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Old 11-22-2015, 01:20 PM   #1
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Fuel Tank Integrity Testing?

Sorry, but this is a YAFTT - yet another fuel tank tread. Here are the facts ...

1. Bought my 1985 OA 38 in August. It surveyed pretty well, EXCEPT there were metal grains or filings in the Racor bowls. Note they were shiny metal, not brown flakes of rust. Both the surveyor and the diesel mechanic said they were likely signs of pending tank failure, and I should replace the tanks before I found diesel in my bilge. Based on their comments I negotiated a reduction in the boat's price and closed the deal.

2. The boat is now on the hard at the shop. I have contracted with a fuel polishing service to polish the approximately 100 gallons in each tank. In speaking to the polishing guy, who does a lot of boats, he thinks I may not have to replace them. Apparently the polishing process vigorously sucks from the bottom of the tank, and cycles all the contents 10 times, eliminated any sludge, water, etc. He said that once that process is complete, one can then test the thickness of the tank walls to determine if they are sound. He said there is some tool that can do this, but he did not know its name.

So my question is ... can anyone tell me how I can test the thickness of my fuel tank walls while the tanks are 2/3 full of diesel? Is there some sort of hand held ultrasound gizmo one can rent, or a service that does this sort of thing? Any advice is most appreciated. Obviously I am trying to cut down the $10-$15k a tank replacement will cost me.
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Old 11-22-2015, 01:28 PM   #2
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Ultrasound service providers also go by the industry name of Non Destructive Testing (NDT) services. Ultrasound is not a DIY process and best left to the pros. Cost are fairly reasonable if a service is locally available. Try materials testing laboratories locally too. Good luck.

Edit: Geo Annalytical labs can help point you in the right direction too.
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Old 11-22-2015, 01:49 PM   #3
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Are you able to get to the backs and undersides of the tanks? If not, not sure ultrasound in is gonna give you what you want to know.....
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Old 11-22-2015, 01:51 PM   #4
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Let's start with the fact that most fuel polishing is a waste of time and money unless you have access plates that allow you to get into most of not all of the baffled areas in the tank.

As to measuring the thickness of the tank walls, I don't know of any way to do a thorough job of it unless you can access each of the tank walls completely.

I would spend my money on adding dual fuel filters or increasing the size of the Racors you have now and worry about the tanks leaking when or if it ever happens.

The metal particles could be left over from when the tanks were made.

What do the exterior of the tanks look like?
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Old 11-22-2015, 02:42 PM   #5
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In a 1985 yr old boat's diesel fuel tanks, be they original or otherwise, shiny metal flakes do not sound threatening, nor due to age. Possibly there was some sort of addition hole cut into tanks over the years (maybe even in the last few/several years)?? The shiny metal may be due to that. Was/were there other reasons why the surveyors mentioned soon-to-be need for tank replacement?

Your mention of..." I am trying to cut down the $10-$15k a tank replacement will cost me."... seems mighty, mighty high to me. If that is a bid you got for completely out-serviced remove/reeplace... get a couple more from others. You could also defer much cost by doing some of the process yourself. Also, with tanks removed it is good time to freshen-up the entire tank placement area[s].

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Old 11-22-2015, 05:41 PM   #6
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Question

to further clarify, there is an 8" access port on the inboard side of each tank, plus one can remove the smaller cover on the top that holds the sender unit. I can easily access the top, front, back, and inboard side of each tank. Getting at the outboard side would be problematic.

As for the quotes I got, two reputable yards quoted $13.5 k and $11k respectively to cut out the existing tanks and replace them with custom made stainless or aluminum. Which is why I am looking for every possible option, including relining the existing tanks with bladders (that was a third yard's idea) and coating the existing tanks (after cleaning) with one of those space age sealants, which was a suggestion here on TF.

Thanks for the suggestions re ultrasound - I didn't know what terminology to search for.

The drama continues.
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Old 11-22-2015, 07:11 PM   #7
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If it were me, I would drain both tanks completely and open the Access ports on both tanks. With one of those key hole cameras that plugs into a usb port on a computer, I would scope the inside of the tanks. Might want to attach the camera to a broom handle for better access to the different areas. From that, you will have a much better idea of the internal condition of the tank.

Depending on how your tanks are secured in place, you may also be able to view the under side and back side of the tanks with that camera. Hopefully an overall external condition can be determined in this way.

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Old 11-22-2015, 08:04 PM   #8
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This would provide a look around and inside the tank at an affordable cost.

http://www.amazon.com/dp/B00EQNCMTY/...I1M6BX1IQAACUE

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Old 11-22-2015, 08:45 PM   #9
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I think the mechanic and the surveyor have drawn a very big conclusion with very little evidence.
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Old 11-22-2015, 10:26 PM   #10
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Quote:
Originally Posted by Capt.Bill11 View Post
I think the mechanic and the surveyor have drawn a very big conclusion with very little evidence.
What Capt Bill said.
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Old 11-22-2015, 11:51 PM   #11
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If I'm right it certainly working in you favor. And it should be a lesson to any sellers.
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Old 11-23-2015, 07:16 AM   #12
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"The metal particles could be left over from when the tanks were made."

"I think the mechanic and the surveyor have drawn a very big conclusion with very little evidence."

Fuel is seldom clean , unless you run it thru your own filter before the tank.

A more likely source might be the addition of a hole for a fuel gauge or installation of the inspection port , if not factory.

Some engines return lots (some almost none) of the fuel supplied to the engine., another possible source of metal.

If the tank is fine visibly , no wet seams , no rusting seams, " don't worry be happy" and watch it over the decades.

You may have got $10K from the PO as a gift!
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Old 11-23-2015, 07:58 AM   #13
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The shiny filings may have come from the fuel dock or when the inspection hatches were installed.
Ultrasound equipt needs complete access of the exterior of the tank in the area of interest. Not happening in the boat.
I completely agree with jumping to assumptions.
Why not drop a small magnet on a string or rod and see if you can capture said particles for analysis. If they are not attracted to the magnet, most likely aluminium or high grade stainless, IE not a tank problem.
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Old 11-23-2015, 09:35 AM   #14
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While it is certainly a lot of money, I'm thinking 10K to 15K (5k to7k per side) sounds dirt cheap to me considering whats involved. Wouldn't the custom made s/s tanks be at least 3k to 4K each? (15K CDN is about 11K USD)

Hopefully someone here on TF who has had "a yard do this start to finish" can advise what it cost them for comparison?

How many gallons each are your tanks David? I know you said they had 100gal in them but I'm assuming that they are not full.

The bladder idea at first glance seems an ideal solution but if you have to cut a large hole to get in to cut out all the baffles than it seems to me one would be better off to just keep cutting & remove them completely.
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Old 11-23-2015, 09:49 AM   #15
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Metal flakes from rusting tanks is an oxymoron. Rust is ferrous hydroxide and non metallic.
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Old 11-23-2015, 10:59 AM   #16
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I had the middle 400 gallon tank leak, which was not a big concern for years as there are two other 400 gallon tanks. Anyway one winters day having nothing better to do, I decided to cut open the tank. The tank was drian of fuel by the leak, but still causes so cut slow with plenty of lube. Cut a square hole, 24"24", big enough so I could crawl into the tank. The leak was easy to see in the bitch dark tank. A weld had cracked.

I cleaned the inside of the tank, and hired a local welder to weld the crack from the inside. Used a small 120 volt 30 welder, we used a wet vac to pull out the fumes smoke. Total cost at this point was a couple hundred bucks. I sanded and zinc primed the inside of the tank filled the tank with water as the cut was 6" off the bottom to test for leaks.

The most expensive and hardest was a cover for the hole, which required a collor to go around the hole on the outside, and a hatch with tack welded bolts on the inside, and a gasked seal. Cost around 500 bucks. So if a tank leaks, I would drain and open up first to inspect and evaluate.

If the tank need replacement, it would be replaced with several smaller tanks. Small enough to fit thru in the engine room. Besides several small tanks would be better than one big tank. I would do the majority of the work as I am retired and hopefully have more time than money.
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Old 11-24-2015, 07:42 AM   #17
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"Wouldn't the custom made s/s tanks be at least 3k to 4K each? (15K CDN is about 11K USD)"

Except the best material is STILL steel not SS with all its welding problems.

The steel tanks may suffer from poor maint (deck leaks) , SS dies just sitting.

A good coat of paint and a proper installation is all steel needs.

Have a real self servicing fuel tank built , not just a cheap box for fuel.

The design is in the archives.
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Old 11-24-2015, 08:53 AM   #18
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Dave,
I don't see how diesel fuel would cause metal filings, flakes, grains to an aluminum or steel tank? The shinny metal filings would be from the original fabrication,
weld lets brackets or access panels that were cut into the tank when it was built or modified. It could also be from new hose fittings on the fuel fill or venting? Go with Craig's suggestion if you want to know the wall thickness with out drilling holes in the tank. NDT testing. I like Capt Bills idea in reference to the filters. No need to spend tens of thousands of dollars on a possible problem, new tanks. Be sure you identify a real issue before wasting money. A fuel leak form one or both of your tanks would be a real problem.
Just my two cents.
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Old 11-24-2015, 10:14 AM   #19
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David

A few random thoughts on this post:
  1. Do you have any tank leaks?
  2. A steel/iron tank will rust out (not metal flakes) on the INSIDE bottom and sides if water is present in great quantities in the fuel and the boat sits around a lot.
  3. Rust and metal flakes are not the same, so what was in the Racor bowls? Find this out before doing anything. If your Racor is lower than the fuel level, disconnect the fuel line at the Racor feed and get about a gallon of fuel and let it settle, see what it looks like and if any crud or water. A glass container is best for this.
  4. Assuming you have a deck fuel fill with a straight hose into the tank, check what is in the tank bottoms with a dip tube. Very easy to do.
  5. Did the surveyor note any exterior rust on the OUTSIDE of tanks, especially on the tops? How about the tank bottom area, any water sitting there?
  6. Generally a steel fuel tank will leak at welds/seams. thickness testing will offer no help here.
Like CSI, you need a victim and some evidence. Maybe the surveyor could help. I met a fellow this summer who just finished examining the insides of iron fuel tanks on a 40+ year old wooden DeFever. He showed me pictures, spotless inside and out and no rust or debris. Good build, no deck leaks, constant use and clean fuel were his answer. And his vessel had no diesel smell which a woodie will exhibit if any past or present fuel leaks.

Good luck and wait for the evidence, it will show up if some nefarious happening is occurring.
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