Corrosion of ship distance piece (Scrubber system)

Currently, several reports for incidents that sea water leakage was detected from distance piece attached to hull on SOx scrubber discharge water line.

Until now, the leakages were detected at an early stage and did not cause heavy water ingress into E/R.

Upon the above incidents, we would like to recommend the owners and the managers as follows:

  • To inform the above incidents of the masters of your vessels on which SOx scrubber is installed
    and instruct them to inspect the discharge water lines especially around the distance pieces
    externally from E/R with more attentions and frequencies.
  • To inspect the distance pieces internally when there is an opportunity of arranging a diver for hull cleaning, etc.

If a leakage were detected, temporary countermeasure to stop it (e.g. covering the distance piece with cement box) should be taken immediately, and Occasional Survey by the surveyor should be arrange as soon as possible.

Based on the circumstances of the situation, the damage is assumed to begin at locations on welded parts where the paint has been peeled off. The underlying surface is thus directly exposed to discharge water, and it causes corrosion that then spreads over the distance pieces over time.
We believes that one of the effective ways to prevent this type of incident is to apply pre-treatment prior to the painting of welded parts in order to ensure proper paint performance, and some specific pretreatments are introduced below as examples. In addition, please be sure to comply with the pretreatment procedures specified by paint manufacturers, if any.

For the purpose of preventing insufficient local paint thickness and non-uniform paint thickness:

  • Grind edges
  • Grind welded surfaces
  • Remove welding spatter
    For the purpose of removing dust and any remaining welding material components
  • Clean and remove any surface dirt from the welded parts In addition, the use of corrosion-resistance material such as stainless steel for distance pieces is another effective measure to be considered. Please note that welding procedure specification (WPS) approval is, however, required for stainless steel materials prior to any welding work.

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