Newbie repairing a Scubapro Mk11, R395, R295 regulator set. Progress report and questions

[stepfen]

Today I received the DIN assembly so I managed to finish assembling and adjusting the regs!
I adjusted the IP to 9.5 bar.
One thing I noticed is that the very first time the 1st stage gets pressure (when I turn the tank valve) the IP shoots over 10 bars (around 10.5 bar) - unless I turn the valve veeeeeeeery slowl. Then the IP stabilizes there and stays there until I breath or purge some air. From that moment onwards the IP returns to the correct pressure (9.5 bars) after every breath.
Is that normal?

Now I've left the system pressurized to see if there is any slow drift in IP and if everything goes well tomorrow I plan to dive it.

Thanks in advance.

 

[rsingler]

the very first time the 1st stage gets pressure (when I turn the tank valve) the IP shoots over 10 bars (around 10.5 bar)

That's not uncommon, and it's not a problem. Valve closure is prompted by the interplay between main spring pressure and Intermediate Pressure. When starting from 0 (a closed tank valve), the time it takes for the IP to rise and move the HP seat, as opposed to from perhaps 8 bar during inspiration, allows a little overshoot.
However, this can also be caused by heavy greasing of the balance chamber making seat movement sluggish.
In any case, it's nothing to worry about if there's no IP creep.

 

[stepfen]

Great - so it seems all normal. Thanks a lot for all the info!

 

[stepfen]

So yesterday I dive with my newly serviced reg set. All was good. After I adjusted the second stages they both breath quite nice/smooth for me.
I don't particularly like the venturi effect of the R395 in the "dive" mode as it feels like my lungs get inflated too much by it. The best feeling I get is with the level somewhere halfway between dive and pre-dive.
Anyway thanks a lot once more for all the help! Keep up the good work guys
All the best

 

[rsingler]

While the R390 troubleshooting guide makes mention of "violent freeflow" being a reason to adjust the VIVA vane to less than max, the manuals have stopped giving more specific advice.
Before the G250 had a user adjustable VIVA, and instead just had a barely adjustable ridge on the outside of the case, they used to prescribe a vane adjustment that would permit a brief freeflow that then "will shut off by itself after a brief interval." That is the correct VIVA position, and not full on.

What is happening is that venturi pressure changes are pulling the diaphragm in to the "full on" position. On a flow chart, the breathing effort drops closer and closer to zero with higher flow rates, until "crossover" occurs, and the reg shifts to freeflow, which as you described is an active "inflating of your lungs." You have correctly adjusted your regulator.
This issue gets worse at depth, when "thicker" air makes venturi changes more pronounced.
It is rare that shops even do a flow check and fine tune venturi adjustments. Here is a picture from Regulator Savvy that shows crossover in action. Cracking effort is fine at 1.2", but venturi effects produce lower and lower breathing resistance until the reg crosses over into freeflow at 8 CFM in this example.

 

[uncfnp]

A search on SB and I found this fortuitous thread. Have been looking for a used Din Mikron for a while but they are a rare bird. Just saw 2 Mk11 din’s for sale today at what seems a good price and might work well as a substitute.

Built 2011 and 2012. Any problems sourcing kits or concerns about dated parts or needed upgrades. Known issues? Anyone with kits for sale?

 

[rsingler]

Mk11's can be great lightweight diaphragm regs.
The service kit is the same as for the Mk 16/18, and the seat is the same as in the current Mk17. The kits are still sold by Scubapro.
If there's no great corrosion, since you can replace both the seat and the orifice, you can make them as good as new.

 

[buddhasummer]

A search on SB and I found this fortuitous thread. Have been looking for a used Din Mikron for a while but they are a rare bird. Just saw 2 Mk11 din’s for sale today at what seems a good price and might work well as a substitute.

Built 2011 and 2012. Any problems sourcing kits or concerns about dated parts or needed upgrades. Known issues? Anyone with kits for sale?

Lisa, if you need, just ask.

 

[uncfnp]

Lisa, if you need, just ask.

Thanks. I know I can count on you. I decided to hold off for now and bought a new truck instead!

 

[buddhasummer]

Thanks. I know I can count on you. I decided to hold off for now and bought a new truck instead!

Sounds like way more fun than a service kit.