Do you still use a SPG with a AI computer?

[stuartv]

But you guys brought up the valid argument about an extra failure point (another port, etc). Although as I'm thinking about this...technically most of us have a port or 3 plugged with a cap and o-ring. If the Tx (sorry, transmitter) was small enough that it didn't get bumped or shake or anything, I don't know if I would consider A/I + SPG an extra failure point. Maybe this has been discussed here already. I recall something about gripping/bumping the Tx... Maybe the future holds Tx's that are soft and look like hose whips

My opinion:

A physical SPG on a HP hose has more potential failure points than a hoseless AI transmitter.

A transmitter has 2 O-rings, both static. One in the HP port and one for the battery compartment. Failure of one of those would result in loss of gas. As they are both static, failure of either is very low probability. There are also two threaded openings (at least, on the PPS ones). The part that threads into the reg and the part where the battery compartment attaches. Either is subject to coming loose. One would result in gas loss.

An SPG on a HP hose has at least 4 O-rings, I think, at least 2 of which are dynamic. One in the HP port, 2 on the HP spool (they dynamic ones), and (I think) at least one sealing the gauge itself. Plus, the HP hose itself is subject to rupture. Failure of any of at least 3 O-rings, plus failure of the HP hose are all failures that would result in loss of gas. And the 2 O-rings on the HP spool are more likely than failures on any of the static O-rings. This also has 2 threaded connections. The part that threads into the reg and the threaded connection between the gauge and the hose. These are also subject to coming loose. Either one coming loose would result in loss of gas.

My single tank rig has an AI transmitter and a good quality button gauge on it. The button gauge lets me check the tank pressure (with somewhat low precision) without powering up my computer. And I can compare the button gauge reading to the AI computer to verify they are at least roughly in agreement.

The button gauge does not have as many potential failure points as a regular SPG on a HP hose, so I deem the "risk" to be worth the benefits.

I have had a spool O-ring blow out on a regular SPG. I don't see any reason for me to keep a regular SPG on my rig that has a transmitter on it.

My sidemount regs also each have an AI transmitter on them, with no SPGs. This definitely seems to be a nicer arrangement (combined with a Perdix AI that will display both) than my friends that use regular SPGs on their sidemount regs.

For my NDL diving, I dive with only AI. If my tank pressure reading were to go out during a dive, I would probably not abort the dive until and unless I knew I was getting low on gas. In my most common NDL diving, I always run out of NDL way before I run low on gas. For dives like that, I would have no reason to abort the dive early just because I lost my tank pressure readout. Also, that is what my buddy is for. To be sure, if my tank pressure readout did go out, I would be making dang sure I stayed close to my buddy AND let my buddy know the situation.

 

[Kevrumbo]

My opinion:

A physical SPG on a HP hose has more potential failure points than a hoseless AI transmitter.

A transmitter has 2 O-rings, both static. One in the HP port and one for the battery compartment. Failure of one of those would result in loss of gas. As they are both static, failure of either is very low probability. There are also two threaded openings (at least, on the PPS ones). The part that threads into the reg and the part where the battery compartment attaches. Either is subject to coming loose. One would result in gas loss.

An SPG on a HP hose has at least 4 O-rings, I think, at least 2 of which are dynamic. One in the HP port, 2 on the HP spool (they dynamic ones), and (I think) at least one sealing the gauge itself. Plus, the HP hose itself is subject to rupture. Failure of any of at least 3 O-rings, plus failure of the HP hose are all failures that would result in loss of gas. And the 2 O-rings on the HP spool are more likely than failures on any of the static O-rings. This also has 2 threaded connections. The part that threads into the reg and the threaded connection between the gauge and the hose. These are also subject to coming loose. Either one coming loose would result in loss of gas.

My single tank rig has an AI transmitter and a good quality button gauge on it. The button gauge lets me check the tank pressure (with somewhat low precision) without powering up my computer. And I can compare the button gauge reading to the AI computer to verify they are at least roughly in agreement.

The button gauge does not have as many potential failure points as a regular SPG on a HP hose, so I deem the "risk" to be worth the benefits.

I have had a spool O-ring blow out on a regular SPG. I don't see any reason for me to keep a regular SPG on my rig that has a transmitter on it.

My sidemount regs also each have an AI transmitter on them, with no SPGs. This definitely seems to be a nicer arrangement (combined with a Perdix AI that will display both) than my friends that use regular SPGs on their sidemount regs.

For my NDL diving, I dive with only AI. If my tank pressure reading were to go out during a dive, I would probably not abort the dive until and unless I knew I was getting low on gas. In my most common NDL diving, I always run out of NDL way before I run low on gas. For dives like that, I would have no reason to abort the dive early just because I lost my tank pressure readout. Also, that is what my buddy is for. To be sure, if my tank pressure readout did go out, I would be making dang sure I stayed close to my buddy AND let my buddy know the situation.

As per proper annual maintenance procedure and pre-dive protocol @stuartv , you're supposed to meticulously perform pre-dive and surface pre-descent bubble checks to catch these potential failure points, and bring "expedition spares" of everything (a spare transmitter, O-rings & batteries in your case @stuartv ). They just don't spontaneously "let go" and drain away breathing gas on you at depth in the farthest point of penetration in a wreck, nor does a hose "always" cut and rupture maneuvering past a piece of jagged metal.

In ten years of diving on overseas Indo-Pacific tech wreck charters, I've only had three small SPG "champagne bubble" leaks caught on surface bubble checks; and one hissing blow-out/O-ring extrusion when a boatman accidentally stepped on the SPG. All were either quickly re-torqued and/or changed out with a spare SPG & HP hose.

 

[Diving Dubai]

When the term additional failure points is brought up on SB, I normally roll my eyes. It's become a fashionable buzz word in many instances.

For example, if we were that concerned we could easily remove, a hose, and a couple of O rings plus some other bits n bobs by throwing away our alternate 2nd stage. After all its got these additional failure points, and if we have a problem we could buddy breath (sharing our buddies primary while ascending) But we don't. We deem the additional equipment to be necessary enough to not bother about the extra items.

The same with SPG's and AI transmitters (TX). SOme people chose to get rid of their SPG for streamlining or weight saving etc etc.

I personally keep my spg on all my reg sets, and they are all fitted with a 6" hose and QD so I can put on a TX if I want. While I like my AI for fun diving, I have no need of it say if I'm teaching OW. I'm not going to use my air faster than my students so keep my SPG where I can glance at it.

I also like to use my SPG when setting up my gear to confirm gas pressure etc and then only get my computer out when I actually kit up to splash.

So here I am with multiple extra O rings and another hose, why am I not dead?

Easy. Hoses and O rings rarely go, and if they do the generally go when taking the initial surge of pressure when turning a tank on. Otherwise the tend to leak a little first

Now while I do carry spares (and these have always been used to help others) I mitigate my failure risk with maintenance. I service my gear yearly, and have all the O rings changed and throw out my HP swivels. My hoses I change every 2 - 3 years - but this is because I live in the Middle East with high heat and high UV (car tyres are limited by law to a 4 year max life even if if you still have a legal depth of tread)

I've never had a failure - and I dive quite hard and my gear doesn't get treated gently. And compared with teh rest of my geat teh cost of new O rings and occasional hoses is inconsequential

So rather than this constant debate of the additional failure points, I recommend people dive the configuration they want and carry out basic maintenance at regular intervals - inc a pre-use inspection before you pack your gear. But hey that's just my opinion

 

[Dan]

When the term additional failure points is brought up on SB, I normally roll my eyes. It's become a fashionable buzz word in many instances.

For example, if we were that concerned we could easily remove, a hose, and a couple of O rings plus some other bits n bobs by throwing away our alternate 2nd stage. After all its got these additional failure points, and if we have a problem we could buddy breath (sharing our buddies primary while ascending) But we don't. We deem the additional equipment to be necessary enough to not bother about the extra items.

The same with SPG's and AI transmitters (TX). SOme people chose to get rid of their SPG for streamlining or weight saving etc etc.

I personally keep my spg on all my reg sets, and they are all fitted with a 6" hose and QD so I can put on a TX if I want. While I like my AI for fun diving, I have no need of it say if I'm teaching OW. I'm not going to use my air faster than my students so keep my SPG where I can glance at it.

I also like to use my SPG when setting up my gear to confirm gas pressure etc and then only get my computer out when I actually kit up to splash.

So here I am with multiple extra O rings and another hose, why am I not dead?

Easy. Hoses and O rings rarely go, and if they do the generally go when taking the initial surge of pressure when turning a tank on. Otherwise the tend to leak a little first

Now while I do carry spares (and these have always been used to help others) I mitigate my failure risk with maintenance. I service my gear yearly, and have all the O rings changed and throw out my HP swivels. My hoses I change every 2 - 3 years - but this is because I live in the Middle East with high heat and high UV (car tyres are limited by law to a 4 year max life even if if you still have a legal depth of tread)

I've never had a failure - and I dive quite hard and my gear doesn't get treated gently. And compared with teh rest of my geat teh cost of new O rings and occasional hoses is inconsequential

So rather than this constant debate of the additional failure points, I recommend people dive the configuration they want and carry out basic maintenance at regular intervals - inc a pre-use inspection before you pack your gear. But hey that's just my opinion

Talk about hoses, I have 6 hoses (2 HP & 4 LP) in several colors (black, blue, yellow & red) to make sure I know which hoses for which gadgets, coming out of my reg & no problem yet (knock on wood).

 

[MMM]

Yes and today was a perfect example of why. For the first time in my life, I forgot my AI computer AND its backup on my kitchen counter. One guy on the boat had 3 computers so he loaned me his Shearwater Perdix. (It was a very nice computer!). If I hadn't had an SPG, I would have been sitting on the boat watching everyone else do 2 dives.

 

[woodcarver]

Interesting debate. I use both an ai and an SPG. Having both saved a nice dive in Bonaire when I noticed the SPG was several hundred PSI lower than my D4i. Somehow in the process of setting up, my ai paired with my girlfriend's transmitter. She stayed close enough that I hadn't seen the occasional comm drops (saw them later looking at the profile). Figured out what was going on when I checked her ai and it was identical to mine for pressure. Spent the rest of the dive enjoying the reef and using the SPG. Figure I carry a pony for redundancy, having backup SPG on my primary is fairly inexpensive way to keep diving. The extra hose has never gotten in the way (neither has the 2nd inflator hose for my drysuit-too lazy to take it on and off). My SPG also has a depth gauge-just in case the computer decides to quit me mid dive. As DD mentioned, regular annual maintenance greatly reduces the likelihood of one of those extra o-rings failing at an inopportune time.

 

[scubadada]

Interesting debate. I use both an ai and an SPG. Having both saved a nice dive in Bonaire when I noticed the SPG was several hundred PSI lower than my D4i. Somehow in the process of setting up, my ai paired with my girlfriend's transmitter...

Interesting problem I would not have thought of as PPS transmitters remain paired with your computer by serial number.

 

[Kharon]

Figure I carry a pony for redundancy, having backup SPG on my primary is fairly inexpensive way to keep diving.

The extra hose has never gotten in the way (neither has the 2nd inflator hose for my drysuit-too lazy to take it on and off).

I keep both and use which ever seems easiest at the time. Diving solo, redundency is my mantra.

Haha. I leave the inflater hose on when I dive my soft backplate/harness with an orally inflated bladder under it. I rationalize it because it has a Diver Alert noise blaster on it in case I need to get someone's attention on the surface. Really doesn't get in the way and it's there in case of need.

 

[woodcarver]

She and I have identical D4i systems. Just different colored watch bands and a matching color on the reg set. Apparently her transmitter was still in pairing mode when I set my gear up and mine paired to her transmitter instead of mine. Any Suunto will pair to any Suunto transmitter (except for the Eon). Just have to pay attention when setting up the tank; if there's a leak, don't depressurize and repressurize quickly or it puts the transmitter in pairing mode.

 

[dbnewton]

Well I also carry a SPG with my AI unit. I keep SPG coiled up behind me.

Today I had the AI lose communication on one dive and reverted to the SPG. So carrying the SPG saved the dive.

Then on the second dive I popped the o- ring on the SPG. That was easily repaired.

Fascinating that simply carrying the SPG can solve problems but can also cause problems.