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Old 11-02-2005, 08:51   #1
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cleaning heat exchanger

How can I clean out the heat exchanger on a freshwater cooled engine?
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Old 11-02-2005, 11:53   #2
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There are so many different styles of heat exchangers (HE) that this will be just a simple start.

There are chemical washes, but I don't recommend them due to the longevity of your job. There’s nothing worse then a mechanical break down or contamination of your fresh water system. And the chemicals may just eat thru the wall of one of the tubes.

I would recommend removing the core of the HE if possible. If not, there will be end caps that can be taken off. And others are just throw-aways.

If you can get the core out, it's a well-built system. You can inspect the tubes for erosion or other possible leakage.

To clean, it best to start with a piece of brass rod half the diameter of the inside of the tubes. With the end ground square to the length, push it through gently. It's best to have the core mounted to something solid so you can get straight smooth strokes. DO NOT dent the tubes!!!
If it's fairly clean then use a larger brass rod that will just slide easily thru the tubes. Chances are they will not be perfectly straight. And you do not want to gouge the metal but just scrape out the alkali build up. It doesn't have to be a perfect job, but just so you can see thru clearly.

I've seen people run long drills thru with damaging results. If it's so bad you have to use a drill then do it by hand and gently. Also, grind a radius on the corners of the drill. That keeps it from digging into the metal allowing the flutes do the cleaning. The tubes are between .015" to .060" wall thickness depending on the size of your HE.

Well, that's a start. Enjoy................................_/))
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Old 11-02-2005, 13:14   #3
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A Car radiator flush product is safe to use. they are designed for copper cores of Vehicle radiators. There effectivness to cleaning properly is still in my debating list. I have had mixed results with these products. The most effective way of cleaning a Radiator, and I suggest an HE as no different, is to flush clean water through mixed with compressed air. It bubbles away inside and the surging inside the Radiator/engine dislodges rust from the core quite effectively. However, Delmarrey's advise is good and will ensure a whistle clean core at the end of the excersise.
Good luck.
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Old 11-02-2005, 18:41   #4
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Delmarrey's post made me wonder if using a gun cleaning kit would be a worthwhile idea. The rods are aluminum and there are different sized brush ends available. I have never cleaned a heat exchanger so I do not know what works.
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Old 11-02-2005, 19:36   #5
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The deposits are the same as in radiators. Much like the crust that forms around water faucets in Arizona.

As for a gun cleaning brush, the copper brush after it's scraped with the brass rods may clean it up a little better but would probably ruin the brush

The problem with chemicals is, what desolves alkali (acid) also eats metals except high grade stainless, monels, ferrillium, titaniums, ect. and some aluminums.

The car stuff is for maintenance purposes but you can ask any radiator shop and they'll tell ya it won't unplug. Some car rad's are now made of alum. and the big problem is if you let them set they'll self distruct. I've seen one in a Jeep CheapOcree that looked like a yard sprinkler......................_/)
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Old 12-02-2005, 05:43   #6
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Cleaning Heat Exchangers:

Condensers & Heat Exchangers will foul after several years in warm water, due to scaling & deposition (and/or biofouling), which interferes with efficient heat transfer. Other factors that can affect the heat exchange process include water velocities (flow rates), ingress of air (entrainment), and bacterial contamination. Most marine FWC thermostats open at about 160̊F, and will be fully open at approximately 180̊F. A new clean system, under moderate load, should operate at the lower end of this range - and a fouled system, under full load, might operate in the upper range. Any temperature that reads outside of this range is abnormal and should be investigated.

Heat exchangers are generally cleaned by Chemical* or Mechanical methods, or a combination of both.

CHEMICAL CLEANING:
Chemical cleaning can be performed “in situ”. Proper cleaning is a two-step operation. First, clean the unit with a strong alkaline solution, to remove organic dirt such as oil. Second, clean the unit in an acid solution to remove scale. The preferred solution is to remove the heat exchanger and take it to a radiator shop for a complete professional cleaning.

WARNING: Strong chemicals (alkalies & acids) can be dangerous and difficult to use effectively and safely. I do NOT consider cleaning heat exchangers to be a DIY job for the casual handiman.

FWIW,
Gord
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Old 13-02-2005, 05:36   #7
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I totally agree with Gord. There are radiator shops in every port that are fully equipped to recondition heat exchangers at a cost to the owner that will, ultimately, be less than the damage done by unskilled persons. The use of acids and alkalies is dangerous when properly equipped; more so when not equipped properly. Let the professionals do their job. It would be terrible to nick a tube only to find out some time later when the raw water is mixing with the fresh water and the whole thing becomes a mess.

Jim
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Old 13-02-2005, 22:46   #8
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I agree, one should probably take it to a professional. BUT, suppose you are out in the deep blue and suddenly your engine starts to over heat.

I think every motor powered boat owner should know the basics about maintenance and repairs.

At least, every sailorman should watch to see what is inside and see how it's repaired. Not everyone can be a Captian, some have to be the Engineer.

................................._/)
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Old 24-05-2005, 17:01   #9
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The easiest way to clean a hear exchanger is use a boiler 'de-scaling' compound. Such de-scalers are organic acids that do not attack/dissolve the base metal. Drain, then just pour in the descaler, let soak, then flush. Muriatic (HydroChloric) Acid can be used, but will dissolve the scale and will also dissolve the base metal.

Marsolve (www.marsolve.com) ... sometimes available at West Marine, etc.
or
Rydlyme.
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Old 24-05-2005, 18:20   #10
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any suggestions on how offen the heat exchange should be checked. I have a fresh water boat and always check for proper flow from the exhaust on start, but I would hate to have this clog at a bad time
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Old 24-05-2005, 19:30   #11
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Fouling is totally dependent on the amount of dissolved carbonates in the water AND the operating temperature of the cooling water. The hotter the water the faster the 'salts' will come out of solution and foul.

Best way is to monitor the engine temperature under a 'control' condition (say ... 2000 rpm for 10 minutes ... and the intake raw water is about 75degrees. Simply keep a 'running' plot of the engine temperature and consider to descale if the running plot and the temperature changes. You dont have to make a formal list, just keep the 'number' in your head and check occasionally. Just be aware of the 'personality' of you engine. :-)
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