Repair to burst underwater pipeline in Vilanova i la Geltrú

Emergency repair work on the underwater pipeline at the port of Vilanova i la Geltrú: installation of 432 m of DN900 HDPE pipe, the different pieces of which were welded according to UNE 53394 at three sections.
 

At the end of each section, an HDPE flange was sealed and a loose flange was fitted.  For every 5.5 metres of pipe, a ballast of 1 m³ was made. These ballasts are made from RC-30/B/20 IIIb+Qb concrete (marine environment) reinforced with 8-mm diameter rebar.
 

At the ends of the existing section, a fine cut was made and a universal flange with a tolerance of 860–890 mm was attached. All flanges are coated to Im2 category, for elements permanently submerged in seawater.

The sections of 144-metre pipe were placed in the water in a complicated manoeuvre, involving five 120-tonne cranes equipped with 10-metre spreaders. Once in the water, the three pipe sections were towed offshore to the connection point, where they were submerged by gradually being filled with water. Once the pipe was in its final position, the flanges were tightened to attach the new section to the existing one.

Finally, the seabed was dredged to bury the lower part of the ballasts and allow the lower part of the pipe to rest on the sand.