestonpans is a combined sewage pumping station, this means it is responsible for transferring raw sewage and rainwater run-off from the local area, as well as a volume transferred from Cockenzie pumping station, to the pumping station at Levenhall.

Prestonpans pumping station was constructed in 1994 and utilised a SquareD SY/MAX PLC system with 5 remote IO racks and a legacy ProFace HMI. Due to the scarcity of spares, as well as the lack of programming devices, it was felt that a failure of any part of the system would result in lengthy downtime until a replacement part could be sourced, and if required, programmed. The client decided to upgrade the control system to the latest hardware in order to mitigate the risks.



The Client:

Scottish Water look after Scotland's most precious natural resource. From source to tap, they're trusted to keep Scotland supplied with world class water and care for the environment every minute of every day.

The Solution.

iTech engineers were engaged to develop the automation functional design specification, electrical schematics, network diagram as well as determining the existing functionality of the plant through thoroughly examining the current PLC program. The program had then to be rewritten for the new hardware using more efficient coding standards e.g. function blocks for commonly used code and user defined data types to allow for faster development and easier modifications to be made in the future.

Siemens were chosen as the automation supplier for both hardware and software for the upgrade. The PLC hardware selected by iTech centred on an S7-1513 due to its increased performance and memory capacity compared to the base model. This CPU utilises Profinet as the communication protocol, which is designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data under tight time constraints. Profinet ET200MP remote IO was selected due to the high channel density and low parts variance. As a result, ordering, logistics and spare-parts inventory are considerably simplified. In addition, the small footprint enhances utilization of control cabinet space. A Siemens SIMATIC HMI Comfort Panel was selected for the visualisation application. Siemens Comfort Panels are the first choice for solving complex HMI applications. They feature state-of-the-art technology, outstanding performance as well as integrated functionality and high-quality construction.

Siemens TIA Portal was used as the software development platform, this allows seamless configuration and integration of all of the automation components, from PLC to HMI and also allows configuration of the network switch and all of its security functions including firewall and VPN.

iTech performed iFAT, cFAT and SAT testing as well as on site IO testing and full commissioning activities within planned timescales.

The Benefits.

Latest hardware means that spare parts are now no longer an issue, any downtime will be at a minimum.

Standardised PLC / HMI software means any future updates, modifications or additions to the program can be easily made.

Remote access can now be implemented safely and securely due to the Siemens SCALANCE switch at the heart of the communication system..