Normal intermediate pressure drop during purging?

[brtlmj]

So, I got myself an intermediate pressure gauge and started playing...

I noticed that the pressure drops whenever I breathe or purge the second stage. This makes perfect sense - the pressure has to drop for the first stage to open, right? What I am curious about is the normal/acceptable magnitude of the drop. In my case, it is roughly 0.75 bar at full purge.

Thanks!
Bart

 

[buddhasummer]

Some of my regs, piston, will drop 20 psi, my diaphragm regs less. 10 isn't much. What reg is it?

 

[herman]

The range varies with different regs, .75 BAR/ 11 psi is pretty good for a full purge. There are a lot of factors that determine the drop including the tank valve.....which might be the major contributor to the drop.

 

[The Chairman]

10 to 20 is acceptable for me. I'm more worried about it not flowing enough.

 

[rhwestfall]

Is it @awap or @halocline that theorized that the drop may actually not be happening at the stage, but rather the drop measured on the dead end just might be due in fact to the flow creating a reduced pressure zone as air flows across the orifice to the LPI hose... Only a flow meter will really answer this....

Now, as to a measured 10 psi drop with an IP gauge? I wouldn't find it worrisome at all.

YMMV

 

[The Chairman]

flow creating a reduced pressure zone as air flows across the orifice to the LPI hose

The venturi effect.

Only a flow meter will really answer this....

Which is overkill for most of us. I love my buddy @sphyon, but he has bought a Dodge Hell Cat that is soooooo rad, that he'll never really get to enjoy it to it's fullest. His lovely wife has a fairly low performance jeep. Guess which they take diving?

The crappiest reg built today is more reliable than the best regs that were around when I first learned to Scuba. IOW, there is no "crappy" modern reg. For me, the very best reg is the one in my mouth.

 

[halocline]

So, I got myself an intermediate pressure gauge and started playing...

I noticed that the pressure drops whenever I breathe or purge the second stage. This makes perfect sense - the pressure has to drop for the first stage to open, right? What I am curious about is the normal/acceptable magnitude of the drop. In my case, it is roughly 0.75 bar at full purge.

Thanks!
Bart

You can't really measure active IP drop accurately with a standard IP gauge on a LP inflator hose. I'm certain they are only accurate when air is not moving through the hoses.

 

[rhwestfall]

The crappiest reg built today is more reliable than the best regs that were around when I first learned to Scuba.

Yes they are updated, but I still find my DH regs to be on par (or above?) my modern ones.

 

[The Chairman]

Yes they are updated, but I still find my DH regs to be on par (or above?) my modern ones.

I don't find them to be even close. I think there's a reason they aren't mainstream anymore and marketing isn't one of them.

 

[RainPilot]

I don't find them to be even close. I think there's a reason they aren't mainstream anymore and marketing isn't one of them.