Exam Question

(a) A Cracked Weld:
Non-Destructive Testing (NDT) methods such as Dye-Penetration Testing (for surface cracks) or Magnetic Particle Testing (for subsurface cracks) are essential to determine the crack's size, location, and orientation. This information dictates the repair strategy.
A small crack might be ground out using an electric or pneumatic grinder, allowing for proper weld preparation (edge beveling). Larger cracks might require gouging with a pneumatic chisel to remove the damaged metal. In either case, the crack must be completely removed before welding. A crack arrestor hole drilled at the crack's root before grinding/gouging can prevent further propagation during these operations.
Finally, the crack should be repaired by welding, using appropriate filler material and welding techniques. Pre- and post-heat treatment should be performed to minimise stress and improve the weld's quality and longevity. This will depend on the material of the hull and the weld itself.