Are regulators specifically tuned for Trimix?

[Pressurehead]

3 pages of 'weird".
Bent on helium you are seriously bent, If you are going to "mess with" this stuff, you have to know your S#!*.

 

[Raphus]

Bent with helium is different?

 

[Pressurehead]

Bent with helium is different?

You are correct.
I read all these posts and I don't know if some of you are joking or serious.
Found this in my saved notes, can't remember where I saved it from. 'Diving rant" I think ? just liked the way he wrote it:

A note on Helium and bends
The real problem with helium is that it is a 'fast' gas.
So what do I mean by fast?

On the Bühlmann model there are 16 'compartments' which represent overlapping tissue types. It isn't that your spleen is a compartment four and your leg is a compartment six just that all 16 overlap enough for all cases to get represented. Also when one compartment feeds another it is just represented by a slightly longer compartment. The system dates from Haldane and it's good physics.

For nitrogen they have one set of 'half times' for each compartment representing how long gases take to dissolve and release but for helium they are about a third as long.

This implies that helium dissolves in your tissues at nearly three times the rate so, in very approximate terms, a dive on helium is three times as long. However, as your deco is three times as long too, it evens out and a helium dive isn't all that much different from a Nitrox dive.

Until you miss stops. Then those ten minutes you missed on your 40 meter dive is effectively half an hour missed on a dive with three times the bottom time and your problem has moved up an order of magnitude.

Conversely when they haul your messed up carcass into a chamber all those helium bubbles redissolve at three times the rate and you then are back to doing the re-deco at 'normal' rates. Your untreated bend is much worse but, if they get to it in time, the prognosis is much better than the same level of bent on nitrogen.

One of the consequences of this is that your ascent needs to be spot on. The deeper stops can have some compartments off gassing while others are still on gassing so hitting those numbers is much more important. The fact that only a two minute stop is called for doesn't make it trivial (think six minutes). I much prefer a computer on helium precisely because in the deep ascent stage of the dive it is recalculating 'on the fly'. If I were diving tables I would select a far more conservative algorithm because I know I'm not going to hit my numbers to the second and all my errors are multiplied by at least three.

PS: I have stated in the past that you gas on 'more' helium and I think I mislead people. You gas on about the same total volume.
Edit:
Google found it: Diving Rant

 

[Raphus]

You are correct.
I read all these posts and I don't know if some of you are joking or serious.
Found this in my saved notes, can't remember where I saved it from. 'Diving rant" I think ? just liked the way he wrote it:

A note on Helium and bends
The real problem with helium is that it is a 'fast' gas.
So what do I mean by fast?

On the Bühlmann model there are 16 'compartments' which represent overlapping tissue types. It isn't that your spleen is a compartment four and your leg is a compartment six just that all 16 overlap enough for all cases to get represented. Also when one compartment feeds another it is just represented by a slightly longer compartment. The system dates from Haldane and it's good physics.

For nitrogen they have one set of 'half times' for each compartment representing how long gases take to dissolve and release but for helium they are about a third as long.

This implies that helium dissolves in your tissues at nearly three times the rate so, in very approximate terms, a dive on helium is three times as long. However, as your deco is three times as long too, it evens out and a helium dive isn't all that much different from a Nitrox dive.

Until you miss stops. Then those ten minutes you missed on your 40 meter dive is effectively half an hour missed on a dive with three times the bottom time and your problem has moved up an order of magnitude.

Conversely when they haul your messed up carcass into a chamber all those helium bubbles redissolve at three times the rate and you then are back to doing the re-deco at 'normal' rates. Your untreated bend is much worse but, if they get to it in time, the prognosis is much better than the same level of bent on nitrogen.

One of the consequences of this is that your ascent needs to be spot on. The deeper stops can have some compartments off gassing while others are still on gassing so hitting those numbers is much more important. The fact that only a two minute stop is called for doesn't make it trivial (think six minutes). I much prefer a computer on helium precisely because in the deep ascent stage of the dive it is recalculating 'on the fly'. If I were diving tables I would select a far more conservative algorithm because I know I'm not going to hit my numbers to the second and all my errors are multiplied by at least three.

PS: I have stated in the past that you gas on 'more' helium and I think I mislead people. You gas on about the same total volume.
Edit:
Google found it: Diving Rant

Thanks! Jeah makes sense. Missed stops or to fast ascent rates are worse on helium

 

[happy-diver]

Google found it:

Nigel Hewitt base server

Yeah you have to read Nigel Hewitt

 

[PfcAJ]

You are correct.
I read all these posts and I don't know if some of you are joking or serious.
Found this in my saved notes, can't remember where I saved it from. 'Diving rant" I think ? just liked the way he wrote it:

A note on Helium and bends
The real problem with helium is that it is a 'fast' gas.
So what do I mean by fast?

On the Bühlmann model there are 16 'compartments' which represent overlapping tissue types. It isn't that your spleen is a compartment four and your leg is a compartment six just that all 16 overlap enough for all cases to get represented. Also when one compartment feeds another it is just represented by a slightly longer compartment. The system dates from Haldane and it's good physics.

For nitrogen they have one set of 'half times' for each compartment representing how long gases take to dissolve and release but for helium they are about a third as long.

This implies that helium dissolves in your tissues at nearly three times the rate so, in very approximate terms, a dive on helium is three times as long. However, as your deco is three times as long too, it evens out and a helium dive isn't all that much different from a Nitrox dive.

Until you miss stops. Then those ten minutes you missed on your 40 meter dive is effectively half an hour missed on a dive with three times the bottom time and your problem has moved up an order of magnitude.

Conversely when they haul your messed up carcass into a chamber all those helium bubbles redissolve at three times the rate and you then are back to doing the re-deco at 'normal' rates. Your untreated bend is much worse but, if they get to it in time, the prognosis is much better than the same level of bent on nitrogen.

One of the consequences of this is that your ascent needs to be spot on. The deeper stops can have some compartments off gassing while others are still on gassing so hitting those numbers is much more important. The fact that only a two minute stop is called for doesn't make it trivial (think six minutes). I much prefer a computer on helium precisely because in the deep ascent stage of the dive it is recalculating 'on the fly'. If I were diving tables I would select a far more conservative algorithm because I know I'm not going to hit my numbers to the second and all my errors are multiplied by at least three.

PS: I have stated in the past that you gas on 'more' helium and I think I mislead people. You gas on about the same total volume.
Edit:
Google found it: Diving Rant

Do you have any data to back up that claim or just a rant?

 

[jale]

Hi
As a "specific tuned regulator for trimix", I suggest you get the Apeks MTX, XTX or ATX as they have "Tx" in their label

 

[Pressurehead]

Do you have any data to back up that claim or just a rant?

I will bow to your greater knowledge on the subject, I have been out of this scene a long time .
Modern decompression theory and practice and helium protocols can be explained by others more 'in the the know' and help to explain deep trimix dives with multiple switches.
A lot has changed in the last 10 years.
Deleted the rest, bored now.

 

[Centrals]

Isobaric counterdiffusion - Wikipedia

At least two well known cases:
1. Late John Bennett on his 308m dive in Puerto Galera 2001.
2. Don Shirley on Dave Shaw dive in South Africa 2005.

Both of them suffering "vertical" around 60m after a gas switch.

 

[Raphus]

Isobaric counterdiffusion - Wikipedia

At least two well known cases:
1. Late John Bennett on his 308m dive in Puerto Galera 2001.
2. Don Shirley on Dave Shaw dive in South Africa 2005.

Both of them suffering "vertical" around 60m after a gas switch.

That's interesting.
So the problem occurs when the new gas is saturating faster, then the old gas diffusing. Right?

So this would be a problem, if diving on air and decompressing with helium(which makes no sense ofc).
But when does this happen in real life Szenario?
Switching from helium to air is not a problem, or is it?