At present in South Africa, boiler tube leaks are something of a ‘hot’ topic, as the country’s national power supplier continues to contend with various complex challenges – including that of boiler maintenance issues caused by, amongst other factors, boiler tube leaks.
This is not a uniquely South African issue, as the US–based organisation, the Electric Power Research Institute (EPRI), reports that power generation plants in the US and Europe have, ‘on average, around 6% loss of plant availability due to boiler tube leaks’ – a major loss factor for these facilities.
However, in South Africa, industrial solutions provider RTS Africa Technologies has an effective solution to the challenge of boiler tube leaks. This is in the form of a boiler tube leak detection system from UK-based principal Procon Engineering, a global leader in the field of acoustic leak detection, which invented the technology and introduced it to the world in 1974.
With more than 250 installations in over 20 countries worldwide, Procon Engineering can proudly claim more experience and success than any other company in the field.
This is according to Ian Fraser, Managing Director of the RTS Africa Group.
He explains that the benefits of the early detection of boiler tube leaks include the following increased operating profit, personnel safety, availability and tube life.
“In addition, early tube leak detection means unscheduled outages can be avoided or at least reduced; as can repair costs and secondary damage, with the attendant reduction in financial penalties and insurance costs,” he adds.
Commenting on how the technology works, Fraser says that Procon manufactures specialised ‘microphones’ – which bear little resemblance to conventional audio microphones. These microphones detect the very particular noise made by steam leaking from a boiler tube.
“The sound of a boiler tube leak has a particular frequency which Procon microphones are selectively able to detect. In itself, this is quite a technical feat, as the firebox of a boiler is a fairly noisy environment,” he advises.
The microphones are installed at the end of long steel tubes which target specific points in the boiler tube system. As high levels of soot are usually present in boiler fireboxes, as an option, the Procon acoustic detectors can also be fitted with an air pulse system which clears in the soot deposited in the tubes.
The operational importance of the Procon leak detection system is that it can detect small leaks before they become catastrophic failures.
“A leak in a boiler tube can start as small as a pinhole – and remain an undetected problem for an extended period of time. But, eventually, the size of this hole will grow to a point where the growing diameter of the orifice leads to a major tube burst. When an incident such as this happens, there can also be expensive secondary damage inside the boiler,” Fraser points out.
A further key advantage of the Procon system lies in the number of microphones installed in a boiler. For example, a typical power station might have as many as 24 of these Procon acoustic devices installed in a boiler. The output from the Procon microphones is fed into an IT- controlled display – each microphone being represented by a bar on the display. This shows the sound levels from each microphone inside the firebox. For record-keeping purposes and system analysis, it is possible to print out the data from a Procon system.
When the leak occurs, the microphone nearest to the leak will display an elevated bar level. What is particularly useful is that other microphones in the area will also pick up the noise.
“Power station technicians are then able to look at the computer display and – judging from the varying sound levels from the microphones – predict with some precision where the leak is occurring,” he says.
For boiler maintenance teams, this is most helpful, as even during physical inspections of the inside of a boiler and its tubes, a pinhole size leak can be difficult to detect visually. However, with the evidence from the Procon system in hand, technicians are aware that there is a leak and then can search for it until it is found in the shortest possible time.
What the Procon detection system also allows is for power station technicians to assess the seriousness of a particular leak. Depending on their assessment of the extent of the leak, it is possible to plan a scheduled boiler maintenance shutdown so that the impact of the downtime is minimised.
In South Africa, Medupi and Kusile power stations both employ Procon tube leak detection system; and RTS Africa installed a complete Procon system on the six boilers at Arnot power station some years ago.
“Compared to the cost of a boiler failure in a major power station, the cost of the Procon system is minimal,” continues Fraser, adding the proviso that the system becomes increasingly cost-effective on larger boilers of 200 MW capacity and more.
“The Procon system has been designed not only to serve power stations; but also the host of boilers used in the broad spectrum of industry,” Fraser explains. “With boilers which might service manufacturing or production environments, prevention of major failures will also assist in the avoidance of punitive financial penalties, and ultimately bring about a marked improvement in the company’s bottom line,” he concludes.