Intelligent engineering and systems puts Unitied Utilities ahead

When upgrading its Ingleton water waste treatment works United Utilities, one of the UK’s largest utility companies, took the opportunity to install an integrated intelligent control and monitoring solution to simplify the control, improve maintenance and provide increased facilities for remote monitoring. With the emphasis on increased communication, the traditional reliance of process controllers on telemetry alarms to warn of plant failure are replaced by plant status using Internet Explorer. This ability to view the status of the plant remotely allows for more frequent checking and earlier warnings of failure or the opportunity to reset the plant without the need to always visit the plant.

To underpin such as radical approach United Utilities chose to base the systems on the capabilities of Totally Integrated Automation from Siemens. This allowed the system integrators to meet the users requirements with both a simplified control system and increased functionality

However a good the technology United Utilities had clear ideas about how the system would lead to better operation and improved management of the facilities. The system’s user requirements were uncompromising:

  • Operational security must not be compromised in the event of a single point of failure
  • Internet Explorer access to facilitate remote access to Human Machine Interface (HMI) graphics pages
  • Status and diagnostic data from each field device shall be made available for remote control and monitoring
  • System cost not to exceed a conventional installation, preferably to show a cost reduction
  • An Ethernet gateway into the network was required for the Telemetry outstation
  • Remote configuration of instrumentation should be possible
  • Cyclic real-time communications were required from field devices to PLC.

To meet the specification Siemens and its system integration partner needed to provide the right level of intelligence. A single Motor Control Centre (MCC) controls the works using a Siemens S7- 400 series PLC. This includes an Ethernet communications processor for remote monitoring and control. Site-wide Profibus-DP and PA networks serve intelligent motor starters, process instrumentation plus actuated valves and penstocks. In all, the site has six Profibus networks. Two process areas both with two treatment Streams have dedicated PROFIBUS DP and PA circuits. The DP circuits being connected to process valve actuators and magnetic flowmeters and the PA circuits being connected to a range of level, flow and pressure instrumentation. In addition the second process area has one Intrinsically Safe loop and one remote I/O Rack.

At the MCC one Profibus DP network serves the “duty” drives, the second DP network serves the remaining “standby” drives plus an I/O rack for some hardwired backup instrumentation. Remote I/O racks serve field devices to reduce cabling. Siemens Simocode intelligent motor starters or variable speed drives control 22 motors and there are 13 analogue process readings (via PROFIBUS) and 27 actuated valves.

The MCC has a radical appearance since most of the operator interfacing is through a duplicated Siemens OP370 Human Machine Interface (HMI). The operator can also access the plant status pages using Internet Explorer on any PC with an Internet connection. This is in addition to monitoring through United Utilities’ dedicated telemetry outstation reporting to its regional Operational Response Centre. HMI graphics include depictions of traditional starter faceplates as well as process mimics alarms and trends. Data logging is to the integral flash memory card. In the event of PLC failure motor starters can be operated independently using the dedicated operator panel to provide limited status, reset and start/stop capability.

With such intelligence across the plant the benefits are definable. Operators now have better access to a range of information. For example an operator can remotely start, stop and reset a motor, view its running history or see its phase currents and trends. Such control and monitoring is not restricted to motors, across the range of instruments and actuators operators can see fault codes, upload control parameters and transmit digital information around the plant or to the Operational Response Centre.

Return on Investment

The design of the plant also looks to the future. The Ethernet connection into the PLC will also enable much greater amount of plant performance historical data to be gathered and archived to a remote server. Provision of detailed time and date stamped operating histories trends and alarms will in the future enable better management of maintenance and quality. Uploading of PLC software modifications or instrumentation reconfiguration will mean that sites can be upgraded without the need to visit. IP based web cams will