New pipeline to be built between Sundsvall and Alnön

"FVB joined forces with Sundsvall Energi to establish whether the old district heating pipe to the island of Alnön could be renovated, but we decided that a new pipe would be a better economic alternative in the long run," says Pär Christiansson at FVB, the Project Manager for the new underwater pipe.

The pipe's dimension is DN 200 with a steel mantle, coated on the outside with polyethylene.

"We chose steel because a steel mantle makes the pipe heavier, which helps it sink, and it's more resistant. You don't have the same level of control over a pipe submerged to a depth of nearly 30 metres – which it is most of the way – compared with pipes laid in the ground," says Pär Christiansson.

The pipe comes in 16 metre sections, which are welded together on land into four sections of around 350 metres.

"When welding and jointing, we conduct an extensive testing programme to ensure the quality of the media and the mantel pipe. We then submerge the sections and weld them into two sections just under 700 metres long." he adds.

Submerging pipes requires special permits and liaison work with the authorities, pilotage at sea and closing off sea lanes.

"It's a bit different compared to what we normally do when laying pipes in the ground, and it requires a long- term planning perspective. But we have done several similar jobs previously and are therefore confident we can do this one as well," says Pär Christiansson.

The work started in May with the manufacture of the pipe sections a few kilometres south of where the pipe will be laid. Underground chambers have to be built on both the mainland and the island where the pipe transitions from seabed to land, and where the submerged pipe expansion can be absorbed. The pipe is expected to be commissioned in the autumn.

For more details, contact:
Pär Christiansson: +46 (0)8-5947 61 62

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