DIN Plugs

[Pez de Diablo]

Roakey,

True, it's not primarily the volume, but with a large volume you would have a sustained force on the threads. I only have hands on experience with a pipewrench, I'm not an engineer, and I know that you will damage the threads on a tapered connection if you unscrew a plug with pressure on it. But we are not dealing with a tapered thread, all you need to do with the plug is unseat the O-ring - maybe a 1/16". I didn't describe the mechanics well on my post

So it is only 4 lbs, cool even better. But you don't have to move the plug 1", it's not a tapered thread. You release the pressure almost instantly.

Can anyone confirm (other than my hands on experience) that you are not putting damaging stress on the threads when removing a plug on a din connection.?

 

[wetman]

See, this is the reason i didnt just want to jump on these things... I'd really like to know for sure. Oring, have you ever tried taking them out pressured?

steve

 

[Pez de Diablo]

Wetman,

They do come out and with no *apparent* damage. Because there is no apparent damage we could leave it at that. But is there hidden damage? I wouldn't think so, but lets see if someone can shed light on it.

 

[O-ring]

wetman once bubbled...
See, this is the reason i didnt just want to jump on these things... I'd really like to know for sure. Oring, have you ever tried taking them out pressured?

steve

I know people that have, but I didn't want to shred the o-ring and then change it...jeez, that sounds lazy now that I read it.

Hopefully someone will come along with real experience and get us squared away. If not, I will try it and report back.

 

[roakey]

A first hand account can be found at:

http://www.scubaboard.com/t20496/s.html

The topic, amazingly, is "DIN plugs"

Why oh why can't people use the search function before establishing a base note?

Roak

 

[wetbehindtheear]

Umm, i know it was fun calculating the force required to remove the plug pressurized, but you guys are turning the valve off first aren't you? With the minimal volume in there, a half turn should drop the pressure significantly, such that the plug would be pretty easy to remove...

 

[roakey]

Relatively, there *is* a significant volume behind the plug in a 300BAR valve, from the dowstream side of the valve, the relief behind the seating face and the seating area itself (the latter probably being the smallest of the three).

So in terms of moving the sealing face out 1/16" or whatever one turn is, the pressure will drop some, but not significantly.

But you're right, just a twist or two should break the seal and the pressure will be released and then it comes out with your fingers.

Roak

 

[Genesis]

I have some of the SS plugs you guys are talking about, and use them.

The problem with them is that if you do manage to pressurize the space and use the wrench sometimes the O-ring will wedge and not release until you turn the bolt a couple of turns outward. While not dangerous, its a PITA, and has damaged an O-ring on me (big deal, just grab another one)

BUT, if that plug had been Delrin, it might have sheared in the valve and turned into a missle. That would have been BAD.

 

[Scubaroo]

...but the last ones I bought have a string in the middle for tying it around the valve, and air also escapes through the hole cut for the string. So I don't think you could get a Delrin plug stuck in the valve from pressure, but I'm still betting you could punch a nice 1" hole through a wall with one if you were unlucky...

 

[bigDave]

I have some of these: Stainless Steel DIN plugs. A lot of the folks I dive with have bought them and we're all pretty happy....