Filled housings?

Genesis

I have read with some interest that some folks who are doing "truly extreme" dives have filled handsets and such with a non-conductive fluid (e.g. silicone oil, etc) to avoid the risk of implosion.

Why is this not standard procedure for isolated spaces (other than a battery compartment as the obvious exception)?

For instance, a handset. Why not eliminate the issue of leaks into the housing by removing the compressable space from the equation?

Am I missing something here? It appears to make the requirement for pressure-proofing things pretty much a non-issue, as now the pressure differential that must be withstood is close to nil, instead of the full differential between 1 ATA and whatever depth you're at.....

Steve

Why is the battery compartment the obvious exception?

It isn't done as a general rule because:

1. It isnt necessary
2. It is messy
3. If any work needs to be none on the board ect due to circuit or component failure, the oil has to be removed and the surfaces have to be cleaned well.
4. Most mineral oils when exposed to current will cloud over time and refilling is a PITA. Some don't but working out which is which is a bit of a fiddle.

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Genesis

Let's think about this a bit.....

1. Necessary. Well sure, but you could use a much less-heavily-built housing if you had it filled. It also removes the issue of water leaks into the housing via the cable (same pressure on both sides, no migration)

2. Messy. Only once.

3. Work needing to be done - uh, how are you going to work on a board that has had salt water get into it? 99% chance its junk in that case....

4. Mineral oils clouding - the mineral oil in the compass on my boat is 20 years old (OEM gear) and has been out in the open for the majority of its life. It is not cloudy. Is 20 years long enough?

Just seemed to be an obvious solution to water migration problems that can occur if a cable gets nicked - if you have equal pressure on both sides then there is no pressure gradient and as a consequence pressure ratings becomre much less of an issue.

Don't know if its really practical, but it might be. I'm considering going this route with the handset I'm working on - I realize this makes it not rebuildable, but I'm not sure I care, given that water intrusion into electronics nearly always toasts 'em beyond economic repair.

jdz

This is only an issue if the handsets/guages are sealed! In most cases the pressure differential is zero because the handset is part of the loop...

My ppO2 guage has been to 142m comfortably.. similar to this... http://www.rebreatherworld.com/gallery/img595.html

Cheers, JDZ

Genesis

I like it a lot!

But - "part of the loop" is really unintentional in your case (e.g. creep through the cable), right?

Have you determined that you really are getting creep through the cable in an appreciable amount?

jdz

The "cable" is plastic tubing.. and by design.. there are no obstructions in the unit as I didn't want any squeezes... http://www.rebreatherworld.com/galle....php?i=593&c=$
Cheers, JDZ

Genesis

Aha! Cool design.

I'm somewhat surprised you haven't had trouble with exposing the battery in particular to high ATA pressures. That's what has given me pause with going this route. How deep have you been with it?

Those look like "P" connectors, yes?

jdz

I asked Dr Bob the same question 2yrs ago after seeing his circuitry in his Rebreather...
Couple of comments,

"Is it now that I have to add the disclaimer. "........ and using prototype homebuilt closed circuit life support equipment is inherently dangerous,.............." Everything that I have shown to the public on my webpages are my R&D prototypes, (dive toys).
No where will I ever say that what I am 'playing' with is ready for "prime time". I am not in the rebreather manufacturing business, just out to share some of my experiences and pleasures in this hobby with you. "....... the basic caveat of all homebuilds...

and, generally the loop environment is approaching 100% humidity....

Yes things might be different with dry high pressure O2 if I have a short or spark.. I'll worry about that if it ever happens anywhere..

and wrt the battery, it has not distorted...

yes, that was a p plug which houses the O2 sensor...

Cheers, JDZ

Genesis

LOL!

Yeah, I certainly understand that. I've been working towards a "dry" (1 ATA) environment for the "power side" due to concerns about the battery and electronics not tolerating being at ambient all that "nicely".

Then again I'm not efforting a mCCR - I'm working a full eCCR..... more power running around, etc.....

I found where you got the housings from.... have to check and see if the LCD I intend to use will fit in there (I think it might not, but if it does the price being asked for those housings is VERY reasonable.....)