Cutting of Concrete Shafts with Diamond Wire

Case Study

During the summer of 2007, Proserv Offshore Scandinavia performed the deck separation of the platforms TCP2 and TP1 on the Frigg field in the North Sea.

 

Data

  • Number of concrete shafts to be cut: 5 (3 on TCP2 and 2 on TP1 platform)
  • Outer diameter of the shafts: 11,6 and 13,6 m
  • Wall thickness: 1,1 to 1,4 meters
  • Obstructions in the concrete: reinforcement, crushing tubes and 35 mm bolts connecting the MSF to the shafts.

Proserv Offshore decided to use diamond wire and to perform all work from the inside of the shafts to reduce the risk of exposure to bad weather.

 

The job sequence was

  1. Build scaffolding inside the shafts to create a working platform
  2. Drilling of holes in the concrete, dividing the shaft into 12 "pieces of a cake".
  3. Pull diamond wire through the holes and connect the diamond wire machine on the inside of the shaft.

diagram_440

 

 

 

 

 

 

 

 

 

 

 

 

 

Graphic shows the cutting sequence on TP1.

Graphics below show the holes drilled through the wall, the diamond wire machine mounted on the inside of the wall, and the pattern of the diamond wire as it is being pulled into the machine.  Also, the small circles indicate the 271 35 mm steel bolts in each shaft.

Before PictureBefore Picture

 

After PictureAfter Picture

The deck on TCP2 weighed 9,225 tons and was lifted off during the summer of 2007.

The shafts on TP1 were cut and secured and the deck lifted off in 2008.

 

Other Case Studies