Water supply automation via Profibus
23 Jan 2007
To this end, Water Corporation has been implementing Profibus DP and PA networks for over four years in both water and wastewater treatment plants. Profibus will become an integral part of its planned networking of all the metropolitan water treatment plants over the next five years.
As Dennis Yovich, Principal Engineer, Electrical, in the Water Corporation Mechanical and Electrical Services Branch, commented: “We chose Profibus because we wanted a fieldbus technology that would enable us to optimise our management decisions, and support our long-term aim of networking our major plants - initially in the Perth area, and ultimately, across the whole state.”
As Western Australia’s many water treatment plants - plus over 980 pumping stations - are spread across 2.5 million square kilometers the company needed to maximise the information obtained from these remote sites, continued Yovich.
“Measurement and control equipment is becoming more sophisticated, there are less and less people available in the remote sites, and the time and distances to reach some of the plants are excessive. In the event of a problem, we firstly need to know that a problem exists and then we need to access the problem area to analyse what has to be done, who has the necessary skills, and what spares and equipment are required should our tradesmen need to travel to site,” he said.
Profibus enabled centralised maintenance staff to remotely re-range a flow meter, to understand the precise nature of the service required by a distant analyser unit used for the chlorination and dosing of the potable water distribution network, or to be alerted to a faulty gas leak detector.
Flow instruments needed to be re-ranged regularly due to the wide variation in seasonal demand for water, where output rates can swing between from 0-500 ML/day to 0-50 ML/day. Seasonal re-ranging of flow meters was crucial for better resolution, particularly for example to improve accuracy of chlorine dosing and thus ADWG (Australian Drinking Water Guidelines) compliance.
The latest part of the Water Corporation intelligent network using Profibus is the new AU$28 million Water Corporation owned Kwinana Water Reclamation Plant (KWRP). This is not only Australia's largest municipal wastewater reuse plant, but also the site of the country's most comprehensive application of the Profibus to date.
For KWRP, John Holland Engineering was contracted to deliver the project and they engaged Veolia Water to undertake the process design and commissioning of the plant: electricals and instrumentation were contracted to PCT, and maintenance is handled by KBR Water Services, the maintenance provider for the Water Corporation.
Dennis Yovich explains the particular advantages of Profibus at KWRP as follows: 'The integration of digital I/O, utilising ASi-bus, in the Profibus world - such as alarms, chlorine gas leaks, chlorine residual, low level alarms, empty pipe detection - is exceptional.
“We use ASi-bus combined with Profibus PA, making all analogue measurement - such as flow, temperature, pressure, level - and digital switching, completely homogeneous. This homogeneity is a unique advantage of the Profibus system, and makes so much more data available,” said Yovich.
“The more information we have, the better management decisions we can make - enabling us to boost our management and maintenance efficiencies in unprecedented ways, optimise our processes and, ultimately, to pass on big savings to end-users.
“For the network automation to be successful, it is critical that an operator in the Leederville control centre can perform detailed diagnostics of any instrumentation or control problem across the plants and the distribution network, and then decide what action is required. Having Profibus in operation on the plants makes much of this possible,” Yovich concluded.
