Fighting corrosion on submarine hulls

Stress data from the CNBC helped Canada leverage closer research collaboration with allies.

Source: Canadian Neutron Beam Centre (CNBC)

Managing aging fleets of submarines is a challenge common to all western navies. Canada, the United Kingdom, and the Netherlands joined hands in 2011 to establish the Submarine Structures Working Group to perform collaborative research and share information about such common challenges.

A significant maintenance activity is addressing the corrosion of the pressure hull.  Over time, corrosion eats away at the pressure hull, gradually thinning it in spots. Overlay welding is one of the few methods suitable to restore this material loss without resorting to the more expensive alternative of replacing an entire section of the hull plating or scantlings.

In 2009, Defence Research and Development Canada (DRDC) accessed the Canadian Neutron Beam Centre (CNBC) in an effort toward defining the maximum size of the corroded area over which weld overlays could be used effectively. Sections of hull plates with different sizes of overlaid areas were examined at the CNBC to measure the residual stress distribution deep inside the plates as a result of the weld overlays. The data was then used by DRDC to successfully validate two different finite element approaches that simulate the effect of welding on the properties of the hull plates, demonstrating the value of both the data and the models.

This success recently helped DRDC to leverage closer research collaboration with the United Kingdom within the Submarine Structures Working Group in order to develop standards for weld repairs in submarine hulls. The UK will benefit from access to unique experimental data, while Canada will benefit from leveraging the UK’s alternative submarine hull repair procedures.