Participants at Riviera’s Asian Sulphur Cap 2020 Conference discussed ways to minimise yard time and lead time while also minimising engineering work
Addressing scrubber installation bottlenecks during a conference panel discussion on retrofits, Pacific Green Technologies technical director Ken McClelland said a lack of coordination has led to pile ups and delays at shipyards.
Mr McClelland pointed out that scrubber retrofit operations are a cooperative solution between the supplier and the customer and that proper preparation is key to a successful retrofit.
“Adequate time should be spent on 3D scans, physical checks to ensure drawings are correct and that the components are indeed what the drawings say they are,” he said.
Baltec Marine commercial director, Göran Fransson, said extended lead times, uneven skill sets at shipyards, as well as uneven welding skill sets of workers were contributing to delays.
“Two quality control personnel need to be deployed full time in the yard for a successful project,” he said.
Average installation time takes between 21 to 28 days for a retrofitted scrubber system, according to the panel’s experts. A few days can be shaved off if all the material and equipment is already on standby when the vessel is docking in the yard.
Shanghai Marine Diesel Engine Research Institute’s senior area sales manager Yao Yuxiang said time spent at the yard depends simply on the yard’s proficiency in scrubber retrofits. In the case of an open loop system, yard time is typically two to three weeks, he added.
Will yard time reduce in future?
Mr McClelland said it is common to have a lead time of five months between a shipping company’s decision to retrofit to the point when the company makes its final design review before going to the shipyard. He said time has to be found to do a complete 3D scan, which can take a few days to a week. Then the 3D scan has to be verified and the ductwork made accessible and other similar preparations made.
However, Mr McClelland said it would be reasonable to expect that shipyards would be able to reduce average yard time by at least three or four days within the next six months.
Mr Fransson said dry docking can be avoided for cruise ships and smaller vessels. The scrubber retrofit can be scheduled in such a way that the overboard discharge work is performed during regular dry docking for smaller ships, but bigger ships would need dry docking exclusively for scrubber retrofit, he said.
In larger ships such as tankers and bulkers, trim and stability may also need to be considered. In container vessels, the challenge is to ensure a minimal compromise of container space, often requiring work outside the funnel. In cruise and roro vessels, inline solutions may be optimum due to space limitations.
A case study by Panasia team leader James Seungha Han brought out stability considerations in scrubber retrofits, especially in smaller vessels. Mr Han also referred to changes in SOLAS rules that mandate an inclined test if the vertical centre of gravity changes by 1%.
In a small tanker of 4,000 lightweight tonnes (lwt), a scrubber retrofit of 60 tonnes along with ballast water treatment system of 20 tonnes changed overall weight by 1.75% in lwt, Mr Han reported. This meant a stability recalculation was essential although an inclined test wasn’t necessary, he said.
For a much larger Aframax tanker of 22,000 lwt, a scrubber of 130 tonnes and ballast water system of 50 tonnes created a overall weight change of 0.81% in lwt. Again, no inclined test was required, Mr Han said, noting that his company had launched new retrofitting models for smaller vessels that would ensure that stability tests and inclined tests would not be needed and that cargo space losses would be minimised.