How to clean a fuel tank with no inspection hatch?

[Tim D]

cutting a hole in it is the easy part, if its a square or rectangular hole you would mark its position then drill out the corners first with say a 10mm or 12 mm drill then disc cut the rest with a plasma disc, gas cutting wouldnt work as its a stainless tank so wont work as it wont oxidise, the harder part is rendering the tank safe so as to not explode it by igniting any fuel vapours which are left inside it with the sparks from the cutting disc, this can be done quite easily by forcing a diesel engine exhaust through the tank for a while, not so easy though on an installed fuel tank on a boat, easy if the tank is removable.

 

[Dougie_the_Mate]

It isn't. We had to have the job done last weekend- Every other solution to the engine cutting out had been tried. Eventually we had to have the fuel siphoned out and filtered through 7 - yes 7 filters. The tank was removed and cleaned after having a hatch cut out. It was manky inside and the fuel was being blocked at the tap. What was most annoying was the fact that we had the tank taken out and cleaned 4 years ago - but once you get deisel bug it appears there is no option.

She is running very sweetly now, but I am dreading the bill.

 

[prv]

how do you actually cut an inpection hatch in a steel tank? It doesn't sound that easy

See post 51

Pete

 

[prv]

She is running very sweetly now, but I am dreading the bill.

Mine cost £35 for the two bits of stainless from Metal Supermarkets :encouragement:

Probably would have been less via eBay but I didn't get organised in time

Pete

 

[sailaboutvic]

We did our this year , 160 lts , we run it down to the last twenty lts or so then managed to lift the tank out , once out we tip the rest of the fuel out of the tank , then pours a little fuel in at a time and shock the tank and tip it out , we did this a few time , you want to see the **** that came out , being a plastic tank help , A little history , the boat five years old , we almost always buy out fuel in contains which we then filter in our tank at time we had no end of **** in our filters funnel , the biggest culprit are the small fuel tankers in Greece , personal now I would never buy fuel from them again unless I filtered it . After taken all this care we still had **** in the tank .
www.bluewatersailorcroatia.webs.com

***=rubbish

 

[Gordonmc]

Bear in mind, if you are set on cutting an inspection hatch, that the tank is likely to have internal baffles which will prevent access to all sections.
It might be worth getting hold of a cheap endescope to take a look inside before you start cutting.
I had similar problems on my Port side tank, approx. 68 litres.
My solution was to use the sender hole which was a large retro-fit and copper pipe long enough to get into all the corners. I used a 12v pump downstream of two old CAV filters with the fuel returned to the same tank.
By constantly circulating the deisel and occasionally replacing filters I eventually got clear deisel coming through. The movement of the fluid meant gunk from all sections between the baffles was sucked out.
I flattened two batteries in the process.
Happily the St'bd tank was clean.

 

[prv]

Bear in mind, if you are set on cutting an inspection hatch, that the tank is likely to have internal baffles which will prevent access to all sections.
It might be worth getting hold of a cheap endescope to take a look inside before you start cutting.

It's a good point. I assumed mine would have baffles, and poked in a tiny eBay camera on the end of a bit of fencing wire to see where they were before cutting the hatch. Turned out there were no baffles on my 80-litre tank, which made life easier.

Pete

 

[Deleted member 36384]

If possible make a round hole as as a round hatch cant fall through it's own hole.

 

[prv]

If possible make a round hole as as a round hatch cant fall through it's own hole.

But then you also can't insert the reinforcing ring needed on a thin stainless tank, without clever tricks like hinges etc.

Dropping the cover into a tank which you're about to reach into anyway is not really a problem. Just take it out again.

Pete

 

[Chris_Robb]

It's a good point. I assumed mine would have baffles, and poked in a tiny eBay camera on the end of a bit of fencing wire to see where they were before cutting the hatch. Turned out there were no baffles on my 80-litre tank, which made life easier.

Pete

Baffles - in general terms a tall thin tank will not have baffles, but the low flat tanks probably will.

 

[Chris_Robb]

We did our this year , 160 lts , we run it down to the last twenty lts or so then managed to lift the tank out , once out we tip the rest of the fuel out of the tank , then pours a little fuel in at a time and shock the tank and tip it out , we did this a few time , you want to see the **** that came out , being a plastic tank help , A little history , the boat five years old , we almost always buy out fuel in contains which we then filter in our tank at time we had no end of **** in our filters funnel , the biggest culprit are the small fuel tankers in Greece , personal now I would never buy fuel from them again unless I filtered it . After taken all this care we still had **** in the tank .
http://www.bluewatersailorcroatia.webs.com

***=rubbish

We changed our tank last year following a bad leak. The old tank - 20 year old - was remarkably clean, and the failure it would appear was in the baked bean can type sump. Obviously over the years water had been sitting here and there was no provision to empty it other than a small screw plug - which was a nutty thing as dropping the nut would mean 100 litres of diesel in the bilge!

I was disturbed by your observation that the biggest culprits were the small fuel tankers in Greece. I always used them in preference to under water tanks as in marinas. I have never filtered in, other than returning the annual effort at scavenging the bottom of the tank into large water bottles. The last time I did this (in april 2013) the fuel was generally clear apart from what looked like some black granules that settled quickly to the bottom.

I then poured these back into the tank through a Racor water separator funnel including the last dregs of the first bottle. I then started to pour in the next bottle - it would not run through the filter at all. I then cleaned the copper mesh filter and found it clogged with a black waxy mess (the black granules). Just a tiny amount had totally blocked the course copper filter. I understand that this substance was the drop out from the Bio-diesel (fame) we all now use in Greece. That was the accumulation of 2 years filling from tankers from when we arrived in the Med.

It is a worry in that even though you filter off the solids when filling, you can not remove this carp as it is precipitated out during the short shelf life of the fuel. This will just accumulate in even well looked after tanks and has the potential to cause mayhem even in small amounts going through to your filters.

It would be interesting to get feed back from others as to the accumulation of this black waxy substance which could cause unexpected blockages in heavy weather.

In terms of filtering - is there any form of in line filter that could be applied to the nozzle of the filling pump. Or perhaps one should just take a 5 litre sample at the start of filling and see what it looks like.

I had an engine failure on my last boat on its delivery trip in a gale in the north sea from dirty fuel - I vowed it would never happen again!

 

[sailaboutvic]

Hi Chris
I am not claiming that my problem was cause by the tankers in Greece only , what I will say about them is I nearly always found some **** from them , the two worst ones or should I say , was things may have changed , are the one in Prevezza town quay , not only I found that there was quite a lot of stuff but also his meter wasn't calibrated he could get 11. Something in a 10 litre can , (my 10 lts can if fill to the top will hold 10.5 , ) has so many found out over time , there use to be some big rows when on there at time involving the PP . with my own ear I heard him tell on French guy , ( ok how much do you want to pay )
The other one was in Sami , who so many on this forum have said that his such a nice guy , I laugh every time I read them comments , off cause he is ,he as to be to take you in before he screw you , he another one who meters wasn't Calibrated and maybe still isn't , no wonder his fuel was slightly cheaper then the garage on the road out of Sami , any away , I would never buy fuel from any of these two guys again ,
Now if any one else want to , then please do , I am only letting people on this forum know what I found .
I have also taken fuel from tankers in other parts of Greece and found them clean .

www.bluewatersailorcroatia.webs.com
PS my fuel was clean when I had my problem ,but in the bottom of the tank was this black matti stuff and and bit that when you touch it , it just fell apart .

 

[prv]

For what it's worth you can get a dirty fill in the UK as well. In our old boat, with a brand new tank the previous season, we filled up from a floating barge and then started noticing a lot of dirt in the filter bowl. We hauled out a few weeks later, and since we had obviously specified an inspection hatch in the new tank, I opened it up for a look. Lots of rusty black flakes in the bottom (not the same gunge as in Ariam) which I scooped out. No big deal if you have the hatch. My dad mentioned that, a few days after we'd filled up, he'd noticed the barge gone, presumably towed away to be refilled. So our fill must have been from the dregs of their tanks, hence the crud.

Pete

 

[Seanick]

I have a six inch hole saw ;-)

 

[Phoenix of Hamble]

+1 - I used a Scotchbrite pan-scourer to remove the black deposits from the sides and bottom of mine. It took quite a bit of elbow-grease, no way you could do the same through a tiny hole except perhaps with steam or something.

Pete

+1 A throughly filthy and unpleasant job, but huge peace of mind knowing that the tank is spotless inside.

My inspection hatch was cut with an air powered knibbler, rather than worry about lots of fine dust ending up in the tank.

 

[prv]

My inspection hatch was cut with an air powered knibbler, rather than worry about lots of fine dust ending up in the tank.

Back when this thread was new (before Nick urgently needed to tell us about his six-incher ) I think I mentioned that I started with a nibbler but the end fell off. It was a cheapo eBay drill-mounted job and I was really asking it to do more than it was meant for, so I don't blame it. But I couldn't justify buying a compressor for one job, and all the real nibblers seem to be air-powered.

Sod's law says that a week after cutting the hole, a mate gave me a compressor he no longer wanted :hopeless:

Pete

 

[vyv_cox]

I removed my tank last week when rusty marks began appearing around and below the drain plug. So a few comments from my experience:
1. No inspection hatch but there is a gauge sender unit in the top. This has six setscrews that screw through the metal of the tank into a heavier ring behind, threaded to take the screws. The ring is a 'C' shape so that it can be inserted through its hole. Would also be applicable to an inspection hatch.
2. The sender unit was faulty and I replaced it. Although it was 30 years old a new one fitted it without modification.
3. No bug as such but some rusty sludge in the bottom. I was able to blast most of this out with Greek water pressure through the sender port but a pressure washer might have done better.
4. All our diesel for the past seven years has been bought from mini tankers. The turnover in many of these is quite high, so in general I trust their quality.
5. The rusty marks were due to galvanic corrosion between the brass drain plug and the stainless steel tank. I had never removed it in 20 years of ownership but the threads in the boss welded to the tank were almost gone. When I withdrew the plug half a turn it fell out! I had it drilled and tapped to take a larger plug, 3/8 BSP.

 

[Chris_Robb]

I removed my tank last week when rusty marks began appearing around and below the drain plug. So a few comments from my experience:
1. No inspection hatch but there is a gauge sender unit in the top. This has six setscrews that screw through the metal of the tank into a heavier ring behind, threaded to take the screws. The ring is a 'C' shape so that it can be inserted through its hole. Would also be applicable to an inspection hatch.
2. The sender unit was faulty and I replaced it. Although it was 30 years old a new one fitted it without modification.
3. No bug as such but some rusty sludge in the bottom. I was able to blast most of this out with Greek water pressure through the sender port but a pressure washer might have done better.
4. All our diesel for the past seven years has been bought from mini tankers. The turnover in many of these is quite high, so in general I trust their quality.
5. The rusty marks were due to galvanic corrosion between the brass drain plug and the stainless steel tank. I had never removed it in 20 years of ownership but the threads in the boss welded to the tank were almost gone. When I withdrew the plug half a turn it fell out! I had it drilled and tapped to take a larger plug, 3/8 BSP.

Hi Vyv, did you get a sensible price out of the marina in the end???

 

[vyv_cox]

Yes, they halved it when I objected to Nicos.

Yes, they halved it when I objected to Nicos. Still a bit over the top for 15 minutes' work IMO but Nicos said he took 45.

Edit, sorry for this nonsense, replying to myself. Finger problems on iPad.

 

[Spirit of Glenans]

The problem is that to remove the crud you will have to give the walls of the tank a really good blast. Otherwise you will end up doing as above and simply making a couple of scrapes through it. Imagine trying to clean a filthy saucepan with a small tube through a hole? It really needs a scrub. I wonder if something could be done with a high pressure hose to blast the crud off the interior. You would need to undo all the pipes to allow the pressure out. You would either have to use diesel as the medium (I don't know if pressure washers can handle this) or you could use water and then use something to absorb the water residue once pumped out(I think acetone works). I don't think simply pumping it all out will really get the crud out as it will simply go to the bottom. This is why the hatch is the only practical option as you can get a hand in and literally scrub the tank. I completely replaced my old mild steel tank as it had crud, rust and no hatch. I now have a plastic job with hatch. No probs since.

I think alcohol (meths) would be a better medium to soak up residual water as this is also the recommended cure for doused electrical items.
Edit: Oops! I'd forgotten I'd said that before