Question 1st stage recommendation for use with FFM and conventional 2nd stage

[Nemrod]

Hello,

I have a follow up question regarding the Neptune III. The first stage that OR bundles with the mask has a flow rate of 4800 L/min or 171 cfpm. Why such high flow rate? The accepted maximum RMV for heavy work is 100 L/min so at a depth of say 50 m that 600 L/min which is only 21 cfpm. The flow rate of OR first stage is 8 times more than the maximum required. Even considering a 20% overhead that is much more than would ever be needed unless one has multiple octopi hanging off the same 1st stage being used all at the same time. What am I missing here???

First stages with high advertised flow rates is mostly for that, advertisement. Well, a high performance first stage will not draw down under demand as much and will have a quick recovery. But the cylinder valve is the choke point as the flow rates there are between 40 and 60 cfm. A chain being only as strong as the weakest link.

An IP that varies over a dive of 10psi is a fairly tight specification and not unusual. A balanced second stage will not notice and a good downstream second should be just fine with a minimal IP change.

 

[DeepBlueDog]

First stages with high advertised flow rates is mostly for that, advertisement. Well, a high performance first stage will not draw down under demand as much and will have a quick recovery. But the cylinder valve is the choke point as the flow rates there are between 40 and 60 cfm. A chain being only as strong as the weakest link.

An IP that varies over a dive of 10psi is a fairly tight specification and not unusual. A balanced second stage will not notice and a good downstream second should be just fine with a minimal IP change.

I guess in that regard Apeks is an excellent choice then as it is as stable as the pyramids

 

[Nemrod]

I guess in that regard Apeks is an excellent choice then as it is as stable as the pyramids

I was not recommending a brand. Apeks owned by Aqua Lung is now been sold to a holding investment group. Many dealers have reported problems with not getting stock and spares. I was unable to get an AL DIN kit from local sources but was able through a scubaboard member. There has been an issue with some Apeks first stages and leakage at the diaphragm to body joint from inadequate pinch (?) but which models and how wide spread this issue has been I cannot say. Nothing is perfect.

 

[DeepBlueDog]

I was not recommending a brand. Apeks owned by Aqua Lung is now been sold to a holding investment group. Many dealers have reported problems with not getting stock and spares. I was unable to get an AL DIN kit from local sources but was able through a scubaboard member. There has been an issue with some Apeks first stages and leakage at the diaphragm to body joint from inadequate pinch (?) but which models and how wide spread this issue has been I cannot say. Nothing is perfect.

Yes I know about Apeks going to Aqualung and quality deteriorating. However, I bought my DS4 and XTX200 about 10 years ago so it was the true Apeks. I never had a problem with them. Now I don't know how it is in North America but in Europe there is no problem getting service kits for all the old Apeks.