Blanks & Cofferdams


The ability to blank off sea inlets and overboard discharges safely and quickly underwater is essential if costly delays or even unscheduled dockings are to be avoided. SeaTec hull aperture blanks are supplied to vessels in service and new builds. They are also suitable for semi-submersible installations and other offshore structures that cannot easily be brought to a docking facility. Vessels such as FPSOs that are on station for 10 to 25 years rely on blanking technology to remain in service and in class.

SeaTec blanks have been supplied to hundreds of ships and vessels and individual blanks have been refitted many times to achieve a successful and safe sealing system. Easily fitted by divers, the SeaTec design incorporates an adequate safety factor with all blanks being quality checked to the highest standard. Many of the blanking systems carry class approval from the major classification societies.


SeaTec is an industry specialist in cofferdam design, fabrication, installation and execution of works, providing support for vessels and offshore installations. Cofferdams provide the environment to complete more complex in-water ship engineering tasks. They can remain in position for extended periods, which allows for any unforeseen scope growth to be captured and completed. Cofferdams are frequently required to execute weld repairs to rig and vessel hulls, where wet welding techniques cannot be used, or dry-docking facilities are not readily available.

Cofferdams fall into three main categories:

  • Fully enclosed ‘limpet’ type cofferdams used for a variety of repairs where an area needs to be sealed off from the sea on all sides, for subsequent internal intervention to the hull or equipment.
  • Man entry cofferdams used where engineers or technicians need to have external dry access. The working environment of the cofferdam allows for specialist surface equipment and personnel to be utilised below the waterline, which expands the range of underwater engineering tasks.
  • Open bottom or hyperbaric cofferdams used where a dry space is required to carry out a repair below water, but that can only be accessed by a trained diver.

SeaTec can design a cofferdam system to suit any application across the maritime industry. Applications for cofferdams can be extremely varied but typically include:

  • Repair projects for damaged vessels
  • Hull aperture blanks for sea chests and discharges
  • Replacement of stern seals
  • Repair and replacement of tunnel thrusters
  • Bespoke cofferdams for rudder/stabiliser replacement
  • Propeller maintenance
  • Transducer maintenance
  • Steelwork replacement
  • Impressed current anode replacement
  • Permanent class approved hull insert plate repairs
  • Installation of new build civil structures at water front developments
  • Repairs to concrete structures such as docks and jetties
  • Repair and inspection of rig spud cans
  • Repairs to turret systems

Contact us to find out more about our blank and cofferdam solutions.

Talk to one of our team

Latest SeaTec News

Find all our latest news articles and press releases relating to SeaTec and all our brands.

Talk to one of our team

    I require a quoteI have a general enquiry

    What service do you require a quote for?

    Projects & New Builds
    Conversion & RefitEngineering & ConsultancyNew Building

    Please select an option from the menu

    Navigation & Communication

    Survey & InspectionHull Cleaning & Propeller PolishingSubsea Engineering & RepairsBlanks & CofferdamsMarine ConstructionSpecialist ServicesEquipment Sales

    Please select an option from the menu
    Mini Pamper Hull Cleaning VehicleTwin Brush Cleaning ToolSingle Brush Cleaning and Polishing ToolBrushes and padsHydraulic UmbilicalsWD80 Hydraulic Power Pack System

    Condition Monitoring
    LO analysisFO analysisBWTS water analysisScrubber analysisPortable water analysisVibration surveyOther


    Please email me backPlease call me back

    Social Media

    Call or Email Us

  • Glasgow +44 141 305 1300
  • Southampton +44 23 8026 9866
  • Rotterdam +31 10 438 6644
  • Copenhagen +45 35 14 30 00
  • Monaco +377 92 05 10 10
  • Shanghai +86 21 2026 7012
  • Chennai +91 44 4647 9922
  • Singapore - Keppel Towers +65 626 11340
  • Singapore - Benoi Place +65 6351 8720