16” and 24” Grillages

IK Norway has design, fabricated, tested and prepared 16” Grillages and 24” Grillages to be fitted to the Alvheim FPSO.
Grillages intention is to prevent debris from entering the Alvheim FPSO hull intakes.
Since 2012, replacement grillages have been installed using magnets. On two occasions since, the magnets have been seen to corrode away, leaving the hull intake un-protected. There are two sizes of grillages were provided:

  • 2 of 16” Grillage;
  • 2 of 24” Grillage;

IK has also supply preparation, methods and special tooling to perform this work.


Main operational parameters of the location:

  • Working Area – Subsea
  • The depth of the unit is appr. 150 mm into the hull.
  • The grillages is delivered in stainless steel quality and there is no need for coating of sacrificial anodes
  • The design life is at least 5 years before the unit needs to be replaced due to corrosion / wear
  • Internal / External force from water column for 16” Grillage: 151kN/m2 / 268kN/m2
  • Internal / External force from water column for 24” Grillage: 95kN/m2 / 230kN/m2


The Grillages were installed using a ROV. Grillages are designed as ROV friendly; ROV are capable of installation and removal of grillage Grillages has wedges/slips concept for setting and releasing functions, which actuated by removable IK special Torque tools; The grillages has been installed flush with the hull, i.e. with minimal potential for fouling debris in the water column.


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