Skanska Norway has used an Aquajet robot water cutter in renovating structural parts underneath a pier in Oslo harbour.

Because of the tidal flow and an inaccessible subsurface working area, this operation would have been both difficult and dangerous to undertake by manual means.

The large pier, with an area of 4,000 sq m (43,000 sq ft), is located at Pipervika Quay, and Skanska found extreme damage to the bearing elements below the structure.

Not only did the tidal flow make the pier structure an unsafe environment for Skanska’s workers, the restricted space was inaccessible for large demolition robots.

A spokesman for Skanska confirmed that in the past they would have relied on unpredictable rail systems and very old, ineffective pumps; making the project “virtually mission impossible.”

Skanska therefore chose the small and manoeuvrable Aqua Cutter 410A hydrodemolition robot, supplied by Aquajet Systems AB of Sweden.

This remote controlled robot was fitted with a disconnectable power control module and an Ecosilence power pack.

The operator was able to disconnect the power control module from the tracked crawler, and safely drive the crawler into the tight and flooded areas under the pier.

Standing on dry land, the operator used the remote control to access all the required horizontal, vertical and overhead operations.

The Ecosilence power pack is a super-silent high-pressure unit, specially designed for hydrodemolition in urban environments with highly regulated noise levels.

For this project the pressure and flow were set at 1,000 bar and 180 l/min. Skanska said that the operators were experiencing increased efficiency of 50% when using efficient and flexible robots that also can work under water.

During a period of just 100 days, more than 750 t of badly corroded concrete had been removed.

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