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

[Zaphod]

I just serviced a TX-100 first stage this evening that had a very strange failure mechanism that I thought might be of interest to the community here. The reg. was brought in for no particular reason but an annual and is owned by one of the staff at the shop. It was serviced last year. It is equipped only with a yoke fitting, so no HP air.

Before anything was done, the IP was checked and found to drift from about 135 psi to about 150 psi in about 1 minute. It "softly" locked up at 150 psi and didn't drift from there.

So, when time came to remove the "valve lifter" on the diaphragm side of the reg., I noticed what looked like a small o-ring surrounding the lifter pin. Once I got to the HP side and removed the seat, I found the problem, but first a brief description of what normally happens to the seat, for those unaware. The seat material seals against a relatively sharp "knife" edge or crown. During use, this seat material takes a set and develops a small indentation (visible) where it rests on the crown.

Now, the problem. The portion of the seat material inside of this normal set was missing, had blown through the crown and ended up on the valve lifter pin!! There was a hole in the seat material so I could see the metal underneath. (I'll see if I can take a picture of it).

I called Aqualung. They've never seen this before and are alarmed. Unfortunately, this reg apparently has been like this for a while because the bare metal surface of the seat came into contact so much with the crown that the knife edge on the crown was gone. So, the whole first stage is going back.

I don't know if we Apeks users should be concerned about this type of failure or not. It's somewhat reminiscent of old Aqualung seat delamination problems, but in this case, the reg didn't fail catastrophically. I'll update when I/if I get a response from Aqualung.

 

[detroit diver]

Some info please.


Which model?
How old is it?
Has it been serviced before, and if so, by whom?

 

[Bob3]

Apeks has in the past experienced a couple of things they felt justified recalls, they were exceptionally responsible & immediately jumped on things with a no BS attitude.
Hope the "new management" has the same policy.

 

[Zaphod]

dd,

Most of this was in the original post, but here goes:
TX-100
2 yrs old.
Serviced last year by same shop and by somebody whose work I respect.

detroit diver once bubbled...
Some info please.


Which model?
How old is it?
Has it been serviced before, and if so, by whom?

My biggest concern is that Apeks may never know about the problem. Unfortunately, I have to deal with Aqualung and depending on the results of their "investigation" Apeks may not get involved.

 

[LUBOLD8431]

I wouldnt be alarmed. SOunds like a bad HP seat. That happens sometimes. I certainly dont think it would generate a recall from one reg. Now, if a few more show up with the same problem, then maybe. Like I said, I wouldnt be alarmed...

BTW, I have four Apeks regs, and one of mine was recalled during the last recall that wasnt supposed to affect the US customers. I do believe that they will take care of this. Aqualung customer service is excellent, from my experience...

 

[detroit diver]

You're right. Sorry. It's late and my eyes are blurring...

Zaphod once bubbled...
dd,

Most of this was in the original post, but here goes:
TX-100
2 yrs old.
Serviced last year by same shop and by somebody whose work I respect.




My biggest concern is that Apeks may never know about the problem. Unfortunately, I have to deal with Aqualung and depending on the results of their "investigation" Apeks may not get involved.

 

[brian cooper]

Just a thought on the matter, it might be pertinant it might not but take it for what its worth....

When you strip down an Apeks 1st stage if it is done from the dry sealed end first, ie remove the outer diaphragm And slacken off the IP pressure spring then the push ror moves back under the main diaphragm AND the HP poppet sits on the valve orifice.

Now when the other end of the reg is stipped down (whether it is a DST or not) as the centre bolt is undone then the HP poppet is caused to rotate on the orifice seat just like a pastry cutter and a thin piece of dough.....and you could have the damage initally mentioned.
Ditto for rebuilding the push rod/mushroom diaphragm and spring MUST repeat MUST be assembled first AND SOME compression put on the spring to keep the mushroom forward so that when the poppet/balance chamber/centralbolt are refitted the poppet is held off its seat and not rotated against the orifice.

Once assembled you can screw the spring in or out as you wish to set the IP.

I know if you find that the IP is creeping, all be it slowly, then the HP poppet is the first thing to check for damage. I know because I've pastry cut a HP poppet myself....I was that soldier....

Also, from experience, after rebuild DON'T press the outer dryseal diaphragm to watch to see if the IP increases to simmulate "depth" 'cos when you let go the HP poppet is shut by more than the 9.4 bar in the balance chamber and as you can see is forcing the poppet onto the orifice edge which is nice and sharp.

Thats my penneth for today

Cheers

Brian C

 

[Zaphod]

I can understand your rationalization for working from the HP side first, but the Apeks service manual has the LP side being disassembled first. I've been following their instructions now through somewhere around 100 overhauls and never seen this problem. Also, if this was a common problem in following their procedures, I'm sure the folks at Aqualung would have seen it by now. They haven't.

Besides, it was clear that the cut did not occur during disassembly, because the removed material was already on the other side of the crown and firmly secured on the valve lifter pin near the head of the lifter. I can't see how that would be possible unless there was sufficient HP air to push it through the orifice. I'm confident this failure occured while the regulator was in service.

Lastly, I've found that it's actually quite useful to apply a small amount of pressure to the outer diaphragm during reassembly just as the outer collar is being screwed down. This allows much of the excess air to escape from the dry chamber. This advice was given to me by the service tech giving my Apeks training.

Essentially, I think the HP seat is not supposed to be very fragile and easy to cut. I believe that's why Aqualung is so anxious to see the failed part.

 

[brian cooper]

When stripping down the reg it doesn't matter what order you do it in IF you are replacing all the service bits.(Apeks do show the Diaphragm end being taken off first)

On rebuild they show the spring assembly being built up first with the spring compression ring screwed in 1/4" from the top....That is to keep the poppet from the seat.....I rest my case.

Once the HP poppet has any cut or blemish in it other than the settling in mark it could start to leak till the IP rises to lock it off or damage the poppet face more. I've had an IP go up to 9.4 bar normally then creep upto 17 bar, the 2nd stage still worked beautifully 'cos its balanced, however 17 bar blasting through the orifice could well grab hold of a chunk of the poppet and rip it off and jam it somewhere..

My prognosis is that the rubber seat on the poppet was somehow damaged either on assembly or in use then over time deteriorated and finally broke up, this is partly confirmed by the fact that the IP was creeping all be it from 135 to 150 psi beforestripping down.

Cheers

Brian C

 

[Asweptwing]

If I am following the concept you are describing, then I've experienced the same malfunction on a Dacor Enduro with the high pressure seat. This manifested itself by a freeflow when the tank valve was turned on. In this case a circle of the seal material was removed from the poppet valve seat. Here again less than an annual period which makes me wonder if the annual service was performed properly by the tattoed, ski cap, earring equipped son of the shop owner.