Monday, November 12, 2007

Tanks, good news bad news...

We originally hydroed one tank to failure. It failed at 495 PSI.
We made the end cap that failed thicker, and assumed we fixed the problem.

Today I asked my son to hydro the test stand to 500 PSI since we had not done so. The first tank in the test stand failed at 475. He then hydro tested the tank we had heat treated. It failed at 425. So to complete the set we tested the other tank on the test stand to failure it failed at 560PSI. All three failed in exactly the same spot in the weld between the end cap and tank end. Its clear that our quality control needs some work. On Tuesday we will hydro all 8 tanks on the actual vehicle and see how that goes. Its really hard to tell if the failure is in the heat effected zone on the margin next to the weld, or if the welds them selves are too thin.


Carl Tedesco said...

What alloy are your tanks again? Is there any temper? If they are tempered, say T6, the heat from welding has to be affecting it and thus weaken the area. The company I sent you to for the brazing also does heat treating. So does a company called Bodycote in Mira Mesa.
--- Carl T.

Paul Breed said...

They cant heat treat closed tanks.
They can't quench the tanks without colapsing or blowing them up.



Carl Tedesco said...

Then what about just placing them in a furnace to stress relieve them and let them cool slowly? I'm no heat treating expert, but could welding cause thermal induced stresses? Would your welder know?

--- Carl T.

Paul Breed said...

We did that with one tank and it failed at 425 PSI.
But it looks like an obvious welding flaw.