Atomic M1 vs ST1 reg for a rec diver toying with the idea of tec diving in the next 2-4 years

[Wookie]

I use piston regs only, not a fan of diaphragm after seeing one blow at 300 feet. I have Ti2 for back gas and M1 for Deco bottles.

 

[divezonescuba]

what did the manufacturer have to say about that?

 

[eelnoraa]

Many years ago, I asked why not Ti for backgas since we will never use high O2 there. I got consistent answer from two different tech divers/instructors. PM me if you want to know who they are

The reason is in the case you have reg issue for deco gas, you can actually swap backgas reg to deco bottle instead of staying with backgas for deco. It is a very corner cases, I have never seen or heard it happens ersonally. Being able to do that is a nice option.

 

[eelnoraa]

what did the manufacturer have to say about that?

as long as you don’t expose Ti to >40%, why would manufacturer care? And you will never use that kind of O2 in back gas.

 

[Wookie]

what did the manufacturer have to say about that?

Don’t use the M1 on any O2 over 80%, or the Ti on anything over 40%

No rocket science here.

I do know folks who use them on their rebreathers using 100%, but Atomic doesn’t recommend it.

 

[stuartv]

I am with Stuart. All AA breath the same. M1 has advantages in high O2 contents

Don't forget, the M1 also comes with the wider exhaust tee and an extra heat sink that is supposed to make them better in cold water.

The Z2 is great for single tank because it does have a LP port on the bottom, and it's pretty darn inexpensive. For any reg that might be used in something other than single tank, I would just buy M1s. I bought my Z2 set after I already had regs for doubles and knew that my Z2 set would be strictly dedicated to only single tank.

 

[stuartv]

Don’t use the M1 on any O2 over 80%, or the Ti on anything over 40%

No rocket science here.

I do know folks who use them on their rebreathers using 100%, but Atomic doesn’t recommend it.

The manufacturer only rates the M1 for up to 80%, but do you have any idea why it's not rated for higher?

I have never seen a single thing in the preparation of equipment for Oxygen service that differentiates between "okay at 80%" and "okay at 100%". In other words, it seems like anything that is suitable for more than 40% is suitable for up to 100%.

I would think it must be an issue of materials, but what material could they possibly be using that is suitable for 80% but not 100%?

 

[Wookie]

The manufacturer only rates the M1 for up to 80%, but do you have any idea why it's not rated for higher?

I have never seen a single thing in the preparation of equipment for Oxygen service that differentiates between "okay at 80%" and "okay at 100%". In other words, it seems like anything that is suitable for more than 40% is suitable for up to 100%.

I would think it must be an issue of materials, but what material could they possibly be using that is suitable for 80% but not 100%?

Yes.

Metals are rated for how they burn with exposure to 7500 psi oxygen when the neoprene catches fire. If exposed to 80% O2, neoprene doesn’t burn hot enough for the Monel to burn. The monel burning isn’t self sustaining, but some is consumed with neoprene.

In reality, if your o-rings are Viton and not Neoprene, and your grease is O2 compatible, and your O2 is somewhat less than 7500 PSI, you should be fine. I expect Atomic was being hyper careful.

The report is here if you like reading that kind of thing…

https://apps.dtic.mil/sti/pdfs/AD0608260.pdf

 

[Wookie]

Many years ago, I asked why not Ti for backgas since we will never use high O2 there. I got consistent answer from two different tech divers/instructors. PM me if you want to know who they are

The reason is in the case you have reg issue for deco gas, you can actually swap backgas reg to deco bottle instead of staying with backgas for deco. It is a very corner cases, I have never seen or heard it happens ersonally. Being able to do that is a nice option.

The reason that titanium is not compatible with high O2 is not fire, it’s cracking of the titanium. If the choice was to miss deco, I’d swap regulators in a heartbeat.

 

[eelnoraa]

Yes.

Metals are rated for how they burn with exposure to 7500 psi oxygen when the neoprene catches fire. If exposed to 80% O2, neoprene doesn’t burn hot enough for the Monel to burn. The monel burning isn’t self sustaining, but some is consumed with neoprene.

In reality, if your o-rings are Viton and not Neoprene, and your grease is O2 compatible, and your O2 is somewhat less than 7500 PSI, you should be fine. I expect Atomic was being hyper careful.

The report is here if you like reading that kind of thing…

https://apps.dtic.mil/sti/pdfs/AD0608260.pdf

I agree AA has a lot of lawyers worked on their documentation.