Aluminum fuel tanks and brass fittings
Hello Trawlers-and-trawlering,
I'm replacing old steel fuel tanks with new aluminum ones, and
wonder if there is any worry about using brass fittings on the tanks.
Should I have some insulation (nylon or pvc or ?) between the tank and
fitting, or is a direct connection OK.
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
My 1981 Nordic Tug had brass nipples and bronze gate valves into the
aluminum fuel tanks. There was a fair amount of galvanic corrosion on the
aluminum coupling and on the adjacent area of the tank wall. I checked the
tank wall thickness with UT, and found it was still acceptable. When I
repowered, I replumbed the tanks with SS nipples and ball valves.
I also found some corrosion on the tops of my fuel tanks (in a lazzarette).
If your tanks are in an area that will experience condensation, I would
consider sloping the tops of the tanks ever so slightly, so that water
doesn't pool on top. Don't use any foam or rubber that trap moisture on the
bottoms of the tanks either.
Regards,
Mike Pedersen
Powell River, BC
On Fri, Apr 29, 2011 at 8:57 AM, Peter Bennett
peterbb4@interchange.ubc.cawrote:
Hello Trawlers-and-trawlering,
I'm replacing old steel fuel tanks with new aluminum ones, and
wonder if there is any worry about using brass fittings on the tanks.
Should I have some insulation (nylon or pvc or ?) between the tank and
fitting, or is a direct connection OK.
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
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Not only will galvanic corrosion occure with brass fittings attached directly to the aluminum tanks, but I've read about corrosion occuring just from water dripping onto the tops of tanks, off brass/bronze fittings or copper tubing that runs over the top of a tank.
Kinda makes a fella think, because I know, at least in our boat, I seriously doubt that I could convince Jill to get up a few minutes earlier each morning just to wipe down the tops of our tanks. Besides, her beauty sleep is something I'm all in favor of her getting, not that she needs any more!(I need to make that last point very clear... just in case.)
Maybe, as you thought of doing, use nylon or pvc bushings to isolate the fittings and fabricating cute, little, one-of-a-kind drip catchers for installation below each fitting? (Just kidding about the drip catchers... kinda.)
Whatever you use to isolate the bottom of the tank from its bed, it should be such that moisture or water cannot get between it and the tank. One popular approach is to attach strips of rubber, set in 5200, against the tank where the bed will touch.
Rudy
Briney Bug, Panama City, Fl
Peter,
Don't do it! For examples of the horrors of brass-on-aluminum corrosion,
stop by any sailboat yard and look at some masts and booms where a brass or
bronze fitting has been attached.
Use stainless or black iron (really mild steel, usually) fittings, not
galvanized, since the zinc reacts badly with the sulphur in the diesel. Or
for a first-class job, find aluminum pipe fittings at an automotive hot-rod
shop or website. They have beautiful color-anodized fittings for show-cars
that are a bit pricey. But you only need a few that will be in contact with
the aluminum tank, so it's not too bad. I used stainless on Pooh, BTW, when
installing my two new 160 gal diesel tanks in 1996. No problems since.
Mark Richter, Ortona, FL on the Okeechobee Waterway
"Winnie the Pooh" 46' troller-yacht
I'm replacing old steel fuel tanks with new aluminum ones, and
wonder if there is any worry about using brass fittings on the tanks.
Should I have some insulation (nylon or pvc or ?) between the tank and
fitting, or is a direct connection OK.
--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
I'm replacing old steel fuel tanks with new aluminum ones, and
wonder if there is any worry about using brass fittings on the tanks.
(endsnip)
Not no, but H$LL no. You can use a ss bushing, then brass, but don't use
brass and al together.
Better yet would be al fittings.
Brent Hodges
Friendship
43 Albin
Not no, but H$LL no. (endsnip)
Re reading my message it sounded a little strong. Just meant to make it
clear that is a no-no.
I was taking a class on marine systems a few years ago and we had just
discussed this in class. Broke for lunch to go down to the repair yard to
look at work in progress. They were installing a new al fuel tank with all
new shiny brass fittings. There was quite the uproar amongst the students!
By end of day, they all had ss bushings or fittings installed.
Brent
Gee, I guess that point was made by enought folks that you'll take the hint.
But I'd like to make another one. If you bush the fittings, the fittings will end up being smaller than those that would have been used without bushings.
So... if you have the option, you might be wise if you increased the size of the holes so that a good size fitting can still be used, including the bushing.
2"+ fills, 1"+ vents, minimum 1" exhausts; I think you get the point.
A too large hole can always be made smaller, but a small hole cannot easily be made larger. Besides, most folks don't have big enough fittings to begin with. 5/8" vents are too small and 1.5" fills will not conveniently accommodate a Baha Filter, nor some fuel nozzles. Bigger is better, at least in my thinking.
Rudy
Briney Bug, Panama City, Fl
I though SS and AL were a problem together as well? Maybe just not as much of
a problem and Brass and AL?
On Apr 29, 2011, at 8:14 PM, Brent Hodges wrote:
Not no, but H$LL no. (endsnip)
Re reading my message it sounded a little strong. Just meant to make it
clear that is a no-no.
I was taking a class on marine systems a few years ago and we had just
discussed this in class. Broke for lunch to go down to the repair yard to
look at work in progress. They were installing a new al fuel tank with all
new shiny brass fittings. There was quite the uproar amongst the students!
By end of day, they all had ss bushings or fittings installed.
Brent
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I though SS and AL were a problem together as well? Maybe just not as much
of a problem and Brass and AL? (endsnip)
Very true. It kind of depends on where the application is I guess. Of course
we use ss screws on al all the time, but where you get into problems is when
salt water (or even salt air) get into the crevice between the screw and al.
Therefore we always use TeffGel, or some other sealant around the screw and
this helps tremendously. Same with these fittings, use a sealant. Guess with
al tanks there is always some long term liabilities, you just have to pick
the lesser of the evils?