Cleaning Diesel Tanks on Princess 415

[NigelChattin]

Does anyone have any experience cleaning diesel tanks? Access is limited with one inspection hatch in the middle of each (long) tank and a baffle plate on either side of the inspection hatch.

Removing the tanks isn't really an option as we would need to remove the engines first, but can anyone suggest how we could do this with the tanks in the boat?

 

[hlb]

You dont say what your probem is. But I've replaced the bung at the bottom with a tap with pipe attached. I'll explain why if it's relevent.

 

[NigelChattin]

We just have dirt in the bottom of the tank - we've drained the diesel and it looks like every time the boat has been filled up in the past 20 years they've treated it to a hand full of soil each time!

There's a balance pipe between each tank with a stop cock on each end - is that what you're refering to?

 

[hlb]

Well I sort of made my own "Balance pipe" after I stuck ten gallons of water in the tank. /forums/images/graemlins/blush.gif So not sure if it will help you.

How it works, espesially for water. Presuming your ballance pipe is at the bottom of tank. Take a T off it and pipe down to the bilge. Tap at the tap and one on the end. Leave all taps open, except the one at the end. Water and hopefully sludge, will find it's way down there. So you just, close the other taps and open the last one and drain it off.

Maybe you can flush the tanks out, with a similar method??

 

[volvopaul]

Cut the floor away and cut some nice square hatches in the tank tops, make your own cover plates and gaskets, though beware a boat at that age will be getting towards needing new tanks, my 1988 coniche had one leaking tank when i bought her in 2005, so i removed both tanks to try and repair it, it was like a piece of paper at the bottom, these tanks were made of 16 gauge mild steel by whittall marine for fairline they were a cheap option for them at the time.

Stainless ones went back in worth every penny i would say if your keeping the boat long term.
We have tried cleaning out tanks before, its not a great sucess unless you can get at every part of the tank.
There is a company south coast based that travel all over the uk and have a recycling pump filtration system its about £ 800.00 PLUS VAT for them to come up this way, but its a proper job and its cheaper than new tanks.

 

[ms1]

Be aware that crud can get caught behind baffles such that no end of 'extract/ filter/ return cleaning' will be totally satisfactory. If you are able to create inpection hatches and clean inside then I think you will be more satisfied with the outcome.

 

[markdj]

I would be very careful about using SS tanks in any boat...

Taken from http://marinesurvey.com/yacht/corrosion_2.htm

Previously banned, ABYC has recently approved stainless for use as fuel tanks. This is unfortunate for stainless has a very poor track record for use as tanks. Stress, corrosion cracking and welding problems are among the reasons why. Place a stainless tank flat on a deck and the same thing will happen to it as an aluminum tank. Water tanks are even worse; metallurgically altered metallic structure around the welds results in unacceptably high corrosion failure rates. Weld failures in stainless water tanks are legion and can't be stopped.

Stainless piping and other fittings for sea water use is not recommended. Not so much because it isn't any good, but because no one can tell what grade of material it is. If it's a low grade, there always exists the danger of failure. Bronze is easy to make and is not subject to the alloying problems like stainless, so when buying plumbing hardware, it's best to opt for bronze. The stainless that looks so pretty today, probably won't after a few years anyway.