Failure points vs redundancy
- Thread starter datho87
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I'm a new diver looking to buy gear and have been debating if a backup SPG is worth the potential failure point it introduces. Probably over thinking it but decided I'd probably rather just have the AI and save the money on the SPG. I'm a long time pilot so I have some background in redundant equipment considerations.
The gear I rented on my first dives had an SPG leaking air, which was repaired on the boat and then started doing it again, it was more than champagne bubbles. I also discovered later that it was reading 300psi higher than actual. Our DM even told a story of having to do a CESA from 100 feet due to a stuck SPG.
That experience convinced me AI was the way to go. As I understand it, when AI fails, it's an obvious failure, which of course, is vastly preferable. There is also a lot less linkage to fail between an AI transmitter and and a tank than and SPG and a hose.
The failure mode is often as important as the failure probability.
If any of my thinking is off, please enlighten me.
Thanks for starting this thread.
The gear I rented on my first dives had an SPG leaking air, which was repaired on the boat and then started doing it again, it was more than champagne bubbles. I also discovered later that it was reading 300psi higher than actual. Our DM even told a story of having to do a CESA from 100 feet due to a stuck SPG.
That experience convinced me AI was the way to go. As I understand it, when AI fails, it's an obvious failure, which of course, is vastly preferable. There is also a lot less linkage to fail between an AI transmitter and and a tank than and SPG and a hose.
The failure mode is often as important as the failure probability.
If any of my thinking is off, please enlighten me.
Thanks for starting this thread.
In over four decades of getting wet, I have yet to experience an SPG problem, that wasn't remedied by two minutes, minor swearing, and a fifty-cent spool from my dive kit; that it happened to you with rental gear on a boat, comes as little surprise, since that gear is generally Tall-Toad, bargain basement crap and poorly if ever maintained.
Many divers -- nearly two-thirds of them, on my last boat dive, alone -- now utilize short transmitter hoses, to prevent them from being sheared off by clumsy deckhands, which I have seen happen on more than a few occasions; so that popular notion of some "less linkage between an AI transmitter and a tank" has mostly becomes moot.
I have, though, seen myriad failures with transmitters over the years, especially when I worked boats, years ago -- from straight-up interference between them and intermittent losses of signal; incidences of overpressure from which there was no return; and outright flooding -- and always carried an analogue backup, should I be using one.
Buy a decent SPG as a backup and don't look back . . .
Many divers -- nearly two-thirds of them, on my last boat dive, alone -- now utilize short transmitter hoses, to prevent them from being sheared off by clumsy deckhands, which I have seen happen on more than a few occasions; so that popular notion of some "less linkage between an AI transmitter and a tank" has mostly becomes moot.
I have, though, seen myriad failures with transmitters over the years, especially when I worked boats, years ago -- from straight-up interference between them and intermittent losses of signal; incidences of overpressure from which there was no return; and outright flooding -- and always carried an analogue backup, should I be using one.
Buy a decent SPG as a backup and don't look back . . .
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