Regulator gave too much air

I recently completed my NAUI OW checkout dives. On our 2nd to last boat dive (Barge wreck, 45-58fsw, 72F, mild current), I noticed that as I inhaled, my 2nd stage seemed to give me more air than I wanted. Topside, I mentioned this to my instructor (LDS owner, rented me the gear) and he pointed out that there was an anti-freeflow setting (Zeagle reg and Octo) and I had it wide open.

On our last dive, I had forgotten about it, but at around 55fsw I got the same sensation. I popped my reg out (blowing tiny bubbles like a good boy), throttled it down, and popped it back in. No noticable difference.

I wound up tonguing my reg for the rest of the dive, that kept the airflow down. What's up with that?

Ian

Let me ask a few questions?

is it a new regulator

was it recently serviced

were you in a sandy area or losts of murk floating around

Standing bye to respond.

Hallmac

And was it actually free flowing or did it just feel like it was giving you more air than you wanted? Like it was 'forcing'air into your lungs?

I'm sure it had been serviced quite recently, and the conditions weren't very silty or anything. It wasn't freeflowing, it was just that once I got it flowing, it would flow harder than I drew, or so it seemed.

based upon the following:

You believe it was recently serviced and I'm quessing it was not your personal unit. No contamination problems, and no freeflows while it was out of your mouth.

I would hazard to guess one of two possible explanations.

1st would be that the second stage was set too light and after use it seated and allowed the lever to hang slightly.

or

2ed the LP seat spring is worn out/defective and is not rebounding with enough force to smoothly control the air flow.

of course without actually looking at the unit and testing it I can only guess.

Hallmac

its turned up too far.

Many regs are set this way by divers who think its the "right" place to put that knob. It isn't.

Many non-externally-tuned ones are set this way by techs that think it makes them "breathe better". It doesn't.

If its a rental/loaner for the class, well, now you know what kind of crap this shop is willing to shove in your mouth. Not a good thing, IMHO.

I'm not familiar with zeagle, but some regulators are know to be "postive pressure" breathers. That is, once they start to deliver gas, they actually exceed the demand and WOB takes on very small negative (minus) values. They are actually forcing gas into your airway. These tend to be high performance regs but some divers find it uncomfortable.

I have a bunch of Zeagles and I haven't ever noticed such a thing. I would say that it's not set up right.

What these other guys a re talking about with the pos breathing thing is the venturi effect that's designed into the second stage. The idea is that once air is flowing through the second stage there is a pressure drop due to the veturi that assists in keeping the valve open.

To see what I mean notice that with the dive/predive switch in the dive position the reg will continue to flow on it's own if you freeflow it by pressing the purge and letting go. However at lower flow rates (like when breathing) that pressure drop isn't enough to keep the valve open and actually create a pos pressure. It just requires less efort. At shallow depths, in fact, you probably won't even notice a difference between switch positions.

The other thing, as much as I like these regs, the seat in the second stage seat is very soft and seems to require adjustment fairly often. The seat on your reg may have just been leaking a little. Being an adjustable reg you should be able to adjust it the way you want on the fly without taking the reg out of your mouth.

In my experience, when having students use regs like this it's important to instruct student on how to use the adjustments. I know that sounds like common sense but...common sense isn't so common.

What about a reg that doens't give enough air? It didn't have a switch to turn it the flow up and you really had to suck to get anything out. I ended up using the octopus which was fine.

Many high performance regs use a positive pressure phase in the middle of the inhalation cycle. This sort of force feeds the diver and I have never liked it much. It is however becoming more common as it leads to total work of breathing scores that are very good as the positive pressure phase in the middle can cancel out even a very high cracking effort. The marketing types love it.

In my opinion, a well designed high performance second stage will have a low cracking effort and a very smooth delivery of air at ambient pressure. The older Scupapro D400's (with metal orifices) are in my opinion the best performing regs I have ever encountered from this perspective. The Balanced Adjustable and the G250 are also excellent (as long as you maintain a moderate setting on the venturi assist on the G250 and don't turn it all the way up).

Most downstream second stages suffer from the problem of the low pressure seat either taking a set over time due to prolonged contact with the orifice or from being engraved by being turned against the orifice. The end result is a slow freeflow with a few small bubbles coming from the reg throughout the dive. It's a clear indicator that the second stage needs serviced.

The correct fix is to replace the seat (or to flip the seat over as many are reversible) and to adjust the orifice for maximum performance with the new seat. However what often happens is that a quick fix is made by tightening the fit between seat and orifice which temporarily solves the freeflow problem but with the side effect of a high cracking effort. Taken to extremes it also reduces the travel of the demand lever and can result in inadequate airflow.

I have also encountered regs that were just not properly adjusted after an annual service. On a reg with an unbalanced first stage and unbalanced second stage, the second stage needs to be adjusted for peak performance at the maximum tank pressure that will be encountered. Otherwise, if it is adjusted for minimum cracking effort at, for example, 1500 psi it will freeflow when connected to a full tank at 3000 psi. as the intermediate pressure will be slightly higher.

The result is that many techs using a shop air tank that is nearly always at less than 3000 psi will crank the orifice down a little farther to prevent a freeflow. This unfortunately increases the breathing resistance of the reg. Sadly, if the customer complains the comments usually run more along the lines of "if you want easier breathing you should buy a new high perfromance reg like this one over here in our display case" than they along the lines of "ok, I'll properly adjust your reg this time and won't charge you a penny".

This type of mis adjustment also occurs on high p[erfromance balanced regs as it is more conveneinet for the tech. Most customers (who unlike 20 years ago are for the most part infrequent divers) will not return a recently servcied reg because it breathes a little harder than it should as it probably still breathes better than it did before being serviced, and they don't realize that it is not performing to it's potential. On the other hand, nearly all divers will return a reg if it freeflows. So if you crank it down a bit you virtually guarentee that it will not be returned for further adjustment.

To be fair, it is not uncommon to adjust a high performance reg for minimum cracking effort and then to have to readjust it slightly a week or so later after the orifice and seat have ghottn to know one another better. Ideally, the customer won't be in a hurry and the reg can sit in the shop a week or so before a final check and adjustment is made. But I'm not many techs care that much - but then why should they, they aren't the one diving the reg. This is one of the many reasons I do my own service work.

Second stage orifice adjustments are relatively easy to do on most regs and can be accomplished after minimal training. Learning how to adjust your own second stage is a good thing to consider and will help you get peak performance out of your reg no matter hoe expensive it is. Our dive club used to teach a class on this periodically and it was well recieved. Divers would bring in their own regs and get one to one instruction on how to adjust it for peak performance.