metal cutting with poor oxygen %

[papyone]

Hello everyone,

Thanks for approval in this forum.

My question concerns the cutting of metals.

Whether by gas cutting torch or thermal lance, all manufacturers recommend using oxygen with a purity of about 99.5%. They also specify that the performance of the cutting will decrease by about 25% per missing percentage and they place the limit at which it is no longer possible to cut around 95% oxygen.

I recently did tests with ultra-thermal electrodes (models that are used under water but which works on the same principle as the conventional 3 m oxygen lance) and I still managed to cut on the surface with a mixture oxy / nitrogen 70%.

Hence my question: Given the difficulty I had to cut at the surface, I am convinced that if we use such a mixture to cut under water at shallow depth it would not work properly. But when would it be if we did this test at about 132 m depth? There we would again have a PPO² equivalent to 99.4% oxygen at atmospheric pressure and therefore equal to what is recommended by manufacturers. So I would like to know if at this depth and with such a mixture (70%), the thermal electrode would cut normally.

FYI, in practice this will never happen, but it is a question that is currently running on a commercial dive forum and for now nobody can answer it.

So thank you in advance for your help.

Edited June 7, 2018 by papyone