Few responsibilities are greater for a control system than the reliable running of a waterworks, as failure to keep the water flowing for 24 hours a day leads to expensive and awkward workarounds. However, one Danish facility has found a way to enable its personnel to monitor water quantity, pressure drops and salinity directly on their PCs.
The works in Ballerup, near Copenhagen, is in the middle of a modernisation programme that will see technicians provided with direct access to large amounts of data that, among other things, will allow them to check for leaks in pipes.
'We check the amount of water running between two wells and if the amount is higher the following night, the risk of a leak is very high,' explains foreman Erik Lyhne.
The Ballerup waterworks currently receives data from four measuring wells in the municipality, but this is to be increased to ten, making it possible to use the data for much more than just monitoring.
'We may be able to reduce the size of the water pipes because there is standing water in them,' says Lyhne. Water is not allowed to remain in the system for more than 48 hours, and it should be out after 24 hours.
'We have long suspected that some of the water pipes are too big, but now we'll find out for certain.'
Data sent via GPRS
The lack of efficiency of the existing plant was highlighted when PTA Electric carried out a controlled cutting-through of the communications cable between Ballerup water tower and the waterworks a few years ago. It was then that Ballerup waterworks and PTA Electric got together to find the most innovative solution to cover future needs.
Among other things, it was required that personnel should have access to any operative data even while on the road, which required a GPRS solution. Using a mobile network, they can connect to the secure virtual private network via a multiprotocol label-switching network at TDC (a leading provider of communications solutions in the Nordic region). However, they are not the only ones using the GPRS solution as it was impossible to connect a physical network to four of the measuring wells, so they send data via GPRS too.
PTA Electric opted for the Siemens Sinaut system for its data transmissions because it is capable of sending data via fibre optics as well as via GPRS.
'We chose Sinaut because we require a very high degree of data security,' says Kim Husmer, one of the three founders of PTA Electric. 'Sinaut ensures that the data is stored locally, which means we will not lose any data if the GPRS network should not work, or if TDC cut the cable. The Sinaut system has such a large storage capacity that, if it collects data every five minutes, it is able to store the data for a month or so with no problem.'
Two of the four wells transmitting data via the GPRS network are located under bikeways and, because the signal was not strong enough to be transmitted from the well, PTA Electric built two goose-neck pipes that stick out of the ground close to the bikeways. Antennas hang out of the necks of the pipes.
Husmer says that programming Sinaut was very simple. The result of the programming is very visible on the graphical user interface created by PTA Electric. Users are able to see models of wells and waterworks and to click their way through to the required information.
PTA Electric also made great efforts when it came to documentation. Until recently, no updated diagrams of the waterworks and the technical components were available, but now users are able to view diagrams of all the water systems from any workstation.
Previously, the waterworks was dependent on a few people's specialist expertise but everybody now has a clear picture of the interconnection and the functions of the various elements and maintenance has also become much easier.
'We had to find a method of communication everyone could live with, and had to meet security demands relating to the operation as well as to possible hackers,' says Husmer.
'For reliability reasons it is important to us that we use commercial, off-the shelf components. A waterworks must run constantly; our one experience of having to wait two weeks for components cost a huge amount of money in buying water from other municipalities,' says Lyhne.
Jesper Thomsen is promoter for Simatic Net with the Industry Automation Division of Siemens
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