Aqualung Legend LX First Stage Failure at depth

[reefrat]

Okay, I will correct myself. The older Mikron yoke connector would likely not work with a Titan, Titan LX, or Legend. The light weight Mikron yoke is thinner at the base, so that was a unique connector. But there is an older Titan non-ACD yoke retainer that looks it could be used on most if not all recent generations of Titan, Titan LX, and Legend in place of the ACD, as they all have the same yoke. And again, there is a pre and post 2013 version for filter placement, and both appear to be in stock for ordering.

Só it sounds like the yoke retainer is either an ACD compatible one or not and that is the fundamental difference. Funny that until a few years ago the standard Titan first stage (current shape) was sold non-ACD but advertised as ACD compatible, maybe part of the ACD ‘upgrade’ would have been to change the yoke retainer?

 

[Magnus Lundstedt]

Só it sounds like the yoke retainer is either an ACD compatible one or not and that is the fundamental difference. Funny that until a few years ago the standard Titan first stage (current shape) was sold non-ACD but advertised as ACD compatible, maybe part of the ACD ‘upgrade’ would have been to change the yoke retainer?

I have Titan LX DIN, both ACD and non ACD, And they are apart from a few parts identical. I have changed the DIN-parts between them.

 

[JackD342]

Só it sounds like the yoke retainer is either an ACD compatible one or not and that is the fundamental difference. Funny that until a few years ago the standard Titan first stage (current shape) was sold non-ACD but advertised as ACD compatible, maybe part of the ACD ‘upgrade’ would have been to change the yoke retainer?

The Yoke retainer is not simply ACD compatible yes/no, it is a separate and distinct part for ACD. Excepting filter, when moving from non-ACD to ACD, the one part yoke retainer is replaced with four parts: Valve, crown, spring, and retainer. Plus a couple more o-rings.

That Titan ACD upgrade is a long, odd story. Based on the Aqualung Buyers Guide in 2013, I bought two conversion kits for my 2013 Titans, only to find they would only fit previous version due to filter placement change in 2013. I was pissed, reported it, and then that same verbiage appeared in 2014 publication also. It was corrected in 2015 due to my calls and emails.

Thanks to the research I have done in this thread, I found the old conversion kit description is still misleading, and should be fixed next year. I also realized I don't need a non-existent conversion kit, I can (and just did) order the 4 individual parts for the new body version. So yes, you CAN convert current and recent Titans, but NOT with a kit. It requires ala carte parts. Do it along with overhaul service, and it will include the filter and o-rings that would be in a conversion kit. Now you need to use a different service kit than before the conversion, to have the correct filter and o-rings.

 

[rsingler]

So yes, you CAN convert current and recent Titans, but NOT with a kit.

How do you handle the cutout for the inverted filter that is now excess space without the ACD? Is there an Aqualung authorized washer or oring? Pics?

 

[JackD342]

How do you handle the cutout for the inverted filter that is now excess space without the ACD? Is there an Aqualung authorized washer or oring? Pics?

Not sure I understand your question.
This is a straight up 4 parts replace one part, plus o-rings and a shorter filter. No "shims" required.
Do you have one you are working on? If so, which direction are you converting? And which body, pre 2013 filter in yoke connector, or 2013+ body mounted filter?

 

[rsingler]

Here's what I mean. We are trying to go from ACD to non-ACD, in a post-2013 Legend.

Below is a picture of two older Aqualung Legends (with and without ACD).
They are clearly pre-2013, and I think around 2003-2009 or so.

As you can see, both have flat lands in the body of the regulator. So as you say, it should be a straight parts swap.
But unless I'm mistaken, due to the patent issue, the old yoke bolt #129124 is no longer available?
That's the non-ACD yoke bolt on the left in the picture above.
Assuming it IS available, then we get to the next issue:
Here is the cross section of the regs above:
It has the flat land in the reg body like the pics above.
But HERE is the new body after the patent issue was resolved:

Note the depression in the body of the regulator that accepts part of the rim of the filter, and (more important for our purposes) the shallower land in the yoke bolt where the filter cone is widest.
Even assuming we can get the old non-ACD yoke bolt, as you can see in the cross section of the new reg body (after 2013), there is a cutout in the reg body that will cause the filter to drop out of position without a shim. Hence my question about the parts for your proposed swap.

In other words, whether you get a non-ACD bolt from scavenging or from Aqualung directly, I am unaware of a non-ACD yoke bolt that was manufactured AFTER the patent change, that has a shallower placement of the filter. And if you have to use the yoke bolt #129124 in a post-2013 Legend, then you'll need a shim to keep the filter from dropping out of position the first time it is pressurized.

 

[JackD342]

Here's what I mean. We are trying to go from ACD to non-ACD, in a post-2013 Legend.

Below is a picture of two older Aqualung Legends (with and without ACD).
They are clearly pre-2013, and I think around 2003-2009 or so.
View attachment 485816
As you can see, both have flat lands in the body of the regulator. So as you say, it should be a straight parts swap.
But unless I'm mistaken, due to the patent issue, the old yoke bolt #129124 is no longer available?
That's the non-ACD yoke bolt on the left in the picture above.
Assuming it IS available, then we get to the next issue:
Here is the cross section of the regs above:
View attachment 485817 It has the flat land in the reg body like the pics above.
But HERE is the new body after the patent issue was resolved:
View attachment 485818
Note the depression in the body of the regulator that accepts part of the rim of the filter, and (more important for our purposes) the shallower land in the yoke bolt where the filter cone is widest.
Even assuming we can get the old non-ACD yoke bolt, as you can see in the cross section of the new reg body (after 2013), there is a cutout in the reg body that will cause the filter to drop out of position without a shim. Hence my question about the parts for your proposed swap.

In other words, whether you get a non-ACD bolt from scavenging or from Aqualung directly, I am unaware of a non-ACD yoke bolt that was manufactured AFTER the patent change, that has a shallower placement of the filter. And if you have to use the yoke bolt #129124 in a post-2013 Legend, then you'll need a shim to keep the filter from dropping out of position the first time it is pressurized.

Okay, limiting to post 2013 and later bodies at this point, I am saying the current Titan yoke retainer that you are calling a bolt can replace the ACD in Legend, Core, & Titan LX.

• All of those 3 models use identical ACD parts.
• All of those 3 models use the same yoke.
• Current non-ACD Titan uses same body as ACD Core/TitanLX, and same yoke.
• So current Titan yoke retainer can replace ACD in any of those models. With possible exception of # of HP ports, we are only talking about 2 bodies and 1 yoke across Titan, Titan LX, Core, and Legend.

The one note I need to add over what I previously wrote, is that after “downgrading” you will need to use a different filter than what is in the ACD kit. I have not looked close enough to see if you can use a different kit, or if you would need to order a separate filter. That answer may be different depending on whether it is a Titan/Core body or a Legend body. I know I have no reason to stock filters outside of kits.
I did check the other direction. Once I convert my 2013 Titan to ACD, I can just use the ACD kit instead and will have all the parts.

I have also confirmed that the issue is the shutter valve sealing against the face of the cylinder valve, it is NOT blocking flow THROUGH the first stage. So a loose ACD valve won’t affect a DIN valve, and is less likely to affect a non-convertible yoke that doesn’t have a DIN insert with the face closer to the ACD valve.

 

[rsingler]

I have also confirmed that the issue is the shutter valve sealing against the face of the cylinder valve

Thank you! It is wonderful that you have been able to pry out the truth of the matter from the sources you have. That explanation makes some sense if one has only a very shallow depression between the face of the valve and the slightly loosened shutter valve. You seem to be telling us that an inadequately torqued shutter valve can lead to unscrewing of the valve, with subsequent metal to metal sealing against the valve output area. As I look at various valves in my collection, there seem to be two distinct variants, only one of which is at risk.
The following photos show an insert valve with a very shallow face, vs a classic yoke valve with a conical depression.

When I place a shutter valve against both valves, the insert valve is completely obscured, while the conical valve would require excessive loosening of the shutter valve, and its oring would probably leak or the valve would come apart. At minor loosening, there is likely still an airflow gap. The recommended check of the ACD should show the problem.

What remains perplexing is the cause of that square-wave shutoff noted by @databob at 900 psi. It suggests some change in the geometry due to a combination of spring pressure and hydrostatic pressure on the back of the shutter crown. And that still doesn't make sense to me. But in any case, it will be interesting if @databob can supply info regarding the type of valve with which the problem arose. If it was a rental, we're probably out of luck. But maybe it was one of his own tanks? The other thought is regulator rocking while pressurized. If clearance is down to almost nothing, and the shutter valve is loosened, it is conceivable that just a couple of rocks of the reg on the tank valve might unscrew the shutter a hair more. How that might happen during a dive is difficult to visualize, though. No wonder this problem is so rare.

In any case, given the very shallow clearance in the face of the insert valve above, this explanation is much simpler than my original proposition of the valve sealing closed via normal valve function of the shutter crown rising up against the valve. One mm is just too much movement to posit. Occam's razor probably wins again. I couldn't be happier to be wrong.

On the basis of @JackD342 's information, I guess my thought would be that ACD owners might want to reconsider the use of a shallow faced insert valve like the one I photographed above. There must be vanishingly small clearance between a slightly loosened shutter valve and the tank valve face in a case like that. Then again, just following Aqualung's service bulletin, and ensuring that the shutter valve is torqued appropriately is probably enough. I guess this is one first stage that I wouldn't run longer than the recommended service interval. And I'd maybe even ask to see the 3mm shop fitting that attaches to a torque wrench before I'd believe a shop's assurances. That's a relatively uncommon tool.


Thank you again to @databob and @JackD342 for this information.

As for the yoke retainers, if one wanted to downgrade from ACD to non-ACD, I'll try to obtain the Titan part and report back. I'm still unclear how an old fashioned longer filter will be held in place, given the new land in the post-2013 reg body. But I appreciate the suggestion.

More to follow!

 

[rsingler]

For those with Aqualung parts access, the non-ACD yoke retainer in question is #129252 for the 2013 and later models, and #128633 for the pre-2013 models with the flat land inside the reg body. The filter that accompanies this for the Titan is part #129151

Note the reference in that schematic, to Service Bulletin #38 from which I harvested the cross section pictures above, showing the differences in the reg body, pre and post 2013.

 

[JackD342]

Thank you! It is wonderful that you have been able to pry out the truth of the matter from the sources you have. That explanation makes some sense if one has only a very shallow depression between the face of the valve and the slightly loosened shutter valve. You seem to be telling us that an inadequately torqued shutter valve can lead to unscrewing of the valve, with subsequent metal to metal sealing against the valve output area. As I look at various valves in my collection, there seem to be two distinct variants, only one of which is at risk.
The following photos show an insert valve with a very shallow face, vs a classic yoke valve with a conical depression.
View attachment 485826 View attachment 485827
When I place a shutter valve against both valves, the insert valve is completely obscured, while the conical valve would require excessive loosening of the shutter valve, and its oring would probably leak or the valve would come apart. At minor loosening, there is likely still an airflow gap. The recommended check of the ACD should show the problem.
View attachment 485828 View attachment 485829
What remains perplexing is the cause of that square-wave shutoff noted by @databob at 900 psi. It suggests some change in the geometry due to a combination of spring pressure and hydrostatic pressure on the back of the shutter crown. And that still doesn't make sense to me. But in any case, it will be interesting if @databob can supply info regarding the type of valve with which the problem arose. If it was a rental, we're probably out of luck. But maybe it was one of his own tanks? The other thought is regulator rocking while pressurized. If clearance is down to almost nothing, and the shutter valve is loosened, it is conceivable that just a couple of rocks of the reg on the tank valve might unscrew the shutter a hair more. How that might happen during a dive is difficult to visualize, though. No wonder this problem is so rare.

In any case, given the very shallow clearance in the face of the insert valve above, this explanation is much simpler than my original proposition of the valve sealing closed via normal valve function of the shutter crown rising up against the valve. One mm is just too much movement to posit. Occam's razor probably wins again. I couldn't be happier to be wrong.

On the basis of @JackD342 's information, I guess my thought would be that ACD owners might want to reconsider the use of a shallow faced insert valve like the one I photographed above. There must be vanishingly small clearance between a slightly loosened shutter valve and the tank valve face in a case like that. Then again, just following Aqualung's service bulletin, and ensuring that the shutter valve is torqued appropriately is probably enough. I guess this is one first stage that I wouldn't run longer than the recommended service interval. And I'd maybe even ask to see the 3mm shop fitting that attaches to a torque wrench before I'd believe a shop's assurances. That's a relatively uncommon tool.
View attachment 485830

Thank you again to @databob and @JackD342 for this information.

As for the yoke retainers, if one wanted to downgrade from ACD to non-ACD, I'll try to obtain the Titan part and report back. I'm still unclear how an old fashioned longer filter will be held in place, given the new land in the post-2013 reg body. But I appreciate the suggestion.

More to follow!

In either filter version the body mounted filter requires a little extra care assembling. Keep the body steady and upright with the o-ring and filter installed, then lower the yoke and yoke retainer carefully down and engage the threads. The insert mounted version made more sense, but this modification was due to patent problems, not design.

I do have one THEORY of how one might loosen a properly torqued unit. If an old hard rubber dust cap (non OEM) with a very shallow recess is tightened down hard. First it would compress the spring, then the hard flat face would bind against the valve, which actual adds torque. But once cranked down hard, twist the yoke itself (not the knob) counter-clockwise. There might be enough binding friction for the rubber to turn the valve too, loosening it. Ever open a jar or a tin just by pushing down on the top with a flat palm and twisting, rather than grasping the edges of the cap? I once had ACD threads “shaved” during service requiring replacement of two parts, and couldn’t figure out what happened. Then I realized the non standard valve cap the customer or a previous shop had installed could have been the cause, since you use it for spring compression during disassembly/reassembly.

Just a theory.

And yeah, it took me a while to find a 3mm hex for my torque wrench. May have been Lowe’s. They aren’t my first choice, but sometimes surprise me.