In the past two years, power service systems and solutions provider Clyde Bergemann Africa has placed special emphasis on strengthening its aftermarket service offering to the local power industry, aftermarket service executive director Badrish Nathoo tells Engineering News.

“This is particularly important for South Africa, as State-owned power utility Eskom operates an ageing fleet of power stations, which requires a significant amount of regular maintenance to ensure it remains operational,” he emphasises.

Clyde Bergemann provides Eskom power stations with soot blowers to keep the boilers clean when in operation.

“Soot blowers use steam to clean the heating surface. Steam is used to clean the boiler tubes to prevent thermal blanketing occurring in the system,” Nathoo explains.

He adds that the company is also installing water lance blower systems at the Medupi and Kusile coal-fired power stations, in Limpopo and Mpumalanga respectively.

Clyde Bergemann business development executive director Jeremy Kirsch says the water lance blowers use water at ambient temperature to clean ash deposits off the heating surfaces.

“Water lance blowers are only used in the furnaces of boilers. It was originally developed to clean the walls of boiler systems, which had experienced extreme ash slagging after different coals were used in the 1990s in Europe and the US. When the jet of water passes through the furnace, it changes its form from a solid jet to a stream of finer water droplets. These droplets penetrate the layer of ash on the boiler wall and, as a result of rapid expansion as water converts to steam, the layer of ash is broken down,” he explains.

Kirsch adds that the blowers use low-quality water that power stations either discard or treat at a cost and which would eventually have been transferred to the power station’s ash dam.
“One water lance blower can replace at least 15 steam-based wall blowers, reducing the maintenance and spares requirements,” he states.

The Clyde Bergemann system uses heat flux transmitters embedded into the heat transfer pipes to supply heat transfer rate information into the Clyde Bergemann SMART Clean technology system.

“This allows our system to accurately pinpoint the areas which need cleaning and prevent clean areas from being unnecessarily cleaned,” Kirsch explains.

The water lance blower modules are complete with drive motors, lance tube, sealing and cooling air supply, a fast opening and closing valve, as well as a pumpstation and control system.

Further, Nathoo notes that the purpose of efficient onload cleaning maintenance is to clean only when and where necessary.

“Continuous cleaning operations on clean tubes could be detrimental to the boiler, as they could cause surface damage, and subsequent failing, of the tubes.”

“Maintenance of the cleaning devices is also important. The equipment must be lubricated according to original-equipment manufacturer requirements and maintained accordingly. The quality of the lance tube must be inspected to ensure the steam is flowing well. Defective or worn nozzles could cause the boiler tubes to fail, resulting in the boiler having to be shut down,” Nathoo warns.

He says that the feed tube, which is used to transfer the steam from the supply pipework, should be checked for scouring on the sealing surface, as a defective feed tube could lead to steam waste and system failure.

Tutuka Power Station

Clyde Bergemann was awarded a short-term contract by Eskom in September last year, which ran to the end of May this year, to under- take the maintenance of the soot blowers at the Tutuka power sta- tion, in Mpumalanga, on a daily basis.

A further contract was issued to the company for the outage maintenance of the power station’s dust handling plant, which collects the pulverised fuel ash that the plant produces in the process of generating electricity.

Kriel Power Station

Clyde Bergemann has been carry- ing out maintenance work for Eskom at the Kriel power station since January 2011.

“The Kriel power station ranks as one of the most challenging environments in which Clyde Bergemann Group has installed the water lance blower system. The design of the station and its boilers is unique; therefore, the only place where the blowers could be mounted onto the surfaces of the boiler was between the boilers’ pulverised fuel burners, which can reach more than 100 °C,” Kirsch points out.

He adds that, in addition to the boiler room being an extremely hot area, the pulverised fuel pipes erode and leak over time, which results in the boiler room section of the power station being covered in a fine coal dust that can negatively impact on equipment.

“Therefore, regular maintenance, repair and replacement of the water lance blower system is undertaken by Clyde Bergemann to ensure the power station remains opera- tional,” Kirsch notes.

Nathoo adds that the company has a fully equipped on-site service depot at the Kriel power station to service its systems and provide spare parts. The com- pany’s workshop is staffed by six of its employees.

“The water lance blowers are operating at almost 100% and are available to the power station operators whenever they are required to clean the plant’s boilers,” he says.

Further, Kirsch notes that, since the installation of the water lance blowers, the facility has been able to operate at its maximum capac- ity of 500 MW, with high avail- ability levels. Prior to the installation of the water lance blowers, the station was running at a maximum output of between 470 MW and 480 MW.

He says Clyde Bergemann improved the efficiencies of the power station’s coal burners, which has assisted in improving the generation output, over the past three years.

“During the past five years we have replaced the existing 48 soot blowers in each unit at the Kriel power station with only four water lance blowers in each unit, which are performing significantly better and running more efficiently than the soot blowers,” Nathoo enthuses.

Matla Power Station

Clyde Bergemann won a five-year maintenance contract in July 2011 for the Matla power station, in Mpumalanga.

The company is responsible for servicing the power station’s boiler cleaning equipment and the plant’s turbine auxiliaries, which includes valves and pumps maintenance.

Although Matla power station uses soot blowers that were installed prior to Clyde Bergemann’s involvement, Kirsch says there have been no major mechanical failures since the company has been maintaining the plant.

Fourteen staff members operate a company workshop at the power station to provide services and spares.