What's the purpose of 'freeflow'?

[Kim]

I have been doing some reading on maintaining/servicing regulators (2nd stage). When a serviced regulator is reassembled it's adjusted so that the purge functions properly with an adjustment screw. The positioning of this screw will also dictate how easily the reg freeflows. Reading about testing a reassembled reg part of it concerns when it should freeflow. What is the point of the freeflow? If the reg is assembled so that it's not leaking and the purge is working properly and it breathes OK etc - why is it important that you can also make it freeflow?

 

[Charlie99]

1. Some people have problems clearing a reg when inserting it underwater and push the purge to clear out the water.

2. Not very often, but sometimes I'll take my reg, hold it at arm's length and purge it while doing a 360 degree spin. It's a very quick way to make a very visible bubble cloud on the surface to warn away a boat getting ready to pass over you.

3. Once in a great while I'll do a weight check and will freeflow the tank to get rid of excess air.

On some regs, what you call a freeflow adjustment might also be adjusting the cracking pressure, or at least getting something into the proper range so cracking pressure can be adjusted.

 

[Kim]

Yes I understand the purge. What I mean though is that if the purge is working properly (by pressing the button it streams air at a high volume) - why should you also be able to make the reg freeflow on it's own with a certain setting of the Venturi lever? (in relation to an Apeks reg)

 

[Charlie99]

I'm not a reg tech, but I do know that if the cracking pressure on my reg is too high, I don't like how it breathes. A very simple test of cracking pressure is to turn the reg upside down in water. With most regs, the distance between the diaphram and the mouthpiece openins is big enough that the differential of 1" of water or so will cause the reg to free flow. Kind of like a poor man's manometer.

The venturi lever is whole different ballgame. It is kind of like a power assist that reduces wob by adding some positive feedback. Once you get air flowing, the venturi lever is hit by that air and opens the demand valve/orifice even more.

 

[Chad Carney]

Kim,

The venturi lever/deflector can make a regulator breathe better under greater pressure/depth. That is it's purpose.

There is no reason for a regulator to venturi when not being breathed upon, other than perhaps showing off on the sales floor.

Chad

 

[spectrum]

As said in normal use the is no value to a freeflow unless you purge intentionally to fill a bag, get attention or clear the regulator.

Also as mentioned laying the regulator into the water mouthpiece up will demonstrate how much water column is needed to initiate flow. It's the same thing that sends a regulator off sputtering when it's carelssly dropped on the water diaphram down. Like wise one that starts flowing when not deep enough in the pan will be prone to freeflowing in a current or other disturbance and can be adjusted based on the observation.

Once you get it entirely underwater it's not as touchy because the pressure is water over water instead of water overcoming air.

Pete

 

[Kim]

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.

 

[Snowbear]

Yes I understand the purge. What I mean though is that if the purge is working properly (by pressing the button it streams air at a high volume) - why should you also be able to make the reg freeflow on it's own with a certain setting of the Venturi lever? (in relation to an Apeks reg)

I'm not a reg tech, but I do work on/service/rebuild my Apeks regs. My understanding of this test is that it's a behavior of the reg if it's adjusted correctly. Part of that test involves getting the freeflow to stop when you adjust the venturi. It should NOT freeflow if the venturi is at about 1/2 or less. Yes, it has to do with cracking pressure, but also has to do with being able to adjust the reg to breathe easier at deeper (as in beyond recreational) diving. As you know, the air coming from the tank and through the regs is denser the deeper you go. One of the features of the Apeks is being able to keep the reg breathing easily at such depths as well as being able to adjust it so it does not unintentionally freeflow shallow.

All that said, I will still forward this question to the buddy who *is* an Apeks tech and who taught me to work on mine

 

[MarkH]

My understanding is that you adjust the screw so that the reg just starts freeflowing, then back it off just a bit. This ensures the least possible resistance to breathing (makes the reg have a "hair trigger"). I think that if adjusted like this, the diaphragm in the 2nd stage is just about to act on the lever that lets in airflow. All it needs is the slightest inhalation from you to "crack" the valve and give you air. If I'm wrong, please let me know so I don't kill myself.

 

[Kim]

If I'm wrong, please let me know so I don't kill myself.

LOL. I have similar feelings which is why I thought it prudent to ask the question!