Apeks DS4 alternatives for rebreathers

[slimshady]

I concur. I like the rEvo CMF, but LOVED Fathom's needle valve.

So a Hybrid has a needle valve and a blocked first stage as well as a solenoid?

 

[formernuke]

Correct

 

[Wibble]

So a Hybrid has a needle valve and a blocked first stage as well as a solenoid?

There’s two ways of injecting a fixed amount of oxygen into a loop:

• A small "orifice", literally a tiny hole, with a fixed intermediate pressure of gas behind it forcing a fixed amount of oxygen through provided there is at least 2bar/ata more intermediate pressure than the ambient pressure. These require a blocked first stage to provide a fixed pressure that doesn’t vary with depth. The flow volume is adjusted by adjusting the first stage intermediate pressure or changing the size of the orifice.
  The drawback with this is that a certain depth around 2ATA less than the intermediate pressure the oxygen flow slows and stops.
• A needle valve is adjustable but it’s not possible to know how much oxygen is flowing each moment. Some needle valves can be adjusted with a "click" mechanism and need vigilance.

Revo’s use the fixed orifice due to its simplicity and reliability. Revo’s also have an oxygen solenoid that injects oxygen on command of the controller computer, just like all other eCCRs but due to the orifice continuously injecting oxygen, rarely need to fire — if stressed or working hard then it will inject more frequently.

Manual (mCCR) rebreathers use an orifice or needle valve so that oxygen levels don’t suddenly decline as there is no controller electronics and a solenoid as per an electronic (eCCR). As Revo’s have both an orifice and a solenoid+controller, Revo calls them hybrid rebreathers (hCCR).

A Revo’s intermediate pressure is fixed at 11.5 bar/ata or thereabouts. This equates to 105m/350ft meaning that a Revo needs special techniques to dive beyond 85m/280ft (2ATA above the IP), e.g. having a separate oxygen source and manually injecting when below the IP shutoff point.

It is possible to plug the orifice on a Revo, unblock the oxygen first stage, then run the revo just like any other eCCR. This means the solenoid fires far more frequently so the solenoid battery needs replacing more frequently.

 

[J-Vo]

I've been using some third party Apeks kits for over a decade and have had no issues. First thing to go is always the turret o-ring (just small bubbles). Most of my DS4s are currently 5+ years without service.

 

[The_Sea_Hunter]

Back on topic here. I would suggest you consider sealed Scuba Pro MK17's for Dil and Halcyon HD-50's for O2. Both are same breed and have adjustable IP's. I believe Scuba Pro uses reg service kits found more plentiful worldwide. I carry a spare HD-50 so I send one off for service while using the other.

Good Luck

 

[formernuke]

Back on topic here. I would suggest you consider sealed Scuba Pro MK17's for Dil and Halcyon HD-50's for O2. Both are same breed and have adjustable IP's. I believe Scuba Pro uses reg service kits found more plentiful worldwide. I carry a spare HD-50 so I send one off for service while using the other.

Good Luck

They are both balanced and as such not good for O2

 

[The_Sea_Hunter]

They are both balanced and as such not good for O2

Thanks for your input Nuke. Can you please educate me as to why Balanced Diaphragm regulators are NOT good for O2? Please cite reference material OR if this is from a personal experience. Manufacturers like DiveRite produce a Balanced diaphragm for O2 use. I think it is the FT1??

All sources withholding the O2 cleaning and handling that one should adhere to.

Thanks in advance

 

[rddvet]

Thanks for your input Nuke. Can you please educate me as to why Balanced Diaphragm regulators are NOT good for O2? Please cite reference material OR if this is from a personal experience. Manufacturers like DiveRite produce a Balanced diaphragm for O2 use. I think it is the FT1??

All sources withholding the O2 cleaning and handling that one should adhere to.

Thanks in advance

I’ve heard that claim for many years. I dive the halcyon regs on my and my wife’s ccr oxygen bottle no issue. Including both plugged and unplugged.
I just ignore it. I’m not a reg tech but I have never had a single issue with balanced oxygen regs.

 

[formernuke]

Thanks for your input Nuke. Can you please educate me as to why Balanced Diaphragm regulators are NOT good for O2? Please cite reference material OR if this is from a personal experience. Manufacturers like DiveRite produce a Balanced diaphragm for O2 use. I think it is the FT1??

All sources withholding the O2 cleaning and handling that one should adhere to.

Thanks in advance

The revo is a mccr or hccr depending on which one you have. This means there is a orfice constantly adding O2 to the loop using a non balanced reg means the flow adjust as you go deeper. If you use a balanced reg the adjusting IP will feed to much O2 into the loop and result in a high ppo2. This is why if revo divers want to go below below 300 feet we would need offload o2 etc.

 

[Angelo Farina]

The revo is a mccr or hccr depending on which one you have. This means there is a orfice constantly adding O2 to the loop using a non balanced reg means the flow adjust as you go deeper. If you use a balanced reg the adjusting IP will feed to much O2 into the loop and result in a high ppo2. This is why if revo divers want to go below below 300 feet we would need offload o2 etc.

I think you are confusing depth-balanced with tank-pressure balanced.
As we already discussed, for feeding an orifice with constant flow you need to eliminate the depth-balancing (which is better known as depth-compensation), ensuring the IP stay constant at the same absolute pressure independently from the ambient pressure.
This is obtained closing the holes which allow to the ambient pressure to act on the piston.
The fact that the reg is balanced relatively to the tank pressure, instead, is a good thing even when the ambient pressure compensation is disabled.