2nd stage adjustment...Why?

[graham p]

Hi all.
So I just replaced my wife's old conshelf SE3 second stage due to a crack in the main body. I bought her a shiny new DGX D6 second stage, and while admiring it and showing her all the cool features she didn't have before, she asked " Why would anyone want to make a regulator harder to breath off of ?" Refering to the adjustment knob on the side of it.
I didn't have an answer...
On her unadjustable Conshelf I would set the cracking pressure to 1 inch, and all would be good. No need to fiddle with a knob underwater.
So I am wondering why do other divers out there intentionally stiffen the breathing on thier adjustable regulators?
Thanks.

 

[Jcp2]

To reduce free flow when not using regulator.

 

[DiveGearExpress]

What is the knob and lever on my second stage? | Dive Gear Express®

The knob and lever are used to alter the breathing characteristics of some types of regulator second stages. All our downstream design high ...

www.divegearexpress.com

 

[graham p]

@DiveGearExpress. Thank you for the write up on the hows and whys of the adjustment knob, That gave me everything I needed to answer her question. I guess I need to spend more time exploring your website.

@Jcp2. In my mind, if the second stage is free flowing while not being used, it's out of adjustment. Either the IP is too high, or the cracking effort is too low. Both of which need to be corrected before diving.

 

[rob.mwpropane]

Personally, I like it. Diving in cold water the ability to "de tune" a 2nd and not have to worry about a free flow at all gives warm fuzzies. Plus I've also had the 2nd start to bubble a little after a few dives on a fresh rebuild as the LP seat wears in, no issues just turn the knob and mess with it later.

 

[graham p]

Why the need to "detune" for cold water? Is a regulator more prone to free flow in colder water?
I have only dove down to 50f (10c) water and haven't noticed any change in my regulators performance.
I'm not trying to be pedantic, just curious as to why and when people are using this feature.

Your second point makes sense to me. Why scrub a dive if the adjustment on site fixes the problem. That is a good benefit to an adjustable cracking effort.

 

[divad]

Personally, I like it. Diving in cold water the ability to "de tune" a 2nd and not have to worry about a free flow at all gives warm fuzzies.

re "warm fuzzies";
I thought I was the only one...

 

[halocline]

In my mind, if the second stage is free flowing while not being used, it's out of adjustment. Either the IP is too high, or the cracking effort is too low. Both of which need to be corrected before diving.
[/QUOTE]

That's a little over-simplified. It is true once you're deep in the water, but entering and exiting water, hanging around on the surface, etc can cause free flows in properly adjusted regulators that are not in your mouth, like the alternate 2nd stage. I keep mine on a bungee necklace (as do 99% of all technical divers) and as such it tends to hang mouthpiece-up. So it's nice to be able to adjust it to prevent free flows. The old school way of dealing with that for recreational divers was just to adjust the alternate 2nd stage with higher cracking effort. That's not so good if you want your alternate to breathe as well as your primary.

 

[rob.mwpropane]

Why the need to "detune" for cold water? Is a regulator more prone to free flow in colder water?
I have only dove down to 50f (10c) water and haven't noticed any change in my regulators performance.
I'm not trying to be pedantic, just curious as to why and when people are using this feature.

Your second point makes sense to me. Why scrub a dive if the adjustment on site fixes the problem. That is a good benefit to an adjustable cracking effort.

You don't know until you know... I'm still learning.

I haven't had a catastrophic free flow, but I've been told that in colder air that a free flow can cause ice crystals to form and then that might not be able to be stopped. We dove last weekend in 40f water, 25f air temp. No free flows and I had the warm fuzzies knowing mine were set to predive and detuned a good bit until under water.

I believe air temp has more to do with an uncontrolled free flow, but please if someone would explain that better than my cave man understanding....

cold air bad, free flow in cold air (can be) very bad.

 

[Centrals]

It is a nice feature to have but is it essential/necessary is something else.
I will need an Allen key to turn it in some of my Apeks 2nd stages(depend on model).