When Sasol’s Secunda power plant in South Africa was looking for ways to improve productivity and maintenance responsiveness, it approached remote monitoring experts, Omniflex, for real-time monitoring of its electrostatic precipitators (ESPs) across 17 substations. Omniflex provided hardware solutions and consultancy to enable full visibility and data flow to the control room, improving operational efficiency, reducing downtime and modernising ESP oversight.
Sasol’s Secunda is one of the largest synthetic fuel plants, with 136 electrostatic precipitators, a form of electrostatically charged plates, distributed across large multi-storey boiler buildings on its East and West plants. Electrostatic precipitators are used to remove dust from flue gas in coal-fired steam generation.
The challenge
When boilers burn coal, there is a need to get rid of the ash that is forced into the electrostatic fields of the precipitators. The electrostatic precipitator panels charge wires inside the precipitators, inciting polarity in the ash passing through and causing it to be attracted to the plates of the precipitators.
The plates shake periodically to dislodge the ash before it is collected. If these are not working properly, the ash is not electrostatically charged and therefore not removed, leading to a reduction in boiler output.
To address this, Sasol identified the need for alarm equipment to alert the control room when the panels were full. To investigate if the panels were full of ash, Sasol personnel previously had to do manual inspections across the 17 substations to identify if there were any issues, a time-consuming process. In addition, an inability to remotely detect faults slowed maintenance and reduced ESP time.
Maintenance electrician, Johan Oosthuizen suggested that motors, auxiliary equipment, panels and alarms should have monitors providing wider visibility of the plant. “As well as the alarms we wanted to look at voltage, current, analogue signals and trip status of auxiliary systems. These are all important operating conditions of electrical panels,” explained Oosthuizen.
The proposed solution
Sasol was looking for something simple to implement, with proven reliability at a manageable cost. While Sasol handled system design and human machine interface work in-house, Omniflex provided consultancy on network architecture, hardware and the equipment that would be required. Sasol wanted a hardware solution to monitor the status of each substation reliably. The distances between substations and the control room involved approximately 1 km of cabling. This could easily be covered by Omniflex’s CONET protocol, which can bring field data back to a control room or supervisor’s office in a cost-effective way, covering distances of up to 10 km.
Omniflex supplied its Maxiflex modular rack system, a process automation controller that allows the user to choose their I/O and bring in the data. Approximately 64 analogue inputs and 96 digital inputs are required for each network node. Maxiflex nodes can support 15 I/O modules, which can accommodate up 960 points for monitoring. After it is plugged into the system, it automatically registers the presence of modules and processes their data into the Omniflex Data Interchange table for the Conet Network to access.
“We’d already proven the reliability of our Maxiflex systems in other departments at Sasol, so they knew they were getting trusted technology,” explained Ian Loudon, head of international sales and marketing at Omniflex. “The scale of the project – with over 130 panels and thousands of data points – was ideal for our architecture. With CONET and Maxiflex, distance and volume were not a problem.”
Results
With a new system in operation, Sasol’s plants no longer required manual inspections. Previously, 48 field controllers had to do checks every morning, whereas now, one person can observe remotely from a control room. Instead of the five hours it took previously, Sasol personnel can identify problems within five minutes, spotting errors earlier and freeing up staff to perform other tasks.
In addition, the data acquisition builds up a bank of historical information where trends can be identified to detect if panels are underperforming, allowing Sasol to take preventive action, leading to less downtime and a more efficient process. Maintenance technicians can see a panel’s status and every trip and signal from the control room.
This monitoring has led to the implementation of a standardised system across Sasol’s East and West plants, providing full visibility across every substation with an upgraded alarm and trip detection system for electrostatic precipitators.
“I’d rate the project a nine out of ten. It’s doing exactly what we wanted. My bosses are happy, which means I’m happy too. What impressed me most was how helpful and responsive Omniflex were. Even though they weren’t on site, we always got the support we needed,” Oosthuizen concluded.
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| www: | www.omniflex.com |
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