Installation of 32 T grids of Kardzhali Dam’s left main exhaust – depth of 76m.
Execution time – 60 days. The dives were performed by Surface Supply Diving System using Oxygen-Helium Breathing Mixes. For descent and ascent of the divers was used a Diving LARS.
Prior to the start of the actual installation, the divers conducted a detailed metrological measurement at the installation site and descending the grid mold.
In the channel in front of the exhaust tunnel has been found a substantial bed of dense clay, which required the use of specialized equipment for breaking and pumping 350 m3 of material.
The grids are lowered to the installation site at a depth of 76 m using 2 electric winches with a total capacity of 16 tons placed on a special BulDock mobile pontoon. The grids lowering was controlled by a Video Ray Pro 4 ROV equipped with a HD Camera, Oculus Multibeam Sonar and Sea Trac Navigation. By using a Hydraulic rotary hammer drills Stanley Spitznas powered by the surface, divers drilled the holes with a diameter of 32 mm into the concrete and installed the Hilti heavy duty HSL-3 anchors. A sealing cement was injected beneath the mounting plates.
The final controlled tightening of the heavy duty anchor bolts was done with Stanley hydraulic underwater impact wrenches IW 12.
On December 18, 2017 the work was completed, a detailed video inspection of all details of the installation was made and the work was handed over to the client.