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***jradomski*** · 17th April 2007, 12:15

Quote: (Originally Posted by DeepBlueInnovation)

The prism solenoid is interesting in the way that the gas flow path is reversed, so that if it fails, it fails shut. To be more precise, the 02 flows into the chamber through two large orifices and pressurises the chamber in the solenoid. There is a small central orifice that is sealed by a central spring loaded seat that is drawn down when the current is activated, allowing a small measure of gas to pass through the orifice. So, if the electronics were to fail and the solenoid cease to work, it would fail in the closed position.

The prism has a seperate manual 02 addition line that can be used to maintain the P02. The only situation I can see where gas venting would be an issue is if an 02 line were to blow, and as they are made of stainless steel, this is unlikely.

As I stated earlier, I took separate bailout and undertook a dive in a controlled manner with the specific intent of identifying a problem. It was not a deep dive and it was not in the open ocean. I constantly validated my P02 and the function of my electronics.

So, with a HUD, a secondary that enables me to manually (electronics switched off) validate each cell's reading and adequate bailout, I am yet to be convinced that the process i undertook is any more dangerous than any other dive on a rebreather.

The PRISM solenoid is basically a copy of a snaptite solenoid.. The failure we are talking about can EASILY fail open.. this is not due to electronics failure but rather a mechanical failure..

ALL the Rebreather solenoids I am aware of pull open against the source pressure, so the higher the pressure (or no current flow) the solenoid is forced shut..

But what you are describing is RUST.. since the solenoid chamber has to be made of a ferous metal, so don't fool yourself.. After sitting the likely failure is to fail shut and not be able to open, but if its operating intermittingly all bets are off..
the rust particles can jam the chamber and rust flakes can prevent the orifice from sealing..

So in this case, diving manual may not be a normal option.. even if it did work, unless you totally cleaned up and lubed the solenoid, it working proves nothing and may have caused a problem on the next dive..

17th April 2007, 12:15	#11 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,011	Re: What is the lifespan of a solenoid? Quote: (Originally Posted by DeepBlueInnovation) The prism solenoid is interesting in the way that the gas flow path is reversed, so that if it fails, it fails shut. To be more precise, the 02 flows into the chamber through two large orifices and pressurises the chamber in the solenoid. There is a small central orifice that is sealed by a central spring loaded seat that is drawn down when the current is activated, allowing a small measure of gas to pass through the orifice. So, if the electronics were to fail and the solenoid cease to work, it would fail in the closed position. The prism has a seperate manual 02 addition line that can be used to maintain the P02. The only situation I can see where gas venting would be an issue is if an 02 line were to blow, and as they are made of stainless steel, this is unlikely. As I stated earlier, I took separate bailout and undertook a dive in a controlled manner with the specific intent of identifying a problem. It was not a deep dive and it was not in the open ocean. I constantly validated my P02 and the function of my electronics. So, with a HUD, a secondary that enables me to manually (electronics switched off) validate each cell's reading and adequate bailout, I am yet to be convinced that the process i undertook is any more dangerous than any other dive on a rebreather. The PRISM solenoid is basically a copy of a snaptite solenoid.. The failure we are talking about can EASILY fail open.. this is not due to electronics failure but rather a mechanical failure.. ALL the Rebreather solenoids I am aware of pull open against the source pressure, so the higher the pressure (or no current flow) the solenoid is forced shut.. But what you are describing is RUST.. since the solenoid chamber has to be made of a ferous metal, so don't fool yourself.. After sitting the likely failure is to fail shut and not be able to open, but if its operating intermittingly all bets are off.. the rust particles can jam the chamber and rust flakes can prevent the orifice from sealing.. So in this case, diving manual may not be a normal option.. even if it did work, unless you totally cleaned up and lubed the solenoid, it working proves nothing and may have caused a problem on the next dive.. __________________ 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.
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