In new guidance for shipowners, marine insurer Gard advises its members that the installation of scrubber units must be carefully monitored in order to minimize the risk of premature corrosion and potential piping failure. Additional potential casualties from improper workmanship include the possibility of sparking a fire within the unit during shipyard hot work and the failure of poorly-executed shipyard welds during operation. With these factors in mind, Gard advises shipowners to monitor and evaluate their shipyard’s work to ensure a proper installation.
Rapid corrosion is a significant concern for scrubber discharge piping. The washwater exiting the scrubber tower is acidic, and all piping routing the effluent to the overboard discharge must be painted internally with a protective coating. The absence of or poor application of the coating, along with poor application of paint on the outer hull plating near the discharge port, have been identified as potential causes of dramatically accelerated corrosion. Gard has already seen a few incidents where the overboard discharge piping has corroded away within about a year’s time, resulting in water ingress into the engine room, ballast tanks or cargo holds. The damage required temporary repairs by divers and permanent repairs at a shipyard.
During installation, the yard also has to perform considerable amounts of welding to build a new compartment to accommodate the scrubber tower and affix the scrubber to the vessel’s superstructure. Gard has seen several incidents in which sparks from hot work got into the scrubber’s inner chamber through uncovered openings and ignited flammable material inside. Shipyard workers may not be aware that the scrubber contains combustible components, and in several of these incidents, it emerged that the crew had asked the yard workers to cover over the openings in the scrubber but the workers failed to do so. In all cases, the fire was extinguished, but not without damage to the brand-new scrubber.
Gard has also observed damage to the scrubber from thermal shock when switching from “dry” mode – washwater turned off – back to normal operation. After departing a port with a scrubber ban, a ship started up its scrubber’s washwater pumps, spraying cold seawater through nozzles which had previously been exposed to hot exhaust gas. During a subsequent inspection, damage was observed to the nozzles, demister housing and drains. The causes included thermal shock, poor design and poor installation welding on support structures.
To avoid these issues, Gard recommends careful supervision by the shipowner during shipyard installation. In addition, it recommends that owners may wish to approach their scrubber manufacturer to request information about technical failures which may have occurred aboard other vessels carrying the same unit.