[PSUBS-MAILIST] Bellows add

Sun May 24 21:39:08 EDT 2020

 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 belowmy requirements but at a level I could survive on ( as per DW) but toppingup with a rebreather solenoid valve that opens based on readings fromThree 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 O2flow 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 scenariowhere the scrubber takes the C02 out of the air but instead of replacing with O2from the bellows add, it is replaced with air from an air leak, & the cabin O2 contentwould 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 youhave an air leak that increases the cabin pressure then the Bellows Addsystem won't add O2. Ultimately you are relying on your O2 sensor & even then O2 sensorshave 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 effectthan 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 wantwith the water pressure pushing on a thin diaphragm that has a lever theother side that opens the valve. Maybe if you glued the lever to the insideof 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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