Project definition
The client had initiated a contract to construct a new 500 NB (nominal bore) pipeline to supply potable water to the municipality from its pump station approximately 36 km away. The pipeline needed to transport this water into a reservoir approximately halfway along its length at a place called Midpoint. The Midpoint storage tank would retain approximately 10 Ml of water, which can gravitate to a reservoir of the same capacity at the municipality. Part of the contract was awarded to Autotronix to provide flow metering, instrumentation and control.
This project involved the installation of flowmeters, pressure sensors and level meters for the monitoring of flow and pressure along the pipeline, and tank levels at Midpoint and on the municipality reservoirs, as well as the remote monitoring of these parameters at the central control rooms.
The pipeline parameters flow, pressure and tank levels data, had to be transmitted by a GPRS telemetry link to two control rooms where it was displayed on the Wonderware scada for operators to monitor and control the water flow. This data was also made available to various subscribers.
There were a number of stakeholders in this project including the municipality, the client, the pipeline contractor, the civil contractor on the Midpoint reservoir and Autotronix on instrumentation. The coordination of the various contractors was handled by the client and all parties were required to meet a common deadline, which unfortunately commenced later than planned due to government intervention and therefore timeframes had to be accelerated. In spite of difficulties, all of the cited deadlines were met.
Project implementation
From the start, fortnightly project meetings were held and progress was continuously monitored. The client requested the Magflow meter to be installed in the pipeline and the concrete chamber built around it. This was not an ideal situation but was stipulated and necessary in order to ensure compliance with the government deadline.
Two Magflow meters were installed, the first at Midpoint and a second at the municipality. The client and Autotronix selected the Endress+Hauser Promag DN500 electromagnetic flowmeter for its inherent accuracy for billing purposes and long-term reliability. The meter was electrically isolated from the pipeline to avoid stray currents from influencing the sensors. The isolation is achieved with insulating sleeves and washers that fit around the bolts.
Electrical continuity and earthing in the vicinity of the meters was also maintained in order to prevent corrosion and electrical noise. On completion of the installation, the meter was checked and certified by Endress+Hauser personnel. A Modbus output from the meter was routed to a GPRS modem for transmission to a central control room. The transmitter also provided digital and analogue I/O for processing level and pressure signals, including alarms.
All process instrumentation was housed in an outdoor galvanised steel kiosk and particular attention was paid to unauthorised entry and frequent power failures. Microwave radar level transmitters were mounted on the roofs of the reservoirs and housed inside galvanised steel containers to protect from lightning and mechanical shock. Visual readings of flow in Ml/day, and reservoir level in percentages, are available inside the kiosk.
The client is extremely pleased with the final outcome of the project – a product of the highest quality in terms of excellence of engineering design and functionality. Training and operating manuals were delivered to the client to assist the maintenance staff when necessary.
For more information contact Roy Ward, Autotronix, +27 (0)16 422 7644, royw@autotronix.co.za, www.autotronix.co.za
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