Potential Safety Improvements in Rebreather Design

[tomfcrist]

Let us start with the Meg.

The report identifies faulty O2 Sensors and incorrectly assembled solenoid.

The faulty O2 sensor is a fault inherent with a component and not its assembly by the user.

So, it does not count.

The solenoid assembly is a factory technican approved job, not an end-user assembly task.

So, it does not count.

Equally, there is a solenoid in the HP2. Incorrect assembly by the factory (or the user tampering with it) cannot count towards non-compliance with the Clause.

Same goes with the O2 Sensors if they develop a fault intrinsic to one of the failure modes of the O2 Sensor.

The Clause is only concerned with user assembly of the rebreather (not factory assembly of user non-serviceable parts, or failure of components like O2 sensors).

Can a user physically take it apart? If so, the user can physically assemble it as well.....If it can be done wrong...its not compliant.

Where in this clause “It shall not be possible to assemble or combine the components or parts in such a way that it can affect the safe operation and safe use of the apparatus, e.g. by incorrect connection of the hoses to the breathing circuit.” does it say that the clause only refers to the user anyway?

I like how you try to add conditions to the clause though...Good try.

 

[descent]

... there is not one single rebreather on the damn planet that is compliant with Clause 5.1 of BS EN 14143: 2013 or BS EN 14143: 2003. Please provide some specific examples of units that you "Think" comply.

There is not one, yet. And I don't want there to ever be any.

The sad thing about a one-size-fits-all system like a body of laws is that after you put it in place, everyone begins to game the system.

In the case of Clause 5.1, I suppose I could design a totally compliant rebreather. One-piece, one-use. Workers at my factory (when they were not making ballpoint pens or plastic cigarette lighters) would charge each molded rebreather body with gases and fill the scrubber perfectly every time. Then they would seal it shut forever.

This machine would be exempt from Clause 5.1, because the user cannot detach or rearrange any of the parts.

I could sell them in blister packs, hanging in the Camping & Outdoor Dept next to the snorkeling kits and mosquito repellent.

Because I am making them at an industrial scale, they would be really inexpensive. Like, sixty bucks, max.

To get a "real" rebreather, then, you would have to illegally import one from some jurisdiction that had not agreed to the European CE standards and didn't want to trade with other markets where they think that those CE codes are important. Which nations are left? Those in less-developed parts of Africa?

I think a proper rebreather must have a user-serviceable interior. When I look inside, I expect to see highly engineered, craftsman built artifacts. Even if the materials are common, the design and elegance should impress me every time I open the thing up and touch any part of it.

I think every sane person wants to avoid a marketplace full of molded, one-piece, one-use rebreathers -- each one made on razor thin and shrinking margins. For most casual vacation divers, Walmart, and the gigantic new manufacturers of disposable closed-circuit toys, it would be a nice additional line of business.

For many of us here on ScubaBoard, this would be a highly undesirable end state of affairs.

To me, that means that BS EN 14143: 2013 needs to be rewritten or junked.

--

Also, hello Tom, it is great to hear from an instructor.

 

[gianaameri]

Can a user physically take it apart? If so, the user can physically assemble it as well.....If it can be done wrong...its not compliant.

Where in this clause “It shall not be possible to assemble or combine the components or parts in such a way that it can affect the safe operation and safe use of the apparatus, e.g. by incorrect connection of the hoses to the breathing circuit.” does it say that the clause only refers to the user anyway?

I like how you try to add conditions to the clause though...Good try.

Not really.

The HP2 I understand comes with a Shearwater Controller.

If as a user I perform an action I am not supposed to, and it is reserved for an approved factory technician, like taking the screws off the Shearwater Controller, and fiddle around with the electronics (or the solenoid), this has nothing to do with the Clause.

The user is performing an action he is not competent to perform or permitted to perform. So, it falls outside of the Clause.

It is reckless tampering with the unit life-support electronics.

I think we are still on topic as the conversation has served to clarify the meaning of the Clause which the HP2 has been found to be non-compliant by the Coroner and HSL as it pertains to this fatality.

Jillian Smith did not tamper with the electronics (solenoid or controller) of her rebreather.

She failed to assemble it correctly, or as HIGHwing has suggested, somebody else failed to assemble it correctly on her behalf (the latter being pure speculation by HIGHwing at this stage).

That is why the HP2 failed the Clause. It was possible to assemble it incorrectly resulting in a dangerous failure.

 

[tomfcrist]

Not really.

The HP2 I understand comes with a Shearwater Controller.

If as a user I perform an action I am not supposed to, and it is reserved for an approved factory technician, like taking the screws off the Shearwater Controller, and fiddle around with the electronics (or the solenoid), this has nothing to do with the Clause..

You are still making up the rules as you go along. What is in Black and White?

The user is performing an action he is not competent to perform or permitted to perform. So, it falls outside of the Clause..

Quite honestly she wasn't competent to perform the action of DIVING the unit....Does that also make the unit non-compliant?

I think we are still on topic as the conversation has served to clarify the meaning of the Clause which the HP2 has been found to be non-compliant by the Coroner and HSL as it pertains to this fatality..

The Coroner and HSL are completely disregarding the human error/ignorance/lack of give a damn in this accident.

That is why the HP2 failed the Clause. It was possible to assemble it incorrectly resulting in a dangerous failure.

You still don't get it. I can assemble ANYTHING improperly. If it is capable of being taken apart, someone will put it together wrong.

Lets get off that point though. What was the proximate cause of her death? The ability(obviously) of the unit to be assembled incorrectly? Or that whoever assembled the unit did so incorrectly, followed by an obviously improperly performed/omitted predive check along with a user that couldn't recognize that her unit was a cluster?

John, this post is WAYYY off topic to the thread you put it in. Nothin but love for you though

 

[Omisson]

Just an update on the rebreather death that started this thread-

The incident occurred March 2014- 3 minutes after submersion.


- the oxygen sensors were labelled “Do not use after Nov 2013";- and gave inaccurate readings of 0.0, 0.16, and 0.18 when exposed to air, 0.21.

 

[boulderjohn]

John, this post is WAYYY off topic to the thread you put it in. Nothin but love for you though

Tom, the problem is blending of topics. The other thread is explicitly about the death of an individual. References to her rebreather and putting it together are on topic.

Suddenly we were talking about whether Megs were compliant. A couple different posters pointed out that such discussion was off topic, and I agreed. I started moving posts. Suddenly we went back to the actual incident.

 

[mmadiver]

That is why the HP2 failed the Clause. It was possible to assemble it incorrectly resulting in a dangerous failure.

It is possible to incorrectly assemble any rebreather. A manufacturer can key the loop hoses so they can only be attached in the proper orientation but that doesn't stop me from cross threading them, leaving off an o-ring, or failing to tighten them down all the way. How is a manufacturer supposed to prevent someone from failing to screw down their loop hose all the way?

The answer is the implementation of standardized assembly procedures via checklists that incorporate steps to verify proper assembly (i.e. step one: install loop, step two: negative check). Just like every CCR manufacturer already provides.

Adherence to the manufactures checklist is, in my opinion, step one of the assembly procedure. Manufactures can build the most intelligently designed piece of gear that minimizes the potential for human error but at some point it has to be assembled and operated by a human. Errors in assembly and operation are mitigated via checklists.

So, in the case of the casualty at the center of this discussion - this was not a case of poor design on the manufactures part, this was cognizant user decision to not follow the prescribed assembly procedures, which if followed would of resulted in a correctly assembled rig.

 

[tomfcrist]

Tom, the problem is blending of topics. The other thread is explicitly about the death of an individual. References to her rebreather and putting it together are on topic.

Suddenly we were talking about whether Megs were compliant. A couple different posters pointed out that such discussion was off topic, and I agreed. I started moving posts. Suddenly we went back to the actual incident.

John I get it.. I really do. Im busting your balls.

Sometimes you have to let the topic wander a bit to prove someone's point though. The MEG/EVO/Inspo comments were in direct relation to the fact that any rebreather can be put together FUBAR.

Like I said, no hard feelings.

 

[Dr. Lecter]

It is possible to incorrectly assemble any rebreather.

That. Given the right - er, wrong - tools and level of mindless (or mindful) effort, I can put anything as complex as a CCR together wrong in some serious way. Whether by mistake or intent, it'll go and hang together. The only way to prevent this is to build according to a checklist, and test things as you do so. Then once you're done, you test some more.

None of which is to say that it's a bad idea to implement designs where deemed effective (saying where "possible" is just more junk language) that make mix-ups harder to do and easier to detect. But the silly little standard Gian keeps waving around as somehow important and/or capable of being met or failed is just word salad.

 

[Douglas Ward]

What body certifies rebreather to the CE standard?

If they said it was compliant before release I don't think the opinion of a coroner can deem it irrefutably non compliant.

Is that how it works in Europe?

Are coroners trained in high tech dive equipment?