Regulator Question, is this normal?

[bractime]

I don't dive ScubaPro.

Aqualung / Apeks only.

Anything greater than 0 inches-h2o feels awkward, due to years of being a land dwelling animal with no breathing resistance. Yes, I'm picky.

But nonetheless, my primary cracks at a hair below 0.5 and my octo cracks at about 0.9. My Apeks regs freeflow on dry land if you max the settings out. I'm not quite that OCD with customers, but I do chase the fine line. Increased breathing resistance can cause CO2 buildup in during strenuous diving conditions. With new divers, the feeling of not getting enough air can onset panic.

I'd rather have too much air than too little.

Looking at the cracking effort specs for both Aqualung and Apek none of them that I could find spec below 0.5" and for most models do not spec the cracking effort below 1.0".

To quote from another good book earlier mentioned earlier on this post Vance Harlow's SCUBA REGULATOR MAINTENANCE AND REPAIR
"There's also little to be gained in attempting to adjust the regulator to obtain a cracking pressure that is lower than the regulator manufacturer specifies. Some techs like to boast about how low they can get it on this or that regulator, but tuning a regulator this way usually will only make it finicky and prone to free flow, without improving its performance significantly."

 

[KD8NPB]

Looking at the cracking effort specs for both Aqualung and Apek none of them that I could find spec below 0.5" and for most models do not spec the cracking effort below 1.0".

No, for pretty much all of Aqualung and Apeks regulators the manual specifies a tuning of 1.0" to 1.5".

Do I gain anything by having my regulators set low? Slightly, I notice a performance benefit. Does it come at a cost? Yes.

I completely accept the costs with the benefits though. I blame the hotrodder in me. I couldn't keep my motorcycle or my car tuned to factory specifications either.

 

[redacted]

If your reg. was adjusted to spec. before the " leak ", then you detune it. It will increase work of breathing (WOB). It may or may not still be in spec. For example a S600's spec. is 1.1 -1.3. If it was set to 1.1 and then you detune it to 1.3. It may be OK. It is your reg., it is up to you if you are satisfied with how it breathes.

However as you use the reg. over a period of time, it will continue to go to " free flow " and need service. Yes you can continue to detune, but each time increases WOB.

If the reg were adjusted to spec, it would not leak. If the leak is due to an adjustment more aggressive than specs, then using the adjustment knob to just stop the leak should return the reg to spec or perhaps still slightly aggressive. I set my adjustable 2nds fairly aggressively, sometimes leaving them with a slight leak which I control with the user adjustment. This insures I enjoy minimum cracking pressure and maximum performance.

Sure, all other things equal, increasing spring pressure by tightening the adjustment knob will increase the WOB, but not to the point of putting it out of spec. In fact, adjusting cracking pressure for a slight leak should always provide better WOB results than adjusting to specification.

To me, a slight freeflow (leak from the 2nds stage seal) indicates a probable need for adjustment, not a need for service. On a dive trip, I make a small adjustment. If that does not correct the problem, then I swap out regulators and leave the more serious troubleshooting for after the trip.

My wife dives an S600. I usually set it quite aggressively a good bit below 1.0" cracking pressure. It is a shame to waste the potential performance of that regulator on an in specification adjustment by the service tech. But I do understand that some users are simply incapably of managing such high performance - and it may occasionally require some management.

 

[bractime]

No, for pretty much all of Aqualung and Apeks regulators the manual specifies a tuning of 1.0" to 1.5".

There are a couple of the models that are below the 1.0" the Micra has a spec of 0.6" to 1.0" for Aqualung and the ATX200 has a spec of 0.8" to 1.4" for Apex. Not knowing which model you have I will stand by my statement of models do not spec the cracking effort below 1.0".

IMO what you lose in stability you don't gain enough benefit. When you are looking at quantity of air supplied it has more to do with proper lever height than cracking effort. If you don't maximize the lever height then the value will not open to the maximum level and you will get a reduced quantity of air regardless of cracking effort. I will leave you with one more quote from Harlow's book:

"I should add that it's not worth getting too hung up on cracking pressure. Cracking pressure alone, especially when measured on the surface, doesn't really tell all that much about the regulator's performance in the real world, since some regulators have a very low cracking pressure, but don't deliver much air at that pressure. Others may have a higher cracking pressure but better delivery of air once they do crack. And then, cracking pressure and WOB generally increase with depth, so tests done dry at surface ambient may not really tell you much about how the regulator performs in the water”

 

[halocline]

Small differences in cracking effort don't really do much for a regulator's overall performance. It's dumb to get hung up on fractions of an inch. What is important, especially in technical diving, is to not tune the reg so aggressively as to cause problems with case geometry fault.

Any time a 2nd stage is tuned to cracking effort less than the difference in distance between the diaphragm/lever interface and the shallowest edge of the exhaust valve, it will free flow in certain positions. Think of it this way; the diaphragm will ensure that there's a minimum amount of pressure in the reg body; more or less equal to ambient at the point of contact with the lever. If there's lower pressure than that, the diaphragm collapses, pushes the lever open, and air flows into the reg.

The exhaust valve sort-of does the opposite; ensures that air pressure in the reg body will not exceed ambient at it's upper (shallowest) edge. That's because if the pressure in the reg exceeds ambient, it pushes the exhaust valve open until pressure equalizes.

So, when you're diving in a face down position, on most regs the exhaust valve is a good .75" or so (maybe more) shallower than the lever/diaphragm point of contact. This means that the pressure inside the reg case cannot be greater than .75" less than ambient at the diaphragm. So when you set a reg to cracking efforts lower than this, it can (and usually does) start flowing in that position. This tendency is inhibited a bit by friction, I suppose. But it's also increased by venturi assist.

All this is well explained in the Wolfinger book Regulator Savvy.

So all this talk of super-low cracking effort is just that, talk. In the real world it doesn't work, and it doesn't matter.

 

[Zung]

... like the top speed of your car.
What? Yours doesn't do 150mph?