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Old 01-27-2017, 01:36 PM   #1
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Acid Flushing Your Engine

As discussed in another thread, I have decided that routine fresh water flushing does minimal good and has a problem with using the proper zincs for fresh and salt water protection. So I wrote the following article instead, but specifically for acid flushing to remove scale and marine growth, not fresh water flushing.

I had hoped to have it published in boatdiesel, but Peter Compton's requirement that no references be made to Tony Athen's site Sbmar.com led me to stop following and participating in boatdiesel.

So, here it is for your reading pleasure. I will also upload it to the Library hee after I edit it for any comments that I receive.

David
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File Type: pdf Acid flushing.pdf (887.9 KB, 200 views)
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Old 01-27-2017, 01:52 PM   #2
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Dave- Two comments:

1. Do you think it is beneficial to end the process with a basic solution to neutralize acid hiding in crevices? This is more in your realm than mine, you being a ChemEng and me MechEng. I don't know the answer.

2. One thing I rec to my guys is try to schedule acid cleaning before some sort of long trip so it naturally gets lots of post treatment flushing.

Just a case in point: A guy flushed his engines then it sat on the dock for a month or two. He had a starting issue and called me out. I got that sorted and fired up the engine. Walked back to the transom to check for water flow as I usually do. Out the tailpipe came a large plume of reddish something. Best I could figure it was some sort of Cu oxide that was being created in the acidic environment remaining in the coolers. Nothing was leaking, but it could not be good for cooler life.
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Old 01-27-2017, 02:00 PM   #3
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"1. Do you think it is beneficial to end the process with a basic solution to neutralize acid hiding in crevices?"


An excellent point ..... when I must acid flush which is rare - I follow up with a mixture of soda ash available cheaply at any pool supply store. Circulating the soda ash for at least 5 minutes before a water flush will neutralize the acid 'hidden' in the small places.Those hidden places ate typically where the soldered and brazed joints live affectively the weakest locations.
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Old 01-27-2017, 02:59 PM   #4
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Well, guys soda ash neutralization can't hurt. When I did this on big industrial heat exchangers a hundred years ago we finished with a 100 lbs of soda ash and then checked the pH of the return solution after circulating the soda ash for 30 minutes or so to make sure it was alkaline. But we often had dead piping legs that needed some help to get them neutralized.

The reason I didn't explicitly recommend it, is that the raw water flow in a marine engine turns over the volume in the heat exchangers in less than a minute at idle, whereas in our industrial world it was more like several minutes. The turbulence at that high flow rate should get even the pockets flushed out and they aren't deep in any case.

To Ski's point, the best way is to run the engine up to a couple of thousand rpm to really push the water through it while underway. Fifteen minutes of that and I guarantee there will be no acid left anywhere.

And, yes letting the acid sit there for months will certainly corrode the cap and tubes and result in a reddish solution when finally flushed out. I can't quote specifics but if acid will eat through 1/8" thick carbon steel in 24 hours (it will), then it would certainly eat through ten thousandths or so of cupro-nickel in a few months.

Also, I should note that what we used on industrial equipment was HCl with a corrosion inhibiter that reduced corrosion 100 fold so it could be used on carbon steel. There is no corrosion inhibiter in Barnacle Buster which is nuts when you are paying $50 per gallon for the stuff.

FWIW, industrial plants that use direct sea water cooling used to use cupro-nickel tubes in my day and they would last 20 years or so. That of course is 24/7/365 service and probably a lot hotter temps on the other side than we see in our engines. They now use titanium tubes, but that would be way overkill for our engines.

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Old 01-27-2017, 03:07 PM   #5
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Quote:
Originally Posted by djmarchand View Post
As discussed in another thread, I have decided that routine fresh water flushing does minimal good

David
Thanks for letting us know about your decision.

Just curious if that's a decision based on some sort of sample that was compared between the different techniques over long periods of time?

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Old 01-27-2017, 03:51 PM   #6
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great article, thankyou.You do not recommend a yearly treatment, but would you only do on temperature rise, or would a much gentler schedule be advised (say every three seasons) as a preventative measure, instead of waiting? thankyou
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Old 01-27-2017, 04:08 PM   #7
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Kev:

That opinion was based on observing how after coolers fail. Protecting my after cooler was the prime reason for starting fresh water flushing several years ago. I looked at a dozen or so pictures and descriptions of failed after coolers on boatdiesel and they all failed first from corrosion on the air side, which fresh water flushing won't do anything for.

I only have personal experience with one after cooler, the one on my Yanmar 6LY and it is in pretty good shape. I believe that Ski agrees with my conclusion and he has seen many more first hand.

Fresh water flushing also brings into question which pencil anodes to use to protect the raw water side components. If you do a fresh water flush then you should probably use aluminum anodes which are effective in salt and fresh water. (Source- ABYC and aluminum anode manufacturers).

But I believe that the metals in raw water systems- mostly bronze and cupro-nickel are very corrosion resistant in salt water, particularly if protected with zinc anodes, so that fresh water flushing does minimal extra good.

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Old 01-27-2017, 04:14 PM   #8
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tinped:

I think a lot depends on your engine and how it reacts to raw water system fouling. Mine seems to just get a little worse, ie higher wot temps, each season so there is plenty of time to catch it and do an acid flush. As best i can tell mine has been acid flushed only once about 3 years ago at the 10 year age and it dropped the temps about 5 degrees.

So in my case, I am just going to watch the temps. It certainly helps that I boat in LI Sound where water temps are relatively low. If I were in the Gulf Coast, I might acid flush on a 3-5 year schedule.

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Old 01-27-2017, 04:52 PM   #9
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One question, is there any heat echanger out there made of more "high tech" material like carbon fiber?
I am surprise to see that in a highly corrosive environment like sea salt material used seems always the most prone to corrosion on the engine side.
Sure a heat exchanger made of carbon fiber would cost more than cast iron but compared to the overall cost of a boat... peanuts.
But I may also be totally out of my mind here
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Old 01-27-2017, 05:36 PM   #10
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Lou:

First of all, after coolers are made with aluminum housings because they have to be BIG to pass all of that air. My after cooler's diameter is double the main heat exchanger's. So aluminum is used to keep the weight down. Other heat exchangers are made with cast iron housings which last much longer.

Yes, I think that carbon fiber could be used to build after cooler housings. It would have to have precise, machined quality flanges for the core and caps to seal up to it. But I have seen carbon fiber masts and booms with that kind of quality. The Cummins QSB 6.7 uses composite caps but has an aluminum housing. Maybe there is hope for the marine engine industry if they will just take the next step and make the housing out of composites also.

I think that another reason is that most engine manufacturers only understand metal casting and fabrication and don't know beans about composite construction. They also don't see it as a big problem. Even if you don't do a thing about service, a Yanmar after cooler will last at least ten years (mine did) and maybe 20. Cummins after coolers will last half of that time because the core is mounted vertically and air side condensate just sits on the lower air/water o-ring joint.

So maybe there is an opportunity for some smart carbon fiber composite firm to make after market after cooler housings.

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Old 01-27-2017, 06:40 PM   #11
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Just a comment on the Cummins coolers. The end caps are quite concave. They would probably hold 6 oz of water. The bottom cap has a condensate drain, so water does not sit in there in the O ring joint. The bottom end cap will drain completely when the engine is shut down.
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Old 01-27-2017, 07:04 PM   #12
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I recently thought of buying a boat with a single, large CAT engine in it. As it had been serviced by a CAT agent I rang them (with the owners permission) to ask what needed doing.

Almost the first question was had it had a new heat exchanger (it was 10 years old). It hadn't so the CAT man explained on this engine the heat exchanger needed pressure testing and cleaning every two years and replacing every 6 years (the cost a mere 4200 for the part {about $US5K)). They recommend changing not because of wear but because of corrosion.

Yes I know you may say its unnecessary but I couldn't take the admiral across the English Channel or down the Alderney straight without an engine I feel 100% sure about, especially as it was the only one in this boat.

The engine is designed to do 3 - 5K hours a year. If you do this then 1000 a year for this one part doesn't matter, but to me with my 200 hours a year it is a tad expensive.
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Old 01-27-2017, 07:40 PM   #13
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Not all Cummins engines have or had condensate drains and that has led to a lot of damage with these assemblies.


I have seen many (all actually) cast bronze aftercoolers last 25+ years up to 30 years with little or no service and no failures on Hino engines.

On the heat exchangers which I am aware of - maybe 60 or more- they have rarely been acid cleaned and run in salt water for at least 15 years with no issues and with some up to 25 years. In most cases these boats run at higher engine loads (60-75%) and temps as they are mostly used at 15-18 knots in larger heavier boats.


With some limited experience with carbon fiber assemblies in association with non ferrous metals the TCE was too excessive to allow for a reliable seal. Most of these testing applications were in military assemblies and had continuous failures at junction points and required heavy maintenance which was determined to be above its worth at the time. Perhaps the past 12+ years with these mixed assemblies has yielded better results but I am no longer aware of those updates and/or improvements.
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Old 01-27-2017, 07:43 PM   #14
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"FWIW, industrial plants that use direct sea water cooling used to use cupro-nickel tubes in my day and they would last 20 years or so"


Hello Dave,

That is very interesting. It has been quite some time but I was inside a bunch of 'very large' tanks and intercooler systems in a past life. We used to clean out these large heat exchangers and commercial systems for power generation as well as inside of multi-million gallon fuel and oil tanks.
I cannot say I miss the work or the stress of being inside a fuel tank.
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Old 01-27-2017, 07:54 PM   #15
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[QUOTE=smitty477;517726]Not all Cummins engines have or had condensate drains and that has led to a lot of damage with these assemblies.

There was a service bulletin issued in 2008 (I think, might have been 2007) to retrofit a drain in the cooler end cap. It was just a small hole drilled in the bottom of the aftercooler.
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Old 01-27-2017, 08:06 PM   #16
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"There was a service bulletin issued in 2008 (I think, might have been 2007) to retrofit a drain in the cooler end cap. It was just a small hole drilled in the bottom of the aftercooler."


This is the way I remmeber it .....
- there were numerous failures and problems with wnterizing
- many engine failures as a resulst of these problems
- Cummins originally said there was no issue and it was due to operator and servcie error
- a number of owners beacme irate and began a campaign to rectify this
- that eventually turned into a class actions lawsuit
- Cummins evetually setlled by repairing/replacing any engines and assemblies claimed at the time
- There remains many owners who did not know about the issue and may have problems now or in the future


Waht I do remember does not share too much with your post above - "The bottom cap has a condensate drain, so water does not sit in there in the O ring joint."


Here is a link to what is left of the lawsuit site....
https://topclassactions.com/lawsuit-...it-settlement/
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Old 01-27-2017, 08:30 PM   #17
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If I was Marin I would post a couple of pages on this issue. Me...all I have to say is this:

1. No engine mfg recommends acid flush. Most say it is harmful to components.
2. Acid will not flow through a completely blocked tube.
3. Acid flush will not clean the air side of an aftercooler.
4. Acid flush can partially dissolve a salt block in the afercooler that will let go once you get the engine up to cruising speed later. You might not know this happened until too late.
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Old 01-27-2017, 08:33 PM   #18
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[QUOTE=smitty477;517730That is very interesting. It has been quite some time but I was inside a bunch of 'very large' tanks and intercooler systems in a past life. We used to clean out these large heat exchangers and commercial systems for power generation as well as inside of multi-million gallon fuel and oil tanks.
I cannot say I miss the work or the stress of being inside a fuel tank.[/QUOTE]

I used to climb inside boiler steam drums when I was younger. Got stuck once, and that 4 ft diameter drum got even smaller. Was never able to go back inside one.

Regarding running the engine when done to remove any residual fluid's is a good idea. The manufacturer videos that I have watched don't say that.

I want to do this soon.
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Old 01-28-2017, 01:38 AM   #19
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Gilbertpark, one of my favourite pubs is in Emsworth! Can't remember the name but it was my favourite cousin's local, full of smokers and wet Labradors and very nice people. The name might come to me some time in the night...
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Old 01-28-2017, 02:39 AM   #20
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The Sussex! Yay!
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