Scubapro chrome plated brass regulators...

[GJC]

With my setup I have micro vac pump 0-10 lpm, I just tested @ 3 lpm and it doesn’t oscillate as much, the more I increase the flow the less it move around and the frequency of movement is far less. I was trying to understand why with my MK10 for example even at 1.5 lpm once the ip dips and recovers it holds solid at the adjusted effort even at the higher flows. Trying to determine if I’m detecting a fault inside the atomic before I open for inspection.

That might be a normal finding at low flow rates for that (and other) first stages.

Anybody else here test their regs at low flow rates like this?

 

[Open Ocean Diver]

I find the flow rate is equal to and much more consistent compared to orally breathing ie sipping on the regulators for checking static cracking effort... enabling fine tuning to a high degree.

With testing this way many question come up, like why is the inhalation resistance inversely proportional to IP with a balanced 2nd stage?

 

[GJC]

I find the flow rate is equal to and much more consistent compared to orally breathing ie sipping on the regulators for checking static cracking effort... enabling fine tuning to a high degree.

With testing this way many question come up, like why is the inhalation resistance inversely proportional to IP with a balanced 2nd stage?

That flow rate is nowhere near equal to normal breathing.

A normal breath at rest is around 350 ml. Rate 12. Inhalation time 1 sec. To inhale a 350 ml breath in 1 sec, you need a flow rate of 21 lpm.

I suspect you are testing at levels that regulators were never made to perform.

If you lower the flow rate even more, to less than 1 lpm, does the ip drift and resistance increase?

 

[Open Ocean Diver]

I’m was referring to a gentle inhale like sipping lightly on a straw, not a full breath. You can easily sip between 1 and 5 lpm. That’s all it takes to just open the demand valve.

 

[GJC]

I get what you are saying, but I think that the level of testing you are doing is way below the level that the regulator was designed to perform. You would need a regulator specifically designed for a mouse to get smooth measurable readings at the flow you are using for testing.

 

[Open Ocean Diver]

You need this low flow to over come the mechanical resistance to just crack the valve to measure effort on the mag gauge, Dynamic flow testing would be from 5-20 SCFM.

 

[rsingler]

All of you are right. Yes, these flows are waaay below anything except initially opening the valve to take a breath. And so, no - I don't think there's anything wrong with the first stage. There is a very slow resonance here between dropping and rising IP, and first stage valve opening and closing. There is a variable flow going on here; I'm convinced of it. I suspect it has to do with the micro pump performance, despite what seems to be a stable pump rpm.

But @Overweighted has a point too! During this brief interval when the valve is just opening, and (to me) flow is slightly increasing (as suggested by the falling IP), why is the cracking effort rising so significantly?

We need a bit more data.

With the second stage left as tuned (0.7" cracking effort) move from the micro suck to your vacuum cleaner.
At 1 to 4 SCFM, what happens to your cracking effort and dynamic IP?? This is where it matters for diving, of course.

But also, these larger flows are where second stage Venturi effects should kick in. With a balanced second like a G250, I would expect dynamic resistance (Magnehelic values) to begin to head back toward 0.7" or even closer to zero. And keep in mind these are negative numbers that we're looking at...

I can't come up with an explanation tool I know where crackling effort/dynamic resistance is going when the valve is fully open. It may be that with a barely cracked valve and slight increases in flow, the relative resistance to flow across that crack increases with the flow, until the valve opens completely.

Fascinating!

 

[Open Ocean Diver]

All of you are right. Yes, these flows are waaay below anything except initially opening the valve to take a breath. And so, no - I don't think there's anything wrong with the first stage. There is a very slow resonance here between dropping and rising IP, and first stage valve opening and closing. There is a variable flow going on here; I'm convinced of it. I suspect it has to do with the micro pump performance, despite what seems to be a stable pump rpm.

But @Overweighted has a point too! During this brief interval when the valve is just opening, and (to me) flow is slightly increasing (as suggested by the falling IP), why is the cracking effort rising so significantly?

We need a bit more data.

With the second stage left as tuned (0.7" cracking effort) move from the micro suck to your vacuum cleaner.
At 1 to 4 SCFM, what happens to your cracking effort and dynamic IP?? This is where it matters for diving, of course.

But also, these larger flows are where second stage Venturi effects should kick in. With a balanced second like a G250, I would expect dynamic resistance (Magnehelic values) to begin to head back toward 0.7" or even closer to zero. And keep in mind these are negative numbers that we're looking at...

I can't come up with an explanation tool I know where crackling effort/dynamic resistance is going when the valve is fully open. It may be that with a barely cracked valve and slight increases in flow, the relative resistance to flow across that crack increases with the flow, until the valve opens completely.

Fascinating!

Ok video attached at varying flow rates, you can zoom in to any of the gauges to see results. Atomic connected to G250V, tank 1200.
https://share.icloud.com/photos/0Pa6Z0c9Q3vB1KuWE7ECCUeoQ#Downtown_Toronto

 

[GJC]

Gauges look more stable at the higher flow rate.

I'm guessing that, at the end, the flow rate increased enough for the venturi effect to kick in, creating a little bit of positive pressure on the magnehelic.

I don't have an explanation for the cycling at low flow and interested in anyone elses thoughts on what exactly is going on here. Must have something to do with low flow rate and size of air chamber in first and second stages.

 

[Open Ocean Diver]

Here’s another video max flow 10 CFM.

https://share.icloud.com/photos/0xYjv-e1FjgqGghEvXTxgyB-Q#Downtown_Toronto