anybody tried 1 atm blending ?

Marc T

Sorry dont read heliox but trimix of course!

Gilles

I don't understand why you need an He analyzer . You're talking about dil, right?

Just put in the desired He and top up with air.

This unless you are going alpinist, and you need a proper trimix in your dil.

I'm of the opinion you can mitigate the risk of using hypoxic dil for non-hypoxic depths (flush with O2 at start, be very diligent with PO2 until you're at safe depth, close dil shut-off when approaching surface at end of dive, amongst other things, ...).

Watch me get and .

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montyg

Thanks very much for that.

Can you quantify the loss of helium through the compressor?

I have been told by people whom I generally hold in high regard that it's in the region of a loss of 30% of the helium put in. The loss is attributed to the small size of the helium atoms/molecules?

rgds
monty

ntokyo

Hi Jean-Michel,
Better to do it separately... I agree. It is a bit complicated.
Personally as I do not have O2 tank higher than 135 bar in Japan. So, I mix first a Nitrox 40% through Continious Blending and keep it (I belend the highest as it allows more combination). When I want to make my trimix, I use my Helium, Nitrox 40% and top-up with air. For Helium and Nitrox I use a modified regulator (regular first stage I put on my bank) and a modifyed 2nd stage I plug on my compressor (I use a Junior II). I bought this custom regulator at Underwater Explorers It works great and I do not need to sevice clean my tank...
Cheers,
Nicolas

divingtoors

Hi There

Nobody seems to want to give me an straight answer on the matter...

Can I put 40% O2 with continuous blending through a normal oil lubricated, Bauer SCUBA compressor, or do I need to change anything such as type of lubricating oil etc?

I so.. what oil must be used and what else must be changed

regards

Johan

jmurba

Hi gilles,

My problerm is not to find a way to blend trimix , I learnt that with Iantd ten years ago, my problem is to find a simple way to top up my trimix dil tanks without having to empty it first.
with no helium analyzer one can top up using partial pressure methode, but only one time, after on top up the mix error is not acceptable any more.
some may top up many times but I don't cause I do what I was educated to do....
I had considered that blendig the necessary trimix to top up in a bag at 1 atm would have been a way to minimized the error givent that there is no compressibility rate problem and that I could have very easily merure fo2 in the bag.. but it does not seems to be as easy as I hoped (((-:

so blending using a continuous methode is mabye a solution to top up tanks....but how to do it ?

a continuous blending makes it possible to top with a premix gas without adding first nitrox and after helium generating errors.

Dales says he is used to do it , but I don't see how to do.
what whould I inject in the mixed, in what order ?

I thougth it was possible in using too mixers ate the same time, one nitrox mixer with and o2 sensor , and a second to add helium in the nitrox higer contiuously blended, but is seems to be very difficult

no solution

regards

jean mi

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rjack

You should be using a synthetic oil, not a mineral oil. Otherwise you might consider backing off of the 40% a bit. But I pump 32% through mine all the time.

Marc T

Jean Mi,

I dont really understand your prob; You use always the same trimix, right?
So blend always the same and top up your tank?

The idea of "you can do it only three time" was right only when you was youngest

Cheers

Marc

jmurba

ok I will try to be clearer :
when one blend trimix using partial pressure method one tranfer each gas ok, but each gas have a different compressibility, in addition one have to deal with different gas temperatures etc.
the first blending is generaly ok one has more or less the desired FHe.
when one get out of the water with half of the trimix pressure in the tank he can do a second blending without releasing the trimix in the air.
the second blending is generaly possible even if the errors statr to accumulate.
the third blend is not accurate enough to be acceptable, the N2/He fraction is not know anymore uneless one has an helium analyzer...
of course if you blend a new trimix in a tanks and then transfer it in you dil tank it is ok but I don't wan't to blend in a tank compressing the 3 gases in a tank and the decompressing it in a bag to recompress it in my dil tank....
I am looking for a simpler way to top up my dil tanks....
in fact I would like to make a trimix has one make nitrox in continuous blending...
regards
jean mi

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ntokyo

For me the only way to do it accurately is to have a double entry mixer (Bigata is cheap) along with an He analyser. Going through the molecular weight formula for each gas and take into account compressibility will not bring you much accuracy with a bag ...
As for topping-up an existing blend, it can be quite accurate as long as you know exactly the amount of He you fill in, control the O2 with an analyser and log the fillings... A difference of few % in the He linked to the compressebility, will bring you only few meters of END difference... It is ok.