A client of Ai2SA oversees the management of key infrastructure distributed across South Africa, which includes the responsibility to create an environment that promotes a pleasant experience for its consumers. To do this, extensive use is made of large heating, ventilation and air conditioning (HVAC), systems which in turn requires a significant amount of municipal water as input for its cooling process.
Given the client’s vast geographical distribution across its sites, these systems are not under constant supervision and at times during the manual ‘top up’ and ‘drain’ processes, the operators would forget to close the respective valves, or valves would fail, both of which resulted in a significant amount of water being discharged to the drain, incurring substantial financial loses. The first system consists of seven cooling towers each with a nominal consumption of up to 500 litres per minute, which equates to a potential 30 kL per hour dumped to drain. At an average cost of R24 per kL, this equates to a potential loss of around R720 per hour. This excludes the reputational damage of not being able to provide the required quality of environment for consumers.
To overcome the wastage problem, flowmeters were installed and inlet (make up) valves automated using an industrial PLC, which is also used to visualise the process via the built in Web server. The solution is designed to monitor the drain flow rate and if a valve is detected as open for too long, the system isolates the valve and sends an SMS to the operator via a GSM modem connected to the Internet. Since the PLC is connected to the Internet, it allows for remote support of the complete system with built-in error escalation that brings problems to the facility manager’s attention.
The ROI of the system is around 30 days of lost water, which while it sounds like a lot, is only a few weekends where a few of the valves are left stuck open. The next phase involves automating the process further and linking all of the systems to a central portal for remote client management.
The main engineering lessons learned were to make use of a dedicated drawing tool meant for this type of work, not simply any drafting tool, and to consider using IO-Link protocol to connect instruments, specifically flowmeters, as this provides more information as well as saving on wiring. Ai2SA’s scope included all aspects from design to commissioning in conjunction with the client who supplied and installed the instruments.
Since the project was only recently commissioned and handed over, it is early to determine if the solution has achieved all the desired objectives. However, it is hoped that the benefits of using a Web-based IIoT system are clear irrespective, and that such systems will attract acceptance in due course. It is also hoped that the approach shared here may assist others in avoiding similar pitfalls.
The full project write up can be viewed at https://instrumentation.co.za/papers/J4335.pdf
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