Yelled at for MOF

[TMHeimer]

Yeah, what happened Here with this dual thread??? Anyway, one thing I was taught (in Rescue course) was to push a second stage purge button in when turning air on. Then quickly release. This give the pressurized air "someplace to go". I would imagine this is more important than which way the SPG glass is facing, but I face it away from me anyway. I rarely see others doing this or mentioning it.

 

[txgoose]

Fair point, and I am not an instructor. But at the recreational level, nearly everyone has a console, where the only potentially hazardous part of an SPG is its face. And even the "point the side at yourself" idea is flawed if it exposes others to flying bits of high-velocity polycarbonate, glass, and such. My (bare) SPGs have no devices on their backs. The glass fronts are pointed away from all humans when I open the valves.

This is analogous to "never point the muzzle (of a firearm) at anything you are not willing to destroy." There might be more than one "muzzle," but all such hazards should be directed away from people if possible. (It's a risk we can easily manage. Let's manage it.)

1) I was using an Aqua Lung console with a relief valve in the back. It isn't rare or specialized gear. And it isn't the only brand putting relief valves in the back. The Cressi and the XS Scuba SPGs I currently run have relief valves in the back. I don't think nearly everyone has a console where the only potential hazard is the face.
2) I also asked the question about how to avoid point things at co-divers on a boat. I get it. I am acknowledging it. I am willing to talk about it. But if you completely disregard the fact that plenty of SPGs have relief valves in the back then we don't really have much common ground. We're just training people in a random fashion hoping that we can easily manage risks that we're ignoring.

 

[txgoose]

Apologies for the digression (that I didn't request! )

We should probably go Exploding SPG gauge faces?

 

[Bierstadt]

Yeah, what happened Here with this dual thread??? Anyway, one thing I was taught (in Rescue course) was to push a second stage purge button in when turning air on. Then quickly release. This give the pressurized air "someplace to go". I would imagine this is more important than which way the SPG glass is facing, but I face it away from me anyway. I rarely see others doing this or mentioning it.

Well, given that the second you are purging is letting out air at somewhere between ambient and 150 psi (at best) and the spg you are hoping to protect with the purging is pressurized at 3000 psi (or more), I cannot imagine pressing the purge button does, well, anything.

I treat my slim spg like a firearm muzzle when pressurizing it and turn on the valve very slowly. It makes no difference to the pressure the spg experiences, mind you, but at least I can minimize the weaponized whipping action that a burst spg would likely engage in.

On the main thread point, I have been experimenting with sliding my mask sideways on my neck. So far I like it, as it keeps the mask secure and away from my necklaced second.

 

[BRT]

Well, given that the second you are purging is letting out air at somewhere between ambient and 150 psi (at best) and the spg you are hoping to protect with the purging is pressurized at 3000 psi (or more), I cannot imagine pressing the purge button does, well, anything.

I treat my slim spg like a firearm muzzle when pressurizing it and turn on the valve very slowly. It makes no difference to the pressure the spg experiences, mind you, but at least I can minimize the weaponized whipping action that a burst spg would likely engage in.

On the main thread point, I have been experimenting with sliding my mask sideways on my neck. So far I like it, as it keeps the mask secure and away from my necklaced second.

Did you ever try pressurizing your high pressure hose without the gauge attached? I'm betting there is no whipping action.

 

[TMHeimer]

Well, given that the second you are purging is letting out air at somewhere between ambient and 150 psi (at best) and the spg you are hoping to protect with the purging is pressurized at 3000 psi (or more), I cannot imagine pressing the purge button does, well, anything.

I treat my slim spg like a firearm muzzle when pressurizing it and turn on the valve very slowly. It makes no difference to the pressure the spg experiences, mind you, but at least I can minimize the weaponized whipping action that a burst spg would likely engage in.

On the main thread point, I have been experimenting with sliding my mask sideways on my neck. So far I like it, as it keeps the mask secure and away from my necklaced second.

It's been a while since I studied all that in the DM course, but I recall that the 3000 psi in the tank gets reduced to about 150 by the first stage. So when it travels through the hoses and to the SPG it is only at 150. So you press the 2nd stage purge button to let the 150 escape for a second or two instead of going directly into the SPG (the air will possibly go to the place of least resistance?). Anyway, I was taught this by an MI who is now a CD. So I figured it had some basis in fact.

 

[Russjstewart]

Tom,
I may not be be reading your post correctly, but only the LP ports of the first stage (second stages and inflators hose for bcd) are at 150 psi, the HP ports (SPG) are at tank pressure, otherwise the SPG would not work.
My apologies if I am mis reading what you said

 

[RainPilot]

It's been a while since I studied all that in the DM course, but I recall that the 3000 psi in the tank gets reduced to about 150 by the first stage. So when it travels through the hoses and to the SPG it is only at 150. So you press the 2nd stage purge button to let the 150 escape for a second or two instead of going directly into the SPG (the air will possibly go to the place of least resistance?). Anyway, I was taught this by an MI who is now a CD. So I figured it had some basis in fact.

Afraid not sir. The HP ports are fed tank pressure, unregulated. Else they would read 150 psi until the tank emptied.

Edit: I see Russ and I were simultyping.

 

[Dizzi Lizzi]

MOF. This weekend I was with a class waiting to submerge, getting last min inst as the objective had changed. My lens was spotty and it was difficult to see so I put my MOF and asked a question. I was promptly told not to wear MOF. I tried not to roll my eyes and instead just pulled and held it 1" away from my forehead. Seemed kinda silly as it was clear I was in no type of distress, but his class his rules

 

[Dan]

The HP hose does have a very small orifice near the 1st stage regulator HP port to slow down the pressure surge when you open the valve & prevent massive loss of air in the event of hose failure while Scuba diving to give time for the diver to ascend safely back to the surface before running OOA.