DIR Manifold

[Dan Gibson]

No kidding.

Kinds scary the first time.

 

[Dan Gibson]

I wonder if the friction tore up the o-ring first and then the torn portion gets pushed through the pin hole. Whenever I do have a SS DIN plug get pressurized, the o-ring is usually toast. I think I have only had one not get chewed up. It usually happens when we take a boat load of doubles on a long trip and everyone just starts grabbing tanks. I'm usually pretty careful not accidentally pressure them myself.

Dan, I've never had the oring crawl out the vent hole :11: , but I have had a couple of occassions where SS Din Plugs got "energized" In both cases I tore up the oring. I assumed it was friction on the face seal.

Now I have to go try one and see with some soapy "snoop" if they do eventually leak past the threads. Can't see how it won't, the threads aren't tapered......


More when I know it.



Tobin

 

[TSandM]

Can I interrupt here and show my ignorance? What is a DIN plug, and why would you use it, and how does one get pressurized?

 

[Soggy]

Can I interrupt here and show my ignorance? What is a DIN plug, and why would you use it, and how does one get pressurized?

http://www.cnsales.net/productspage.htm

It's just a plug that you put in the DIN valve to prevent accidental loss of expensive gas. It has no over pressure valve, so if you turn the tank on, you need a BAW (Big-*****-Wrench) to get it out.

The delrin counterparts are an accident waiting to happen and should never be used as, if accidentally pressurized, they become a delrin bullet.

 

[TSandM]

Thanks, soggy. I'm avidly reading all this stuff in preparation for assembling my own doubles this summer, but sometimes I feel like I'm reading a foreign language

 

[cool_hardware52]

What Soggy says about some Delrin Plugs is true. 3000 psi behind a plastic plug can result in the plug blowing out, with predictably bad results.

To prevent this many plastic plugs have generously sized vent hole, these won't blow out, but they are also useless as a dust cap because they have a generously sized vent hole...........

SS Din plugs or nothing, your just kidding yourself with the plastic ones.



Tobin

 

[Dan Gibson]

Supposedly it also prevents egging of the valve should it take a hit during transport. It's not something I want to verify works.

What Soggy says about some Dlerin Plugs is true. 3000 psi behind a plastic plug can result in the plug blowing out, with predictably bad results.

To prevent this many plastic plugs have generously sized vent hole, these won't blow out, but they are also useless as a dust cap because they have a generously sized vent hole...........

SS Din plugs or nothing, your just kidding yourself with the plastic ones.



Tobin

 

[cool_hardware52]

http://www.cnsales.net/productspage.htm

It's just a plug that you put in the DIN valve to prevent accidental loss of expensive gas. It has no over pressure valve, so if you turn the tank on, you need a BAW (Big-*****-Wrench) to get it out.

Just a quick note. I can remove pressurized SS din plugs with a 8 inch crescent wrench. The 6 inch crescent now stays at home, and my 8 inch as been making frequent excusions to the shore. The 8" is still small enough to change hoses etc., but opens large enough for the 1" hex on the Gulftex SS din plugs.


Tobin

 

[cool_hardware52]

And now I know more about SS din Plugs and their removal when pressurized.

The plugs I used were Gulftex SS din Plugs

The O rings are 112, buna of unknown durometer

The valves tested were:

300 bar Thermo (with vent hole)

200 bar Thermo (with vent hole)

200 bar DiveRite (no vent hole)

Each valve was tested by using a new oring, and screwing in the din plug by hand, cycling the valve on and off, and then removing the Din plug with a wrench.

Results:

For both Thermo valves the Din plug remained sealed for more than two full rotation of the Plug. On both a piece of the Oring was observed extruding out the vent hole. At about 2 1/8 rotations pressure was released from the vent hole and the plug could then be removed by hand. The oring was destroyed.

On the DR 200 bar it required ~2 1/2 rotations before the pressure was vented through the threads. This leaves about 2 1/2 turns before the Din Plug Can be removed. The Oring was intact.

Heres the interesting part; the oring sets in a recess on the end of the din plug, and only about .010" of the ring projects beyond the end of the recess. Why does it require 2+ rotations (equal to about .150") of travel before the gas either vents through the vent hole, or releases through the threads?

I think the Oring is being pushed out of the recess, stretched to a larger diameter and is sealing the space between the OD of the end of the Din Plug and the ID of the valve. Only after the din plug is backed out a distance about equal to the cross section of the oring does the gas vent. The vent hole in the Thermo valves does cause the oring to extrude.

It would appear that even on the DiveRite that lacks a vent hole, the pressure is released when there is still sufficient thread engagement to prevent damage to the valve threads, or risk of a unplanned projectile.

A few extra 112 orings are a handy thing to have around.


Tobin

 

[Dan Gibson]

Tobin,

So what is your best guess on the potential for damage to the threads on a 200 BAR valve? BS or possibility?