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

[Genesis]

... but the issue here would have to be rotation against a closed seat that could cause this kind of "cut-out."

I don't see how assembly (short of botching it) would do this, but heh, maybe I'm wrong. I don't have an Apeks here to play with.....

 

[Diver0001]

Zaphod once bubbled...
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

Seems to me that there could be a simpler explanation. Couldn't this have been caused by adjusting the IP with the reg under pressure?

R..

 

[Zaphod]

Keep in mind that a diaphragm first is intended to be adjusted with the reg. under pressure, unlike a piston. Besides, if we go with the theory that a rotation along a sharp surface is necessary to cause this kind of damage, I can't imagine how the rotation of the adjustment screw would be transferred all the way down to the seat itself. There are numerous places for the rotation to be translated into a simple lateral motion, which means just more pressure on the crown, but no rotation - the same way it works as you decend. Since Apeks regs have been used at extreme depths with this crown/seat interface under huge pressures, I can't see this being a problem.

Diver0001 once bubbled...


Seems to me that there could be a simpler explanation. Couldn't this have been caused by adjusting the IP with the reg under pressure?

R..

 

[Zaphod]

Well, the official response on this failure has been issued by Aqualung and it is a lame one. Officially, they don't know what caused the failure. There is no issue with the seat material or thickness. Asked if this failure could be caused by improper assembly as postulated, the answer was "no," unless it was disassembled and reassembled numerous times incorrectly with the same seat. One single improper assembly will not cause this failure - the seat material is tough enough to take it. Finally, after actually seeing the seat, they acknowledged that there had been one other reported failure of this type. Given the infrequent nature of this failure, I guess they consider the case closed.

The crown inside the body was re-machined and the Aqualung-rebuilt first stage is now in the owner's hands.