DumpsterDiver emergency ascent from 180'

[Caveeagle]

Yes, Things go bad.. Yes, Things just happen... All one needs to do is look at the airlines and for a better one, NASA.. They spend hundreds of millions of dollars and check and re-check and stuff still breaks.. Stuff goes sideways... Parts fail.. Brand new parts fail... Some parts go 1000's of hours and not fail.. Others 10 minutes...

When I had my 1st stage failure (I was testing how long it would go) I met a dive leaving Bonaire who had his 2yr old just serviced by the dealer Titan 1st stage fail one week in ( 20 dives ).....

And, The list is long of vacation divers bouncing deep on single 80cu... Sit in a dive shop on a place like Bonaire and you will see how the 90% of divers are....

Jim....

Love how you stick with your 90% statistic.

Just to reflect on your examples...

Are you aware of how airlines use six sigma failure analysis to maintain airlines safety? I fly several time a month and am pretty glad they push for a 99.99966% level of safety. Even a .1% failure rate in major components would be horrific..

Re NASA, volumes have been written on how failures and warnings were overlooked in the challenger loss. Perhaps this is a good analogy for DD's event. But not in the way you intended.

 

[EricTheDood]

Some here have claimed that a hp seat/seal can spontaneously fail, leading to this type of result. Fortunately, all HP seat failures I have seen show symptoms of IP creep first and gave me plenty of warning to allow me to pull from service.

DGX IP gauge, added to cart.

Yes, Things go bad.. Yes, Things just happen... All one needs to do is look at the airlines and for a better one, NASA.. They spend hundreds of millions of dollars and check and re-check and stuff still breaks.. Stuff goes sideways... Parts fail.. Brand new parts fail... Some parts go 1000's of hours and not fail.. Others 10 minutes...

It's all relative though. A scuba first stage is a very simple device that has gone through countless iterations of refinement over decades of widespread use.

This isn't the same as an aircraft part that is manufactured in low quantities at the absolute cutting edge of technology. And even so, many aircraft accidents are caused by human error. For example, in 1989, an United Airlines DC-10 crashed when a titanium rotor in the tailmounted engine exploded. It was revealed that the rotor had a manufacturing flaw, but more importantly, the flaws (cracks) were revealed during routine maintenance using dye penetrants and the part was put back into service rather than being replaced.

Ultimately, a poorly serviced regulator and a poorly serviced airliner are the result of the same fundamental problem - human error. Even though the bar is set much higher for the aircraft technician, coming up short ends in the same consequences. No amount of shrugging makes these accidents palatable. They don't just happen.

 

[oldschoolto]

T

DGX IP gauge, added to cart.



It's all relative though. A scuba first stage is a very simple device that has gone through countless iterations of refinement over decades of widespread use.

This isn't the same as an aircraft part that is manufactured in low quantities at the absolute cutting edge of technology. And even so, many aircraft accidents are caused by human error. For example, in 1989, an United Airlines DC-10 crashed when a titanium rotor in the tailmounted engine exploded. It was revealed that the rotor had a manufacturing flaw, but more importantly, the flaws (cracks) were revealed during routine maintenance using dye penetrants and the part was put back into service rather than being replaced.

Ultimately, a poorly serviced regulator and a poorly serviced airliner are the result of the same fundamental problem - human error. Even though the bar is set much higher for the aircraft technician, coming up short ends in the same consequences. No amount of shrugging makes these accidents palatable. They don't just happen.

The main rotor in the dc-10 had a single grain in the forging that the rotor was machined from that was the cause of the cracking and it was in-service for years without a problem.. I'm a pilot, former A/C owner... Master parachute rigger and Skydiver... Hotrod builder and years ago worked on and drove a Top fuel car... Stuff breaks all the time... Brand new stuff breaks all the time... You check and test and re-check and the part fails on the next use because of the last testing... You want to look at " Major " accidents .. I'm looking at the 100's of things that fail every day... Aviation is a lot bigger then the major airlines.. and how many flights are delayed or cancelled because of maintenance...

I'm done with this game...
Jim....

edit to add this...United Airlines Flight 232 was en route from Denver, Colorado to Philadelphia, Pennsylvania with a planned stop in Chicago, Illinois. The plane was a McDonnell Douglas DC-10 with three General Electric engines, one on each wing and one mounted in the tail structure (Figure 1). The tail mounted engine (engine #2) had no previously recorded problems and had been inspected approximately one year prior to the crash. The engine had already undergone five other inspections and was 1,101 take-off/landing cycles below the mandatory engine lifetime maximum of 18,000 cycles. While the engine was over fifteen years old, it was compliant with Federal Aviation Administration (FAA) standards. The plane was piloted by Captain Alfred C. Haynes, a former Marine pilot with thirty-three years of flight service with United Airlines. The copilot was William R. Records, and the cockpit also held flight engineer Dudley J. Dvorak and a pilot trainee. Additionally, DC-10 flight instructor, Captain Dennis E. Fitch was a passenger on the plane.

 

[Colliam7]

2. . . . In the UK it's very very common to have ali7 (which are slightly larger) and these tend to be cheaper here. . . . I'm going to be slightly controversial and say an ali7 is a better general stage cylinder than an ali40 (and I have both). But the reasons for that are personal to me and the dives I like to do.

I am not familiar with an AL 7 liter cylinder. What are the exterior dimensions (length and diameter)? And, what is the filled capacity / working pressure? Just curious to learn more about it.

 

[HantsDiver]

I am not familiar with an AL 7 liter cylinder. What are the exterior dimensions (length and diameter)? And, what is the filled capacity / working pressure? Just curious to learn more about it.

200 Bar

8.6 kg bare /empty weight

152mm Diameter

615 mm Length

Although like all cylinders some manufacturers will be slightly different. Not that unusual to get them filled to 220bar if you actually need it.

Price in the UK is about 40% less than an ali40.

 

[Schwob]

I'm done with this game...

Don't be.
Well maybe this thread ok it's in a rut, but I for one happen to enjoy reading the "more controversiol, but pending on viewpoint and background not necessarily unfounded at all point of view".
I am not enjoying it always for the inevitably ensuing deadbeat discussion but I do enjoy to think all those view points over and see where I fall, why I think I fall there. I am not saying I share your viewpoint 1:1, but I value it as well as the reasoning as additional food for thought. And I share some of it.

Stress induced failure can be triggered by a single kerf even if as small as a single grain especially in a highly loaded and somewhat over it's life fatigued part.
But yes, stuff fails. If all were known and all was tested then such failure could maybe be eliminated. But not all is known, not all can be tested and no-one would pay for it (outside of NASA...) and the more testing and servicing is introduced into a system the more it ultimately could contribute to the failure chain root cause statistics.
So, for stuff important to sagety of one sort or another, mostly (racing and flying (heavily weight reduced...) are scratching exception status) stuff is desigened to be on what is perceived the safe side of things... As more is learned all the time that perception changes all the time. And sometimes an overzeleous cost reduction, overpromising new material not tested sufficiently long, or a great improvement with an oversight wrecks havoc...
For so many reasons (improper or lack of service being not the least, but certainly not the only one of them), stuff fails.
But just as proper servicing and monitoring can dramatically decrease (not drive to zero) such failures, it can also contribute if not that proper.

I don't jump. Money & time are reasons, but the real reason is "who packed the chute, on what day, in what mood, how fidtracted,..." just dont want to deal with that thought... I don't climb (who laid that line and why should I trust it)... Planning to do my first own reg service this winter because I just cannot see why to trust someone else more who may be doing it with a two evening class or such and has to crank them out somewhat fast for a living. It's a lesser thing because where I dive 1st stage failures certainly should be recoverable and I have redundancy, "on board" but while I think I am cool-headed, there is only one way to find out and I plan to do what I can to not have to... Just my philosophy...

I certainly value this discussion
includong your contribution
as I would DD's if he were here.

And I am just a Dude working to get a little at a time further away in my habits from the 90% vacation divers you describe. Never mind the % number, I know what you mean, I started that way... but full well knowing what to think of my training and ferling a burning need to augment... when time permits ... every once in a while ... like (are you sitting?) on vacation...

 

[oldschoolto]

Okay... Here is a good look at how people are able to work under pressure and "MOST" can't...

How To Be Calm Under Pressure: 3 Secrets From A Bomb Disposal Expert - Barking Up The Wrong Tree

Jim...

 

[Colliam7]

200 Bar

8.6 kg bare /empty weight

152mm Diameter

615 mm Length

Although like all cylinders some manufacturers will be slightly different. Not that unusual to get them filled to 220bar if you actually need it.

Price in the UK is about 40% less than an ali40.

Thank you!

So, if I have done my math correctly, and made the conversion from what some / many would consider to be an organized, mathematically logical system of measurement to a somewhat 'interesting' one , the AL 7 liter compares to an AL40 as follows:

Cylinder / Length / Diameter / Weight

AL 7 liter / 24.2" / 6" / 18.9lb
AL40 / 24.9" / 5.25" / 15.3lb

IOW, the 7 liter is a wee bit shorter, a wee bit fatter, and a wee bit heavier. If I ever have a chance, I'd like to try one.

Also, it is truly a 200 bar working pressure, or a 207?

 

[EricTheDood]

The main rotor in the dc-10 had a single grain in the forging that the rotor was machined from that was the cause of the cracking and it was in-service for years without a problem.. I'm a pilot, former A/C owner...

The DC-10 accident is now a textbook example of crack propagation used by metallurgists and the solution has been improvements in VAR (vacuum arc remelting) refinement, nondestructive testing, and FEA computer simulations.

Every piece of metal that exists in the world contain multiple defects. Every case of catastrophic failure through crack propagation comes from a single defect - the largest one that happens to be in a high stress zone, orientated in just the right (or wrong) direction. If that defect didn't exist, it would just be a matter of time before the next biggest crack, also in the wrong place and the wrong direction, grew to critical size over repeated stress cycles and caused failure.

This accident wasn't the fault of the pilots, nor the FAA. Not sure how you gathered that from my previous post. The problem should have been caught during maintenance. The technicians performed NDT through dye penetrant testing and somehow the component passed. The call was likely made by engineers at GE, and many people learned the hard way from that bad call.

Anyway, back on topic, I find it difficult to believe that the first stage regulator in this case just blew up by chance. Yes, some first stages will inevitably fail, but the chances that they would happen on a 180' dive to a person who has a long record of riding the fine line between risky and reckless are very slim. I think it was bad servicing.

 

[oldschoolto]

The DC-10 accident is now a textbook example of crack propagation used by metallurgists and the solution has been improvements in VAR (vacuum arc remelting) refinement, nondestructive testing, and FEA computer simulations.

Every piece of metal that exists in the world contain multiple defects. Every case of catastrophic failure through crack propagation comes from a single defect - the largest one that happens to be in a high stress zone, orientated in just the right (or wrong) direction. If that defect didn't exist, it would just be a matter of time before the next biggest crack, also in the wrong place and the wrong direction, grew to critical size over repeated stress cycles and caused failure.

This accident wasn't the fault of the pilots, nor the FAA. Not sure how you gathered that from my previous post. The problem should have been caught during maintenance. The technicians performed NDT through dye penetrant testing and somehow the component passed. The call was likely made by engineers at GE, and many people learned the hard way from that bad call.

Anyway, back on topic, I find it difficult to believe that the first stage regulator in this case just blew up by chance. Yes, some first stages will inevitably fail, but the chances that they would happen on a 180' dive to a person who has a long record of riding the fine line between risky and reckless are very slim. I think it was bad servicing.

Okay, I'm glad you have perfect gear and it'll never fail... You are one special guy... I'm glad you know that every thing you do is safe and you can come to no harm... You live in a world that 99.99% of us don't... I've had brand new hose blow up.. I've had O-rings fail after only a few cycles... The trany in my brand new car went at 3000 miles and the second one had a pressure control problem in the valve body that I had to go to 3 dealers before I found a guy that knew what the hell he was doing and tracked it down and installed a 3rd trany...

People that think they are perfect and they only own the best... Are the ones that end up dead...

Jim....