Keeping refurbishment in Czech16 November 2001
In readiness for this year's Uprating and Refurbishing Hydro Power Plants VIII conference, we report on some of the hydro projects in the Czech Republic
REFURBISHMENT PUMPS UP THE POWER Located in South Moravia, the pumped storage power plant Dalesice, owned by Czech-based CEZ, has four large pump turbines with a runner diameter of 6m. In 1999, an uprating and refurbishment programme was undertaken at the plant, beginning with unit number three. CKD Blansko Engineering was one of the companies involved in this project and CKD Blansko Strojírny was the main sub-supplier.
During the refurbishment programme, the main effort was focused on the distributor. Both the guide vane and the stay vane profiles were reshaped. The new vane shapes were machined out of the existing solid vanes. A 3mm layer of the facing surfaces on both the bottom and the head cover were removed and a new stainless layer was welded in. The bottom cover was field machined and welded, while the head cover was removed and welded at CKD Blansko's works.
During the early days of the project, the lubrication of distributor bushings was discussed with the operator. Based on the company's experience with forced grease guide vane lubrication, CKD applied this type on the guide vane stem bushings. To increase the squeeze effect, new bushes were sailed from both sides using new types of seals, ensuring no escape of grease into the water. The lubrication system is of the similar type as that one used successfully for the pump turbines at Markesbach pumped storage plant in the Czech Republic. The remaining bushes are self-lubricated.
A feature of the turbines at Dalesice is a device where two adjacent guide vane stems can be pressed from each other. Using this device, the dry friction torques acting on the guide vanes can be increased, which in turn increases the resistance against guide vane vibrations. The segments of this device are also self-lubricated.
As part of the project, the runner was dismantled and transported to CKD Blansko works, where refurbishment of the whole runner was carried out. According to the company, a relatively small amount of repairs was necessary.
Originally, the guide and thrusts bearing were of self-lubricated types. This system was changed and a new force-lubricated system was installed. Copper pipe coolers located in oil bath were removed and new plate coolers were installed.
The unit was returned to operation in autumn 1999.
|RUN OF THE MILL RENOVATION|
|Mavel expects to complete the refurbishment of the 856kW hydroelectric power plant located in Benatky Nad Jezerou, Czech Republic, before May 2002. The private owner of the power plant awarded the refurbishment to Mavel with the goal of maximising the economic potential of an existing hydroelectric facility located about 30 minutes outside of Prague on the Jizera river. The site originally housed a large mill that was driven by setoff waterwheels. Upon the development of a new plant for the production of silicon carbide in 1893-94, the power plant was reconstructed to run with turbines. The plant was next refurbished in 1918-19 and fitted with two vertical Francis turbines. This configuration, with installed capacity of 560kW, functioned through the 1960s. After that, power generation was used as a reserve source until the plant was permanently closed in 1989. The weir, physical structures and power house deteriorated from disuse and, during the summer of 2000, a major flood caused additional damage. Mavel worked with another Czech hydro specialty firm to develop a new design utilising as many of the old structures as possible while recommending a new technology design which would boost installed capacity by over 50%. The site has head of 4.2m and flow of 24m3/sec. As part of the technological solution, Mavel is providing two 16m diameter vertical Kaplan turbines with gear box drives and vertical asynchronous generator. Each turbine has the following parameters: • Maximum water flow: 12m3/sec • Minimum water flow: 2.4m3/sec • Head 4.2m • Maximum power output: 428kW • Minimum power output: 77kW • Runner diameter: 1600mm • Number of runner blades: 4 • Number of wicket gates: 16 • Turbine speed: 218 rpm Mavel is also providing the two generators, one hydraulic governor, a building crane, a hydraulic gate system, hydraulic trash rack and cleaning machine.|
|TIME FOR A RE-FIT|
|Rehabilitation of hydro plants and structures is one of the key services offered by Czech-based Hydropol. The company has been involved in a number of projects including the refurbishment of the 70-year-old Spalov hydro power plant. The company installed new Kaplan instead of old Francis turbines at the medium head plant, together with full SCADA automatisation and remote control via a dispatch centre. These new units, combined with compliance with the latest ecological and safety measures, a low budget, high value civil works rehabilitation and project management, allowed the company to cut schedules by 50 %. and lower the budget by 16 %. Hydropol was also involved in the refurbishment of the Moravka dam. The company provided design, planning, project management and turnkey supply of the new, 25,000m2 upstream face insulation layer. During the project, a bituminous concrete surface installed in the 1960s was replaced by a geomembrane system in co-operation with CARPI Tech of Switzerland. The project was executed in three months.|