Another Hole in Dax Tank !

[dave]

Originally Posted by craggle

Apart from looks whats the advantage with the aluminum tank over the steel one?

Craig.

Just the weight.

No steel option these days.

There used to be Alloy,
Stainless,
mild,
and all the above with the option of Explosafe.
An awful lot of stock to carry to cater for all the different needs so they went with the most popular....I think?????

[Purple AK]

Originally Posted by dave

If they tested it to 25psi then your tank would be the same shape as one of these:-

2psi would have shown that pinhole/bad weld Was the welders guide dog away that day?

[craggle]

That's a shame. When I brought mine there was the option of mild steel and aluminium with or without the Explosafe.

I went with the steel version as I have had experiences of aluminium water tanks splitting in busses due to vibration. (one of my past jobs)

As someone who has tried welding thin aluminium sheet I can say it is extremely difficult and the slightest imperfection or speck of dirt on the material or filler rod will create a hole in the weld. Most of these can't been seen but only show up once filled with liquid and allowed to sit for a while.

Craig.

[dolphinboy400]

Originally Posted by craggle

That's a shame. When I brought mine there was the option of mild steel and aluminium with or without the Explosafe.

I went with the steel version as I have had experiences of aluminium water tanks splitting in busses due to vibration. (one of my past jobs)

As someone who has tried welding thin aluminium sheet I can say it is extremely difficult and the slightest imperfection or speck of dirt on the material or filler rod will create a hole in the weld. Most of these can't been seen but only show up once filled with liquid and allowed to sit for a while.

Craig.

correct me if i'm wrong ( which is often :P ), ANY liquid is denser than air so therefore, if it doesn't leak with an air test then it should hold any liquid ( apart from extreme tempretures like liquid nitrogen ) . I test heating systems on copper/plastic/steel at only 20 mbar but those systems can run at 3 bar, not sure what that is in old money but it's way more than 25 psi, right?
The pressures that these tanks hold are minimal and i cant see why an air test wouldn't pick it up , unless i missread something and what your saying is the fuel corrodes the weak part of the weld over time, which would be a worry for everyone

[Toddy]

Danny , a 20 mbar gas test is a different thing all together and You should be testing plastic heating pipework to 18 bar
I will be asking the question tomorrow just what checks are carried out as I now have a lovely firebomb sitting in my garage

[JonnyT]

I don't know what Dax will suggest in the morning but I'm pretty sure that you can purge fuel tanks with nitrogen or something like that to allow them to be welded immediately.

Might even be cheaper for Dax if you know anyone close to you as the courier to Harlow and back ain't going to be cheap! I know its £70 from central london to mine and that's only about 40 miles.

Hope you get it sorted in time for Friday - I need the mirror

[slogger]

Originally Posted by dolphinboy400

correct me if i'm wrong ( which is often :P ), ANY liquid is denser than air so therefore, if it doesn't leak with an air test then it should hold any liquid ( apart from extreme tempretures like liquid nitrogen ) . I test heating systems on copper/plastic/steel at only 20 mbar but those systems can run at 3 bar, not sure what that is in old money but it's way more than 25 psi, right?
The pressures that these tanks hold are minimal and i cant see why an air test wouldn't pick it up , unless i missread something and what your saying is the fuel corrodes the weak part of the weld over time, which would be a worry for everyone

It's all down to how good the tester is! I had a rad rebuilt by a leading rad specialist and it leaked. Phoned them up and the upstart on the phone said that it couldn't leak as it past its test. Took it back and the same guy tested it in front of me. He had 10 psi on it and I could see a small leak that he put down to air trapped on the core. I did no more than to wind his regulator up to 20 psi and the end tank exploded. The solder joint was dry.

Dax are in the hands of their suppliers. I'm sure they will do their very best to help. If a tank isn't available maybe someone on here will loan Toddy a tank for his SVA. The South East is not very local and my tank is one of the old steel ones 17 yrs old.

[craggle]

Originally Posted by dolphinboy400

correct me if i'm wrong ( which is often :P ), ANY liquid is denser than air so therefore, if it doesn't leak with an air test then it should hold any liquid ( apart from extreme tempretures like liquid nitrogen ) . I test heating systems on copper/plastic/steel at only 20 mbar but those systems can run at 3 bar, not sure what that is in old money but it's way more than 25 psi, right?
The pressures that these tanks hold are minimal and i cant see why an air test wouldn't pick it up , unless i missread something and what your saying is the fuel corrodes the weak part of the weld over time, which would be a worry for everyone

Aluminium welding is very critical about clean materials. When welding cylinders or sealed containers it is best to purge the inside of the tank with Argon to prevent contamination getting in the weld pool on the reverse side of the weld. obviously not possible until you have a sealed container to work with!
If there was any oils or contaminates on the opposite side of the sheet these may get into the weld pool then cool down and seal the hole. Oil or grease will melt in petrol however showing a leak.

Maybe the air test needs to be revised but testing with fuel would mean they couldn't send it by parcel delivery.
If I was Dax I would have stuck with the easier to make and cheaper option of a steel tank. Weight difference would be minimal as steel sheet can be thinner than the aluminium needed for the tanks.

I guess they have to go with what the customer demands though.

Does any other kit use aluminium tanks?

Craig.

[Miket]

Originally Posted by craggle

Does any other kit use aluminium tanks?

Craig.

AK supply Stainless Steel fuel tanks which take about 5 minutes to fit, £260 including the sender .

[craggle]

Stainless tanks are a good idea. May weigh a bit more than aluminium but easier and cheaper to produce. Dax ones take about 5 minutes to fit too but can take 6 minutes if you have to lift the carpet up first.

Cant see why Dax would remove the stainless option.

Craig.