Diaphragm HP side issues
- Thread starter _Ralph
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I have seen this instruction mostly on some of the newer diaphragm first stages that use some of the thinner (“more responsive”) diaphragms. As opposed to the Conshelf, Titan, (or any of the other Aqua Lung, previously US Divers) first stages that show assembling the HP side first and then adding the pin, pin support and diaphragm from the other side. The Conshelfs (and its derivatives) use a relatively heavy diaphragm that can be installed at any time.
From my observation on the emphasis in some of the installation instruction to first install the diaphragm; I am thinking that they want to clamp the diaphragm down while it is relaxed, before applying any pressure on it from the hp valve side (with the pin support).
When the design uses these thin diaphragms, I can see why it might be important to install the diaphragm carefully without any initial stress.
This is just what I would call an engineering guess based on observations of some of these newer regulators with thinner diaphragms. But this is just my guess. I could be wrong.
I am not totally suggesting that you always have to follow the instructions directly, but if you decide to deviate, be aware of the possibilities and try to mitigate any issues.
Before you start taking it apart, I have a suggestion.
If the leak is between item 10 (main body) and item 17 (diaphragm cap), try just tightening item 17 to clamp a bit harder on the diaphragm and see if the leak stops. With time the diaphragm might have taken a compression set and it is just not sealing. Tightening it just a bit may be all it needs. You may get a few more years out of it without doing anything else.
Note: you will need to readjust the IP after tightening item 17.
Based on the comments above about the thin (more delicate) diaphragm, this process may not work at all and the diaphragm may not even tolerate to be re-tighten, but at this point you don’t have anything to lose.
If it was a Conshelf, I would just tighten the diaphragm and I would get a few more years of service without doing anything else, but as I mention, they have a tough diaphragm. The diaphragm is thick and sometimes will take a bit of a compression set around the compressed edge.
Good luck.
I should add.
When you originally tighten item 17, clamping the diaphragm, you probably followed the instructions, which probably included a torque value. The issues is that when you are tightening a rubber diaphragm (or a gasket for that matter) the torque reading will change depending on how fast you are rotating the torque wrench. In other words, it is not a precise science.
Because the rubber tends to relax, it you tighten it slowly, you will rotate the torque further to get the same torque readings. If you turn it fast, you will get a reading, but if you check it again, you will notice that you need to turn it further to get the same reading.
It should eventually settle, but that is why it may be good to check it again in a few days or more.
When you originally tighten item 17, clamping the diaphragm, you probably followed the instructions, which probably included a torque value. The issues is that when you are tightening a rubber diaphragm (or a gasket for that matter) the torque reading will change depending on how fast you are rotating the torque wrench. In other words, it is not a precise science.
Because the rubber tends to relax, it you tighten it slowly, you will rotate the torque further to get the same torque readings. If you turn it fast, you will get a reading, but if you check it again, you will notice that you need to turn it further to get the same reading.
It should eventually settle, but that is why it may be good to check it again in a few days or more.
Manufacturers I have queried on this issue have noted what they call "concentricity problems" when the HP side is assembled first. What can occasionally happen with a few models is that an HP seat that is a sloppy fit without the pin present may initially seat just slightly off center, and take a set. Then, when the pin is dropped and the pin hat puts pressure on the seat, it centers itself.
Unfortunately, the slight depression created by the initial off-center pressurization does not match the centered ring that is created after cycling a seat + pin + hat assembly. A tiny IP creep can then result where the two depressions overlap.
I didn't believe there is enough protrusion of the pin + hat to prevent even a thin diaphragm from seating properly. That said, there are, I think, two manufacturers that require you to pre-tension the main spring before assembling the HP side, so you may be right.
I was taught the same way @couv and you apparently were: HP side first. Always. It sure makes checking your seat integrity easy, before you go to the trouble of assembling the rest.
But not knowing where the OP's leak is coming from makes this a bit of a conundrum...
I have noticed similar things with other brands -- what the guy who initially trained me called "possessed" regulators; and the most typical source, after serial rebuilds, bar none, were damaged sealing surfaces from rough tool use (especially o-ring and seat removal), which can be difficult to see, without the benefit of a stereo scope. Sadly, you can occasionally hear it.
One remedy, was to heavily grease internal o-rings; and that would quiet things for a bit, since the grease would temporarily fill those minor flaws; but with regular use, would settle and later exhibit the same problems.
The likelihood of some internal damage, over twenty rebuilds, as you described, can be quite high . . .
Same thing; and probably some of the most valuable advice, regardless of some manufacturer's manuals . . .
One remedy, was to heavily grease internal o-rings; and that would quiet things for a bit, since the grease would temporarily fill those minor flaws; but with regular use, would settle and later exhibit the same problems.
The likelihood of some internal damage, over twenty rebuilds, as you described, can be quite high . . .
Same thing; and probably some of the most valuable advice, regardless of some manufacturer's manuals . . .
Sorry, meant to be read, that I've done about 20 rebuilds across my collection of regulators ... each one has at least 4 rebuilds (I buy most used, so I don't quite know the history prior.. I rebuild when I receive them, as who really knows what they've been doing ... some were really disgusting upon delivery)
_R
the diaphragm is wearing thru from clamping force, gas gets to the centre fibres on the LP side and travels along and exits out the side of the diaphragm and reg starts leaking. New diaphragm is the solution.
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