Failure rate of first stages? what is real need for a spare first stage on a trip

[Bigbella]

What do the above terms (popped & blowout) mean? What are the:
Causes.
Symptoms.
Treatment.
Prevention.

Thx

It's commonly a failure of the high pressure seat -- see photo, upper right -- (a rigid, nylon cup-shaped piece, within the first stage, replaced with each overhaul), along with, potentially, a damaged diaphragm, which would cause a fizzing, akin to Alka Seltzer. The symptoms, short of sudden failure, would include a creeping -- increasing, non-correctable -- IP. Failure, in some newer regulators, would be a sudden release of air through a 1st stage overpressure valve; in some brands, through an OPV in the LP hose themselves. Prevention would include, among other things, consistent regulator maintenance . . .

 

[chillyinCanada]

I've witnessed an Aqualung diaphragm first stage catastrophically blow its HP seat at 40m on the President Coolidge in Vanuatu... the diver was enveloped in a ball of bubbles as the tank drained in a few moments.
Fortunately he kept his cool and buddy breathed off the guide up to the deco stop.
Apparently the HP seat polymer material delaminated from its carrier (!)

I've personally experienced the HP seat 'fail to regulate IP' on my Kraken DH reg and vent air at 200psi through the octo... only at about 20m, apparently a faulty batch of HP seats, a couple of others reported.
Happened on a LOB in East New Britain, PNG, I always carry a spare single hose reg set so switched to it and fortunately didn't lose a dive.

I also carry a fairly comprehensive stock of cable ties, common o-rings (esp those tiny -003 HP swivel ones!), BC inflator kit and tool, silicone grease etc and have either used them myself or helped out other divers on pretty much every remote area LOB I've been on.

A spare reg set is very good insurance on any dive trip, local or remote LOB.

Really amazing to me as I've never seen anyone's reg go sideways on the lob's that I've been on. BCD's, yes, regs, no, at least not to the point of requiring replacement.

(Knock on wood)

 

[Couv]

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[halocline]

I have never had a 1st stage go bad on a trip. I have seen a few extrude o-rings at the yoke retainer or port plugs when pressurized. If you simply check your reg for leaks before the trip, it's really likely it will work fine.

 

[JamesBon92007]

I've been diving for 50 years and have thousands of dives and have never had a regulator fail, other than a slight, slow leak at the second stage. Since I began taking a checked bag I usually bring along an extra regulator and gauges mainly because i rebuilt them recently and want to try them out. On my last trip I ended up switching the octopus second because of one of those small, slow leaks. I was glad I brought it. I also bring along a few little items for "just in case" and on my last trip someone needed a new regulator mouth piece and I just happened to have one. I always check my gear before a trip but sooner or later something is bound to go wrong.

 

[broncobowsher]

Your slightly leaking 2nd stage may actually be a failing 1st stage. If you purge it and it is happy for about 10 seconds before it starts blowing bubbles again, that is probably IP creep. The second stage is overpowered and bleeds off and the leaky 1st stage is stabilized by the amount of leakage in the 2nd stage.

 

[JamesBon92007]

Your slightly leaking 2nd stage may actually be a failing 1st stage. If you purge it and it is happy for about 10 seconds before it starts blowing bubbles again, that is probably IP creep. The second stage is overpowered and bleeds off and the leaky 1st stage is stabilized by the amount of leakage in the 2nd stage.

In one case all it took was about a 1/8" turn of the second stage orifice and it worked fine. In another case it was an old US Divers Calypso and I didn't have a wrench with me to adjust it but I'm pretty sure (based upon my fabulous memory) it was the LP seat was getting worn. Both first stages tested OK for no IP creep on my test gauge but it's certainly good to know the symptom you just described. I can remember having only one first stage with clearly indicated IP creep and it was an ebay "treasure" that looked like sunken treasure--it was very badly neglected and corroded. Is it likely that a second stage that is leaking because of an unstable first stage would work OK on another, stable first stage?

I"m not saying that anything is absolute, I'm simply saying that in my personal experience a first stage failure is unlikely unless it's neglected.