The Noble Pearl, a 25.61m fishing boat, is one of fifteen vessels owned and operated by Raptis. It was up for its two-year survey, which involved wet abrasive blasting and re-coating both above and below the water line.
The first step was to give the entire boat a pressure wash and to clean it up below the water line. We then undertook spot abrasive blasting in places, which involves feathering over a particular spot to clean out the rust. This was followed by sweep blasting, where we wave over the entire surface.
Following abrasive blasting, we then applied new coatings to the boat. The first layer was high-build epoxy everywhere both above and below the water line. We then applied a polyurethane top coat above the water line, while below the water line received a tie coat. This was then followed by two coats of anti-foul paint. In this process, we use two-pack industrial marine coatings. We then completed the job by painting in the draft and plimsoll marks.
Overall, the job took us about 12 days to complete, with 3 - 4 workers on site at any one time. All of the workforce at AEB are blaster-painters who have their EWP and confined spaces tickets.
Wet abrasive blasting is so effective on this type of job, and is preferred over conventional dry sandblasting or grit blasting, because very little dust is produced, and so other trades in the immediate vicinity are not prevented from working. With wet abrasive blasting, all the media falls within a 3 - 5m radius; with conventional dry slurry blasting or media blasting, the media can sometimes fall as far as 20m away.
In addition, wet abrasive blasting uses half the media of conventional dry sandblasting. It also removes salts and chlorides from a ships’s surface and hull more effectively, which means that anti-fouling paints and marine industrial coatings adhere to the surface better and so last longer.
Water in the job was used at the rate of 0.5 litres per minute, so in a day’s blasting we would expect to use between 200 - 500 litres.
The process for cleaning a boat like the Noble Pearl is also different when you utilise wet abrasive blasting as opposed to dry grit blasting.
Dry blasting would involve washing the boat with water, dry blasting, and then washing again. With wet abrasive blasting, the ship is blasted first, followed by a pressure wash, then marine industrial coatings are applied.
This means that the surface is cleaner, with salts and chloride having been removed more effectively. This also means that coatings and anti-foul paint adhere better and so do a more effective job for longer.