Using "locktite" to 'secure' a DIN 1st-stage kit ?

[scubafanatic]

....I've got a Mares MR16 Voltrex reg, bought new 5 yrs ago, still in new condition, which is among the regs I'm preparing this winter for the 2007 dive season next spring/summer.

It's a back-up reg, the last time I remember diving it was a week in Bonaire summer of 2004, where it worked fine, max depth on that trip was 140-145 ft. I had an annual done after that trip, and I think I had the DIN kit installed shortly after that trip as well.

I pressurized the reg and there's a major leak where the DIN kit joins the 1st-stage, and my plan is to take it to a local dive shop for examination. It has been a while since I last dive this reg, but I believe I had a prior episode where something like this happened with this reg, it wasn't leaking that time, but it was in the shop for a checkout and it was pointed out to me how the DIN part had come loose, and I remember thinking how lucky I was it hadn't blown out UW, and that the problem was spotted before I dove with it again.

..... I understand it's possible for a DIN kit to rotate/unscrew by accident, and now I'm paranoid as to the wisdom my my having even installed a DIN kit....so my question is this:

-- is the DIN kit 'unscrewing' spontaneously due to insufficient torque being applied during installation ?

-- is the DIN kit 'unscrewing' spontaneously due to the failure to use "locktite" or equivalent on the threads during installation ? ( I ask this because the 'old' OEM Yoke-kit threads have some sort of residue/gunk on them that look like traces of some sort of thread locker 'substance' that Mares used during assembly.
( FYI, I'm using a MARES OEM 300 bar DIN kit, so there's no doubt the correct DIN kit is being used.)

..... when I get the reg examined I'll be able to rule out other possibilities, like a missing O-ring, etc.

Thanks,

Karl

 

[Jimmer]

I had my DIN connector come slightly loose on my Zeagle as well, I just tightened it down a little firmer and check it periodically. So far no additional problems. One thing my instructor said works really well without the "mess" of loctite, is to use a tiny little bit of toothpaste on the threads instead of loctite. Apparently helps firm up the fit, but easier to undo than loctite. If you do use some loctite, make sure it's blue or purple and definetly not red.

 

[Mo2vation]

Most DIN kits have a hex screw that runs down the center of the DIN threads. I know on my one of my Atomic doubles regs, from time to time, this will come loose - causing the reg to not seat when pressurized. I know right away when I turn on the gas.

The thing is, you can't tell when setting up. Its not "loose" - it doesn't jiggle or behave any differently in my hands. When I hook it up - Hissssssssssssss. Its happened three times in the last 4 months.

I carry the Hex key that fits it in my Drybox. Last time it didn't seat a few weeks ago, I simply tightened it up a bit - no issues.

Not sure I'd introduce a chemical into my breathing path.

---
Ken

 

[Jimmer]

Most DIN kits have a hex screw that runs down the center of the DIN threads. I know on my one of my Atomic doubles regs, from time to time, this will come loose - causing the reg to not seat when pressurized. I know right away when I turn on the gas.

The thing is, you can't tell when setting up. Its not "loose" - it doesn't jiggle or behave any differently in my hands. When I hook it up - Hissssssssssssss. Its happened three times in the last 4 months.

I carry the Hex key that fits it in my Drybox. Last time it didn't seat a few weeks ago, I simply tightened it up a bit - no issues.

Not sure I'd introduce a chemical into my breathing path.

---
Ken

I agree, I don't really like the idea of a chemical being in there either, but it does actually say in Oceanic's tech manual to use blue threadlocker on that spot.

 

[dannobee]

The reason they loosen up is because the first stage is twisted ever so slightly when on the tank, normally by grabbing the kit by the first stage or hoses, or by twisting the first stage when installing/removing the reg from the tank. The DIN wheel is still tight in the tankvalve, and the thing that gives is the DIN adapter/fitting going into the first stage. A small drop of blue loctite on the threads will help.

Oh, and there's no way that correctly applied loctite will get into the path of breathing air, but I personally don't use it. I use Ken's check and tighten when needed method and always carry an allen wrench, just in case.

 

[Rick Murchison]

The reason they loosen up is because the first stage is twisted ever so slightly when on the tank, normally by grabbing the kit by the first stage or hoses, or by twisting the first stage when installing/removing the reg from the tank. The DIN wheel is still tight in the tankvalve, and the thing that gives is the DIN adapter/fitting going into the first stage. A small drop of blue loctite on the threads will help.

Oh, and there's no way that correctly applied loctite will get into the path of breathing air, but I personally don't use it. I use Ken's check and tighten when needed method and always carry an allen wrench, just in case.

dannobee has hit the nail on the head. It can also be loosened when removing the protective cap if you hold on to the first stage instead of the installation/tightening ring of the DIN fitting.
In any case it's a "preflight" item for DIN regs.
To be blunt, loctite is a poor substitute for good maintenance and equipment handling practices.
Rick

 

[Scuba_Steve]

I wouldn't go that far Rick.

To be sure, getting into good practices, like not twisting the first stage when the DIN fitting is tight in the valve is the first line of defense, there's nothing to be lost with adding a SMALL amount of loc-tite to the threads.

To me it's not the point of whether I can change the o-ring OR re-tighten the DIN fitting, but more of a matter of I don't want to waste my time doing so at the dive site. I'll take that extra insurance step at rebuild time seeing as it doesn't add any time there.

Although it's not universal, a huge majority of the DIN fittings out there, adding loc-tite WILL NOT add any chemical to the 'breathing stream'. The chemical is put on 'downstream' of the sealing O-ring which makes it impossible for the chemical to reverse direction.

I've seen a couple DIN's that that isn't the case, but if you have a seal on the end vs higher up on the outside above the threads, you're OK to add the loc-tite. One example of the latter that I can think of is a S/Pro Mk2, but who uses them

regards

 

[Greg Barlow]

Mares specifies that blue Loc-Tite be used on certain threaded portions of their yoke and DIN connections. If done properly, it is not in the path of gas. I use a small drop on the fittings, and then torque the connectors using a torque wrench. When cleaning the parts during service, the ultrasonic cleaning seems to work fine in removing the residue. If not, then a wooden toothpick does wonders on the external threaded areas.

Jimmer mentioned that Oceanic also recommended the use of Loc-Tite. I have several of their service manuals from around five years ago, and they do make that statement.

Greg Barlow
Former Science Editor for Rodale's Scuba Diving Magazine

 

[oxyhacker]

About half the reg manufacturers specify loctite in this spot. Most stress that only one, small drop be used, and that every bit of it must be removed at service time before applying more. Many techs don't like the stuff, and do not use it - at least on their own regs. I really depends on the reg - some just won't stay tight without it, and others seem to stay tight just fine. While I'm not crazy about the stuff, it is still a better choice than overtightening. And DIN adaptors seem to need it more than yokes.

One place I would not use it, unless it proved necessary, in on an adaptor which is being frequently switched out without the reg being service, as for example if you switch from DIN to yoke and back several times a year as some people who travel a lot do. The problem here is that, since the reg isn't being thoroughly cleaned between applications, eventually you'll get a build up of crud from the old loctite which may find its way into some place where it can cause some trouble.

 

[spectrum]

We have had DIN (Sherwoods) from day one and my wife spun hers out twice in our first week. It was not the connection to the frist stage that broke free but rather the mentioned inner core with the hex. When setting up it is all too tempting to turn the reguator like it's on a swivel in order to align hoses. You must hold it still while running the threads into the valve. Once air is applied the pressure applies thrust loading and makes a strong connection. I don't doubt that a misguided deck hand grabbing by a hose could cause it to break free.

Our LDS also did the little drop of Loctite. There is an o-ring in the sub-assembly that can get chaffed in the process. I keep a spare connector in my save-a-dive box. Collectively we're been incident free for the last 250 dives.

Pete