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Cleaning fuel tanks - 505

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kipwrite View Drop Down
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Joined: 14 October 2015
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    Posted: 18 February 2022 at 04:12
After five years I started getting some water in my primary fuel filters while motoring in rough seas. Time to polish the fuel in both tanks. 

I've used biobor algacide since the boat was new. Never any fuel problems. 

Couldn't find a professional fuel polisher where I am presently in SC, US. 

Working at first through the fuel sending unit openings, I was able to use a simple home-made polisher/separator (see photo) to polish fuel and remove about a quart of water from the bottom of the starboard tank. Upon closer inspection, there was evidence of diesel bug in both tanks - a goopy brown green slime, mostly on the bottom. Disgusting stuff. 

I removed the table and floor boards on the starboard side and opened the access port, and was able to clean the inside of the empty tank with rags (with a line attached), a sail batten pusher, and a boroscope camera. There was a fair amount of brown/green gunk on the floor of the tank and some residual water I could not remove with the polisher. Rags did the trick. 

On the starboard side, removing the floorboards on the 505 is much more complex because of the center island, but Hanse thankfully designed the floorboard access opening to allow just enough room to reach the tank access port and remove it, and I was able to clean the inside of this tank too, the same way. 

This was a worthwhile project, and easier than anticipated. There was more water and diesel bug than expected. The overall project took the better part of a day, not including time to build the home made fuel polisher shown below. If I had less fuel aboard it would have been quicker. 

I've since replaced both original fuel cap gaskets (which looked ok to me) and hope things stay dryer going forward. 


Edited by kipwrite - 18 February 2022 at 04:43
Kipwrite
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2022 at 09:25
Hi Kip Wright,
I have just built a similar rig to clean tank.
I used it yesteday to clean debrise from tank.
The pic attached was taken earlier before the fuel tube arrived. Cant update as we in UK are in middle of Storm Eunice currently gusting 70 knts.

I bought , my 315 [2007] 18 months ago, I asked my surveyor to check tanks, he refused saying that the yacht had over wintered with full tank and therefore no condensation?. My pre-delivery service engineer reported water in fuel filter separater and he drained waterfrom tank. When got her home I pulled inspection hatch, I found diesel bug in tank [dead gunge] cloudy diesel and free water in bottom [about cupfull]. I emplied and cleaned and filledfresh diesel.  I found the cause to be the fuel filler cap had totally shot perished 'O' with only about 270 degrees of ring left.
I was confident I had the problem under control.

Over this winter which  I started with full tank, some trips and heating depleted to 1/4 full this month. When I pulled inspection hatch last week I found cloudy diesel, no evidence of bug [I allways dose with anti diesel bug]. So this wasnt caused by filler seal,  so was it condensation?. The whole winter I had on a full enclosure on so even the fuel filler never got wet.

Some googling showed a product called 'fuel drier a snake' that claims to remove water from a diesel or petrol emulsion,  I found it too expensive to save my 15 litres of contaminated diesel. Further googling showed the key ingedient to be Silica Gel. Silica Gel is not soluble in fuel.

So as an experiment I put 300 grms of Silica Gel in a stocking [ladies fine deniere]. immersed it in tank and after 36 hrs I had clear fuel.

I also built a pump and filter, just like yours and used a rigid pipe on the inlet to 'Hoover' out a few bits of debris from bottom of tank.     Result!! a clean tank. I think your Racor type filter superior to my cheap CAV setup, but it did thejob.

My current thinking is the tank breather contributes to the condensation problem, it a large pipe, too large, leading long distance from tank to transom, with a big swan neck on transom.

My solution;--I have bought a filter housing in clear plastic normally used in RO systems to house de-ionising resins [Reverse Osmosis] it has small 1/4" pipe fittings to link to top of breather pipe. I intend to stopper the swan neck of existing breather, and use the dessicator to dry incoming air. So I am filling the filter housing with Silica Gel [self indicating] and will connect output end to breather pip near its highest point. So  under normal use the tank can only breath air in/out through dessicator. But for filling I will remove stopper from big breather to avoid blowback.
I believe the use of similar dessicator breathers is common on bulk fuel storage tanks.

Incidently my previous H301 had small direct breather pipe and didnt suffer water problems over 5 years.

I welcome your comments
Perry
Cowes
Isle of Wight
Current yacht Bloto-4, 315 [2007] , previous Bloto-3 Hanse 301




Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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kipwrite View Drop Down
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Joined: 14 October 2015
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipwrite Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2022 at 15:57
Perry,
Nice idea about the use of silica gel in the vent. Seems like it could work. 
I've resigned myself to an annual clean out/inspection of the tank. Having tackled it once it doesn't seem to be that bad a job. 
Kipwrite 
Kipwrite
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