Aquajet cleans up
By Steve Skinner10 September 2008
An Aquajet HVD robot was used recently to remove the surface concrete on the Motala Ström dam wall at Norrköping, south of Stockhom in Sweden, prior to its resurfacing.
Norrköping’s industrial landscape has been comprehensively transformed into offices, entertainment centres and educational facilities in recent years, and the illuminated waterfall that runs between the Stålbom paper mill and hydro-electric plant is a key feature that’s illuminated at night during the winter.
Initially renovated in 1991, the dam wall behind the waterfall, which is 140 m long and 8 m high, needed strengthening, but before reconstruction work could start, surface demolition was necessary.
Following re-routing of the dam, the hydro-demolition work necessary to allow renovation to take place was carried out by ISS Industriservice AB for main contractor DAB, employing an Aquajet HVD robot, fitted with the company’s new Intelligent Sensing Control (ISC).
ISC has no sensors or electric cables at the front of the machine therefore eliminating the ingress of water, grease or dust. An on-board computer, which can be programmed by the operator, automatically controls and manipulates the pre-set movement of the waterjet nozzle and the tracks or vertical hoist.
By combining the fluid dynamic, geometric and kinetic parameters of the control system, the aqua cutter optimises its settings and applies the minimum required force, removing only deteriorated material. Good sound concrete is left untouched and the reinforcement steel is left clean.
In total, approximately 45 m3 of concrete was stripped away to the rebar – to an average depth of 50 mm – by the high pressure water jet system.
The HVD removed an average of 0,9 m3 of concrete an hour, with the PP480 high pressure power pack operating at a pressure of 800 Bar, connected to the robot with a 100 m-long hose. The pump’s maximum pressure is 1000 Bar with a maximum water flow of approximately 200 litres per minute.