Babcock’s specialised engineering business has secured a contract extension for Units 4 and 5 of the six new 800 MW boiler units at Kusile Power Station, in addition to current work being undertaken for Units 2 and 3. The contract was awarded by Mitsubishi Hitachi (MHPSA), the main boiler contractor for Kusile.

Babcock was originally contracted by MHPSA for the balanced erection of five high pressure pipework systems for Unit 2 in 2014. After an auspicious beginning, MHPSA extended Babcock’s contract to include the same scope of work for Unit 3, and in September this year again broadened the contract to incorporate Units 4 and 5.
“We have steadily increased our scope of work on the Kusile project thanks to the proficient logistical, technical and project management skills we have brought to the table,” says David Brook, Technical Director –Africa for Babcock.

He explains that the scope of work encompasses the complex rigging and geometrical alignment of the piping for the main steam and hot/cold reheat systems in the boiler units that deliver steam between the boiler and turbine, together with feed water and auxiliary systems, entailing in excess of 1 000 welds per unit on piping ranging in diameter from 12 to 1 200 mm. Lasers are used to position the pipework and precision to within 0.5 mm is demanded. As the boiler units are 115 m high, much of this work has to be carried out well above ground level, increasing the complexities of the project. Cranes are used for lifting the piping – weighing up to 782 metric tonnes per unit – into the boilers. Babcock’s scope of work also includes coordinating the synchronised lifting of the pipe systems, with lifting and mechanical gear supplied by Babcock’s plant services business.

Brook reports that 85% of the main piping work has been completed on Unit 2 and approximately 40% has been finalised on Unit 3. By 2017 Babcock expects to be working on all four units simultaneously in various stages of completion and Brook is confident that Babcock has the capacity and resources to execute their growing contract.
Babcock’s on-site crew for the entire scope of works currently comprises a world-class team of over 270 skilled workers ranging from welders to pipe fitters, engineers and quality control specialists. As the scope of work increases, more crew will be employed.

“The Kusile project requires specialised skills and workmanship with a focus on precise installation. We have a team of about 20 technical and logistical staff on site who are charged with ensuring that everything from rigging to alignment is accurately co-ordinated,” says Brook.

Babcock has also placed a strong emphasis on skills development and risk management on the Kusile project and a culture of safety has been instilled, with particular attention given to safety regarding working at great heights and near electrical equipment. The Kusile project team recently achieved 750 000 incident-free man-hours on site.

Colin Davies, Project Manager for Special Projects at Babcock, expands on milestones achieved to date and future expected progress on the project.  “Our team is currently preparing to complete Unit 2 for hydraulic testing and has completed all ground welds on Unit 4, with only a small support installation prep crew assisting in Unit 4. We have also moved onto ground welds for Unit 5.”

Davies believes that the recent extension of the scope of work will mean that by 2017 the Babcock team will be working on units 2 through 5 simultaneously.

The Eskom-owned Kusile Power Station consists of 6 supercritical boiler units that will produce 800 MW each, ultimately making Kusile one of the largest coal-fired power stations in the world. Unlike other power stations in South Africa, Kusile will make use of air-cooled condensers instead of the iconic cooling towers and the electricity generated is expected to ease the strain on the South African national grid.

The supercritical boilers burn pulverised coal to produce steam at very high pressures (241 bar abs and 560°C), delivering this to the steam turbine that generates electricity. The process uses less fuel than in traditional sub-critical pressure boilers, making them more efficient with reduced emissions and operating costs.