A VERY odd Apeks failure....and possible caution

[DeepScuba]

Good point Brian. That same thinking goes for a lot of other 1st stages and 2nd as well.

Folks should "think" about what you're doing to the internal bits when you're turning in/out another threaded or under-pressure part.

Never done a Reg cookie cutter, but I have cookie cuttered a few automotive components!!!

It's from that experience that I've brought to my scuba servicing experience (or lack thereof).

 

[Genesis]

I'm missing something here.

Isn't the HP orifice open when the reg is not under pressure?

If so, how does this failure mode during assembly/disassembly come about?

(Haven't torn down an Apeks yet, but none of the regs I HAVE torn down have their HP seats closed when not under pressure.)

 

[Zaphod]

It seems to me, if this type of failure were as easy to create as the prevailing theory indicates, at least one of the signficant number of inexperienced, unqualified service techs (frequently described by members of this board) out in the world would have reported this problem to Aqualung. Unless the Aqualung tech is lying to me, a failure of this type has never been reported to them. Therefore, I don't believe the seat material is quite so fragile as indicated. Part of the problem may be the assumption that the seat is made of rubber - it isn't. It also isn't very thin at the top, unlike current Aqualung seats.

I would also forget about the idea that this reg was assembled incorrectly. The guy that did this reg taught me many years ago and would not have made this mistake.

 

[LUBOLD8431]

Genesis once bubbled...
I'm missing something here.

Isn't the HP orifice open when the reg is not under pressure?

This is true...

Which makes the claim of how it got damage bunk...

Plain and simple, something is wrong with the reg, either from damage, or incorrect assembly. There is a reason why Aqualung hasnt heard of a problem like this, because it doesnt happen...

And, YES, I am an APeks service technician, and about every other manufacturer too, and I own 4 Apeks regs, which I service myself...

 

[brian cooper]

To Zaphod,
I'm not going to argue the point whether the puck on the end of an Apeks poppet is rubber or not...lets just say thay it is a lump of rubbery/plasticy/polymer injection moulded onto the metal end of the poppet.
And yes, turn on the air and set the IP then when you fit the watertight outer diaphragm squeeze out the air before tightening the lock ring but dont push down on the outer diaphragm to simmulate depth cos the IP will go up and could accelerate wear or cutting of the polymer on the seat and ruin your nice new poppet.

Genesis,
Tear down and rebuild an Apeks, then join in....

Everyone,
Have you got ALL relevant manuals and updates for the regs you service. Do you religously follow ALL the recomendations orders and warnings in the manuals and CD-ROMs when servicing Apeks regs? (careful this is a "Damned if you do damned if you don't" trap)

Please refer to the following sources:-
CD-ROM Apeks Course dated29/02/2000
Seaquest manual TX50 /DST page 12
T20
A/TX100
Zeagle Manual "Tech50D + ZRD" .....The Apeks produced reg

The order of assembly is given as valve lifter side BEFORE HP poppet side on the CD and in the manuals.
Quote in bold letters"Important note: correct order of assembly and disassembly is extremely important. In order to avoid damaging the High Pressure seat the turret end MUST be removed first on disassembly and the diaphragm end MUST be assembled first when reassembling the first stage".......Zeagle manual
This is then repeated twice on the same and following page


Now for the contradiction:-
refer to the Aqualung America.Inc
ATX200 manual.....Rev 9/2002
Where it says the opposite...........
Reassembly Procedures....(page 7)
Starts with Crown( the ATX200 has a removable crown)
Steps 1--3 inc Fitting crown and poppet THEN
Steps 4--7 fitting the lifter

Have any of you serviced a ATX200 to this manual?????What was the result?

Can anyone take up this with Aqualung America Inc? ..Zaphod?

My experience of Apeks regs leads me to believe that when NEW parts are correctly assembled in the correct order then they will be ok, if regs are stripped in either the wrong order or disturbed/used parts reused, and or IP set too high, then you could be open to failure or at least accelerated wear.

The initial damage to the poppet face COULD have been caused as I originally suggested,or just down to wear and tear but once the HP seat starts to deteriorate and the IP starts to creep up then any blemish on the seat will be made worse at an accelerated rate due to the increased IP and a stress concentration in the area of the nick. This continues until the crown/orifice has cut completely through the polymer which then gets blown by the main tank pressure through the orifice onto the valve lifter pin. The metal head of the poppet then burrs the actual edge of the crown/orifce.
I doubt, but could not say for certain, that the reg would go into free flow as the poppet /orifice would probably still make a reasonable seal and the balanced nature of the 2nd stage would cope with the elevated IP. If an Octopus (non balanced),Autoair or a suit inflator were also fitted to the reg one of those would probably started blowing first.

Get your regs serviced by someone that you trust, have him check your IP for drift (or a group of you buy/make an IP gauge/connector) and check them frequently.
A stable IP indicates a healthy reg(Always checked on the same tank contents every time)

He shakes the hornets' nest and then steps back

Brian C

 

[Genesis]

Genesis,
Tear down and rebuild an Apeks, then join in....

I don't have to do that in order to understand how they work (I have perused a schematic)

Any reg that has an HP seat that is closed when not pressurized is an unstream design. I know of no scuba FIRST STAGES that are of an upstream design - including Apeks.

If there is no contact when not pressurized, there can be no "cookie cutter" effect, as there is no contact.

Now I agree that if you assemble things wrong, you can break them. That part's simple.

 

[Diver0001]

Genesis once bubbled...
I'm missing something here.

Isn't the HP orifice open when the reg is not under pressure?

If so, how does this failure mode during assembly/disassembly come about?

(Haven't torn down an Apeks yet, but none of the regs I HAVE torn down have their HP seats closed when not under pressure.)

By adjusting the IP with the reg under pressure?

R..

 

[Zaphod]

Brian,

First off, you're the one that said it was rubber. I'm just pointing out that it's not. If it were rubber, I could see how assembling the seat in the wrong order might be more critical. It seems to be much more durable.

Second, I guess it's time for me to be damned.... I have to say that I follow all of the instruction provided to me by the Apeks manuals and/or training to the letter with the training supersceding the manual, if a dispute arises. And, yes, I have all the manuals and get retrained just about every year. (Yeah, I know - good for you...)

Have I serviced an ATX-200 to the manual? Sure. Mine and at least a dozen more belonging to staff. I'm still here; staff's still here....no failures, no IP creep, rock solid.

Look, I don't really dispute your theory, but I don't think the seat material is so fragile that improper assembly can cause this type of failure (immediate or otherwise). If Aqualung returns from their failure analysis and determines that improper assembly was the cause, then I'll stop tempting fate and ask them to change their manual on the ATX-200. I'll call them this week see if I can get some answers.

I'll also post their explanation of the failure when it comes through. I'm also thinking I'll take a new seat and install it incorrectly several times to see what kind of damage occurs.

 

[Zaphod]

Gents,

The theory is quite sound on possible damage to the seat. I think we can all agree that when it's COMPLETLY assembled and depressurized, the seat does not contact the crown. But, ask yourself the following question: What keeps the seat from touching the crown?

A:The "valve lifter" and it's pin, which goes through and supports the seat.

The issue is that the seat will rotate on the crown and possibly damage the seat surface if there is nothing (i.e. the pin) to keep it from contacting the crown. If the pin is in place and secure before the seat is installed, then it has no opportunity to contact the crown and will not be damaged during assembly.

I don't dispute this damage mechanism, I just don't think the seat material is that susceptible to damage.

MD

 

[oxyhacker]

Take another look at that schematic!

Upstream regs have the "gate" or movable side of the seat, on the high pressure/upstream side of the orifice. Downstreams have it on the LP side. It doesn't have anything to do with whether the seats normally open or closed since this is a function of how the springs bias them. Since the purpose of a SCUBA 1st stage is to flow air until the IP gets high enough to cut it off, SCUBA 1st stages are all normally open, whether they are diaphragm or piston.

Just about all diaphragm 1sts, Apeks included, have upstream seats.

Genesis once bubbled...


I don't have to do that in order to understand how they work (I have perused a schematic)

Any reg that has an HP seat that is closed when not pressurized is an unstream design. I know of no scuba FIRST STAGES that are of an upstream design - including Apeks.Now I agree that if you assemble things wrong, you can break them. That part's simple.