Hull Aperture Blanks

Hull Aperture Blanks


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.

UMC blanks are supplied to ships in service and new builds. Our designs are also suitable for semi-submersible oil rigs and other offshore structures that cannot easily be brought to the surface. FPSO's that are sometimes on station for 10-25 years rely on this kind of technology to enable them to remain on station.


Thousands of our blanks have been supplied to literally hundreds of vessels and individual blanks have been fitted and refitted many times without one recorded failure. Our design incorporates a minimum safety factor of 4 and all blanks may be inspected for class approval on request. All UMC hull blanks are quality checked to the highest standards.


The composition of each blank is varied to suit each individual hull aperture. A specialised computer programme computes the load on the blank from the dimensions and depth of the aperture beneath the waterline, and then designs a composite sandwich that is approximately neutrally buoyant whilst being rigid enough to withstand the differential pressure. This means that divers underwater can readily manoeuvre the largest of blanks. Provided the blanks are stored with reasonable care they have an infinite lifespan. We generally supply blanks in ship sets that are carried on board ready to be fitted, either as part of an inwater survey or to enable repairs to take place. However, individual blanks can be fabricated to deal with a particular repair requirement.