Balanced Diaphragm Reg Performance - Is This Typical?

[Luis H]

I call it the "volcano orifice". Guess why I call it that.

 

[LeadTurn_SD]

Locus,

Don't wrap this up yet.



Did you get the old parts back or at least get a look at them to see what they were like?

I'm curious because I have two MR42T/Abyss regs and one of them might need a Poppet Seat replacement.

I'm presuming that they would've replaced either one or both of these two items in the first stage.

Here is the typical deal with servicing current Mares 1st stages:

The poppet is a "2 year / 200 dive" part. It is inspected at annual service, but if in good condition (and the IP tested good and stable during pre-service inspection) it is re-used. The technician is instructed to etch a " 1 " on the back side of the poppet to indicate that has been re-used once... the next year the " 1 " will be seen, and the poppet will be replaced.

So, for better or worse, Mares does not include the poppet with the annual service kit. It is separate.

The poppet seat (I'm with Luis, I call it a volcano orifice too ) is inspected, but only replaced if it is damaged. Typically this is like, well, never, unless the tech damages it during service or there was a defect. The older MR-12's stages (I still have one) had the volcano orifice machined into the body of the 1st stage.... replaceable is far better, but it should not typically need to be replaced.

Best wishes.

---------- Post added May 6th, 2014 at 04:09 PM ----------

That means that your IP was likely creeping over the course of the dive, the depth change probably had nothing to do with it, just dive time. Replacing the HP seat has no affect on the depth compensation of the regulator.

Yep. I'm puzzled by the whole scenario. I'm still not able to work out what was happening with his regulator. If they felt the HP seat needed to be replaced, I would expect it was because it could not hold a steady IP (creeping up, like halocline mentioned).

Locus, I'm glad it got fixed, but it remains a mystery for me... probably something I'm simply not seeing, or maybe like ams511 mentioned maybe something else got "fixed" as well.

Best wishes.

 

[rjk75]

LeadTurn,

Excellent info as usual, thanks very much for that. It's my understanding that when the 1st stage is depressurized, that "volcano orifice" presses into the polyurethane face of the Tri-material poppet, and then subsequently backs off a little bit (i.e., it opens) when pressurized. If this is correct, wouldn't the orifice create a somewhat permanent dimple in the poppet face if the 1st stage has not been used at all for 8 months?

 

[LeadTurn_SD]

LeadTurn,

Excellent info as usual, thanks very much for that. It's my understanding that when the 1st stage is depressurized, that "volcano orifice" presses into the polyurethane face of the Tri-material poppet, and then subsequently backs off a little bit (i.e., it opens) when pressurized. If this is correct, wouldn't the orifice create a somewhat permanent dimple in the poppet face if the 1st stage has not been used at all for 8 months?

Hi rjk75,

No. That is true for the 2nd Stage soft seat, but not for the 1st stage HP seat (the poppet in this case).

When the 1st stage is depressurized, the valve surface are held OPEN by spring pressure.

When you pressurize the the regulator, the valve CLOSES.

The amount force required to close the valve is IP. You can easily adjust the IP in a diaphragm first stage by adjusting the spring pressure (increasing the spring pressure increases IP).

If the surface of the poppet or the orifice is damaged, it takes a higher pressure to seal the valve.... this is reflected in a higher IP.

When the HP seat begins to wear, you will see the IP rise several psi after initial "lockup", this is called "creep". Depending on how much "creep" there is you can begin to get slight freeflows from the 2nd stages in between breaths, especially unbalanced 2nds (balanced 2nd stages will compensate for small fluctuations in IP).

So a properly-stored first stage can sit unused for quite a long time and still be "ok", but a 2nd stage that has sat unused for a long time will likely freeflow when you try to use it again because the soft seat became too indented to create a good seal.

Best wishes.

 

[herman]

LeadTurn,

Excellent info as usual, thanks very much for that. It's my understanding that when the 1st stage is depressurized, that "volcano orifice" presses into the polyurethane face of the Tri-material poppet, and then subsequently backs off a little bit (i.e., it opens) when pressurized. If this is correct, wouldn't the orifice create a somewhat permanent dimple in the poppet face if the 1st stage has not been used at all for 8 months?

To add a little Ledturns post and to answer your question, yes the seats (both HP and LP) do take a set (depresssion in the face) shortly after installation. This set happens fairly quickly after installation but then is reasonably stable for the life of the seat. Modern materials are much better at being stable than those of years past but even so, I have seen HP seats that are over 30 years old that still hold a solid IP. Taking of a set is normal and expected, any good tech will pressurize the reg and cycle it a good number of times to encourage the set to take shape before doing the final setup of the reg to account for the set he (should) know is going to happen.

 

[rjk75]

That's great LeadTurn and Herman, can't thank you guys enough. I knew about the 2nd stage Seat taking a set, but wasn't sure about how the 1st stage worked (Mares Youtube videos just show the generic operation of their regs).

I stored my 2nd stage disconnected from the LP hose through the winter with a slight pressure on the diaphragm using a milk carton cap that just fits perfectly. I'm quite capable of adjusting the 2nd stage (I have the thin-walled 5.5mm nut driver, the Allen keys) but the 1st stage I'll leave for my LDS.

 

[ams511]

I am not sure what you are doing is good for the diaphragm. It may be better just to remove the cover and the diaphragm and tie a string around the level to hold it down. Diaphragms are $15 to $ 25, new seats are $4 or less.

 

[herman]

With the modern materials I am not too sure holding the seat open is really necessary, not so with the older rubbers of the past. At the few cents a seat cost and how easy it is to replace I don't bother.

 

[rjk75]

ams511,

The demand lever sticks up quite a bit above the 2nd stage body with the cover removed--that made it difficult to adjust the lever height down just a little bit.

The elastic band is barely compressing the cap; the diaphragm has a metal disc inside; with the cover on, the outside of the diaphragm is always in contact with the purge button.

I hate to disassemble the orifice, take off the nylon locknut (holding the demand lever) any more than I have to. I've done this now for three years, still have the original soft seat and have not had any problems. Maybe this year I'll change the soft seat if it starts leaking.

 

[ams511]

I wouldn't go that far. Thinking about it, it would be easier just to do what you are doing and remove the diaphragm. But as Herman points out with modern materials it may not be an issue anymore.