Cleaning fuel tanks.

[JDCAVE]

Prior to refuelling this year, I am thinking about transferring my fuel to a single tank and go through the process of opening the inspection ports and cleaning them out. 4 tanks, 2 ports each. I have an ESI fuel polishing system, but it doesn't address the sludge on the bottom of tanks. Any advice on how to proceed? I understand that the absorbent oil pads shed fibres and these should not be used. I'm expecting it to be a messy job. Thoughts? Experiences?

Jim

 

[Brig]

We here have a fellow who comes to the vessel. Removes all fuel, polishes the fuel, cleans the tank and back in goes the fuel. His prices are very good for the hat it takes to to it yourself. Maybe you have a person around your area that can help.

 

[Larry M]

Jim: You must be caught up on all your other projects to tackle this one. :lol:

We cleaned our old tank twice and did as you suggested, transferring the fuel to the other side. After opening up the tank, I used a drill pump to get the last couple of gallons out. I then used a plastic 4" putty knife to clean the sludge off the bottom and wiped the residual up with cotton rags from old tee shirts. I used a mirror and drop light so I could see in the tank. As your reaching into the tank through the inspection port, the edges of the hole maybe a little were rough. You may want to wear a long sleeve shirt to help protect your arm.

Just a question though, why do think you have a sludge problem? Your tanks are pretty new aren't they?

 

[JDCAVE]

Brig: I have a fuel polishing system but don't run it while traveling so there is no agitation of the tank.

Larry: Yes they are new...2010. I do get asphaltenes on the fuel filters, but not while polishing, so I think the agitation while at sea may contribute to removal via the filters. There must be other stuff there. The plastic Putty knife makes sense.

Jim

 

[JDCAVE]

Larry: Your suggestions make sense. How "tenacious" are the deposits? Would a rubber squeegee work as well? Shop-vac or plastic angled container to remove the bulk of the sludge?

 

[Larry M]

Larry: Your suggestions make sense. How "tenacious" are the deposits? Would a rubber squeegee work as well? Shop-vac or plastic angled container to remove the bulk of the sludge?

The first time I opened a tank on Hobo, which was probably the first time ever, here's what I found. The sludge came up real easy. I used a 1 qt yogurt container in the tank to shovel the sludge into that. It look maybe an hour, if that, to clean each chamber. I'd be surprised if you had even a cup. (I'm always the optimist)

When I cleaned the "new tanks" on our sailboat, after 5 years, that's all we had and I had taken on fuel from 55 gallon drums and other questionable sources.

 

[JDCAVE]

Thanks Larry: That's very helpful. I had heard that the "gaskets" for the port covers are reusable? Did you put a silicone sealant on them to reseal?

Jim

 

[Alaskan Sea-Duction]

The guy in Oakley CA that cleaned my tanks when I bought the boat, polished the fuel then used that fuel in a hi pressure nozzle to clean our tanks. While he was pressure washing the dirt, sludge was pumped back through the polisher.

 

[Larry M]

Thanks Larry: That's very helpful. I had heard that the "gaskets" for the port covers are reusable? Did you put a silicone sealant on them to reseal?

Jim

The first time I reused the gaskets, the second time I had new gaskets made locally using the old ones for a template. I paid ~$20 per made out of nitrile. I didn't use any sealant and never had any leaks. Just follow a good pattern as you're tightening, don't over torque the cover and you should be good to go.

 

[twistedtree]

I tend to do all the maintenance and repair work on our boat myself, but I think this is one that I would hire out. It sounds like a giant mess, and a job where having the right cleaning and filtering equipment would make all the difference is both the ease and outcome of the job.

 

[Xsbank]

Its just a dirty, on-your-knees job that takes some time and you have to breathe tons of diesel fumes and dispose of all the crap...pay someone, watch them, then go boating!

 

[kapnd]

The most onerous tasks are the ones most likely to be done poorly if hired out.
If you want it done right, best to do it yourself!

 

[sunchaser]

Jim

As asked earlier, are you having issues? Have you fueled up from a suspect source? Seven years after new tanks seems pretty early otherwise. Do you have straight down fuel fills that would allow a dip tube sampling of fuel from bottom of tanks? If so, have a peek at what comes up with fuel from bottom few inches of tank.

One of our tanks has the furnace draw from a sloping tank bottom, then on to a Racor. That bowl remains totally clean on the 13 year old tank. I consider it the canary for the other tanks.

 

[JDCAVE]

Tom, Larry: yes, the tanks are newer (2010), but I had thought, if I have these inspection ports, I presume I should put them to their intended use at some point. My primary filter (1 of 2 with the dual racer 900's) is changed annually and was pretty black last time. By contrast I fuel around from tank to tank to trim the boat and the 2 micron fuel polishing filter is clean. I think the reason for this difference is, I transfer fuel around at anchor or at the dock, in benign sea states, while the primary filters operate in rougher sea states, when there is agitation of fuel in the tanks.

So should I bother cleaning the tanks this year or wait another year? Believe me, I'm willing to avoid this messy procedure!

Jim

Jim

 

[dhays]

Tom, Larry: yes, the tanks are newer (2010), but I had thought, if I have these inspection ports, I presume I should put them to their intended use at some point. My primary filter (1 of 2 with the dual racer 900's) is changed annually and was pretty black last time. By contrast I fuel around from tank to tank to trim the boat and the 2 micron fuel polishing filter is clean. I think the reason for this difference is, I transfer fuel around at anchor or at the dock, in benign sea states, while the primary filters operate in rougher sea states, when there is agitation of fuel in the tanks.

So should I bother cleaning the tanks this year or wait another year? Believe me, I'm willing to avoid this messy procedure!

Jim

Jim

I don't know anything but a couple questions come up in my mind...

How black are the filters when you change them after a year?
Are you noticing a rise in your vacuum gauge?
How much fuel does your engine draw through the Racors when running vs your fuel filtering pump?
Why not run your filtering transfer pump while underway?

If I was you, I wouldn't mess with it. You aren't having any fuel problems at the moment. You have a dual filter setup now so in the unlikely event you do have a problem you can quickly and easily switch filters. I would also start running your extra fuel filtering pump while underway, particularly in rough weather. It seems to me that you are kind of doing it backwards, running the filtering when you wouldn't expect it to get anything.

I'm inherently lazy and don't like messy projects. I'd hold off until I needed to.

 

[twistedtree]

I missed that the tanks are new as of 2010.

If the inspection ports are easily accessed, another approach might be to shift fuel out of one tank, open the inspection port, and just do a visual inspection. With only residual fuel in the tank I expect you will be able to see to the bottom and see what crud, if any is present. Hopefully there aren't baffles that block your view.

If it's a mess, you will be glad you checked and can proceed with cleaning. If it's clean, you can close it back up and cruise with confidence for another 7 years. The only down side I see other than the time to open and close the inspection port, is risk of trouble resealing it.

Re the filter, being black isn't necessarily a bad sign. The main filters have fuel constantly cycling through them and will blacken up over time even with clean fuel and tanks.

 

[Snapdragon III]

I just removed the inspection ports and cleaned out two of my four integral to the hull fuel tanks. I was afraid to do it, but once I got into it it turned out to be no big deal. First I soaked up the very small amount of left over fuel, and as much sludge as I could with paper towels. I am having some work done and have the boat on in a yard right now. It was a few days after I cleaned them with the paper towels, before I could clean them further, and I was surprised that they were dry, and the remaining diesel had evaporated, which made disposing of the waste water in the next steps easier. I cleaned them out with simple green, and a dish wash brush to start, then moved on to a small SS wire brush and scotch bright pads. I rinsed them out with my fresh water wash down hose between passes, and very thoroughly at the end. I used a small shop vac to suck all the dirty water out. They came out very nice and clean. I was surprised. I will do the other two on the boat once I use up all the fuel in them.

 

[JDCAVE]

Thanks for your thoughts on this.

Why not run your filtering transfer pump while underway?...If I was you, I wouldn't mess with it...I'm inherently lazy and don't like messy projects. I'd hold off until I needed to.

I'm of the "an ounce of prevention" group! Anyways, if I go ahead and do it, it has to be done before I refuel. I don't really like running the genny while underway. However, I would like to transfer the ESI pump over to the Inverter side of the AC panel. The load isn't so high that it would be a significant burden on the alternator.

If the inspection ports are easily accessed, another approach might be to shift fuel out of one tank, open the inspection port, and just do a visual inspection...If it's a mess, you will be glad you checked and can proceed with cleaning. If it's clean, you can close it back up and cruise with confidence for another 7 years.

Yes. That's how I'm leaning as well.

I just removed the inspection ports and cleaned out two of my four integral to the hull fuel tanks. I was afraid to do it, but once I got into it it turned out to be no big deal.

Thanks for your encouragement and your experience with this.

Jim

 

[JDCAVE]

I’m back thinking about this and phoned a local tank cleaning outfit. They quoted 12 hours labour and appx $3,300 for the 4 tanks. I think I will open one of the tanks and have a look inside.



Any insight into the fitting into which the the bolts thread? Is there a “nut” brazed onto the inner surface of the tank, or what can I expect? How tight should the bolts be torqued? It looks like the PO used pipe joint compound on the threads. Ok?

Jim

 

[FF]

"We here have a fellow who comes to the vessel. Removes all fuel, polishes the fuel, cleans the tank and back in goes the fuel"

That's the story of the polishing service sells , however the "cleans the tank" part is difficult to believe.

A real fuel tank of any size will have sets of baffles built in to tame fuel surging in heavy seas. Just blowing filtered fuel into one section does little to clean the rest of the tank, regardless of the pressure or volume..

In a small box of fuel it might work, but an opening and using a wood scraper will probably work better.

On one cruise we met a fellow with gunked tanks that took a different approach.

He drained the tank and added 5 gallons of HD cleaner from a box store. He let it soak a couple of days and blew compressed air from a small pump to make bubbles every so often.

He then used more water from a hose to agitate the tank, and finally pumped it empty , rinsing with the water hose a couple of times.

After emptying ,no problems from plugged filters from then on , was the claim.

 

[Jeff F]

I think I will open one of the tanks and have a look inside.

Jim

Sounds like a sensible plan. I would think that a quick inspection would show whether further action is required.

Interestingly I was looking at a boat with a broadly comparable system yesterday. The owner made the sensible case that crud could accumulate and not come through the fuel lines until you're one day into a nasty passage and the vigorous agitation has released it in quantities to start clogging filters.

Good discussion and comments.

 

[Jbear]

I cleaned my starboard tank last year. Even with baffles I could see the entire bottom of it. There was maybe a 1/16 of an inch of sediment on the bottom that I wiped up with paper towels. The insides were shiny with just tiny areas showing any rust. Black tank steel on a 1977 Taiwanese trawler. Not bad at all. My inspection ports have a rubber gasket and the bolts are simply threaded into the tank steel. Just transfer all fuel to a different tank. I used a spare lift pump to get the residual fuel into a 5 gallon can and then cleaned it. Overall very happy no big problem at all.

 

[sunchaser]

Sounds like a sensible plan. I would think that a quick inspection would show whether further action is required.

Interestingly I was looking at a boat with a broadly comparable system yesterday. The owner made the sensible case that crud could accumulate and not come through the fuel lines until you're one day into a nasty passage and the vigorous agitation has released it in quantities to start clogging filters.

Good discussion and comments.

If you have flat and level bottoms on your fuel tanks, don’t turn over much fuel and buy from iffy vendors then an inspection every few years likely is warranted. A good check for those of us with fuel fills that go straight into the tanks from the deck is to use a dip tube to see what may lurk, if anything, in the tank bottoms.

Diesel tanks that were routinely filled decades ago with high sulfur fuels are prime targets for crud. Newer boats who have seen low sulfur fuels not so much. The first clue as to tank crud is an unusual vacuum increase on your primaries.

IMHO if you’re the 3rd + owner of an older boat a tank cleaning and/or inspection is a good idea, plugged filters or not, makes sense

 

[JDCAVE]

Based on how quickly the fuel in the sight gauges decreases as the fuel in the tank reaches the bottom, I’m certain the tanks are tapered towards the bottom and the tank is tapered forward as that is where the pickup is for the fuel polishing system.

I’m going to start with the port aft tank. I don’t typically draw or return fuel from the aft tanks for/from the main engine or genny, so the fuel isn’t scrubbed by the primary or secondary filters. Therefore the aft tanks should have the most asphaltenes present. My goal is to have the fuel polish system switched over to the Inverter side of the panel, which would enable me to polish while running in rougher sea states. It’s not particularly useful or efficient to polish fuel if there is no agitation in the tank.

My biggest concern right now (aside from the possible mess) is over torquing the bolts on reassembly and stripping threads on the aluminum tank surface, assuming that’s how it’s threaded.

 

[JDCAVE]

Here’s the update. Forward inspection port opened in the port aft tank. Tank is mostly clean. Minor accumulation of perhaps a couple of tablespoons forward near the bottom and not showing on the photos. Using a mirror, I found the tank bottom at the pickup tube is free of any asphaltenes.


Some evidence of slight corrosion on the face of the tank where the gasket is seated. The port of the tank is reinforced with a ring of aluminum where the bolts thread. The PO used lots of pipe joint compound on the threads. Not sure how effective that is.

I’m going to button it all back together and leave the other port on this tank as well as the other tanks alone. Sure glad I did this myself rather than higher an expensive tank cleaner.

Jim