HOG D2 - o-ring size

[trimmatters]

Hey team

Ended up iwth a HOG D2 first stage as part of my transition to CC last year.

Have had issues with one of the o-rings getting mashed in the screw-in post from the DIN. See pic. Like, I can't get one to last more than 5-10 days of dving, if that.

The original o-ring, as purchased with the reg new for the course, lasted the 5 days of diving for the course, and one day of post-course diving before I started having to replace it regularly.

I have tried every material and slight size difference I can for this o-ring but they all keep getting mashed and dying. I've previously only seen this issue of that o-ring going for Apex first-stages but those o-ring sizes were known to my dive buddy.

The HOG dealer in Australia that did servicing etc has recently closed and that's where this one was purchased from. I'd love to do the HOG servicing course but in the mean time I'm kinda sick of having to replace the o-ring every 5-10 days of diving.

Any thoughts?

 

[VikingDives]

I'm an Edge-Hog dealer... I don't know the answer, but I'll bet @Islandheart knows.

If you don't get an answer in the next day or so, shoot me a DM and I'll find out for you.

 

[rsingler]

I'm not sure I understand the problem. What do you mean by dying? That oring seals the threads between the DIN retainer face and the housing itself. It's a high pressure o-ring, and 3000 psi gas tries to leak up the threads of the DIN housing, forcing the seal against the back of the small DIN retainer at the bottom of your picture, and the land in the housing pictured at the center of the DIN knob in your photo.
It's a static o-ring, i.e., it does not move. Per the D1 manual, it's a 2-013 Viton duro 85. For the D2, it got stiffened up a touch to D90.
But in your pic, there appears to be some fraying of the edge against your fingertip. Based on the deformation of the oring, I'm guessing that that is the side that faces out/up against the retainer. Fraying implies movement, which should not be occurring.
The change in shape is quite typical of Viton, which has a poor long term set capability. But it still shouldn't leak after 5 days. TBH, I have never seen a leak at that o-ring, which is shared in a number of designs.
If you use the reg for O2 concentrations above 40%, the lawyers will tell you you have to use Viton. You can get better quality Viton o-rings from sources here in the US. You might try a 2-013 duro 90 black Viton, with a wisp of lube, in case the fraying is due to the oring sticking against one land and being frayed by the retainer as it is initially tightened.
Apart from high O2 use, I'd have no qualms about making a seal with a Nitrile o-ring for air or Nitrox. There's just no high velocity gas flow at this seal. If your lawyers tell you differently, you could use EPDM, but that's difficult to find in 85 durometer.
Yeah, Viton is only a fair quality seal when long term set is a factor. But there appears to be more going on here.

 

[L13]

It looks like the reg is getting rotated under pressure to me.

Maybe better venting of the reg after the valve is shut before removing it from the valve?

 

[rhwestfall]

As above, torque spec issue?

 

[Jim Lapenta]

If the retainer is not torqued to spec it can happen. Causes? Can be not torqued properly to begin with. Or and this is more common. The reg is pressurized and then rotated, intentionally or accidentally into another position. This turns the reg body into a wrench that loosens the connection. Then someone notices and tightens it back up insufficiently with a plain hex key.
The correct torque for the DIN housing is 220 inch lbs and 150 inch lbs for the retainer.
Full disclosure I wrote the initial draft of the service manual for the D2 so I'm pretty confident on the spec. It's the same for the D1 and D3.

 

[trimmatters]

Thanks team, this is very helpful and the "meant to be static but probably moving" bit rings very true.

I intended to share in the OP but obviously forgot....

This reg is on an S13 with a x-flow under my bum as O2 for my KISS sidekick, so yes, it can get a bit of a shift during the dive.

I do always attempt to set the position of the reg as desired before pressurising, but yeah, it always gets some movement particularly if there's a sump or I walk with the kit on to the water. The course in particular involved quite a walk from the carpark to the water - Kilsby Sinkhole for those playing in Australia.

Now for the "stupid" question... when I put the bit that is on the counter back into the mainbody of the reg, does that get the housing or the retainer tension?

Thank you all for the contributions.

 

[happy-diver]

Yeah, I use the reg as a lever, but there's a way to do it

So take it to the shop mate have them do it and watch

 

[Jim Lapenta]

Thanks team, this is very helpful and the "meant to be static but probably moving" bit rings very true.

I intended to share in the OP but obviously forgot....

This reg is on an S13 with a x-flow under my bum as O2 for my KISS sidekick, so yes, it can get a bit of a shift during the dive.

I do always attempt to set the position of the reg as desired before pressurising, but yeah, it always gets some movement particularly if there's a sump or I walk with the kit on to the water. The course in particular involved quite a walk from the carpark to the water - Kilsby Sinkhole for those playing in Australia.

Now for the "stupid" question... when I put the bit that is on the counter back into the mainbody of the reg, does that get the housing or the retainer tension?

Thank you all for the contributions.

The housing screws into the body. The retainer screws into that and holds the DIN wheel on. So the part on the counter that the o-ring is on is the retainer -150 inch lbs.