Question Regulator Tuning

[TheRavenCT]

Hello all.

I just got my regulator back from being serviced. When the second stage venturi valve is at least 88% open, the second stage will get stuck in free flow if the purge valve is activated. I was told that this is the desired behavior by the shop.

The opening effort is supposedly 1.2 inches of water. The octo is 1.6 and doesn't free flow at all. I am not sure that I am comfortable with this setting that free flows on the primary second stage.

Any thoughts? Does that sound right regarding tuning? Aqualung spec is 2.8-3.8 mbar (1.1-1.5 in h2o). Is there another spec I should check? It is a warm water mikron reg with which I dive in 50F water usually without a problem.

 

[davehicks]

You can just close the venturi if you don't like this behavior. And how do you know it's 88% open?

What 2nd stage regulator model do you have? Does it have an adjustment knob? If so, you can turn that slightly clockwise to increase cracking effort. If you don't have an adjustment knob, someone needs to adjust the main orifice (accessible by removing the LP hose from the 2nd) to increase cracking effort to your liking. It's not difficult, but not recommended if you don't know what you're doing.

If you are not happy with the tuning, take it back and get it adjusted how you like it.

 

[old frogman]

Hello all.

I just got my regulator back from being serviced. When the second stage venturi valve is at least 88% open, the second stage will get stuck in free flow if the purge valve is activated. I was told that this is the desired behavior by the shop.

The opening effort is supposedly 1.2 inches of water. The octo is 1.6 and doesn't free flow at all. I am not sure that I am comfortable with this setting that free flows on the primary second stage.

Any thoughts? Does that sound right regarding tuning? Aqualung spec is 2.8-3.8 mbar (1.1-1.5 in h2o). Is there another spec I should check? It is a warm water mikron reg with which I dive in 50F water usu

I service my own regulators. I set the demand valve opening effort so it does not free flow (referred to as de-tuning). I do this with an adjustment tool. I do not get too concerned about numbers. If you are not comfortable with your service provider there are books which teach you how to service a regulator and also some dive shops that provide technical training and spare part kits for your specific regulator. In addition, there are certain brands of regulators that are available through technical diving on-line shops that will provide you with the regulator and everything you desire for self-servicing.

The advantage of self-servicing is that, during the season of diving, the regulator may need a touch up retune or partial stripping to remove debris, salt encrustation, O ring failure (experienced on balanced demand valves), etc.

There will be some people who will say that servicing your own regulator is taking a risk. I agree. Everything you do in life is taking a risk. Having a regulator serviced by a professional dive technician is also a risk. I have been with people that have experienced a regulator malfunction on the first dive following a professional regulator service. It is a matter with which risk you are comfortable with.

ally without a problem.

 

[chaad]

And how do you know it's 88% open?

I assume there's a protractor involved

 

[old frogman]

Hello all.

I just got my regulator back from being serviced. When the second stage venturi valve is at least 88% open, the second stage will get stuck in free flow if the purge valve is activated. I was told that this is the desired behavior by the shop.

The opening effort is supposedly 1.2 inches of water. The octo is 1.6 and doesn't free flow at all. I am not sure that I am comfortable with this setting that free flows on the primary second stage.

Any thoughts? Does that sound right regarding tuning? Aqualung spec is 2.8-3.8 mbar (1.1-1.5 in h2o). Is there another spec I should check? It is a warm water mikron reg with which I dive in 50F water usually without a problem.

Mikron, that's Aqualung. The Australian Navy back in the 1960s used a single hose, two stage regulator called the Porpoise Universal manufactured by Australian Divers, a subsidiary of US Divers Aqualung. This regulator had a venturi system that used to virtually blow the back of your throat every time you inhaled. Famous for free flowing when you removed it from your mouth. Looks like history repeating itself.

 

[happy-diver]

Unscrew the hose from your reg, then find something that fits, in the slot
and with the purge depressed turn clockwise 1/8th of a turn check repeat

 

[inquis]

Sounds perfectly adjusted. Flip the Venturi once it's in your mouth.

 

[Nemrod]

It is considered desirable for a second stage to free flow when the purge is depressed with the Venturi control in Dive position (when not in your mouth). Many regulator shop manuals will specify exactly that, however, the Mikron manual does not specifically state that but the result of the procedure described in the manual would result in the condition you describe.

The Mikron first stage IP is 130 to 145 psi. Whats is your IP? If it is towards the high end you might (or your store) drop the IP to the lower end of the acceptable range. Typically regulators intended for cold water use will have a lower IP pressure for the first stage and a higher cracking effort range for the second stage to help prevent icing induced free flows. The Mikron never had a designated cold water model being intended as a tropical travel set.

During entry and exit to and from the water, set your adjustment knob in one turn and set your Venturi control to pre-dive. Once submerged you can turn the adjustment knob out and set the Venturi to dive. When you put your reg set away after cleaning make sure to turn the adjustment knob back out fully.

 

[old frogman]

Unscrew the hose from your reg, then find something that fits, in the slot
and with the purge depressed turn clockwise 1/8th of a turn check repeat

And if that fails, for about $20 you can buy an adjustment tool that fits between the end of your low-pressure hose and the demand valve hole where the hose normally screws into. Connect the regulator to the tank, turn the tank on. By turning the adjustment nob on the adjustment tool, either way, you can find the sweet spot for tuning your demand valve to your specific requirements.

Make sure, at the shop, that the adjustment tool is suitable for your regulator.

"demand valve" also known as the "second stage" of the regulator.

 

[old frogman]

It is considered desirable for a second stage to free flow when the purge is depressed with the Venturi control in Dive position (when not in your mouth). Many regulator shop manuals will specify exactly that, however, the Mikron manual does not specifically state that but the result of the procedure described in the manual would result in the condition you describe.

The Mikron first stage IP is 130 to 145 psi. Whats is your IP? If it is towards the high end you might (or your store) drop the IP to the lower end of the acceptable range. Typically regulators intended for cold water use will have a lower IP pressure for the first stage and a higher cracking effort range for the second stage to help prevent icing induced free flows. The Mikron never had a designated cold water model being intended as a tropical travel set.

During entry and exit to and from the water, set your adjustment knob in one turn and set your Venturi control to pre-dive. Once submerged you can turn the adjustment knob out and set the Venturi to dive. When you put your reg set away after cleaning make sure to turn the adjustment knob back out fully.

Just to expand, for the benefit of the young lady. "IP" stands for "intermediate pressure". That is the pressure of the gas inside the first stage (aka the pressure reducing valve). On the top of your first stage there is a large hexagon hole that fits an Allen key. By turning the key clockwise or counterclockwise you can increase or decrease the IP. To measure the IP you need a low-pressure gauge. There are two ways you can go with the gauge. One, you can get the gauge which comes attached to the second stage adjustment tool. Two, you can get the gauge as a separate item that you connect to the end of the Buoyancy compensator inflator hose. There are two ways you can purchase these items, on-line or your local dive store may sell them. To adjust the IP, you need to know what it is, for your specific regulator. There may be service manuals available on-line that provide the technical info.

Also, according to the literature on-line, the Mikron is supposed to have excellent coldwater performance. I suspect that this may be due to it having a balanced diaphragm first stage.