Heat Exchanger Tube Repair?

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RentonRiggos

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Joined
Aug 30, 2020
Messages
13
Location
USA
Vessel Name
Journey
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Queenship
I had my heat exchangers pulled this year for a pressure check. There had been some increased coolant usage on one engine over the other on end of year cruise in 2020.

When tested, one HX was fine and one had a hole in a tube (1 of 15 tubes). I was presented with options to have a new HX fabricated (engines are DD 8.2T's and parts not easy to find) or to have the offending tube plugged. The new fabrication cost was 4.5X the repair.

Plugging the tube will leave me with 14/15 tubes (a loss of 6.7% heat transfer efficiency?). I am deciding to do the repair based on the following assumptions... 1) The HX could have been designed without some factor of safety for heat transfer efficiency. 2) I boat exclusively in the PNW and the raw water is much colder than in other climates (probably 20-30 degF delta T from FL?) that I assume they need to design boat systems to be able to handle.

Am I way off base with my thinking or should this be fine as long as I keep an eye on the running temperatures?
 
Your thinking is reasonable (I am a retired ChemE). But I am surprised that you can't find a replacement at a reasonable price. Often they were generics made by Sen-Dure, Lenco and Mr Cool. Buy the ones with cupro nickel tubes which last much longer than copper.

David
 
RentonRiggos said:
I had my heat exchangers pulled this year for a pressure check. There had been some increased coolant usage on one engine over the other on end of year cruise in 2020.

When tested, one HX was fine and one had a hole in a tube (1 of 15 tubes). I was presented with options to have a new HX fabricated (engines are DD 8.2T's and parts not easy to find) or to have the offending tube plugged. The new fabrication cost was 4.5X the repair.

Plugging the tube will leave me with 14/15 tubes (a loss of 6.7% heat transfer efficiency?). I am deciding to do the repair based on the following assumptions... 1) The HX could have been designed without some factor of safety for heat transfer efficiency. 2) I boat exclusively in the PNW and the raw water is much colder than in other climates (probably 20-30 degF delta T from FL?) that I assume they need to design boat systems to be able to handle.

Am I way off base with my thinking or should this be fine as long as I keep an eye on the running temperatures?
Click to expand...
I think you are relatively safe.

Most HXs are built with 10% overcapacity at design parameters.

Your inlet temperature is, as you say, probably lower than design temperature.

Would it not be possible to cut out and stab in a new tube?

Just an idea.

I have written dozens of repair procedures, plugging procedures, and created a database for required plugs and mapped plugged heat exchangers at my workplace.

But honestly, it has little relevance to our teeny tiny unregulated heat exchangers on our boats cooling systems.
 
If I bought a new one I was going to go cupro-nickel. The initial quote was for almost $2000 for the heat exchanger. I was a little surprised at the plugging costs but At least that includes the testing, cleaning and etc. as well. If both had leaked I would have figured an age related issue (26 years) and probably replaced them both (ouch). Given it was just one of them that was leaking, I was hoping to get by with the repair. I am glad my reasoning is standing up so far.
 
My question is what caused the hole and how close are any of the other tubes to having holes or leaking? Depending on intended length of ownership or till repower, might impact my decision. I would probably plug it also, but not knowing if and when the next one might fail, would nag at me.

Ted
 
Try orcamarine.com in Bellingham. Should have them.
 
dbles said:
Try orcamarine.com in Bellingham. Should have them.
Click to expand...

Thank you for the information. They have a item # for the HX for my engines and I have reached out to them to see what the pricing is.

On an unrelated note... Is that a Great Harbour in your profile pic? I have wondered how the hull shape and windage do specifically in the PNW.
 
Plugging will buy you several more years, maybe. Mr Cool lists CuNi exchanger at $1267 plus shipping. Put one in your capital improvement list.
 
O C Diver said:
My question is what caused the hole and how close are any of the other tubes to having holes or leaking? Depending on intended length of ownership or till repower, might impact my decision. I would probably plug it also, but not knowing if and when the next one might fail, would nag at me.
Ted
Click to expand...
My guess is the other tubes aren't far behind.
 
Lepke said:
My guess is the other tubes aren't far behind.
Click to expand...
My experience is that consistent degradation across a heat exchanger is the exception, not the rule.

Although if galvanic corrosion is the failure mechanism, you may very well be correct.
 
Buy a new one if you are going to keep the boat. I take it the engines are most likely older. So with that all of the heat exchanger tubes may have have several hours on them.
 
O C Diver said:
My question is what caused the hole and how close are any of the other tubes to having holes or leaking? Depending on intended length of ownership or till repower, might impact my decision. I would probably plug it also, but not knowing if and when the next one might fail, would nag at me.

Ted
Click to expand...

Definitely wondering what caused the one hole. Plugging the tube will cause a nagging concern but the cost of the replacement (so far) has exceeded the opportunity cost of the nagging concern.
 
fgarriso said:
Buy a new one if you are going to keep the boat. I take it the engines are most likely older. So with that all of the heat exchanger tubes may have have several hours on them.
Click to expand...

I am planning on keeping the boat for a few years at least. The engines are old but not many hours (26 years and 1200ish hours) so the HX are newer than their calendar age. For 23 of the 26 years it has been docked in freshwater so there has been even less saltwater aging than normal as it gets as good flush between cruises.

If another tube goes (especially in other HX) I would probably replace both HX.
 
Thanks. I had not seen that one. Significantly better than the pricing so far... HX are definitely on the capital improvement list. Just not sure of the timing yet.
 
Plugging should be easy. There isnt much pressure maybe 15 psi depending on cap.

Squire it full of 5200 or epoxy after a thorough inside cleaning. But as Lepke said above dont be surprised on other tubes fail.
 
bayview said:
Plugging should be easy. There isnt much pressure maybe 15 psi depending on cap.

Squire it full of 5200 or epoxy after a thorough inside cleaning. But as Lepke said above dont be surprised on other tubes fail.
Click to expand...

Wondering if you could straight thread tap both ends and put in screws, maybe with a little sealant.

Ted
 
What does it look like? Is it hanging off the engine or incorporated like an aftercooler? Lots of options for heat exchangers, don't be afraid to look at alternative solutions like plate coolers?
 
jleonard said:
:thumb:
This. I would not fret about any loss of efficiency at this point. I would just monitor for additional problems in the future.
Click to expand...

Some of us do not clean the HX until the temp is a problem.
Have it plugged professionally and watch the temps.
Keep hunting for a NEW HX and start saving up to repair the existing HX if necessary.
 
O C Diver said:
Wondering if you could straight thread tap both ends and put in screws, maybe with a little sealant.

Ted
Click to expand...

Probably could but those tubes usually aren't very thick and I would be cautios about any extra stress on the solder joint. Sheet metal screws and faucet washers too but I like the idea of no stress sealant.
 
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bayview said:
Probably could but those tubes usually aren't very thick and I would be cautios about any extra stress on the solder joint. Sheet metal screws and faucet washers too but I like the idea of no stress sealant.
Click to expand...

I was thinking of selecting a standard or metric thread size where maybe you cut threads with 25% engagement. The thread doesn't really need any strength as the screw head is sealing the tube.

Ted
 
The HX is pretty close coupled and well incorporated within the engine envelope. I would hate to rig something up differently (even understanding that the Thermodynamics are OK) as that would almost certainly limit access in one of the few well accessible areas of the ER.
 
Had a heat exchanger start to leak, and all it was is the solder had dissolved.


A local radiator shop with a BIG torch repaired it in about 10 min.
 
I wouldn’t waste another brain cell on this. Heat exchangers, in my opinion, should not be repaired. I believe they are throwaway items. The best place I’ve ever been to to provide me heat exchangers for all of my boats is Lenco located on Long Island. I would bet you one “boat unit “ they not only know the exact heat exchanger for your engine but they probably built hundreds of them over the years. Very knowledgeable folks, very friendly folks.
https://www.lencocoolers.com/
 
Thank you very much. You are correct and they have my engine HX (2 variations actually) listed oin their site. They give important dimensions so I can check which one is a bolt up for my configuration.
 
Even better, if you want something custom, like a petcock for draining which might not be your heat exchanger, they will weld a fitting in for you and provide the petcock. These guys are on markedly accommodating. And I know this stuff called. My friend had a transmission cooler fail while he was on vacation in Long Island sound. It was just his luck to find these guys. He called them with his problem and they told him he should just bring the unit to him, they would match it up, they would build one while he waited.
Two hours later he had a finished product, painted, ready to be installed.
 
RentonRiggos said:
If I bought a new one I was going to go cupro-nickel. The initial quote was for almost $2000 for the heat exchanger. I was a little surprised at the plugging costs but At least that includes the testing, cleaning and etc. as well. If both had leaked I would have figured an age related issue (26 years) and probably replaced them both (ouch). Given it was just one of them that was leaking, I was hoping to get by with the repair. I am glad my reasoning is standing up so far.
Click to expand...

Me, I'd spend the $2000 or whatever quickly and with no quibble. Then repair the other and use it as a running takeout. The lifeblood of wet exhaust marine diesels is the cooling system and associated HXers, pumps, lines and exhaust shower head. As I recall the 8.2 cooling system is a watch out area. You've done well.
 
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HI... I think you are Way overthinking this.... Over the yeas I have had 3 heat exchangers rebuilt by local, Large Auto Radiator shops, at a very reasonable Price, using the correct internal tubing... Call a few in your Area & tell them your problem...Ken
 
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