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Contractors World 2011 Volume 2 Issue 10
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Conjet Robot assists with repairs to Guri Dam spillway - Page 2 of 2

cwmags-Conjet equipment was bought specifically for repairing the spillways, operating from a platform to work the spillways which have an average slope of 51°.The dam spillways have been in operation for over 30 years and the force of the fast flowing water and continuous exposure to the sun light and the environment have combined to erode the surface with caving and loosening of the concrete

Fapco proposed the hydrodemolition technique of using high pressure water jetting to selectively remove only the weakened and damaged sections of the concrete spillway, and leave a very rough surface for bonding on the fresh concrete. Pneumatic breakers would leave fractures and micro cracking in the undamaged concrete left in place.

Conjet equipment was bought specifically for repairing the spillways, operating from a platform to work the spillways which have an average slope of 51°.

Fapco worked closely with Conjet AB, the world’s leading manufacturer of hydrodemolition equipment, and the Swedish company’s hydrodemolition proposal was accepted by Corporación Eléctrica Nacional.

“One of Fapco’s engineers came to our head office and factory in Sweden to assess our equipment and our suggestion to perform the Guri dam spillway repairs,” says Conjet AB executive vice president Lars Göran Nilsson.

“We worked closely with Fapco and recommended using a Conjet Robot 364 operating on a purpose built working platform rolling up and down the steep face of the spillway. Fapco adopted and adapted our suggestion and bought a Robot 364 specifically for the spillway repairs and designed and built the platform for it from which to work.”

The equipment was bought specifically for repairing the spillways and was operated from a platform specially designed for the geometry and slope of the spillway channels, which have an average slope of 51°,” says Fapco project engineer Yerry Cabrera. “Conjet gave Fapco some preliminary ideas about the access platform, which was then designed and fabricated by Fapco. The platform was moved by four manually controlled winches mounted on the crest of the dam, and this combination of the platform and Robot worked very well.”

Fapco had to completely repair one channel and perform partial repairs to another, covering a total area of about 7,500 m². The unit, operating at water pressures up to 1200 bar, selectively removed the weakened and damaged concrete from the spillway surfaces to depths ranging from 20 mm to 150 mm and in some instances exposing the steel reinforcement.

vwmags-Concrete removal was up to 69 mē/day and was intermittent due to a combination of moving the platform, adjusting the Robot to the spillway geometry and refilling the water tank supplying the Robot.     Concrete removal was up to 69 m²/day and was intermittent due to a combination of moving the platform, adjusting the Robot to the spillway geometry and refilling the water tank supplying the Robot.

After concrete removal Fapco followed on with a spray applied 800 kN/m² strength mortar in areas less than 100 mm deep and 500 kN/m² strength concrete in the deeper areas.

Fapco started on repairs to the first spillway in late 2009 and completed its contract earlier this year. Work on the project had to stop several times for several months, during the rainy seasons, when the spillway channels, not being repaired, had to be opened to control the level of the reservoir.

“We have had a very good experience with the Conjet Robot on the spillway and also used it for some hydrodemolition work on other areas, such as the water intakes of some of the generation units,” says Yerry Cabrera. “There is also potential work for repairing another spillway, and possibly some repairs on another dam.”




cwmags: more informationClick here for more online information >>>Conjet Hydrodemolition

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