A boiler tube inspection is currently under way at unit 1 of State-owned power utility Eskom’s Kendal power station, in Mpumalanga.

The inspection, which started on May 13, follows an inspection of the power station’s unit 2, in April, this year.

As with the first shutdown for inspection and maintenance, the second will be undertaken by specialist rope-access company Skyriders, which has a permanent rope- access team based at Kendal.

Further, easy-access inspections that are done using scaffolding will be undertaken by unit inspection company De-Tect.

During the first project, which took ten days, critical internal boiler components were inspected for damage, wear or abnormalities.

“Areas that are historically prone to issues, or where damage is suspected to have occurred, were inspected,” says Skyriders marketing manager Mike Zinn.

He adds it is estimated that well over 10 000 ultrasonic wall-thickness readings were done on more than 5 000 tubes.

With the Skyriders component of the inspection costing around R200 000, the operation employed about 20 people that included inspectors, assistants, data cap- turers and management.

The second outage is expected to take ten days and costs will be similar to those of the first.

“Three days are set aside for inspections and another seven days for maintenance,” explains Zinn.

He adds that the two units have been run to capacity over the past few months and Skyriders expects to find more areas of substantial wear and damage.

Zinn explains that the inspections form part of Kendal’s routine planned maintenance before the winter season.

“All units are inspected on a maintenance cycle. Most units will be inspected once a year either during a boiler tube outage, an intermediate outage, a general outage or an opportune outage, also referred to as a forced outage,” he says.

General outages involve a shutdown period of between four to six weeks. During this time, extensive overall inspection and main- tenance are done on boilers and all the supporting machinery, the turbines and precipitators. Fifteen days are allocated for inspections and the rest for maintenance.

An intermediate outage involves an intermediate shutdown that includes ten days of inspection and ten days of maintenance and repairs. Inspections are done using ultrasound wall-thickness machinery that measures the thickness of the steel tubes and allows the plant care engineers to proactively prevent tube leaks by shielding or replacing worn tubes.

An opportune outage entails doing a general inspection when the opportunity arises. “For instance, during a forced outage, when the unit has been shut down because of a fault, while repairs are being done, the inspection team can conduct quick ultrasonic wall-thickness and visual inspections of areas of historical problems to ensure that no further problems occur,” Zinn explains.

All checks involve the removal of clinkers that build up in boilers, as well as slope washing to allow better inspection.

Skyriders’ permanent six- man rope-access team at Kendal is responsible for undertaking all inspection and maintenance tasks that are located high above the ground or in confined spaces that are difficult to reach.

“Traditionally, access to a boiler in a power station is severely restricted; however, using rope access, the Skyriders team is able to gain access and carry out essential inspection and cleaning work,” Zinn says.

He notes that on-site rope- access inspectors are able to locate tube leaks, photograph them and immediately report the problem to the power station’s engineers. This reduces turn- around times and saves costs.

“With South Africa’s high electricity demand, downtime has to be kept to a minimum. The benefit of using rope access is that it allows for a shorter turnaround time of about 48 hours, compared with the industry norm of more than 72 hours,” Zinn says.

The reduced downtime is essential, as Kendal is one of the biggest power stations in South Africa, with a total installed capacity of 4 116 MW.

“If downtime is not kept to a minimum, the country could face electricity shortages,” he adds.

Further, the rope-access team can assist should a rescue operation become necessary during inspections or shut- downs.

Decreased Regularity
Zinn says, before South Africa’s electricity crisis in 2008, inspection outages were done regularly, with the exception of the winter months.

“Eskom cannot afford lengthy shutdowns anymore; the demand for electricity is too high. Consequently, boilers are running to their maximum capacity.

“When we undertake inspections, the effects of operating at full capacity become evident with significant increase in wear being visible,” Zinn adds.

Inspection times have also been cut dramatically to reduce downtime.

While this does not affect the quality of inspection, the amount of work that can be done during each inspection is severely decreased.

To further save time and money, Skyriders aims to increase its use of video borescopes, where a camera mounted at the end of a fibre-optic cable is used to inspect small areas that cannot be accessed by inspectors.

Generally used in turbines, borescopes are relatively new to the power station industry, says Zinn.

Zero Fatality
Skyriders reports that it has managed to maintain its zero-fatality rate since its establishment in 1988.

Zinn attributes the success to the high-quality training given to rope-access personnel, strict adherence to standards set by the South African National Standards document that was developed by the South African Bureau of Standards, and doing regular risk assessment and re-evaluation of the constantly changing environment within power stations.

Skyriders opened a new training facility in April, equipped with the necessary facilities to do fall-arrest training and rope-access training for personnel who work at height.

The Services Sector Educa- tion and Training Authority and the National Qualifica- tions Framework validate the formal qualification that can be obtained through the facility.

Goal
Zinn says Skyriders aims to establish itself as a valuable role-player in the South African power generation, mining and construction industries.

“We want to move into the rest of Africa through these sectors. In Africa, electricity is mainly generated by hydropower, which offers a lot of concrete-related maintenance, repair and inspec- tion opportunities for us,” he adds.

Skyriders is currently in discussions with some power utilities in Zambia, Tanzania, Tunisia and the Democratic Republic of the Congo (DRC), besides others.

“We are looking at possible involvement in projects such as the DRC’s Grand Inga hydropower project,” Zinn says.

Further, Skyriders also hopes to deploy a permanent rope-access team at Eskom’s new Kusile and Medupi power stations once construction has been completed.

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