Quote: (Originally Posted by
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
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