Single Point Failures

[OutlawCaver]

I am analyzing single point equipment failures in the most typical backmounted cave diver configuration that I see at most common dive sites. I define single point failure as one in which you have no redundant alternate. Please let me know if I have missed any. I realize that other equipment configurations may eliminate some of these failure points. At this point I am only interested in the backmounted, manifolded, drysuited cave diver.

Thanks

a) Drysuit as used for exposure (seals, zippers, seams, valves)

b) BC (buoyancy cell, corrigated hose & clamp fittings, inflation/deflation device, exhaust valves)

c) Fins (strap, springs)

d) SPG & hose

e) Manifold isolation valve & cross over piping

f) Tank bands & bolts

g) Harness (backplate, straps, webbing & buckles)

Assumptions made:

Spare mask is carried
LP inflator hoses are compatable with both drysuit and BC inflators
Single bladder or bladderless BC is used
Drysuit is an undesirable buoyancy device
Brain is working fine (can't assign a probability of failure to it anyway)

[Bill Rotella]

I had first stage failures twice, once in Mexico, and the other at Telford.............Thank God they were both out of the water. You should also add second stage free flow failures.

[FW]

I had first stage failures twice, once in Mexico, and the other at Telford.............Thank God they were both out of the water. You should also add second stage free flow failures.

I think he is talking about single point failures. You *should* have two regulators anyway

[aainslie]

...Then shouldn't drysuit and BC be dropped off the list since both are buoyancy devices?

Fins too - as I've learned the hard way, one is enough to exit the caves!!!

[sskasser]

Go sidemount and you can drop off items D-F as well.

Granted this only applies to Florida caves, but I would strike "a)" as well. I had a wrist seal go at the beginning of a dive, flooding the whole suit, and since I wear Polartec undergarments, I continued the dive and never got cold.

This DEFINITELY doesn't apply to Missouri caves.

[OutlawCaver]

No way I am pushing on with a flooded drysuit. Loss of trim and with a potentially extensive deco obligation, I am out of there. In 1989, I had a complete drysuit flood when a boot split open in a Leon Sinks passage. With a 40 minute swim out with depths to 150, black silt floor and 60 minutes of deco, my dive was over. Regardless of whether it creates a situation for which you call your dive, it is still a single point failure.

[ARY]

h) diaper. i had at least one dive when i turned on thirds of its capacity
Seriously - you can not use fins effectively on long distance swim.

[Gary]

You should also add second stage free flow failures. I think he is talking about single point failures. You *should* have two regulators anyway.

I was gonna say "second stage free flow" anyway because his assumptions didn't say that he'd be able to reach his valves at all times. What is it? 30 sec to drain an 80? Bad news if you're stuck in a restriction when this happens (with a manifold).


You should throw out "SPG & hose" though. There is not enough air lost thru them to support a swimming diver. It'd be a concern worthy of turning a dive on but not critical.

[skip]

lp hose failure is more serious than the hp hose failure, so maybe lp hose should be added/kept on list? but honestly, i don't really know what a single-point failure is. clue me in please. thanks.

-skip