Fuel Tanks Safety

I will be test driving my GT40 in the near future. I am a little bit concerned about the safety of the fuel tanks considering the place they are fitted.

Has there ever been any kind of safety issue due to the way they were mounted?

What if they leak a little bit? Could that cause major safety issues while test driving?

What is your opinion on my concern? What can I do to maximise safety regarding fuel/fire/tanks.


Thanks!
 

Howard Jones

Supporter
I only used one tank until I was happy with how it was sealed, it's lines, and it's pump system. Then I ran the other until it was sorted. Makes it easier to trouble shoot a leak.
 
I only used one tank until I was happy with how it was sealed, it's lines, and it's pump system. Then I ran the other until it was sorted. Makes it easier to trouble shoot a leak.
That make so much good sense it's a head-slapper.

If you're really concerned about those first drives, a second car following may id when a leak occurs -hard braking -left hand cornering, etc. by watching the pavement for wet spots, and if its carrying an extinguisher, you've got a third layer of safety on top of Jan's alloy tank and suit. Do you have an on-board system?
 

Seymour Snerd

Lifetime Supporter
What if they leak a little bit? Could that cause major safety issues while test driving?

Some thoughts on this:

1. If the leak is really little it can be far more dangerous in the garage than driving. Here's why:

My SPF tank had a couple tiny leaks in the welds barely visible to the naked eye; you had to know where to look to see them at all. This allowed gasoline to leak at about one drop every few seconds. Of course these leaks were up high enough that they didn't operate until I put in enough fuel to reach that level. Even then, if I weren't looking in exactly the right place with good light right when a drop fell I would never see it. Gasoline has viscosity much less than water, so when it forms smaller drops that when they hit a shiny surface immediately spread out so thin they disappear from view (although if you dragged your finger across you would feel and see it).

My floor is plastic (Racedeck) tile over a concrete slab. This went on for several weeks until I finally went on a serious hunt for the gasoline smell in my garage (which wasn't all that strong, especially the car is carbureted).

Around that time I noticed that some of my plastic tiles had visibly warped. That's when I finally realized what was going on: gasoline was dripping very slowly, seeping across the garage floor to the nearest low spot, accumulating there and either soaking into the concrete or evaporated or both.

Any time in that period a source of ignition could have caused the garage to go up in flames.

So I would argue that a very slow leak can be just as dangerous as a fast one.

2. Regarding fast leaks: Another thing I realized early on is that if I did have a fuel system leak that I discovered after filling the system with gas, I would want a very fast way to remove the gas from the tanks. For that reason I installed an AN male Tee in my fuel system plumbing just downstream from the pumps, with an AN cap. With that I can quickly remove the cap, connect a hose with matching AN hose end, point the hose into a fuel container and turn on the fuel pumps. This evacuates the tanks in a matter of a few minutes.

3. My car has a Safecraft on-board fire system with nozzles in the passenger and engine compartment and pull handle on the dash. It also has a pair of small extinguishers on the firewall next to the driver and the passenger seats. Finally, whenever I am working on the car I have a 10 lb Halon fire extinguisher in plain site.
 
Sounds like some darn good advice.


Some thoughts on this:

1. If the leak is really little it can be far more dangerous in the garage than driving. Here's why:

My SPF tank had a couple tiny leaks in the welds barely visible to the naked eye; you had to know where to look to see them at all. This allowed gasoline to leak at about one drop every few seconds. Of course these leaks were up high enough that they didn't operate until I put in enough fuel to reach that level. Even then, if I weren't looking in exactly the right place with good light right when a drop fell I would never see it. Gasoline has viscosity much less than water, so when it forms smaller drops that when they hit a shiny surface immediately spread out so thin they disappear from view (although if you dragged your finger across you would feel and see it).

My floor is plastic (Racedeck) tile over a concrete slab. This went on for several weeks until I finally went on a serious hunt for the gasoline smell in my garage (which wasn't all that strong, especially the car is carbureted).

Around that time I noticed that some of my plastic tiles had visibly warped. That's when I finally realized what was going on: gasoline was dripping very slowly, seeping across the garage floor to the nearest low spot, accumulating there and either soaking into the concrete or evaporated or both.

Any time in that period a source of ignition could have caused the garage to go up in flames.

So I would argue that a very slow leak can be just as dangerous as a fast one.

2. Regarding fast leaks: Another thing I realized early on is that if I did have a fuel system leak that I discovered after filling the system with gas, I would want a very fast way to remove the gas from the tanks. For that reason I installed an AN male Tee in my fuel system plumbing just downstream from the pumps, with an AN cap. With that I can quickly remove the cap, connect a hose with matching AN hose end, point the hose into a fuel container and turn on the fuel pumps. This evacuates the tanks in a matter of a few minutes.

3. My car has a Safecraft on-board fire system with nozzles in the passenger and engine compartment and pull handle on the dash. It also has a pair of small extinguishers on the firewall next to the driver and the passenger seats. Finally, whenever I am working on the car I have a 10 lb Halon fire extinguisher in plain site.
 

Seymour Snerd

Lifetime Supporter
Has no one considered putting an air test on the system prior to filling with petrol, 2 or 3 psi would show up any dodgy joints or welds.

Bob

That was certainly the question I would raise to the makers of my tanks, and I would strongly recommend doing so now that I've had the experience. If you can work out how to seal the filler caps that is definitely the way to go.
 
Gents:
Good advice and info on this thread. Al I can't believe all those leaks on a new set of tanks, but your advice on the extinguisher is a must.
I can tell you guys I have made quite a few tanks in all kinds of shapes and sizes, and I always test at pressure, and use soapy water. Usually about 5 or 6 PSI, any more and the tank looks like a pillow.
All of the seams need to be mechanical as well as welded, in other words when permitted two mating parts should have one folded to go against the side of the other, not butted as those joints are weak and will fail.
When welding aluminum tanks we always inside purge, and it is essential that when you stop a seam the current must be dropped slowly to avoid what we call "suck holes"...this is what Al's problem sounds like. Sometimes the hole is barely visible but still leaks.
I have never made a tank that didn't leak, they all need to be gone over until it is absolutely tight...there is no option there.
I have seen tanks made from 6061 alloy and in my opinion I think this is a mistake as this material age hardens and enevitably cracks.....we use 5052 alloy, usually .080 (2 mm) and I have accidentally pressurized tanks over 20 psi without them popping so it holds up well.
Lastly I believe in mounting tanks with supporting straps as I have seen many tanks that were hung from welded on bracketry develop cracks or even break away....it also allows them some "breathing room" as aluminum does respond a lot to heating and cooling.
Darrin: Use a good sealer on those tank connections such as some teflon paste, not tape, and test your tanks but use caution and don't overpressure.
Cheers
Phil
 

Seymour Snerd

Lifetime Supporter
As I look back on the whole sequence I realize if I had set out to do a low pressure system test it would not have been that hard; I've already introduced the tee mentioned above for a different reason. That can be used for a gauge and a Schrader valve for pressurization. All that's needed then is a temporary modification of the filler caps to defeat their vent mechanism. So my advice now would be to plan for that as part of building the system.
 
I have seen tanks made from 6061 alloy and in my opinion I think this is a mistake as this material age hardens and enevitably cracks.....we use 5052 alloy, usually .080 (2 mm)

I have absolutely no experience with fuel tank design and construction, but my concern would be that aluminum alloys have no fatigue strength, and repeated flexing, no matter how small, eg engine vibration, road bumps, etc., will eventually cause it to crack. I'm sure that life cycle limits are taken into account in tank design, and cracking doesn't equal failure, but some drivers may be unaware of the danger that hard-mount hoses or fastening components directly to the tank itself can pose. Aluminum fuel tanks must be safe or they wouldn't be legal, but 5,000 RPM creates a lot of cycles over a car's lifetime.
 

Howard Jones

Supporter
I tested my tank with 2-3 psi (hooked up to my compressor with the regulator turned way down) and sealed the filler neck with several strong wraps of plain ol duct tape. It blows up like a balloon but it will hold long enough to check all the welds for leakes. I just dipped the tank into a grabage can full of water one end at a time and looked for bubbles.
 
I know this was 1 weeks ago.
I make tanks out of 5005 and use 4043 welding rod.
The 4043 rod is more flexible and reduces the chance of cracking.
I have never had a tank crack.
I use a radiator pressure tester and spray the welds with soapy water,you find them fast enough.

Jim
 

Pat

Supporter
This is certainly not my area of expertise but in the military we had welded tanks on some of our self propelled guns (needless to say vibration was an issue) and we always used sealant on the interior welds. I believe it was a 3M product. Wouldn't you want to seal welded tanks in the same way?
 

Chuck

Supporter
As I look back on the whole sequence I realize if I had set out to do a low pressure system test it would not have been that hard; I've already introduced the tee mentioned above for a different reason. That can be used for a gauge and a Schrader valve for pressurization. All that's needed then is a temporary modification of the filler caps to defeat their vent mechanism. So my advice now would be to plan for that as part of building the system.

Alan

Just curious, how did you repair the leak in your fuel tank?
 
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