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Gard: Challenges with the Use of Exhaust Gas Scrubbers

Gard: Challenges with the Use of Exhaust Gas Scrubbers
Ahead of the upcoming IMO 2020 regulation, marine insurance provider Gard said that there are concerns associated with the two most popular options to comply with the new rule, namely compliant fuels and exhaust gas cleaning systems (EGCS).

IMO 2020 is fast approaching and it is estimated that nearly 3,000 vessels will have scrubbers installed by 2020. For the majority of owners and their crew members, scrubber systems are new technology “and, as with any new system, teething problems can be expected. Compliant fuels too, would bring about their own challenges,” according to Gard.

The association, that previously handled a few scrubber related claims, looks back at the cases where there has been a breakdown of or damage to or by the scrubber.

Fire during retrofitting of scrubber

Scrubber installation requires extensive hot work to facilitate the extension of the funnel area and attaching the scrubber tower to the vessel’s structure.

Gard has seen a few fire incidents where sparks from welding, metal cutting, and other hot work activities fell into the inner chamber of the scrubber through uncovered openings, and in one case the fire also spread to the engine room through glass reinforced epoxy (GRE) piping. Heat generated from the steel cutting for the supporting brackets, also contributed to the build up of heat inside the scrubber. In all these cases the yard fire fighting team responded and extinguished the fire with vital assistance from crew.

Later investigations revealed that crew had requested that the yard to cover the openings but this was not done. The fire risk to scrubber packing during the hot work activity had not been identified by yard personnel, and many of them were not aware that internal components of the scrubber were combustible, Gard noted. These fire incidents arising from shortcomings in hotwork safety procedures are not peculiar to scrubbers and can occur in any location onboard a ship where welding, cutting or grinding works are undertaken.

Sea water ingress due to corrosion

Gard explained that scrubber waste is corrosive, and there were a few incidents where within 10-15 months of the open loop scrubber being installed, corrosion of overboard distance piece or in its immediate vicinity has resulted in water ingress into areas such as the engine room, ballast tanks and cargo holds. Absence of or poor application of protective coatings on the inside of the pipe and at the welds, along with poor application of paint on hull plating near the washwater discharge were identified as the causes of accelerated corrosion. In all these cases, temporary repairs to plug the leak were carried out by divers followed by permanent repairs at a yard.

Scrubber damage due to poor workmanship and thermal shock

A vessel was regularly trading in Northern Europe and had installed an open loop scrubber. It had to changeover to low sulphur fuel when visiting a port that had regulations in place banning discharge of washwater from open loop scrubbers. It was still required to run the scrubber in dry mode, i.e. with washwater supply pumps turned off, to allow for the passage of hot exhaust gasses with a temperature of nearly 400° C.

After departure from port, washwater pumps would be started and cold sea water sprayed through the nozzles inside the scrubber. During inspection of the scrubber by crew, damage was noticed to the nozzles, demister housing and the drains.

A survey was carried out and indicated a variety of concurrent causes, such as thermal shock, poor workmanship by the yard, for example, only spot welding done on demister supporting plates; and poor design, Gard informed. The scrubber had been in service for nearly two years.

For such incidents, the marine insurance provider issued recommendations, stating that fire risks can be mitigated if hot work safety procedures are followed.

The risk assessments carried out prior to the work should cover which parts of the scrubbers are flammable. These should be protected during the hot work by covering any openings to prevent sparks from finding their way to these parts. Measures should also be put in place to prevent transfer of any heat generated during metal cutting, welding, grinding, and other hot work activities.

Additionally, Gard said that the metallic distance piece is normally coated for enhanced protection. There should be a regime to measure the wall thickness in order to avoid ingress of water due to corrosion. Any reduction in thickness is indicative of a breakdown of the coating. For leakages from welded joints and holes or cracks in the hull, the quality of workmanship and the paint application should be scrutinised. Also, the bilge alarm and pumping arrangements should be checked regularly so that the crew is alerted of and can respond to any water ingress.

Furthermore, the scrubber installation process should be supervised by owners to help mitigate the risk of damage due to poor workmanship. With regards to design related issues, owners are recommended to have a dialogue with manufacturers to avoid such risks. In this particular case of thermal shock, as preventive action, shipowners changed the design and installed a water cooling system for the scrubber which will continuously run in a closed loop when the scrubber is operating in dry mode.

“In time, managers, their crew, and the manufacturers gain more experience in such matters and the frequency of such incidents will decrease. Until that time, it is important for the industry to share the lessons learned from scrubber related breakdowns to benefit the industry overall,” Gard concluded.

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