Continuous heat exchanger cleaning?

[Mainstreet]

Like most folks, I have at least four heat exchangers on Odissea; Two for the AC units, one for the fridge/freezer, one for the main engine and one for the generator. Guess that adds up o five!

My mooring for the last three months and the next three months is a very biologically active South Carolina creek. Cleaning raw water strainers is a weekly headache. I've heard of putting hot tub bromide pellets in the strainers but am loathe to do so until I hear of that process being neutral to the metals associated with the equipment.

Are there other methods for continuous cleaning of heat exchangers out there that are proven and effective?

[Greg H]

I purchased our cat in st Augustine and live on the west coast. While in St. Augustine I had a A/C guy to come check out our two systems. He suggested using chunks of clorine tablets in the strainer baskets that are normally used for swimming pools. He was a nice guy had his own business took a lot of time answering my questions. I wish I had his info because I would recommend him. He knew I was taking the boat to the west cost so he had no reason to give me information that would shorten the life of my A/c system. Having said all of that I have read varying opinions on using clorine. It's been working for me for over two years.

[tkeithlu]

I hope that someone who knows about this topic will post. I really want to know the answer.

[ranger58sb]

I have read chlorine may be corrosive whereas bromine may be less so, or even not corrosive. (Conflicting info, on that last.) A boat neighbor uses bromine, and still has to clean out his strainers periodically.


I have read a piece of copper in the strainer will discourage critter growth. Sounds plausible, given copper was a traditional anti-fouling ingredient. I have a small copper elbow in our AC intake strainer, but can't tell if it's useful or not. No marine growth, but that might be coincidental. And it doesn't do anything about the mud or jellyfish (sea nettles).


It is possible to add an easy-flush mechanism to a raw water intake system. Google Groco's safety seacock conversion (SSC) and flush adapter for an example of an already-made-up system of fittings that could be useful for the job. OTOH, dock water pressure may or may not be sufficient to clean out mud, and I know it probably won't clear a sea nettle from the strainer (too gooey)... and you'd probably not want jellyfish being forced through your AC or similar system, anyway.


Our SSCs are immediately after the seacock and before the strainer, so attaching a garden hose is easy and fresh water through the strainer and follow-on system helps a bit. OTOH, I still have to clean mud -- and the occasional jelly, sometimes -- from the strainer manually.


I have used the flush adapter to clean the system with "product" -- in this case, Rydlyme -- and that's much more effective than plain pressurized fresh water. OTOH, when I did it, I still removed the strainer baskets and cleaned those manually... so not sure whether Rydlyme (or Barnacle Buster, or similar) would have done that or not. And the cost of "product" can mount up a bit... so I haven't used that more often than about once/year.


In my AC system, I used a small electric transfer pump to fill the AC plumbing with the stuff... then let it sit... then flushed. Worked like a champ. For the main engines and genset, I did it slightly differently, using a recirculating approach... which also worked like a champ, possibly even better. But even for mains and genny, I removed the strainer baskets and cleaned them separately.


Doesn't hurt to have spare strainer baskets, especially for the AC system in hot climates. That can at least make part of the process faster. Out with the old, in with the new, clean the old one at your leisure.


-Chris

[svHyLyte]

Originally Posted by Mainstreet

Like most folks, I have at least four heat exchangers on Odissea; Two for the AC units, one for the fridge/freezer, one for the main engine and one for the generator. Guess that adds up o five!

My mooring for the last three months and the next three months is a very biologically active South Carolina creek. Cleaning raw water strainers is a weekly headache. I've heard of putting hot tub bromide pellets in the strainers but am loathe to do so until I hear of that process being neutral to the metals associated with the equipment.

Are there other methods for continuous cleaning of heat exchangers out there that are proven and effective?

If your strainer basket is of the plastic type, you can cut a small length of copper foil of the type sometimes used for grounding on SSB's; roll it loosely around a pencil and then drop the roll in the filter basket. The copper will dissolve over time but prevent "growies" from taking hold in your water lines. For easier flushing, either with fresh water or recirculating something like "Barnacle Buster" to dissolve scale and barnacle shell build-up, if you have a Groco strainer, you can fit a Trac FLUSHcap to your unit to make it easier to clean/flush.

FWIW...

[a64pilot]

Both chlorine and I believe Bromine are very active in oxidizing metals, I can't link to a source that proves that though.

OK a quick Google resulted in this

the effect of having chlorine and oxygen in the same solution is to incease the corrosion rate or velocity of corrosion. the corrosion rate of steel in water is a function of the concentration of oxygen. if chlorine is present then the corrosion rate will be a function of the total concentration of oxygen + chlorine.
in the paper below you can find graph that show the relationship between oxygen content and corrosion rate and also the effect of the conc of NaCl.
In simple terms the effect of the NaCl is to increase the electrical conducibility of water that increase the corrosion rate.

V
Source(s):
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=...
http://www.corrosionist.com
http://www.corrosionist.com/Corrosion_Co...

[Lepke]

I have used both chlorine and bromine for controlling organisms in the tropics, but not at the same time. There are chlorine or bromine dispensers that are used in industries with tanks using raw water.
I have a wood boat with a copper plated bottom. I still have to paint it.

[CaptTom]

We had a spa (hot tub) with all kinds of different metals in the pumps and fittings. The manufacturer recommended bromine tablets. There's a test kit you use to keep the bromine levels up all the time. So, at least in that application, it's considered non-corrosive. They also recommended keeping the water in a narrow pH range (another test kit), so that may be part of the equation.

I did try the copper penny in the AC strainer once. Corroded into a black mess. I was worried it might be from electrolysis. We're not in an area that supports a lot of growth, and we don't use the AC much, so I can't say if it was effective.