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Old 10-15-2021, 12:57 PM   #1
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opinions on cupronickel heat exchanger anodes

i have a bowman heat exchanger on my engine and i was looking for a place to install an anode. couldn't find any fitting on it anywhere.
sent an email to bowman, the manufacturer of the exchanger, and they say they make the unit from cupronickel, and zinc anodes are actually harmful and can strip the protective layer from the metal and cause corrosion to start.
does anyone have experience with this? i've been around boats for 60 years and haven't been aware of anything like this.
the note they sent back says the royal navy uses they're products, and they install a sacrificial piece of black iron plumbing in line and replace it as needed.
can someone school me on this?
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Old 10-15-2021, 01:06 PM   #2
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I have never heard of that and I am a retired chemical engineer. Usually they say that the cupronickel is sufficiently corrosion resistant that you don't have to worry about it.

I generally agree although I have always used zinc anodes in my Yanmar engine's heat exchangers.

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Old 10-15-2021, 01:08 PM   #3
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Cupronickel is the gold standard material for HXers. Our Perkins Sabre/Cat3056 uses them for engine and transmission HXers with no zincs to replace. Industrial use of nickel alloys for all manners of solution applications is about a century old. One of the better known nickel alloys is Monel, a wonderful material for fuel tanks.
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Old 10-15-2021, 01:15 PM   #4
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I found the same on my cupronickel exchangers. There is a little plug on them, but when I pulled it it was just a plug. No place to screw in an anode. I just assumed that was okay and didn't get around to looking into whether I was right. Nice to know.
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Old 10-16-2021, 06:04 PM   #5
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ok, happy to have some input on that.
so those of you that run these cupronickel exchangers, do you use a sacrificial piece of black iron plumbing inline or not worry about it?
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Old 10-16-2021, 06:41 PM   #6
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ok, happy to have some input on that.
so those of you that run these cupronickel exchangers, do you use a sacrificial piece of black iron plumbing inline or not worry about it?
Fuggetaboutit.

David
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Old 10-16-2021, 07:14 PM   #7
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Consider setting up a tee above raw water intake valve so you can flush with fresh water. Works for me.
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Old 10-17-2021, 08:38 AM   #8
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Consider setting up a tee above raw water intake valve so you can flush with fresh water. Works for me.
i was thinking of doing that exact thing. do you use a hose at the dock or just valve it into your pressure water system?
i imagine keeping it totally separated from the domestic water system would be the proper way.
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Old 10-17-2021, 09:25 AM   #9
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Take a look at the following pic to see how I set up a fresh water flush for my engine. I drilled and tapped the sea water strainer and installed a bronze street elbow, a ball valve and a hose fitting.

To use it I hook up a water hose and turn the water pressure on while the through hull is open. Then I start the engine. I close the through hull so that only fresh water is being sucked up. The raw water pump on my Yanmar 6Y would suck more water than the limited water pressure at my dock would supply so the hose collapsed a bit. No problem.

Then wait a couple of minutes with the engine idling. Close the water valve and immediately shut off the engine. Then open the thru hull and you are finished.

There is some debate that if you do this you should use magnesium anodes made for fresh water use since that is what is in the engine 90% of the time. I won't comment on that as I don't know what is right.

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Old 10-17-2021, 11:13 AM   #10
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Take a look at the following pic to see how I set up a fresh water flush for my engine. I drilled and tapped the sea water strainer and installed a bronze street elbow, a ball valve and a hose fitting.

To use it I hook up a water hose and turn the water pressure on while the through hull is open. Then I start the engine. I close the through hull so that only fresh water is being sucked up. The raw water pump on my Yanmar 6Y would suck more water than the limited water pressure at my dock would supply so the hose collapsed a bit. No problem.

Then wait a couple of minutes with the engine idling. Close the water valve and immediately shut off the engine. Then open the thru hull and you are finished.

There is some debate that if you do this you should use magnesium anodes made for fresh water use since that is what is in the engine 90% of the time. I won't comment on that as I don't know what is right.

David
I would use aluminum anodes since they are good for salt water or fresh water. Magnesium should only be used in freshwater.
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Old 10-17-2021, 12:45 PM   #11
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Freshwater flushing your engine(s) regularly is probably the single most important step you can take to "slow down" the ravages of saltwater induced corrosion also called "marine age". This marine age happens even when not running your engines (probably more so as they sit full of saltwater when not in use). Saltwater is a much better "electrolyte" than freshwater (think battery acid in a lead acid battery) and allows the passage of corrosive current way better than freshwater. Regular freshwater flushing can extend the time between fully (off engine) servicing your raw water cooling components (such as fuel cooler, aftercooler (needs more maintenance than the other components), gear oil cooler, heat exchanger, and exhaust elbow). It will not eliminate the need to take all of these components off the engine for deep (acid) cleaning, installing new O rings and/or seals, and PRESSURE TESTING, but can extend the timeframe between servicing (see info on sbmar.com). With aftercoolers, not only is corrosion often a bigger issue (than with the other items), but the air side of the aftercooler needs cleaning properly as well as the raw water side, and pressure testing is vital.

David M's setup and advise is exactly what I did with my engine and generator.
Comodave is also correct about the use of aluminum engine anodes being "best" if utilizing freshwater flushing to protect your engine. Zinc will develop a "coating" when exposed to freshwater (so those of you who operate in both freshwater and saltwater could benefit from aluminum anodes as well) that will "isolate" the zinc greatly reducing it's effectiveness. It can be "reactivated' by cleaning, but this requires a "mechanical" cleaning not just running. Aluminum will provide the required protection in all types of water. I discovered this info (aluminum vs zinc) from several sources like Performance Metals, Martyr and other (what I trust as) reputable sources.
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Old 10-17-2021, 01:13 PM   #12
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i like the idea of aluminum anodes, i'll probably fit one to the genset if i can ever get the plug out of the end of the heat exchanger. i've been putting penetrating oil on it for a week now.
fisheries supply doesn't seem to carry them though. all the pencil type anodes they carry are zinc.
like i said at the beginning of the thread, my main doesn't have any anodes, no place for them in the cupronickel exchangers. that's probably the biggest reason i want to install a fresh water flush system. i may be overthinking it though, the boat has been like this since it was built in 1972 and it looks great. the exhaust elbow was replaced before i bought it and the original heat exchanger/header tank look fantastic.
i don't know if my raw pump will draw more than the dock supplies but i doubt it. my dock water has higher pressure than usual, no problem with low output. i think i'll just install a t after the strainer and leave the seacock open. it's pretty tough to get to the engine while it's running unless i pull up the floors. the front access makes me crawl right next to the alternator.
i figure if i'm going to actually use the flush system i need to make it really easy to use, so a fitting in the cockpit or laz would be best.
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Old 10-17-2021, 01:51 PM   #13
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Here's the potential problem with securing the seacock while running shore pressure water into a tee at the sea strainer or, as in my case, to a tee in the seawater hose between the strainer and the pump. First, you could over pressurize the seawater pump's water seal creating a leak there - this is especially the case if you shut the engine down with the pressure still on. Second, you could forget the hose and possibly hydro lock the engine. I have a pretty seawater-hungry cooling pump in my Yanmar 315 HP, but at idle with the seacock open and the water pressure from shore on full flow to the tee, I get plenty of water out the exhaust as well as out of the bottom of the hull though the seacock. So my take is that by all means one should freshwater flush the system but without shutting the seacock off. Just shutdown the engine and shore water in that order.
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Old 10-17-2021, 07:46 PM   #14
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Yeah, I pull fresh water from a 5 gal bucket on the dock, no pressure issues.
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