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questions regarding filters of seawater for cooling systems

questions regarding filters of seawater for cooling systems

(OP)
Hello,
I am a Msc student for oceanography, and, for the sake of a small project about marine plastic, I would be very thankful for the kind help with some questions regarding suction filters of seawater used for cooling on ships:
1. What is the average size of those filters in ships of varied sizes (container’s ships, gas carriers, other bulk carriers, and passengers ships )?
2. What is the average filter hole size?
3. How often do these filters have to be cleaned, and how much garbage is found in them each time?
4. What is the average flow rates of seawater into cooling systems of ships of varied sizes?
My thought is to look at the idea of collecting the garbage and plastic that is filtered in those filters of cooling water on ships, instead of tossing it back to sea – and try to calculate whether it could be a meaningful contribution for ocean cleanup…
Would appreciate your help – either answering those questions or directing me to where I could find this information. Thank you very much,
Oriya

RE: questions regarding filters of seawater for cooling systems


The recommended flow rate at the shipside sea inlet is 0.5 m/sec. The shipside screen size is then dependent on the sea water pump/ pumps flow rate. Screen hole size is calculated to produce this flow.
The reason for the sizing relates to the environment (protection of fish) mainly but also to the inlet pipe sizing.
Factor in also your pump discharge filter ,which also affects flow rate.

Offshore Engineering&Design

RE: questions regarding filters of seawater for cooling systems

The fish will swim away from any current in a horizontal plane; this is why schools of fish all turn in unison.
Not so for vertical currents; fish are relatively insensitive, and would be drawn into a vertical flow, up or down.
However, most of the sea chests I have seen (on medium to large yachts) open directly into the bottom of the hull.
Some have bar grate size screens at the hull surface; some don't.
Some have scoops facing forward, with or without bar grates.
Most have additional filtration within the suction plumbing for each system, hole size 1/4" or smaller, mostly to trap barnacles, which are unfortunately not a viable cash crop.

One fleet of my acquaintance uses suction pipes in the side of the hull, just below the waterline, and sturdy but frangible 'blocks' just ahead of the inlet piping, because they deal with a lot of floating ice.

Any device that could be arranged to scoop plastic from the water would necessarily have a lot of drag, even before it caught any plastic, so the boat owner would be paying a huge penalty in fuel consumption, to harvest a 'crop' that is at best very diffuse, so even if a market could be found for what you could scoop up, you couldn't get near breaking even economically. Absent government intervention, harvesting flotsam is probably not a viable business.





Mike Halloran
Pembroke Pines, FL, USA

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