Dual valve, single regulator

[diver-man]

I met a lady at aowd course, while assembling her stuff and had a short chat with her and her instructor next to her.

She had a single cylinder with dual DIN valve, and just one first stage reg. So far all good.

What catched my eye was the other valve had no DIN plug (such as on the attached photo) that would protect the air in the cylinder from a freeflow in case of accidental opening the valve during the dive.

I said I would never dive the cylinder without protecting the second valve if has no regulator mounted.

The instructor argued this is fine, because the buddy will shut off the valve in case of accidental opening. According to him, the plug is just for transporting cylinders in the car to protect agains freeflow.

Who was right?

 

[inquis]

A plug seems pretty cheap insurance to me.

 

[Angelo Farina]

I always used two-valves tanks (double tanks or a single 15-liters steel).
Whilst most of the times I use two first stages, which is undoubtly safer, it also happened to use just one.
If you accidentally open the second valve, you have simply to... close it!
I have never seen that sort of plug. And installing it defeats the purpose of a dual valve tank, that is the possibility to move the reg on the second post if, for any reason, the first valve is not working (which happens typically when the tank falls over a hard surface).

 

[rick00001967]

first....why would anyone dive a cylinder with a dual valve and only one 1st stage? whats the point?

perhaps she owns that cylinder and normally dives it with two regs? we have people where i live that do this.

second.....the pic you attached looks like a burst disk. not a DIN plug

if you are are asking why people use plugs to screw in to the valve when not in use.....the answer is to prevent anything for getting in there when not in use. they are not for use when diving.

 

[stretchthepenn]

In the past, when I rented tanks from a particular shop, the tanks came with an H-valve. The add-on port was never plugged.

 

[fenichelar]

If you put an unsealed plug in it (i.e. a dust cap) and accidentally turn on the valve then it might slow down how fast it drains but it is still going to drain. If you put a sealed plug in it and accidentally turn on the valve then the plug can become a projectile when you try to remove it. Neither option is good...

 

[diver-man]

I have never seen that sort of plug.

second.....the pic you attached looks like a burst disk. not a DIN plug

Beleive me or not, it is a 230 Bar DIN plug (not a dust cap!).

It holds the pressure. You cannot unscrew it by hand when pressurized, until you release the hex bolt.

 

[diver-man]

If you put a sealed plug in it and accidentally turn on the valve then the plug can become a projectile when you try to remove it.

bs. You cannot remove it when pressurized. You have to unpressurize it first with the allen key.

 

[fenichelar]

Beleive me or not, it is a 230 Bar DIN plug (not a dust cap!).

It holds the pressure. You cannot unscrew it by hand when pressurized, until you release the hex bolt.

I see, so it is sealed but the hex bolt allows you to release the pressure if the valve is opened without creating a projectile. That is a better design than the basic sealed plugs I have seen before.

 

[fenichelar]

bs. You cannot remove it when pressurized. You have to unpressurize it first with the allen key.

Not all plugs have a way to depressurize them: DGX HP Sealing DIN Plug.