What's the purpose of 'freeflow'?

[jonnythan]

Ok. It's just that in the Apeks manual one test is to put the Venturi lever to the + position (no deflection) and then by pressing the purge initiating a free flow. If it doesn't then it's supposed to mean that the purge lever is set too low and you need to screw out the adjustment screw a fraction to let the lever sit a little higher. I have tried this on an AT20 but without success. As soon as the screw is in far enough so that it doesn't simply leak air - so the lever is left in the highest possible position - although the purge works fine and it breathes OK - it won't freeflow by pressing the purge. I'm wondering therefore what it means. All the other tests are fine - just this one.

The purpose is just to insure that the spring isn't pushing the seat too tightly against the valve, which will make it harder to breathe. It's sort of a quick sanity check when you don't have one of those expensive WOB machines handy

I'm not very familiar with the A-series, but I've never had trouble adjusting my TX's to that point. Are you sure you have the venturi all the way on + when performing this test?

 

[Kim]

I'm not very familiar with the A-series, but I've never had trouble adjusting my TX's to that point. Are you sure you have the venturi all the way on + when performing this test?

Hmmm... that was a typo...I meant TX20! Yes...venturi all the way +. When it wouldn't freeflow I adjusted the screw about 1/8th of a turn out and on reconnection had a leak so I had to tighten it back the small fraction. Like I said....it breathes fine and the purge works in the correct place (depressed around 2mm). The IP from the first stage is 138 (I didn't do anything to that) Although the specs say it should be 135 I can't really see that it's a big enough difference to effect anything. If anything I'd have thought that the slightly high IP would make it freeflow sooner.

 

[jonnythan]

Weird.. I dunno. If it works, I wouldn't worry about it, but I'm no reg tech or anything

 

[Kim]

Weird.. I dunno. If it works, I wouldn't worry about it, but I'm no reg tech or anything

Yes...unless I hear a concrete reason why I should be concerned I agree with you. It's not really a problem as it's normally my backup and my TX50 (primary) tested out perfectly. My wife has the same setup which has hardly been used so I'll take her's with me to Thailand in a couple of weeks to be on the safe side. When I get back I can test mine in local waters gently to make sure that there are no problems at depth. At least I know mine now has all new O-rings and is clean etc.

 

[jonnythan]

Ahhh.... I intentionally detune my backup reg so that it *doesn't* freeflow when the venturi is on +, just so I can be sure it never freeflows. It works fine.

 

[redacted]

I have tried this on an AT20 but without success. As soon as the screw is in far enough so that it doesn't simply leak air - so the lever is left in the highest possible position - although the purge works fine and it breathes OK - it won't freeflow by pressing the purge. I'm wondering therefore what it means. All the other tests are fine - just this one.

You say the purge works fine .... but it won't FF when you press the purge. I do not understand these two contradictory statements. Please explain what you are doing when you say "it won't freeflow by pressing the purge."

A properly tuned reg breathes well but is right on the verge of freeflowing. Exposing it to a pressure differential of about 1 inch of water (whether by inhaling, pressing the purge, or submerging it in water) should initiate gas flow. If the gas is flowing and it is nat caused by your inhaling, then it is freeflowing. The venturi adjustment can be used to exercise some control over the strength of this freeflow.

 

[jonnythan]

The Apeks manual states that when the venturi is on +, pressing the purge button will initiate an automatic freeflow.. ie, it keeps freeflowing after you let go of the purge button, and you need to stop it by turning the venturi to - or blocking the mouthpiece somehow. "Purging" vs "freeflowing"... freeflowing implies you're no longer doing anything to the reg, but air is still rushing out.

 

[Kim]

Ahhh.... I intentionally detune my backup reg so that it *doesn't* freeflow when the venturi is on +, just so I can be sure it never freeflows. It works fine.

Nice to know, Jonny...thanks. eyebrow

 

[Kim]

The Apeks manual states that when the venturi is on +, pressing the purge button will initiate an automatic freeflow.. ie, it keeps freeflowing after you let go of the purge button, and you need to stop it by turning the venturi to - or blocking the mouthpiece somehow.

Yup...what he said. My TX50 behaves exactly like that - a finger over the mouthpiece or moving the venturi stops it instantly. The TX20 won't freeflow when I release the purge button. (with the purge depressed it flows fine) Both breath very easily with minimal cracking pressure.

 

[jonnythan]

BTW, it's the "T20." The T is essentially the series. The X indicates the presence of a heat eXchanger (metal at the hose inlet which helps with cold water freezup prevention), which the T20 doesn't have.