Suggestions for Cleaning a Heat Exchanger

dragoon

dragoon

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Hi,

I have a pair of Volvo TAMD 40s. A couple of years ago one of them started to overheat (gradually at first and then it got to the point where I couldn't run over 3000 RPM without the temperature quickly creeping up).

I did everything at the time to resolve the situation - new thermostats, new impellors etc etc.

In the end, I admitted defeat and took that main heat exchanger off for cleaning and testing. Unfortunately in trying to strip it down, the shop broke it (they basically applied too much force as the tube bundle didn't want to come out of the case) and I had a nightmare job trying to locate a second exchanger for reasonable money (Volvos prices are not what I call reasonable /forums/images/graemlins/frown.gif

The upshot of this was that when I installed the new (refurbished second-hand) exchanger the cooling problems vanished as hoped and, touch wood, have not returned.

Unfortunately I'm noticing a similar pattern with the other engine. It too is running slightly warmer than normal, and pushing the RPMs up to say, 3200-3400 quickly introduces rising temperatures. Same story as before, I've done the easy stuff and I suspect the exchanger needs cleaning.

Now, being someone who learns from their mistakes, I don't want to have this one destroyed in any attempt to get it to bits. So, the question is, what is there I can try to clean it with, without disassembling it?

The requirements are, I suspect, that whatever I use doesn't eat into either of the following;
- stainless steel (tube bundle)
- alloy case
- rubber (o-rings) since I don't want to strip it down.

For example, I've seen references to sulphamic acid and caustic soda. Are these likely candidates?

Any thoughts/experience are greatly welcomed.

Cheers,
Paul
 
Thanks Pete. Any idea as to whether the products (white vinegar, fernox etc. ...) will damage the rubber o-rings?


Thanks,
Paul
 
Fernox & Sentinel products are designed for central heating systems and lots of modern boilers have O rings on them. I have used Sentinel`s Ferroquest on outboards with good results I dont know about vinegar, but I am not impressed with Sentinel`s x400 though.
Pete
 
Thanks Pete.

I took the exchanger home over the weekend. The salt water side was quite blocked with bits of anode, scale etc.

I cleaned it out with a combination of Sentinel Ferroquest and some "elbow grease".

The exchanger is back on the boat again now, but I haven't been out since. Fingers crossed....I'll try it this weekend.

Cheers,
Paul
 
On my last boat I had a similar problem and found a build up of both weed and scale right through the exchangers - oil cooler and fresh / seawater exchanger. This was a VP TMD40A.

I used Fernox radiator descaler to clear the scale and caustic soda to clear the weed. Neither touched the base metals, but I would suggest you apply some solution to a small area first and check the metal does not fizz at all.

Be wary with caustic soda and always always add it to the water and not the other way around. As the solution gets stronger it gets very very hot, and will burn a hole in your skin when properly mixed, so wear old clothes or overalls and decent rubber gloves - marigolds not surgical latex.

Once back on the engine the fog bank that had been following me before disappeared and the engine sat lovely at 86C at full power.
 
superheat6k said:
On my last boat I had a similar problem and found a build up of both weed and scale right through the exchangers - oil cooler and fresh / seawater exchanger. This was a VP TMD40A.

I used Fernox radiator descaler to clear the scale and caustic soda to clear the weed. Neither touched the base metals, but I would suggest you apply some solution to a small area first and check the metal does not fizz at all.

Be wary with caustic soda and always always add it to the water and not the other way around. As the solution gets stronger it gets very very hot, and will burn a hole in your skin when properly mixed, so wear old clothes or overalls and decent rubber gloves - marigolds not surgical latex.

Once back on the engine the fog bank that had been following me before disappeared and the engine sat lovely at 86C at full power.
Click to expand...


Presumabaly you are refereing to Fernox DS3 .. a sulphamic acid based descaler ?.

ds3.jpg


You missed the most important of all the safety equipment when handling caustic soda .... Eye protection........Caustic soda in the eyes is excruciatingly painful and because you cannot open your eyes yourself difficult to wash out without assistance. Permanent damage is very likely!

A plastic or rubber apron is wise. Caustic soda soaked clothing you do not want, Gloves should be long cuffed or gauntlet types.

Stir caustic soda solutions as you dissolve the solid other wise it sits on the bottom a and forms a solid mas which takes forever to dissolve.
 
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