Breaking in 2nd-stage 'seats' by leaving adjustment knobs fully closed for awhile ?

[rsingler]

Not exactly, I believe that setting the orifice pushes the poppet back a bit, this is why the lever drops a small amount. So the spring pressure is actually pushing the soft seat against the orifice edge. The poppet movement is restricted by the lever lugs only when it is at it's highest point possible and the lugs are 'flat' against the side of the holes in the barrel.

Concur, if you use the orifice to set lever height as many manufacturer's manuals suggest. Thank goodness the Scubapro G250 is not one of those (and alas, the Aqualung Legend is). In the good old G250, the lever height is preset or bent to position, and not dropped intentionally by the orifice beyond the designed seal point. At full lever height, then, the G250 poppet should not move more than a miniscule amount when the adjustment knob is screwed in. That, I presume, is why one of our OP's regs wouldn't stop freeflowing despite adding all that spring pressure.

But, halo, a point well taken. Spring pressure is a significant component for many second stages. And actually, we're splitting hairs here. I'll bet that even a correctly set G250 orifice will allow .05mm of poppet shift when the adjustment knob is screwed in enough to make the lever tight against the lugs.

 

[scubafanatic]

OK, the tools and part have arrived, but I won't have time till this weekend to try any adjustments, though based on the most recent thread responses, it's beginning to sound like doing the proper adjustments go beyond just a simple screw in-screw out of the orifice, given the references to cracking pressure, etc. Hopefully I won't mess up something else while messing with the orifice adjustment.

BTW, what would be the recommended initial starting point for the 2nd-stage adjustment knob, the position it should be at when I begin the adjustment ?

 

[Couv]

Hi Scubafanatic,

Actually it is that simple. The height on each lever was checked/adjusted using a special tool, so that will not be an issue. All that is left is to account for is the seat break in by adjusting the orifice. The cracking pressure (if you want to check it) can be determined by pressurizing the regulator and inserting the second stage mouthpiece up into a sink or bucket.

The diver adjustable knob should be all the way out against the stop pin prior to adjusting the orifice. There are other techniques, but let's keep it simple.

Couv

 

[rsingler]

Hi Scubafanatic,

Actually it is that simple. Couv

Yup!
Go for it!

 

[scubafanatic]

I forgot to ask, when adjusting the orifice, which way am I supposed to turn the inline adjuster tool knob ? When to I turn it clockwise and when do I turn it counterclockwise ?

OK, I've got 4 full sets of MK 5's/109-156's assembled. (each set consisting of (1) 1st and (2) 2nds, and an SPG) With trial and error it appears I had to use the inline adjuster tool 'deep reach dimple' feature so the tool had enough "reach" to get to the orifice itself. The 'dimple' feature isn't completely clear in the instruction manual, but I figured it out. I'm just now getting a feel for how to tell when the tool is actually engaged.

I'll only have time to experiment with one set tonight, the IP is in the 125 - 135 psi range for 'unit # 1' as I'll name it, so that should be fine for a baseline on which to adjust the orifices on both '2nd's'.

The inline adjustment tool does appear to be working, so my next question is : what is the optimum free flow adjustment point ? Meaning do I want the 2nd stage adjustment knobs to be dialed all the way out before they begin a hint of free flowing

(BTW, the LP inline shut off valves are proving to be VERY handy too!)

Once I have a chance to fine tune all 4 sets next weekend, I'll then be doing a final leak test on each set via pony bottle/bath tub to eliminate any small leaks, if any.

 

[Couv]

Re: Orifice adjustment-Clockwise to increase cracking pressure, counter clockwise to decrease cracking pressure.

"By the Book" i.e. ScubaPro specs, with the knob all the way out to the stop pin, there should be no freeflow. However, lots of folks who service or just tune their own gear like a slight freeflow (just a hiss) with the knob on the stop pin. Of course, it goes without saying that the hiss should cease when the knob is turned in less than 1 turn. I like mine to stop ff at approx 1/2 turn. In addition to having a low cracking pressure, it also puts less pressure on the soft seat while in storage which extends the life of the seat.

.................................................................................................

Ed it (private joke) LTSD said it in better detail here:

Here are the basics.

Rightie-tightie, Leftie-loosey.

Clockwise = harder breathing. Counter-clockwise = easier breathing.

Turning the orifice clockwise, whether using the fancy inline adjuster, or a screwdriver or allen wrench results in increased seating pressure against the soft seat, AND lowers the demand lever.

Turning the orifice counter-clockwise reduces pressure against the soft seat AND raises the demand lever.

Remember, moving the orifice changes both the amound of pressure being placed against the soft seat and the lever height.

If it hisses at you, turn it clockwise.

If it is silent, turn it counter-clockwise until it hisses, then clockwise until it just stops.

And to think, they said tuning a regulator should only be left to trained professionals

Others will chime in with more detailed (and better!) procedures, but in a nutshell that is really about all there is to it.

Oh yeah, and remember you've already been admonished to ALWAYS hold down the purge while moving the orifice.

Perform all adjustments with the knob on the 2nd stage set to the easiest position (full counter-clockwise).

A very slight hiss (VERY slight) is acceptable at the easiest position, with understanding that just a slight turn of the adjuster will stop the leak, but I typically tune all of my adjustable 2nds to the easiest setting that does not leak... this allows me a little leeway in case I did not adequately break in the seat prior to diving it.... generally the soft seat will take a set after a couple dives, and if you tune right to the very edge you may find you need to break out the inline adjusting tool and retune it... which is acceptable too. After you tune a few, you'll get the feel for how "hot" you can go on tuning.

Best wishes.

 

[Zung]

Sorry brother couv, I'm with LTSD on this one: tune it so it just stop free flowing with the knob all the way out:that's 1 less thing to worry about in the field (my brain capacity is very restricted). Anyway, at this stage of tune, it'll free flow a bit in a head down position, or when facing a strong current, so an extra 1/4 turn or so is in order.

 

[Couv]

No need to be sorry Brother Zung, that is what I should have done with the OPs regs. I was in a hurry to get them back to him so I left the final tune the way I usually have mine (slight hiss.) As it turned out, they needed a bit more than the usual tweak. Lesson learned.

 

[scubafanatic]

About the preferred adjustment position. I like easy breathing, but not to the point of instability, meaning a 2nd stage set up on the knife's edge of high-performance while on dry land may behave differently (become unstable) than while diving face-down underwater or giant-striding off the boat deck and smacking into the water. So, given the trade-offs, where would you set your 2nd-stages ?

---------- Post added August 13th, 2014 at 01:22 AM ----------

Sorry brother couv, I'm with LTSD on this one: tune it so it just stop free flowing with the knob all the way out:that's 1 less thing to worry about in the field (my brain capacity is very restricted). Anyway, at this stage of tune, it'll free flow a bit in a head down position, or when facing a strong current, so an extra 1/4 turn or so is in order.

Can you clarify ? Do you mean first adjust the 2nd stage so it just stops free-flowing with the knob all the way 'out', then do a second final adjustment to the orifice by turning the orifice 1/4 of a turn clockwise ?

 

[Zung]

No, I mean: since your gear is mostly broken-in, tune the orifice just pass the point where it stops free flowing, that'll give you a hair below 1 inch of cracking pressure. That's when you're on land.

Dive it, and if you're always in a head down position, or if you're facing strong current, it'll free flow a bit, so you want to turn the knob clockwise by 1/4 turn or so to stop it. That's when you're diving.

Or, if you prefer, tune the orifice to about 1.1 inch, and it shouldn't free flow at all.

Don't worry too much about all these, even if there's some free flow, it's not catastrophic. And the difference between 1 and 1.1 inch of cracking pressure is REALLY hard to tell when you dive.