What is the lifespan of a solenoid?

jradomski

Thats why I said a copy.. since SMI manufactirers it themselves..

BTW you can still get them from snaptite, you just have to place a large enough order.. Snaptite will build anyting for you as long as you order enough pieces at a time..

__________________
Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

Dave Sutton

Uhhh...... missing that the term "rust" is just a non-technical term for ferrous metal corrosion?


Dave

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

divetheworld

you enjoyed that toooo much

__________________

silent running

To be precise, the stuff in my reg/O2 lines/solenoid was a powdery, white/bluish substance. It might be the same "thing" as "rust", but looked different enough to me...

The question is: why did my solenoid fail/block-up closed? If the substance was plain o' rust, why didn't it block open with the big stuff/rust flakes?

Joe Radomski helped me clean up my O2 tank after the wet O2 contamination, that's where it started, in the cylinder. Maybe it's really aluminum oxide? Either way, it was caused by moisture and O2 mixing in the O2 cyl and moved on downstream to the solenoid. That's my empirical observation and I'm interested to know what difference there is btw the 2 things-the powdery light colored stuff and the coarser, flakey red stuff... -Andy

divetheworld

Andy,

The difference is the parent metal that has oxidized, nothing else. White powdery stuff in scuba is usually aluminium oxide, red stuff is rust from the ferrous material.

Why not just refer to it as oxidization.

Obviously the definition makes a huge difference to the topic of conversation at hand .

IMHO, the reason solenoids fail is due to a limited number of different common modes of failure. Examining only the external influences of oxidization, it is possible that the flakes of material did not cause it to fail but the internal components oxidized and locked up shut. Perhaps contamination through the gas supply was not the cause but not far off being a problem.
You are correct in assuming that one common mode failure due to a contaminated gas supply is fail open. It is the expected failure under those circumstances.
White "stuff" in the gas supply lines could be;
aluminium oxide (powder), O2 grease, chalk from the hose manufacture.

One of the problems of solenoids is inherrant in their design. In order for a magnetic field to move the pressure seat it must have a ferrous component for the magnetic field to act upon. If that ferrous component is not hermetically sealed from the atmospheric gas then it will corrode. The sealing of the ferrous core means it must be further away from the magnetic field and then less force can be exerted (less pressure in the supply line is allowed) or more energy must be used to open or close the valve.
There are few designs of solenoid which solve this problem adequately. So with existing designs, you must regularly inspect or replace the affected parts as required.

Brent

__________________

silent running

Ok dtw, that's why I asked if I was missing something. Is aly oxide not a form of corrosion? Maybe it isn't. I was just pointing out that if it's wet O2 we are concerned about-$450 later I certainly am-the cyl seems to be the first place it will manifest. And the powdery stuff seems more likely to get past the restrictor in the O2 lines and is more likely to block up the solenoid closed as opposed to the good ol' rusty flakes blocking it open. Given that I have heard of more solenoids on the Prism failing closed, I don't know the answer, hence the post... And thanks for the detailed explanation of the magnetic field/sealing issue Brent.

jradomski

ANDY,

It probably failed closed because the solenoid was sitting and it gave the oxidation time to join to the base metal.. If the solenoid managed to open its just as likely it mike not now close.. Most of the time you will probably see a solenoid stuck just beacsue there are long periods of non use that give it time to stick..

Your cylinder definately had lots of powered al oxide..

__________________
Joe Radomski
CCR Trimix Instructor Trainer
ANDI Instructor Trainer Director #10

All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

Dave Sutton

And the regulator filter and the internal filter in the rig did not catch the crud before it got to the solenoid?


And I *really* doubt the "wet 02" thing. Even "technical grade 02" (IE welding 02) is generally produced and shipped as a cryogenic liquid, is handled at the gas filling facility as a cryogenic, and is decanted into gas cylinders as HP 02 after it's phase change. There's no measurable water in the gas. It's stored in *steel* cylinders that are never given a visual inspection between the 5 year hydro tests. The *specification* for technical/medical/aviators grades show different water contents, but they are (A) measured in parts per million, and are (B) all generally meeting aviators grade anyhow. I use aviation 02 because I have it, but "Wet 02" is not a realistic concern, even in the third world.


Dave

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

SteveL

Benni Boy - I recently had a solenoid that did not fail shut - didnt fail open either - it just leaked O2 into the loop continuously - everybody has something to add no matter how small -

Steve

silent running

Dave, I think the last good idea put forth around here about the origin of excess moisture in "welding" or technical grade O2 was that when it's decanted after the phase change, it's put into tech grade cylinders which are not vacuumed out, as opposed to vacuuming being a requirement with the other 2 grades-med/avi. I don't know if this holds any water...oh, bad pun, but seems somewhat plausable. Otherwise, it came from the decanting whip, and I'm a dummy for letting the liveaboard boat crew fill my O2. But they were supervised by the owner, who is a very experienced CCR diver...

Is there any other possible explanation for so much water getting in to a cyl?

Anybody ever experiemented with adding some kind of moisture filter to an O2 whip? I guess it might cause more potential friction for the gas flow and might not be a good idea cause of that...