Regulator First Stage for Deco/Stage Bottle

[Ouvea]

Hello All:

My Atomic B2 first stage has an air leak from the ambient pressure chamber. It's a very small leak with a tiny bubble flowing at an extremely slow rate. I only noticed it because I was sitting twenty minutes in deco and the darn thing just floated past my mask.
I overhauled the first stage and installed a new piston (just to on the safe side, although I did not find any damage to the original piston). The piston land on the body does not have any wear. However, the bore of the first stage body where you install the teflon washer, o-ring and metal retainer does have significant scoring. By scoring I mean that the chrome plating has deteriorated showing the brass body.

I believe this is source of the leak. It's a forgone conclusion that as a deco/stage bottle, the regulator has become depressurized during the dive and allowed water to enter the internal passages of the first stage.

Would like to know if the Diaphram regulators would experience such problems if the first stage were to flood? Any pros/cons on the first stage design, strictly for a deco/stage bottle regulator application.

Thanks for your input.

 

[rsingler]

Diaphragms are generally less tolerant of a dollop of water, should you then need to use the reg. A piston will generally just blast that bit through, and then function normally.
The description of your issue is a little strange, though.
Your description is consistent with flooding from the TANK side, but since you're able to strip the reg yourself, I have to say that any indication of flooding should have been accompanied by a rebuild as soon as you got home. That chrome loss only occurs if the salt stays behind for an extended period.
The problem I see is that flooding from a pressurized first stage that is then shut down often comes from the second stage side, since that is the valve most likely to be affected by increased ambient pressure. Since you noticed chrome loss on the HP side, though, that means water must have entered from the tank/reg union. I think the cure of the problem might be a more consistent seal to your tank. But I'm still surprised. Even with a minor leak, once 3000 psi bleeds down to ambient, there should have been no net movement of water. That it did occur suggests that the leak at the tank oring was fast enough that it went to ambient quickly, and then accepted water through the same leak as you descended.
The fix may be as simple as getting a new deco tank valve with an unscratched land, and inspecting the tank connection of your first stage (yoke or DIN) for similar scratches.

 

[halocline]

I overhauled the first stage and installed a new piston (just to on the safe side, although I did not find any damage to the original piston). The piston land on the body does not have any wear. However, the bore of the first stage body where you install the teflon washer, o-ring and metal retainer does have significant scoring. By scoring I mean that the chrome plating has deteriorated showing the brass body.

I believe this is source of the leak.

So, just to be clear, you have rebuilt the regulator and it still leaks?

There are two possible sources for a leak through the ambient chamber ports on a balanced piston 1st stage; the HP o-ring, or the piston head o-ring. I've experienced both on SP balanced piston stages. The usual culprits are a scratch on the bore of the body where the HP o-ring sits, or enough wear/pitting in the ambient chamber to prevent the piston head o-ring from sealing. (Forgive me if this is already obvious to you)

A good way to determine which o-ring is leaking (if it's not evident from scratches) is to pressurize the reg with both a SPG and IP gauge attached, then turn off the tank, wait a while and see whether IP begins to drop (piston head o-ring leak) or supply pressure drops (HP o-ring).

I have on several occasions cleaned up corrosion in ambient chambers with abrasive cloth and micromesh and stopped ambient chamber leaks. I'm not sure what the scoring you are referring to is, but if you're convinced that it is the source of your leak, you might try cleaning all the chrome off with fine sandpaper, leaving a good flat surface for the o-ring to seal against.

In terms of your question about regulators for deco that can tolerate flooding, I would suggest a MK2 or other unbalanced, flow-by design piston reg. There's no balance chamber, no dynamic o-rings subject to tank pressure, and the interior is so painfully simple that they are thought to be much more tolerant of flooding than other types of first stages. In fact, I've been hanging on to my MK2 just for this reason.

 

[Scared Silly]

Halocline hit it when it comes to dealing with leaks. I would not have replaced the piston only the o-rings and I have had issues with the HP o-ring before.

My other comments are that when cleaning areas where there has been corrosion use a Scotch-brite pad or similar before resorting to sand paper. The other item is make sure the o-rings are sufficiently lubricated.

 

[Ouvea]

How would you guys recommend that I polish the inner surface? Tear a piece of scotch brite pad or steel wool and use it with a plastic probe? This almost sounds like it would be ideal too have a dremel tool with an attachment narrow enough to fit inside the bore. Also, assuming that it is the inner surface of the bore and that I am able to remove any imperfection that causes the leak, am I just buying a short period of time until the problem returns? I'm guessing this will depend if the regulator floods again....

 

[Scared Silly]

For the bore look for some jewelry polishing kits : Mini Rubber Silicone Pin Polishers (Pack of 6)

BTW Worse case you could always have the reg re-chromeplated.

 

[northernone]

How would you guys recommend that I polish the inner surface? Tear a piece of scotch brite pad or steel wool and use it with a plastic probe? This almost sounds like it would be ideal too have a dremel tool with an attachment narrow enough to fit inside the bore. Also, assuming that it is the inner surface of the bore and that I am able to remove any imperfection that causes the leak, am I just buying a short period of time until the problem returns? I'm guessing this will depend if the regulator floods again....

Here's the best answer I know:

I have on several occasions cleaned up corrosion in ambient chambers with abrasive cloth and micromesh and stopped ambient chamber leaks. I'm not sure what the scoring you are referring to is, but if you're convinced that it is the source of your leak, you might try cleaning all the chrome off with fine sandpaper, leaving a good flat surface for the o-ring to seal against.

.

 

[halocline]

Also, assuming that it is the inner surface of the bore and that I am able to remove any imperfection that causes the leak, am I just buying a short period of time until the problem returns? I'm guessing this will depend if the regulator floods again....

It's an odd scenario, because of course you know that people use deco regs all the time, some are balanced piston regs, and they don't get destroyed by flooding. It's hard to imagine the HP section getting badly flooded from the 2nd stage; assuming you pressurize the reg and then turn the tank off for your dive. Usually that kind of flooding occurs from the tank side, i.e. soaking with no dust cap or a really wet fill. Usually the filter is corroded. You didn't mention that, so I assume you had water entry from the 2nd stage. That would mean that your IP chamber would also be corroded. I've seen that on a few 1st stages, but never corrosion in just the area where the HP o-ring sits.

Anyhow, you might have to get creative. I've used micromesh (that's excellent abrasive paper in a variety of grits up to 12,000) wrapped around a pencil eraser to clean up bores, it works great on 2nd stage air barrels.

 

[lexvil]

Would you like to try switching the body? I have a few Z first stages sitting in my shop.