The Bulk Water Department of the City of Cape Town (formerly the Cape Metropolitan Council - CMC) is committed to increased automation of its installations to reduce costs and waste, thereby improving efficiency and assuring sustained high treated water quality. It chose the Adroit supervisory control and data acquisition (scada) system on which to standardise for its ease-of-use and local support.
The Adroit scada is installed at all nine of the city's water treatment plants and two major pump stations. These installations range in capacity from 3 to 500 megalitres per day and supply water to the city of Cape Town and neighbouring local authorities.
In 1994, the Faure Water Scheme operations needed an automation application to replace the legacy MultiT Link that was no longer meeting its requirements. Faure is the largest and most modern of the City's treatment plants. Of the nine, it is the only site that is almost completely automated on Adroit. Rocky Fyfe, area manager for the City's East Area of the Bulk Water Department, estimates the plant's automation to be at 90%.
At other smaller operations like Constantia Nek, the Adroit scada currently controls the chemical dosing systems. As money becomes available and the city gains in system expertise, it adds more automation and functionality to the sites. At Blackheath, for example, the scada was only controlling the filter backwashing sequence but now also controls all chemical dosing systems. The Firlands pump station, which transfers water from the Palmiet River and Steenbras Upper Dam to the Faure Water Treatment Plant, is also controlled by an Adroit scada, as is the Melkbos pump station.
"We are in a continual sequence of automating various processes," says Fyfe.
The business benefits of which he says are two-fold: one, to keep up with technology; and two because the city faced staff restrictions as the municipality began to cut costs. The Bulk Water Department has standardised on the Adroit scada. Fyfe says that the local support is a big advantage and that good systems integrators such as Rob le Roux of Spectrum and Woolley Cameron provide outstanding service and maintenance.
The Department is currently running on Version 5.02 and is in the process of upgrading to the latest edition. It is on a Windows NT operating system with a possibility of going to XP or higher and is also moving from Microsoft Windows 2000 to 2003.
The municipality has also chosen to standardise on Modicon PLC and Modsoft as the engineering/application tool for programming. At Steenbrus, Faure and Blackhealth Water treatment plants the PLCs are linked to the Adroit scada via fibre-optics or hard wiring depending on the remoteness and distance. In some instances telemetry is used. At the smaller plants some Samsung and Telemechanique PLCs are in use.
The largest of the waterworks, Faure and Blackheath, both boast unlimited tag point Adroit systems, while the smaller sites enjoy 750 tags. Each site is a standalone installation, with the exception of Faure, where information from the pump station is fed via radio link back to the head office. The reservoir network is also equipped with telemetry to supply the central headquarters with information on water levels and flows. Most of the bigger works run on the hot standby system, with master one and two machines where the second machine automatically updates and takes over should the first machine fail.
Fyfe lists the benefits of the Adroit scada for the operator, as being the one touch access, easy user interface (UI) and its trend tool offering and diagnostic factor. From a developer point of view, he says that the onsite design capabilities are an advantage, and that with training; the user can develop his own UIs. The UI is composed entirely of Adroit graphics with some scripting to do with the screen functionality and on the engineering side.
Adroit is linked via a database to chemical reporting software that sits on an administrative machine. Adroit fetches information from Microsoft Access that is used to poll certain tags and to gather information that is exported to the Microsoft application when the machine is switched on.
Trending
The Bulk Water Department uses the scada's trending function to monitor and record water chemical dosages, pH levels, flow rates, and water levels. Historical trends are also analysed to detect and trace any plant problems. Performance of the process and the process controllers is also monitored with the system. For example, by trending the pump current consumption, the city can plot a curve and trend pump heating. This information can be used to gauge performance and predict maintenance cycles.
Alarms
Alarming is ubiquitous and is used to warn operators if a process goes out of its pre-set parameters, these include notifications of high and low water levels, water flows, chemical tank storage levels, dosage-pump dosing rates, chemical dosage ranges, pH levels and conductivity levels. Daily and monthly standard shift reports are drawn from the scada to monitor all dosages and flows. Fyfe says, "Everything that was previously logged manually is now drawn from Adroit."
For more information contact Megan Davidson, Marketing, Adroit Technologies, 011 658 8100, [email protected], www.adroit.co.za
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