Detuning regulators for cold water

[Oitzu]

Aqualung lowers the mp from 9.5 to 8.5 bar for cold water. It comes at cost of higher wob though.

 

[Umuntu]

Aqualung lowers the mp from 9.5 to 8.5 bar for cold water. It comes at cost of higher wob though.

I'm not sure if the WOB would actually be higher just from the lower IP of 8.5 bar if the second stage is balanced and tuned to the first stage at IP of 8.5 bar. The balancing of the second stage and the tuning will eliminate the effect of the lower IP.

If the cracking effort of the second stage is made higher (also a recommendation to reduce the risk of free flow) then this will increase the WOB.

 

[Oitzu]

I'm not sure if the WOB would actually be higher just from the lower IP of 8.5 bar if the second stage is balanced and tuned to the first stage at IP of 8.5 bar. The balancing of the second stage and the tuning will eliminate the effect of the lower IP.

If the cracking effort of the second stage is made higher (also a recommendation to reduce the risk of free flow) then this will increase the WOB.

I'm not quite sure. The service manual shows the same manual tuning steps for the cracking effort of the second stage (right on the edge of free flow) but a higher range in the actual measured values.
I concluded from that, that the opening effort is higher with lower mp, but i may came to a wrong conclusion.

 

[Umuntu]

I'm not quite sure. The service manual shows the same manual tuning steps for the cracking effort of the second stage (right on the edge of free flow) but a higher range in the actual measured values.
I concluded from that, that the opening effort is higher with lower mp, but i may came to a wrong conclusion.

The service manual for which particular AL regulator ?

If the second stage is unbalanced (like the Conshelfs) then the work of breathing will be higher at a lower IP. For balanced regulators the balancing should negate the lower IP if it's tuned to the lower IP.

 

[Oitzu]

The service manual for which particular AL regulator ?

If the second stage is unbalanced (like the Conshelfs) then the work of breathing will be higher at a lower IP. For balanced regulators the balancing should negate the lower IP if it's tuned to the lower IP.

The older legend models. Where supreme and non-supreme versions were still a thing.
Supreme being the versions with a mp of 8.5 and non-supreme of 9.5.
Afaik the were/are balanced.
The newer versions simply all come with a mp of 8.5 afaik.

 

[Umuntu]

The older legend models. Where supreme and non-supreme versions were still a thing.
Supreme being the versions with a mp of 8.5 and non-supreme of 9.5.
Afaik the were/are balanced.
The newer versions simply all come with a mp of 8.5 afaik.

The older legend (AL's first balanced 2nd stage) also had a different recommended cracking effort for the second stage for the supreme model. This woud have had the biggest impact on WOB. Below are the cracking effort recommendations from 2000:

+0.8 to +1.4 in. H2 O (primary)
+1.1 to +1.7 in. H2 O (Supreme)

 

[Oitzu]

The older legend (AL's first balanced 2nd stage) also had a different recommended cracking effort for the second stage for the supreme model. This woud have had the biggest impact on WOB. Below are the cracking effort recommendations from 2000:

+0.8 to +1.4 in. H2 O (primary)
+1.1 to +1.7 in. H2 O (Supreme)

Yes. They give this values as specification for the cracking effort, but if you look up how they adjust the cracking effort its just: "rise the cracking effort till it stops free flowing when you 'disengage' venturi".
So my conclusion was the lower mp results in higher measured cracking effort. But yeah i maybe jumped into a wrong conclusion.

 

[halocline]

If the second stage is unbalanced (like the Conshelfs) then the work of breathing will be higher at a lower IP. For balanced regulators the balancing should negate the lower IP if it's tuned to the lower IP.

That's true for cracking effort, but probably not total WOB. I say 'probably' because I'm not sure what exact factors go into measured WOB. With lower IP, there is a lower pressure gradient at the 2nd stage valve. This means less flow through that valve at a given opening size. How much this realistically effects demand effort, I don't know. It likely does effect venturi assist. I'm sure it's a small difference for high performance 2nd stages.