Failure points vs redundancy

[macado]

I have no dog in this fight but I have had very little SPGs that have actually failed on me. Some of mine are approaching 15 years old at this point. Unfortunately I have a very poor track record with HP hoses. I've had 4 fail on me and my wife within the last 2 months. Last year we had 5 go in the span of 6 months. I literally cannot win. These are mostly 6" and 9" stage/sidemount hoses so they see a lot more stress but some also were 24" length.

They weren't even bought at one location either, several from EE, Cave Country, Protec Tulum, DiveGearExpress. I'm not blaming any particular vendor. I don't know if it's a systematic problem with current HP hoses.

The last failure yesterday pissed me off. We had to hike 6 tanks, scooters, in the jungle (admittedly not the far), and crawl in a mud pit. I just started getting into gear when the hose burst requiring me to climb out of the cave and go back to my truck.

The end result: I said screw it and bought a bunch of those stainless steel HP hoses. I am going to see if they are any more durable or reliable. I also splurged and ordered a Petrel 3 with 2 Shift transmitters for my primary sidemount bottles. I have no idea if I will like AI or not but if these transmitters are even marginally more reliable than HP hoses I will be happier. My stages will still have traditional SPGs on them so I guess those will just keep failing.

 

[lexvil]

Don’t obsess over failure points, base redundancy on the type of diving you do, cave divers have a whole different set of realities and consequences they face, open water recreational divers have far fewer.

Everything is a potential failure point not just at the ends and o rings. Carry redundancy to fit the situation, stop worrying and dive.

As to the transmitter vs SPG, I have been using wireless hoseless for several years but keep an SPG in a back up in the car, if the transmitter fails turn the dive, don’t worry it’s not the end of the world, except cavers.

 

[J-Vo]

If your brain is the most likely thing to fail, is adding another brain just adding a second most likely thing to fail? Does it double safety or double risk?

 

[boulderjohn]

If your brain is the most likely thing to fail, is adding another brain just adding a second most likely thing to fail? Does it double safety or double risk?

Ironically, when I was first doing tech training, the instruction was as far from the opposite of this point of view as you can imagine. We were taught, in pretty much these words, that we should never, ever use computers because it is possible for them to make a mistake. We should instead rely upon "the computer between the ears," which never, ever makes a mistake. It was simply inconceivable that a diver on a long tech dive would improperly add numbers, not notice if the depth being dived at any moment was deeper than the planned depth, etc. Most importantly, any diver could easily compute average depth during the deepest parts of the dive by doing the simple math required to maintain a running average, and it was inconceivable that the math would be wrong.

 

[dmaziuk]

If your brain is the most likely thing to fail, is adding another brain just adding a second most likely thing to fail? Does it double safety or double risk?

It's called split-brain

We used to run a bunch of active/passive pairs but those were mostly used for zero-downtime maintenance reboots, and even then they'd occasionally get split-brained. For real High Availability you need the tie-breaker node.

Always an odd number, the brains must be.

 

[mr_v]

I have no dog in this fight but I have had very little SPGs that have actually failed on me. Some of mine are approaching 15 years old at this point. Unfortunately I have a very poor track record with HP hoses.

Same! Purchased from the same sources as you've outlined. Will try SS hoses, but for now found stage (mini) SPGs to be quite reliable for what I need. I have a small collection of them.

 

[macado]

I had another HP hose fail a couple weeks before my last post. That brings my total failure HP hose count to 5 since late December / January between my wife and I. I'm not joking.

On the plus side, I've done 7 straight days of cave diving using Shearwater Swift transmitters and my new Petrel 3. They have so far worked flawlessly and have not dropped out. Time will tell how reliable they are. My normal stage bottles still have SPGs on them.

I think the transmitters are pretty well protected directly attached to the first stages. I'm going to keep them like this.

 

[mr_v]

@macado, I heard rumors suspecting hose quality issues at one of the global suppliers. Just out of curiosity, what were the hose brands in your cases?

 

[macado]

@macado, I heard rumors suspecting hose quality issues at one of the global suppliers. Just out of curiosity, what were the hose brands in your cases?

They were all over the map. A lot were from DiveGearExpress. Others were from Cave Country Dive Shop, Extreme Exposure, Protec in Tulum. To be clear, I am not blaming any of these shops. I don't know actually know if they all source from same supplier or location.

 

[mr_v]

They were all over the map. A lot were from DiveGearExpress. Others were from Cave Country Dive Shop, Extreme Exposure, Protec in Tulum. To be clear, I am not blaming any of these shops. I don't know actually know if they all source from same supplier or location.

I am not affiliated, but if you want to try more hoses, check out Piranha stuff. I have purchased a few hoses from these guys and they look a lot thicker/stronger than the alternatives:

9" HP Rubber Hose

Our hoses are made from the highest quality materials available Our High Pressure hoses have a 7/16 fitting and will fit most of today's first stages Working pressure of 4500 - 6,600 psi ensures against hose failures Burst pressure rating of 30,000 psi gives you that extra safety margin Great HP...

www.piranhadivemfg.com