Ok for a Deco Reg?

[Padipro]

I'm starting my Advanced Nitrox and Deco Procedures class this week so I took my stage bottle reg into the shop to have it O2 cleaned in preperation for using it with high O2 concentrations. The tech at the shop, a very experienced individual but old school, said he could clean it but that because it was a balanced piston design he wouldn't reccomend it. He said that because it was for deco that it didn't need to be balanced and that an un-balanced first stage would be better and cheaper. Since I own several back up regs I don't know that buying another "un-balanced" reg strictly for deco would be any cheaper. The better part did make some sense though. Being a balanced design there are more twists and turns within the first stage he explaned that could develop hot spots and result in combustion if used with very high concentrations of O2.

I was wondering what type of deco reg others are using and if you think it's un-wise to use a balanced first stage for this? I understand that if were buying a reg strictly for deco that an un-balanced first stage would work just fine but I don't really want to buy another reg if I don't have to.

 

[mempilot]

Scott,

Which reg were you using on your stage bottle? For the class, you'll only be using ean50 on the training dives. You should be fine with the reg you have. When you start carrying two deco bottles, an ean50 and an ean100, I'd look at a dedicated O2 reg for the second bottle.

Tech divers are even using Apeks DS4 diaphram 1st's on deco bottles. Diamphram vs. Piston is another argument that 'old school' will tell you one thing and current tech divers will tell you another.

I personally am going to stick with the Apeks diamphram's deep performance for the pri and sec, and use the OMS unbalanced piston deco regs on my bottles, but I wouldn't get too worried about an ean50 reg being a balanced piston. You're slowly precharging the hose on the boat with the 2nd purge button held open slightly. At 50 vs. 40, I can't see any real risk. Heck, you'll just be breathing smoother than the rest of us.

BTW, the OMS breathes fine at 70' and shallower. I haven't taken a hit off it deeper than that for obvious reasons.

I'm looking forward to getting in on your training dives. See you on the boat Tuesday.

 

[Padipro]

Hay Eric,

I'm not worried about using the reg for EAN50, thats not much of an increase in O2 but as we've all be tought the straighter the flow path for O2 the better. The reg is a USD Cousteau first stage with a Micra second. It's small and easly stowd so I like it for the stage. I actually have 2 of these laying around, both with DIN connections on them so I thought they'ed be great for the stage bottles. I'm just cerious what others are using and what they think of going this rought.

Hopefully the winds die down a bit before Tuesday but I'll be there. I need to get wet my gills are drying up.

 

[DA Aquamaster]

The "more twists and turns" argument is nonsense. Several years ago Scubapro approved the balanced piston Mk 20 for use with O2 mixes up to 100% at 3500 psi (with proper cleaning) and it is very much a balanced piston design.

In a balanced piston design the gas comes into the first stage and then makes a 90 degree turn past the hard sealing edge and soft seat and up through the piston. In an unbalanced "flow by" piston design and in diaphragm first stages, the gas enters the first stage and makes a 90 degree change in direction as it squeezes past and between the soft seat and the hard sealing edge. There really is no significant difference in terms of twists and turns between the three designs.

Any twists and turns after the initial 90 degree turn in either of the three designs, are in the IP sections of the reg where the gas has already been drastically cooled and hot spots are not going to develop.

In any reg design the prime time for a hot spot is when the tank valve is opened and the reg is suddenly pressurized. Turning the tank valve on slowly and with the purge depressed slightly will minimize the sudden increase in pressure in the reg will go a long way toward preventing ignition in any reg design.

The only real advantage with an unbalanced piston first stage over a balanced piston design is that there are no dynamic o-rings in the reg that are exposed to the gas at full tank pressure as the piston stem o-ring is in the IP section fo the first stage. But with proper lubrication and O2 compatible materials that is a moot issue.

 

[wedivebc]

I'm starting my Advanced Nitrox and Deco Procedures class this week so I took my stage bottle reg into the shop to have it O2 cleaned in preperation for using it with high O2 concentrations. The tech at the shop, a very experienced individual but old school, said he could clean it but that because it was a balanced piston design he wouldn't reccomend it. He said that because it was for deco that it didn't need to be balanced and that an un-balanced first stage would be better and cheaper. Since I own several back up regs I don't know that buying another "un-balanced" reg strictly for deco would be any cheaper. The better part did make some sense though. Being a balanced design there are more twists and turns within the first stage he explaned that could develop hot spots and result in combustion if used with very high concentrations of O2.

I was wondering what type of deco reg others are using and if you think it's un-wise to use a balanced first stage for this? I understand that if were buying a reg strictly for deco that an un-balanced first stage would work just fine but I don't really want to buy another reg if I don't have to.

I find for deco regs, work of breathing is less important than reliability. I don't want a high flow reg that might freeflow when I need it most. Thats why I used to use the old faithful Aqualung conshelf, and have now moved to apeks ds4s.

The problem with balanced piston regs is that they are a little more convoluted due to the fact that ambient pressure has to be able to affect the other end of the piston without letting seawater creep in and muck things up. It seems diaphram regs give a straighter shot to through the valve.
Either way I don't believe there is a true 'oxygen service' reg in the scuba industry.
So my vote is for apeks

cheers,

 

[mempilot]

One more nice thing about using the balanced piston reg you have is that in the remote case you would need to switch out a reg at depth, you'll have a good breather to do so. It might not breath better than a balanced diamphram, but you'll run less risk of having to rebuild the first after taking it off underwater. Then again, if it saves your butt, who cares about having to rebuild it? I like the idea of having all 4 regs being the same model, but I'll stick with the OMS regs for the bottles until I win the lottery.

 

[wedivebc]

but you'll run less risk of having to rebuild the first after taking it off underwater.
.

Why is that?

 

[mempilot]

Why is that?

This goes back back to my previous off-topic comment about Piston vs. Diamphram and 'old school' vs actually what is being used today. As I understand the debate, when removed or pressure is bled from the circuit underwater, a diaphram reg is more succeptible to water penetration than a piston reg and a possible failure ensuing. Saltwater entering the 1st would then require a tear down and inspection. I realize that many divers use diaphram 1st's on deco bottles, have taken them off underwater, and had no problems. Just making the argument that has been around, even though it get's proven somewhat irrelevent.

 

[wedivebc]

This goes back back to my previous off-topic comment about Piston vs. Diamphram and 'old school' vs actually what is being used today. As I understand the debate, when removed or pressure is bled from the circuit underwater, a diaphram reg is more succeptible to water penetration than a piston reg and a possible failure ensuing. Saltwater entering the 1st would then require a tear down and inspection. I realize that many divers use diaphram 1st's on deco bottles, have taken them off underwater, and had no problems. Just making the argument that has been around, even though it get's proven somewhat irrelevent.

So would you NOT service a piston reg after exposing the HP seat and piston to salt water?

 

[mempilot]

So would you NOT service a piston reg after exposing the HP seat and piston to salt water?

yep