Sealed Diaphragms: Ambient Pressure Transmitter Failure at Depth

[rsingler]

Does anyone have a picture of the crushed end of a plastic ambient pressure transmitter when a sealed diaphragm was taken to great depth and the transmitter couldn't sustain the absolute pressure?

Heard a story of an ?Apeks? where the transmitter failed, with loss of relative IP at depth.
For example, if the transmitter below were 1" diam, that's .7 square inches.
At 200 feet (5 "extra" atmospheres), that's about 50 lb force on that plastic tip.

Yeah, I know. Nobody takes sealed diaphragms deep because of "overbalancing".
So is this urban myth?

 

[Centrals]

I always wonder what kind of regulator that the saturating divers used at great depth.

 

[BoltSnap]

This is why a "piston" type regulator SP/Atomic is superior to diaphragm type?

 

[Centrals]

I know the late John Bennett used Apeks FST to 308m in 2001.

 

[lexvil]

Aquatic legend (as opposed to urban) while possible I guess it seems unlikely at 50psi that occurs slowly.

 

[halocline]

At 200 feet (5 "extra" atmospheres), that's about 50 lb force on that plastic tip.

Isn't 200 feet six atmospheres greater than the surface?

Never heard of a sealed diaphragm pressure transmitting piston getting crushed by the pressure, but I guess it could happen. If it did I would think that the outer diaphragm would quickly fail and then you'd have regular depth compensation but no sealing.

 

[rhwestfall]

I guess I'm wondering why you feel that transmitter can't take an axial load of 50#....... That isn't much.

Now I wish I had access to an axial compression machine (UTM)..... my days at the University and the Testing Lab are long behind me..

 

[Geo7]

I always wonder what kind of regulator that the saturating divers used at great depth.

At the end of this video you see a DS4, sometimes saturation divers work at "just" 120 meters...

The transmitter crush is not an urban myth: This thread documented the depth at which the crush occurs: CCR First Stage Regs - IP Stability

There is also this youtube video clearly showing the same IP behaviour and crush depth in a mini chamber: Tek3 (sealed) vs US4 (unsealed).

However, you have to be beyond 600 feet to worry about this... And filling the chamber with Glycerin, Vodka, etc should prevent this for those dives.

 

[Centrals]

The transmitter crush is not an urban myth: This thread documented the depth at which the crush occurs: CCR First Stage Regs - IP Stability

This article has NOT mentioned the complete failure of the transmitter. It was all about the stability of the IP.

 

[Geo7]

This article has NOT mentioned the complete failure of the transmitter. It was all about the stability of the IP.

Ok, but the decreasing IP (red curve) of the DS4 in the second graph speaks volumes. That's an IP of only 4 bar above ambient, and at that depth likely unbreathable. The way that happens is by crushing the transmitter.

In any case those curves give some insights at what depths to expect the deformation to occur, or did I miss something?