XT1 1st stage failed CLOSED at depth

[BRT]

I want to add that, there was a recall on the U S Divers Cousteau regs, back in the day, because the seat could come loose and move towards the piston, resulting in a "fail closed" condition. It had happened once on an actual dive but no one was hurt. The fix was to add a retainer for the seat.

For those not familiar with the Cousteau, it's a flow-through piston design.



Corrosion, in such a shape to make a ramp.

But if it moved 20 thousandths it would move all the air it needed to.

 

[guruboy]

I want to add that, there was a recall on the U S Divers Cousteau regs, back in the day, because the seat could come loose and move towards the piston, resulting in a "fail closed" condition. It had happened once on an actual dive but no one was hurt. The fix was to add a retainer for the seat.

Similar recall/fix was done for the old Calypso as well.

 

[japan-diver]

Has the reg been taken apart an looked at? The XT design is very similar to many other regs produced today and a few would be made at the same factory under different brand names. These symptoms would be very hard to duplicate on a workbench without some major breaking of pieces and then even that should allow the user to notice something not working right even on the surface. This can also be caused by something as simple as the tank valve not being all the way open so air flow is not high enough to refill the lines under pressure but high enough to register on the pressure gauge- this would be my first guess as to what happened as opposed to the reg not working minus some missing or obvious broken part.

 

[guruboy]

Reg is getting shipped back today for DR to look at.

 

[guruboy]

This can also be caused by something as simple as the tank valve not being all the way open so air flow is not high enough to refill the lines under pressure but high enough to register on the pressure gauge- this would be my first guess as to what happened as opposed to the reg not working minus some missing or obvious broken part.

I can guarantee you the tank valve was open.

Also, considering a dive time of 15mins before failure, I don't think this "tank not open" theory is even remotely plausible. My friend has good SAC, but not that good.

 

[snowdog61]

So to keep me straight, the HP plug was pulled to vent the 1st stage after which, it seemed to work nominally. Was the LP side vented prior to pulling the HP plug? Obviously there was no flow in his 2nd stage, but was a LP plug pulled or anything done otherwise to verify that the IP was below the cracking pressure? This must have been a very unnerving episode for your bud. Other than a gross assembly error or catastrophic part failure, there's not much to cause a lockshut. Fail open is pretty easy to see. scary stuff not knowing

 

[guruboy]

So to keep me straight, the HP plug was pulled to vent the 1st stage after which, it seemed to work nominally. Was the LP side vented prior to pulling the HP plug? Obviously there was no flow in his 2nd stage, but was a LP plug pulled or anything done otherwise to verify that the IP was below the cracking pressure?

The 2nd stage purge buttons were pressed and the power inflator inflate button was pressed.

 

[Mouth Breather]

Good job not panicking, glad no one got hurt. I also use XT1s for my technical setup so...watching.

 

[snowdog61]

The 2nd stage purge buttons were pressed and the power inflator inflate button was pressed.

so an ambient IP and locked up solid. WOW! Don't know the XT but will assume it is a dry seal diaphragm (ie MK16/18). With 200ish nominal dives on this prior to his failure, this is an enigma. Lots of people watching this so thanks for posting

 

[guruboy]

With 200ish nominal dives on this prior to his failure, this is an enigma.

This was the first dive with the XT1 first stage in question.