Why is my tank valve leaking?

[liberato]

So, if being used with the default insert and a yoke regulator I actually want to use the "(112) Standard DIN Regulator/Valve" O-ring and not the normal "(014) Standard Yoke Regulator/K-valve" O-ring (to use Dive Rite Express's terminology)?

Does the new "PURPLE O-RINGS AND 1/4" HEX OPENING" insert use the larger (112) or smaller (014) O-ring?

 

[Leadking]

I'll get the spec's posted tommorrow. There are three version of the insert ONLY the the one using the purple o-ring(epdm) with the mm hex key was an issue. Another issue to be aware of is Thermo valves are engineered to use a 90 durometer o-ring softer materials will fail.

 

[Leadking]

Well that's very interesting, I chased down the specs for the Thermo valve and it does appear that the correct O-ring for both sides of the adaptor (insert) are V112, these are the Viton 1/2" inner diameter and the 3/32" width. So I suppose if they were shipped with the "standard" yoke O-rings V014 (2/32" width) then they would be prone to leak. Maybe that was a design flaw, making the insert too narrow and requiring non-standard O-rings??

There are now two versions in the market, one which used the same size front and back and the new version which uses a thicker o-ring in the back than in the front and uses a 1/4" hex key rather than a mm key

In the new version the front has a minor upset in the inner ring formation. This is to allow air from being trapped behind the o-ring and blowing it out.

 

[liberato]

OK, that makes sense. The new version uses a DIN (112) O-Ring on the backside and the normal yoke (014) O-Ring on the front side. An older (but still good) version uses the larger DIN (112) O-Rings on both sides of the insert. A 3rd version of the insert has been removed from the market. But what distinguishes the bad older version from the good older version? Does only the bad version have the metric hex key slot? Can't go by the purple O-Ring because that may have been changed. If I have a metric hex key slot does that imply I should exchange the yoke insert?

 

[mark99]

OK, that makes sense. The new version uses a DIN (112) O-Ring on the backside and the normal yoke (014) O-Ring on the front side. An older (but still good) version uses the larger DIN (112) O-Rings on both sides of the insert. A 3rd version of the insert has been removed from the market. But what distinguishes the bad older version from the good older version? Does only the bad version have the metric hex key slot? Can't go by the purple O-Ring because that may have been changed. If I have a metric hex key slot does that imply I should exchange the yoke insert?

Well I had an interesting time at the LDS trying in O-rings. The factory supplied front O-ring was clearly not a 112. We took out the insert and sure enough there was a purple 112 O-ring in the back. So we re-seated the insert and tried a 112 in the front- no way would it fit, the ring was too large in diameter and would not in any way squish into the channel. As a matter of fact the channel is very flat and doesnt have any sort of groove or retention built into it. What ended up fitting fairly well was a 111( that would be ID 7/16 rather than 1/2, width same at 3/32), and with the regulator the seal appears to be quite secure. I don't really like the "trial and error approach", and look forward to any additional info anyone here can discover. I will be calling DiveRiteExpress tomorrow to see if they know anything more.

What is also interesting is that if you do the math on the outer diameter (which seemed too large on the 112) you find the following:

Width+ID+Width = OD
014--> 1/16+1/2+1/16 = 10/16
111-->3/32 + 7/16 + 3/32 = 10/16
So the 014 and the 111 have the same OD and would fit into the slot about the same,except the thickness would cause the 111 to extend 1/32 more toward the regulator interface, maybe making a better seal.

112-->3/32+1/2+3/32 = 11/16, would be 1/16" larger in outer diameter and harder to squish into the channel.

 

[liberato]

Nothing like a little empirical method to ruin a perfectly good theory! OK, I have PST tanks with the Thermo Pro valves from 2 years, 1 year, and 1 month ago. I guess I need to compare them to each other and to yours. One thing that wasn't clear in your tests. Was the O-Ring that was on the face originally (the leaky one) an 014?

Having the O-Ring be thicker may not necessarily be better if it prevents stable metal to metal contact on the interface to keep the O-Ring captured. I don't want any wobble. Assuming the O-Ring sealing surface is perfect as you mentioned you would also need to rule out that the original O-Ring may have been correct size but defective in some other way.

 

[liberato]

Here is some more info from an email:

There are three versions of the insert.... they can be distinguished by the opening... the "original" version requires a 8mm hex key for insertion/removal, and uses two black Viton O-rings (front and back) AS568B-112. Thermo recently switched from Viton to EPDM (purple) O-rings. At that time they also changed to an insert that requires a 5 mm hex key and uses the more common AS568B-014 O-ring on the front and a -112 on the back... the design did not hold the -014 very well and the O-ring was notorious for just falling out or extruding. Thermo is just now shipping a new third version of the insert, distinquished by using a 6 mm hex and also using the -014 on the front and -112 on the back, this uses a face design similar to their K valve which does a better job of capturing the O-ring and also has a dimple. While the jury is still out on the newest version, in our opinon, neither of the versions using the -014 O-ring is as good as the original using two -112 O-rings. The complaint that drove the change in the first place (which, ironically, continues with the newer designs) is that the orings fall out. This is because divers fail to completely purge their regulators before loosening the yoke nut. The regulator should be purged and held for a count of ten, or purged three times in a row to allow high pressure gas from the HP stage and the HP hose to equalize into the LP side and be released by the purge. If this is done, the original 8mm hex insert -112 O-ring remains in place and also it appears the 6mm hex insert -014 does also... the 5mm hex insert -014 will fall out if you just walk past the tank.

You are welcome to post this reply to scubaboard if you wish ...

-- Mark Derrick
Fill Express/Dive Rite Express...​

 

[Leadking]

The insert in question has a 6mm hex. Be careful as this is only .010" from the new insert which has a 1/4" hex . Again the new insert has a minor upset formed on the inner ring to allow trapped air to escape when removing the regulator. Please do not use larger o-rings than supplied with the valve.

 

[liberato]

So, it looks like Leadking and DiveRite Express are basically saying the same thing about there being 3 different versions with the 2nd one being problematic. There is now some ambiguity, though, as to whether the 2nd version has a 5mm or a 6mm hex slot. I don't think I could distinguish 6mm from 1/4" anyway.

5 millimeters = 0.196850394 inches
6 millimeters = 0.236220472 inches
.25 inches = 6.35 millimeters

(A neat feature of the Google is to type in 6 millimeters in inches or any other conversion and it will calculate it for you!)

 

[Leadking]

I can understand your problem. The easiest I can make it is if the hex is larger than 6mm/1/4" it is ok,OR if there is an upset/dimple on the inner o-ring diameter is is ok.