[PSUBS-MAILIST] Bellows add

Sun May 24 22:17:11 EDT 2020

Hank,
yes I am using a rebreather solenoid for top up.
Alan

> On 25/05/2020, at 1:39 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Alan,
> Based on what Bruce Jones said on the topic on FB, they must use solenoids also.  I am assuming of coarse.
> Hank
> 
> On Sunday, May 24, 2020, 5:10:37 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> 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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