[PSUBS-MAILIST] Bellows add

[Alan via Personal_Submersibles]

Hank,
I am using a combination. 
Am having a click style paediatric flow regulator set at a flow level below
my requirements but at a level I could survive on ( as per DW) but topping
up with a rebreather solenoid valve that opens based on readings from
Three O2 sensors. A piece of electronics reads the O2 level from the three O2 
sensors & takes the average of the two with the nearest readings to each other as true.
This system will pick up when one O2 sensor is faulty.
When I saw the Triton 3000 years ago, the pilot told me they just adjusted the O2
flow from a needle valve. I could have this wrong but I did ask specifically about it.
Mind you they have a big cabin & would have lots of time to make changes.
Alan

> On 25/05/2020, at 10:18 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Alan, The problem with your scenario is there is a preset amount of O2 flowing all the time, so the altimeter would detect an air leak.  Unless the air leak was identical to the lack of O2.  BUT, I am not adding a bellows add because I got some good advice from a saturation dive operator in South Africa.  I am going with exactly what you recommend and just pulled one out of storage.  A regulator with a flow meter on it.  This is much better than a paediatric regulator with set points. 
> Hank
> 
> On Sunday, May 24, 2020, 2:37:16 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Hank,
> the altimeter wouldn't help in the case of an air leak, as you could have the scenario
> where the scrubber takes the C02 out of the air but instead of replacing with O2
> from the bellows add, it is replaced with air from an air leak, & the cabin O2 content
> would slowly diminish with the pressure staying the same (hope that makes sense).
> To save space & cost & if you are the only person diving this sub, you could just have a needle valve & adjust the flow based on O2 readings.
> Alan
> 
> 
>> On 25/05/2020, at 8:08 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> 
>> Alan,  I was thinking the same idea with the scuba regulator.  I rely on the altimeter and am a good habit of checking it.  Also I am like the canary in the mine.  I get real sore ears when the pressure changes in the sub.
>> Hank
>> 
>> On Sunday, May 24, 2020, 1:24:32 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> 
>> 
>> Hank,
>> there is a flaw with the Bellows Add system that I can see, in that if you
>> have an air leak that increases the cabin pressure then the Bellows Add
>> system won't add O2. 
>> Ultimately you are relying on your O2 sensor & even then O2 sensors
>> have a large failure rate & a life expectancy.
>> Rebreathers use 3-5 sensors for redundancy & compare signals.
>> For a large sub you have a lot more time for any failure to have an effect
>> than you would in a sub like your 1 person or Cliff's. 
>> Maybe if you insist on a Bellows Add system, have an extra O2 sensor.
>> The second stage regulator works the opposite way than what you want
>> with the water pressure pushing on a thin diaphragm that has a lever the
>> other side that opens the valve. Maybe if you glued the lever to the inside
>> of the diaphragm you could open a valve with it. You would only use the 
>> regulator valve though, as the rest would be useless.
>> Better still, make a small sealed enclosure with a diaphragm on one face
>> & attach the second stage lever mechanism to the outside against the diaphragm.
>> That way you could make a screw in / out fine tuning adjuster as per DW.
>> Alan
>> 
>> 
>>> On 25/05/2020, at 1:50 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>> 
>>> Hi All, I am looking for ideas on how to make a automatic O2 feed similar to the DW bellows add.  I want a non electronic system.  I was thinking about a scuba second stage regulator conversion, that senses negative pressure to release O2.  Sean???
>>> Hank
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>> 
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