Your offshore supply boat is fitted with cooling water systems serving the main propulsion diesel engines as shown in the illustration. What heat exchanger or cooler location would most likely be fitted with sacrificial zinc anodes which must be periodically inspected and replaced when sufficiently deteriorated? Illustration MP-CW-15
• Sacrificial zinc anodes are installed where sea (raw) water flows, to protect metal surfaces from galvanic corrosion. • On shell-and-tube coolers, the water box (end cover on the seawater side) is usually where anodes are mounted for easy inspection and replacement. • Closed fresh-water or lube oil sides are far less corrosive and normally are not protected with zinc anodes in the same way.
• Look at the diagram and decide which component carries raw seawater versus closed fresh water or lube oil. • Think about which part of a heat exchanger is easiest to open up in service so you can reach and replace zincs: the shell, or the end water boxes? • Ask yourself: which specific cooler in the system has a raw-water side that needs protection from seawater, and which side of that cooler (shell or water box) would be in contact with that seawater?
• Identify on the illustration where raw water in/out is labeled and trace that path to the correct cooler. • Confirm whether each answer choice refers to a part that actually carries raw seawater, not just fresh water or oil. • Make sure the location you select is a water box/end cover on the raw-water side, where zinc plugs can practically be installed and serviced.
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