With the help of systems integrators and telemetry equipment manufacturer, Prodesign, the Blyde Irrigation Board has installed a private irrigation network that stretches through the Blydepoort area from the Loskop Dam.
They chose an Adroit supervisory control and data acquisition (scada) system to monitor approximately 1500 points en route that were cleverly meshed together using telemetry and fibre-optic networks to ensure total communication.
Canal system inadequate
This export quality mango and tomato-growing region used to employ a ground canal system for water. But this method of irrigation proved unreliable. Natural predicaments such as cave-ins affected delivery. In addition, the area faced problems of how to bill for the water. To overcome this, local farmers formed a board supported by a monthly fee based on the size of their land.
New system
The board secured finance for the implementation of a new irrigation system from Rand Merchant Bank. The new system originates at Blydepoort Dam with steel pipes measuring over a metre in diameter and pressures of 1 MPa. As the system progresses away from the dam and through the auto pressure reducing system, concrete pipes are used instead of steel.
There are 70 major stations on the network and about 150 off-take telemetry stations. The major stations communicate via radio with the system master station at the board headquarters. Some stations use digipeating technology, ie, where the stations act as repeaters by relaying messages to other stations in the system.
The terrain makes it difficult for any type of communication. Off-take stations communicate with the major radio stations via a fibre-optic network. Utilising cable layering with the power lines needed for valve control and other functionality, made the fibre-optic network cost effective to install.
Within the system, the Adroit scada is used to monitor water pressures and flow rates at the 70 major stations. The scada continuously checks the system and provides an update of the whole network every two minutes. The system currently monitors valves and pressures to determine if there are pipe breakages.
Stable scada with realistic visualisation
"When conceptualising the Blyde River Project, we chose the Adroit Scada for its stability," says Peter Cherry, managing director of Prodesign. Standard Adroit graphics were used in a schematic representation that Cherry says looks very realistic.
Updating the massive 1500 tag point database in two minutes is quite an achievement over a radio network using standard analog transceivers. Prodesign was able to achieve this feat by writing its own OPC server that communicates between Adroit and the hardware.
Written in Delphi, the server is a mini Scada that keeps its own logs and databases while interfacing with Adroit. Databases and logs were not used on this project because the Adroit Scada package ships with its own.
The irrigation hub makes use of pressure probes and flowmeters by Vega Instruments.
Pressures are graphically represented on Adroit where the system operator is able to look at trends on the many valve chambers and can overlay the pipeline pressures flows, and other variables such as battery status on the irrigation system.
Trending reports are automatically generated on all pressure and flow rates, with flows being totalised by the telemetry stations and passed on to the scada. The Adroit reporting system also features a normal alarm and event page. Prodesign also made use of the scada's SMS alarming capability for instances when pressures measure too high or too low.
The company installed Adroit Version 5.2, which is running on Microsoft Windows 2000. There is one Adroit workstation at the Blyde area base camp and the system relies on the telemetry operating stations for pipeline maintenance.
The project was completed in September 2004 and took about seven months to re-engineer from top-to-toe. The next phase will see the implementation of remote control functionality for the valve components. A small programmable logic controller (PLC) has been installed at each off-take station for this purpose and will receive commands from the telemetry.
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