New Zealand’s Genesis Energy has completed a first phase refurbishment of the 190MW hydro power plant at Lake Tekapo, in the South Island.
Later this year a vertical Kaplan turbine at the Tekapo A generating station will be inspected following the replacement of a competitor’s upper, intermediate and lower wicket gate bearings with new lip seals, operating ring wear pads and wicket gate blade sealing strips with Thordon Bearings’ products.
Through its Auckland-based distributor Henley Group, Thordon supplied ThorPlas-Blue wicket gate bushes, Thorseal lip seals (which replaced nitrile rubber sealing rings in the lower and intermediate wicket gate bearings), and SXL operating ring wear pads. A new SXL turbine guide bearing, upgraded with better tolerances, was designed, supplied and installed. The shaft seal carbon segments were also replaced with SXL segments.
Genesis Energy, operates eight hydro power stations across New Zealand’s North and South Islands. Its Tekapo A Power Station has been using a Thordon water lubricated SXL turbine guide bearing since 2003.
Leny Samuel, Technical Sales, Henley Group said: “We are delighted to have been involved with another Genesis project. The ThorPlas-Blue bearings selected for the Tekapo A unit are a great option for upgrading regulating mechanism in the Kaplan turbine.”
Traditional rubber dovetail guide vane sealing strips were separating from their seats due to forces encountered during the motion of the guide vane over the final portion of closure. Henley Group was approached to evaluate if Thordon products could be a potential solution.
Greg Auger, Thordon’s Global Strategic Account Manager – Hydro Power, said: “We have been investigating the use of our softer Thor-Flex material grades to prevent this particular problem from occurring for several other customers as well. The wearing out and mechanical damage of rubber sealing strips is a recurring issue for plant operators as the rubber ages and becomes brittle. We had a solution more or less ready to go.”
The solution for Tekapo A was to fit 22mm (0.86in) (W) x 10mm (0.39in) (H) x 1700mm (66.9in) (L) Thor-Flex strips, manufactured from Thordon’s proprietary polymer material, Thor-Flex, between the vane’s metal rings.
“The Thor-Flex product is significantly more durable than rubber in most sealing applications, with excellent toughness resisting damage during installation and operation. For this application we selected a relatively low durometer (hardness) of 83 Shore A and produced a custom mold to allow us to produce the strips to the most precise finished dimensions. Thor-Flex can provide a more flexible sealing element if there are large gaps and variations to be sealed between metal components. Traditional rubber grades will harden over time and have limited load bearing capacity compared to Thor-Flex,” said Auger.
While Thor-Flex itself has been used in many industrial applications, this was a new application to solve a tough problem for the customer. Thordon will officially offer the Thor-Flex blade sealing strips once their performance has been evaluated during plant outage inspections in November 2020.
Construction of Tekapo A began in 1938 but was halted between 1942 and 1944 as labour and materials were diverted to World War II. The station was finally commissioned in 1951. Tekapo A Power Station generates electricity from water diverted from Lake Tekapo via a 1.4km intake tunnel.
In 1970, a 25.5km (15.8mi) canal was constructed to take outflows from Tekapo A to Tekapo B. The Tekapo Canal has a maximum capacity of 130m3 (4591cu ft.) per second.
Water in Lake Tekapo can bypass Tekapo A Power Station via water releases through the Lake Tekapo Control Structure (State Highway 8 bridge at Tekapo). When the control gates are open water passes to the canal, down the upper Tekapo River via Lake George Scott.
Thordon is pleased to be able to play a small part in helping Genesis Energy continue to supply clean and reliable hydroelectric power to the New Zealand electricity grid.