DIN Plugs

[wetman]

I'm curious about din plugs. I've got some cheapy plastic ones right now. They seem to do the trick of keeping junk out of the valve.

I was thinking about getting some slightly better ones. Only thing is, i had a thought about this and wondered if anyone else had these issues. I know you can get stainless steel ones with the orings and they claim to save your gas in a potential gass loss situation, but given you cant release the pressure easily, how hard would they be to get off if they were accidentally pressurized? And the next question is, if i get some delrin ones, are they strong enough to withstand the pressure, or just strong enough to become potential bullets or would they give away fairly quickly under even a low pressure so as not to become dangerous. I know the cheapy ones i have barely even fit the threads so i dont think they're much of aworry.

thanks

steve

 

[O-ring]

They seem pretty sweet and I have been assured they come off easily with a wrench if they have been pressurized and the valve is then closed.

Dunno about the delrin ones...never seen those..

 

[Scubaroo]

Delrin plugs are not gas-savers. I use them on my tanks. They're more for keeping crud out of the valve during transport and storage.

As an experiment, I *cracked* a valve on a tank with a delrin plug in it - even though the plug had an o-ring on it, and it was just a crack of pressure, it hissed like mad. I shut it down in a hurry before the bullet theory was put to test. I WOULD NOT DO THIS AGAIN!

Given the infrequency of accidental valve turnons, I'm sticking with the delrin plugs for now as a better-than-nothing solution to keep the crud out.

 

[Pez de Diablo]

If you try to un-thread a tapered plug with pressure behind it, the threads will gaul and the plug will come out in a very destructive way. But not on a scuba tank, the threads are not tapered and the pressure is released almost instantly.

So when I first seen a plug in place with pressure behind it, I ducked, thinking doom - boy did I get dumb looks. With a scuba tank, there is not enough volume between the plug face and the valve to cause a problem and the effort required to release the plug is minimal (total guess, maybe 15 lb torque) with a small crescent wrench. The SS plugs work for me.

 

[wetman]

Ok then - whats the source for the ss plugs? I know i've seen a couple sites in the past but where did you guys get yours?

 

[O-ring]

wetman once bubbled...
Ok then - whats the source for the ss plugs? I know i've seen a couple sites in the past but where did you guys get yours?

I got mine from a friend, but I think dean@tankfill.com was selling them. Can anyone verify this?

 

[daylight]

You may want to check into these. http://www.cavediver.com I have no vested interest. Dive Safe, Larry

 

[O-ring]

http://www.cavediver.com/gulftex/gtprod.htm

 

[wetman]

thanks guys

 

[roakey]

Pez de Diablo once bubbled...
With a scuba tank, there is not enough volume between the plug face and the valve to cause a problem and the effort required to release the plug is minimal...

But it's not the volume, it's the pressure behind the plug (though the small volume makes it vent quickly once the seal is broken).

The pressurized face of a DIN plug is about 1/2" in diameter, which means it's about 3/4" of a square inch in area times 3000 psi tank pressure is about 2400 pounds of force pressing on the plug.

However, you have a mechanical advantage with the threads (which are nothing but an inclined plane) and the length of the wrench handle. To take a SWAG, if a DIN plug is 16 TPI (I don't know, but that's a guess from looking at one) that means that to move the plug one inch requires 16 revolutions of the wrench, or 2*pi*6*16 = ~600 or a 600:1 advantage, so 2400 / 600 = 4 pounds of force on the end of the wrench required to turn the plug.

Ignoring friction, of course, which in terms of significance probably leaves this calculation in the dust

Slow morning

Roak