Here is something I learned today about DIN plugs

[Bigbella]

Here's what's wrong with the Delrin plugs. If they get pressurized they become projectiles.View attachment 588614

And, yes, it frickin' *hurt*.

Scheiß, break out the Bactine! My delrin plugs have a fine vent, where a knotted cord is attached --couldn't be a projectile, in any case; air passes through it, like s**t through a goose . . .

So why use them at all? Why not just leave the DIN valve open?

I have found them notorious for accumulating moisture, especially at the back of the valve -- far more than dust; and the cheap vented plugs easily solve that problem, while riding in the bed of my truck, in the rain; rinsing of tanks, etc . . .

 

[KenGordon]

I think these fall into the category of thing that people buy when they go to a dive shop and have money burning a hole in their pocket but don’t actually need any kit. I bought a second hand twinset with the plastic type and literally have never used them.

I do try to avoid leaving cylinder such that stuff will land in the hole. Don’t cover cylinders with a picnic blanket etc.

 

[Umuntu]

I think these fall into the category of thing that people buy when they go to a dive shop and have money burning a hole in their pocket but don’t actually need any kit. I bought a second hand twinset with the plastic type and literally have never used them.

I do try to avoid leaving cylinder such that stuff will land in the hole. Don’t cover cylinders with a picnic blanket etc.

My DIN tank valves have either a regulator or a dust cap in them at all times.

 

[TrimixToo]

Scheiß, break out the Bactine! My delrin plugs have a fine vent, where a knotted cord is attached --couldn't be a projectile, in any case; air passes through it, like s**t through a goose . . . .

Yeah. That's what *I* thought, too. But when the valve got rolled open with the plug in it, that "fine vent" was incapable of releasing the pressure quickly enough to prevent plug failure. I was lucky it hit me where it did.

 

[Diving Dubai]

Yeah. That's what *I* thought, too. But when the valve got rolled open with the plug in it, that "fine vent" was incapable of releasing the pressure quickly enough to prevent plug failure. I was lucky it hit me where it did.

All my Delrin plugs have had the vent drilled out to accept a loop of caveline. I've had a few tanks vent with the plugs in due to my inept packing allowing them to move and roll the valves on. So far no plugs have come out and even if they did the line would hold them

FWIW the reason my plugs are attached to the tank is so they don't get lost.

When a cylinder has been used it's obvious because the plug is left out, especially when for a weekend trip with friends there's 90+ tanks on deck

 

[TrimixToo]

All my Delrin plugs have had the vent drilled out to accept a loop of caveline. I've had a few tanks vent with the plugs in due to my inept packing allowing them to move and roll the valves on. So far no plugs have come out and even if they did the line would hold them

FWIW the reason my plugs are attached to the tank is so they don't get lost.

When a cylinder has been used it's obvious because the plug is left out, especially when for a weekend trip with friends there's 90+ tanks on deck

View attachment 588682

In my case, the two plugs on my doubles were tied together, and they both were in the valves, but the cord blew out the hole during the process of the plug failure, knot and all. However, it wasn't cave line, but the smaller nylon line they came with. Maybe the cave line holes you drill are big enough to prevent this sort of failure, and maybe not. One thing's for sure--I'm not going to be the one to test it.

Look, everyone. If you want to use them, use them! Life is risk. Choose your own. Now you have some additional information to consider in making that choice. All my Delrin plugs are in a box waiting for lathe projects that can use them, and there they will stay until such projects exhaust the box's contents. (Delrin's a great material for things like bushings, thick washers, and such.) That's *my* choice, and you won't convince me I should change it or that "it'll be OK" if I do.

I don't think I've left anything relevant out at this point.

Last post from me on this topic.

 

[Diving Dubai]

. One thing's for sure--I'm not going to be the one to test it.

Last post from me on this topic.

No that's quite understandable, and I wasn't saying my method was best. For sure the thin nylon supplied line is very weak, I only changed mine because I didn't want to lose my plugs

I just wanted to highlight my experience. The main reason for use is that my tanks are stored outside and the fine desert sand gets into the threads, which is a PITA after a while.

 

[doctormike]

There is a bit of normalization of deviance here.

The total number of events (accidental opening of a valve with a plug in place) in the cumulative experience of the posters in this thread is unlikely to even reach three digits, and yet there are certainly first hand reports of problems related to that (the injury in the photo and other stories). As far as the other problem with sealed plugs, the one time I made the mistake of cracking a tank with a steel DIN valve in place, it required a tremendous amount of torque to get the plug out, to the point that I was worried about damaging the threads. So saying that "in my experience, this has never been a problem" may not be statistically sound.

As I mentioned, I haven't seen people use Delrin or steel plugs in a pretty active tech diving community in my area (or while traveling), but I will concede that my experience might not be universal. Maybe things are different in the desert, in very humid long term storage, etc... So if that's an issue, I would suggest a piece of masking tape as a safer solution. When I rinse tanks, if I accidentally get water in the valve opening, I just crack it for a second to blow it dry, but again, not really a common problem.

And if gas loss is the concern, use the steel plug with the release valve.

 

[Mark IV]

Just wondering, what's wrong with using those rubber (silicone?) valve covers I used to see used on dive boats, that just slipped over the end of K valves ? I'm thinking this simple, inexpensive design would work just as well for keeping dust, water and insects out of DIN valves, and not have any of the above-mentioned problems the threaded caps seem to have.
Found 'em......
Amazon.com : Trident Tank Valve Protector Caps (Each) (Blue) : Diving Tank Accessories : Sports & Outdoors

And these are made for DIN valves.......
https://www.amazon.com/Scuba-Choice...8K9Z9M0MJ0D1&refRID=436N53BT8K9Z9M0MJ0D1&th=1

 

[doctormike]

Just wondering, what's wrong with using those rubber valve covers I used to see used on dive boats, that just slipped over the end of K valves ? I'm thinking this simple, inexpensive design would work just as well for keeping dust, water and insects out of DIN valves, and not have any of the above-mentioned problems the threaded caps seem to have.
https://www.amazon.com/Trident-Tank-Valve-Protector-Caps/dp/B07BQHYFZT

And these are made for DIN valves.......
https://www.amazon.com/dp/B00COBC76...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

Yeah, that would also be safer.

Just to summarize, there are three reasons people use these things:

1) Preventing gas loss - use a steel plug with a relief valve

2) Keeping out external moisture or debris - would use a vinyl cap or masking tape, although a steel plug with a relief valve would also work

3) Preventing valve deformation if accidentally dropped - use a steel plug with relief valve


I can't think of any scenario where a Delrin plug or a steel plug with no valve would be an optimal solution. And in many settings, using nothing seems to work OK for a lot of divers.