Here is something I learned today about DIN plugs

[pauldw]

Both of my tanks have DIN plugs, which I got after losing some air from slightly rolling the valve while one of them was in the back seat. I recently spun off both plugs, to check air pressure on the tanks, Then I put a reg on one of the tanks. Glancing at the plugs on the table top before heading out to dive I noticed that they didn’t look the same. Indeed one had an O-ring and the other did not. So I proceeded to search for the missing O ring, and it had fallen off inside the back of a tank valve. So, my own lesson is, pay attention to things.

Here's one of those plugs, in case it's unclear what I was talking about:

 

[Pressure Group X]

Great post...Thanks for sharing

I’m in the process of selecting a new setup and want to go with a DIN setup. This is great info for me to make note of

 

[doctormike]

Not sure if those are a great idea. I have been using nothing but DIN for years, and have never had a problem with crud getting in the DIN opening. Also, I have never seen them in use on any of the local tech boats for people who dive open circuit and bring a second set of doubles. I guess some people use them to protect the valve in case it gets dropped on the floor, or to prevent the loss of expensive trimix.

I have heard of a serious injury from the pressure that builds up behind them if you crack the valve while they are in place, with something like a Delrin plug, which can fragment and explode. And if you have steel plugs inserted and you crack the valve, good luck getting them off. If you really think that you need one, get one with a relief valve.

And of course, don't use a sealing plug like that with high O2 mix.

 

[pauldw]

My crescent wrench removes them if a little air gets in there. And I'd heard they protect the shape of the valve in a fall, from deforming. But exploding plugs? That doesn't sound good.

 

[Scared Silly]

The all metal plugs are great. The plastic ones are decorative. That said one must always have a wrench to remove said plugs. Nothing worse than getting to the dive site and not being able to remove it because of the pressure. Guess how I know ???

Oh and yes the o-rings do have a habit of coming off inside the valve. One does learn to check for that too.

 

[doctormike]

The all metal plugs are great. The plastic ones are decorative. That said one must always have a wrench to remove said plugs. Nothing worse than getting to the dive site and not being able to remove it because of the pressure. Guess how I know ???

Oh and yes the o-rings do have a habit of coming off inside the valve. One does learn to check for that too.

Or just get the ones with the relief valve. Sometimes you can crack the unvented ones with a crescent wrench, but that can be VERY difficult, and you may end up damaging the thread. And definitely not to be done with a rich mix.

 

[pauldw]

And definitely not to be done with a rich mix.

You mean nitrox? Explain?

Also, do the pressure relief ones stop any accidental valve opening leaks? (Like from little kids on the loose.)

 

[doctormike]

You mean nitrox? Explain?

Also, do the pressure relief ones stop any accidental valve opening leaks? (Like from little kids on the loose.)

I mean 100% O2 or close to it. It take a huge amount of torque to force open an unventilated steel DIN plug that has accidentally been pressurized, and the friction can cause ignition. A number of manufacturers note this.

I don't see any downside of the pressure relief ones, I'm not sure why anyone would ever buy one without that valve. They still will keep your gas from leaking out if you accidentally crack the valve, but if that happens, you can easily depressurize the space behind the plub and remove it...

 

[O-ring]

I find if you have to use a wrench to get them off a lot of times the o-ring will come off the DIN plug and be inside the valve like @pauldw stated in his original post. I have never had a problem wrenching them off with a crescent after valves got accidentally turned on in transit. Fish o-ring out of valve, stick it back in the DIN plug and you are back in business. Before using them I had a few instances where you hit a bump or swerve to avoid something, hear bottles rattling around in the truck followed by the dreaded loud hiss. You yank the wheel and pull over on the shoulder as fast as possible, throw it in park and run around back and feverishly try to find the right valve. Of course, it always happens when you are heading somewhere that doesn't have the gas you need for the dives you have planned so every second of leaking gas has you praying you haven't lost too much of whatever it is that is leaking. I've never tried the relief valve ones, but that sounds like a pretty ideal solution vs. the big crescent.

 

[lexvil]

I use the plastic ones, never tight enough to hold any pressure but I use them to keep the leaf cutter and or mud dauber bees out.