Sekela Bearings technical manager Warwick Steinhobel says bearing consumption at the utility’s Arnot power station is unusually high, owing to floor vibration that causes damage to the cast iron bearing components used in the seal-air fans.
“Seal-air fans are two-stage fans and the bearings sit between the impellers, so you cannot strip it, which is why split bearings are used,” he explains, adding that the bottom part of these bearings cannot be changed, as it cannot be removed from the fan.
Steinhobel alleges that the cast iron bearings base used in the Arnot station’s seal-air fans becomes damaged or breaks, damaging the rest of the bearing parts; however, as Eskom is unable to replace the entire bearing, it replaces only the top part.
“Eskom is fitting brand-new bearings to damaged cast iron, which is why the bearings do not last, resulting in the high bearings consumption,” he claims.
He states that Sekela Bearings has developed its SNQ support bearings to mitigate this problem at the power station.
The SNQ support bearings will, unlike standard support bearings, enable the replacement of the entire bearing, says Steinhobel.
“We believe that, with our product, Eskom’s bearings consumption will be reduced dramatically, which we believe currently amounts to about 15 to 20 bearings a year for Arnot.”
Sekela Bearings has approached the power utility with this solution, but says the utility has not shown an interest in buying the product.
Eskom denies that the utility is wasteful in terms of bearing consumption at the Arnot power station.
“There are 72 seal-air fan bearings in service at Arnot power station. During the last year, the station only had three failures. The bearing replacement cost was R23 000 and the replacement time was about three hours for each incident. These failures had no impact on production, as the spare mill was put in service,” the utility states.
Meanwhile, Steinhobel says Sekela Bearings also offers a type of bearing, which was used in the Grootvlei power station, in Mpumalanga, before it was mothballed in 1989/90
The six units at the Grootvlei power station were mothballed between 1989 and 1990, owing to surplus electricity generation capacity in South Africa; however, its six 200 MW units were demothballed by the end of 2011 as part of Eskom’s return-to-service projects.
“When Eskom closed the Grootvlei power station, it sold off all the spares. I have managed to get my hands on some of the bearing spares.”
Steinhobel claims that one of the spares was specially made for the Grootvlei power station and is not manufactured anywhere else in the world. It is used in the Rothemühle air heater of the power station.
“We believe that the bearings currently in service at Grootvlei have been patched and are damaged.”
Eskom also denies this claim, saying that, while the utility may sometimes switch parts between power stations to save costs, it ensures that all power station components are well maintained.
In January 2011, Eskom launched its quarterly State of the Power System briefings, in line with its commitment to keep stakeholders informed about the state of South Africa’s power system
Public Enterprises Minister Malusi Gigaba said, in February, that the utility had a highly developed maintenance policy designed to ensure that areas at risk are dealt with in order of priority through a consistent schedule of maintenance and inspection work across its fleet of power stations.