SPG or not

[Belzelbub]

We were also once told to back valves off a turn and a lot of other nonsense.

True, but as I understood it, the 1/4 turn back was once a good idea due to the valve designs of the day. Not required on modern valves, but some are still taught and do that to this day. I probably did this after my first course, but it was probably not required then either. Haven't done it since.

The lens is either plexiglass or tempered glass and there is a blow out plug in the case. I do not think we need to fabricate reasons to switch to an AI computer.

True. However, whether there is a real need or not, doesn't change what's taught. I was definitely taught to turn the spg away from faces, and to open the valve slowly. Probably not so much of a real issue anymore, but it's a practice that doesn't really have a downside. It doesn't hurt anyone to face away from people's faces. Probably just want to make sure that the blowout plug isn't pointed at anyone's face either.

 

[Nemrod]

True, but as I understood it, the 1/4 turn back was once a good idea due to the valve designs of the day. Not required on modern valves, but some are still taught and do that to this day. I probably did this after my first course, but it was probably not required then either. Haven't done it since.

Basic valve design has not changed and there is no reason then or now to back it off, of course I was taught the same thing. It just causes confusion. I still, usually, back mine off. Force of habit, I cannot stop myself, I just do it automatically. I just hear my instructors long gone voice, Jimmy, turn the valve on like this and then turn it back a half turn, now give me ten (pushups). My OCD is not quieted until I have done so, my universe is not right until , because my instructor 56 plus years ago said so.

In 1966 we did not have SPGs, at least I had never seen one nor did we use them in the course, we all had J rods. In 1970 when I took my advanced course, we did have SPGs and I was taught to turn it away from my face as you were, same instructor, now Jimmy, drop and give me ten! Again, the lenses are Plexi or tempered glass and there is a pressure relief plug built into the case. I certainly would not put it right up to my eyeball when turning on air but an SPG is not going to explode and send shrapnel all over.

If a DM or deck person lifts a tank by the AI transmitter is it going to blow off and put a 90 caliber hole in something? I need to start that urban legend. Those little screws in the side of the AI case look awfully little and do they have a blow out plug?

 

[Belzelbub]

Still a good idea. Most dive charters are going to check your valve before you splash. If you cut the valve back a quarter turn the person who turns it knows it's definitely on when it twists open that last little bit. If it's all the way open they really gotta give it a twist to make sure it's not firmly closed. Makes their job easier and repetitive attempts to twist an already valve open even more isn't going to do it any good.

Doesn’t sound like a good idea to me. I prefer it to be fully on or fully off. No chance in making a mistake then. If it’s somewhere in between, it could be mostly on or mostly off. If it’s mostly off, it will turn either direction when the crew checks. Breathes fine until higher flow needed at depth.

 

[jellycatsdad]

I still have an SPG on my setup though I’m using a Shearwater Swift.

 

[Valerii Vakshul]

comprehensive check of my gear +2teriс

 

[Belzelbub]

I didn't say it should be turned mostly off. A quarter turn off won't make any difference unless perhaps if the diver has severe COPD.

I know you didn’t say it, but that’s what happens in some cases. When it’s not fully on or off, it can be anywhere in between. The valve can turn in both directions. When fully on or fully off, it can only turn one direction.

 

[USdiver1]

1970s explanations

The valve quarter turn from full was always explained to me as a precaution against hitting the valve wheel against a hard object [wreck / cave /etc.] so that it wouldn't crack or over extend [strip] past its set limit. Several manufactures used bakelite plastic valve handles which were somewhat brittle and could get damaged.

The SPG faceplate [front] / relief valve [back] positioning away from one's face was to protect from the plexiglass / tempured glass faceplate or air from the relief valve damaging one's eyes in the event of a failure.

PS when not diving my DH and J-valve, I use a rig that incorporates both SPG and AI transmitter.

 

[Bigbella]

SPG or not?​

Yes . . .

 

[ImpotentSeaSnake]

Not sure if this thread is the right place for this question, but it seems relevant. I’m a rec diver with AI Teric for main computer, a simple hosed SPG for analog backup, and just got Scubapro Z1 as a back up wrist computer. I like it because it is simple and with solar, it doesn't need a separate charging mechanism.
Does this seem like a decent set up or does my backup computer really need AI?

 

[Still Kicking]

does my backup computer really need AI?

No