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Pipeline Crossing

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With the enormous number of pipelines and cables providing a complex network subsea, many pipelines have to cross existing infrastructure laid by other operators

Usually a minimum separation distance is required, therefore pipelines need to be lifted above the seabed to cross other cables and pipelines.

Subcon provides multiple solutions:

  • Sleepers
  • Pre-filled Bulk Bags
  • Grout Inflated Fabric Formworks
  • Concrete Mattresses
  • X-Mat

FAQ’s

The choice regarding which solution to implement will depend on the following:

  • Product type ie flying lead, pipeline
  • Crossing height
  • Clearance requirements
  • Pipeline lateral expansion
  • Scour risk
  • Available installation spread

DNV standard prescribes a 0.3m minimum separation distance.

When settlement issues can arise, the sleepers can be produced with a hybrid base of voided concrete and geotextile, reducing the weight while maximizing bearing capacity.

Most sleepers can be transported by barge or even by truck, when the large size of certain sleepers complicate transportation, they can be fabricated on a local quayside, removing costly logistics.

Scour can be mitigated by using mattresses to build the support or by including grouted roll out skirts on the sleepers. Fronded mattresses can also be deployed to assist with scour protection and remediation.

Run away scour at the touch down point can be mitigated by a mattresses or frond matts at the touch down point.

If lateral pipeline movement occurs at the touch down we recommend pre installing an X-Mat to effectively engineer in the touchdown support.

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