R108 Assembly Order

[vintageair]

Background:
My wife is the original owner of a ScubaPro R108 HP, Purchased in 1983., with a MK3 unbalanced 1st.
We always had it coupled to that MK3 until that literally wore-out.
Because the rig was STILL "under warranty", in 2015 ScubaPro replaced the 1st with a Mk2 evo (at reasonable cost).

We have been getting the rig serviced by authorized ScubaPro Dealers forever. The parts warranty is still valid.
Up to this last service cycle I have been happy with the result.
Whenever it was serviced it always breathed 1.0 @ 3000PSI primary.

Now for some reason (after the last service) it can't make even 1.2 and its "cracking effort" is worse than the Oceanic Alpha8 Octo on the same 1st. at any tank pressure. The 1st stage is in spec. (approx. 124 to 145 PSI over normal primary range)

I'm familiar with the 108, since over our diving career I have had to make small field adjustments to compensate for slight free flow issues. The wife really likes the way it used to breathe -effortlessly. So I kept it that way between service cycles, with slight adjustments of the orifice. (I was always mindful of the inside lever adjustment, and how the two adjustment effect each other, and how I must always push the lever before adjustment).
Sadly, all the LDS in my area have started to become unfamiliar with the R108. I never wanted to overhaul the rig myself, so I am unfamiliar with its proper assembly order. (My Bad) They are fine with my "balanced" R109 because they see so many.

My Problem - Question:
After looking at the available assembly diagrams, I think the last LDS tech assembled it incorrectly. I have already brought it back once, but the techs are really not familiar with this 2nd stage, and claim that its working "in spec". That may be true, but it suddenly cracks harder than it ever did before.

In the assembly drawings, there always seems to be a small washer under the lever adjustment nut. In some old drawings its shown as "demand valve washer" in another (from Jul 1988) its shown as "washer, plastic". Try as I might, I can't see it when I look for it. I really didn't want to disassemble the nyloc nut to look for it unless I had to, so at least in my external viewing it doesn't seem to installed, or its installed under the lever.

Should it this washer be visible without disassembling the (5-40?) nyloc nut?

I've attached pictures of what I see when I look. Note the close-up has me pushing the lever to open the valve to get a better look under the nut.

Thanks in advance for your help.

 

[DerekR]

Yes, there should be a metal washer under the lever fingers. The way that it is assembled, it will wear the nylon. It was either assembled in the wrong order, or the washer was somehow lost before assembly. Either way, you need to take it back apart and start over.

 

[vintageair]

Yes, there should be a metal washer under the lever fingers. The way that it is assembled, it will wear the nylon. It was either assembled in the wrong order, or the washer was somehow lost before assembly. Either way, you need to take it back apart and start over.

So if the washer was there, it would be visible in my photos?
AND note the assembly order in the 1988 diagram (attached) lists item 30 as a PLASTIC WASHER. And its listed as being between the nut and the lever, not under the lever.
Is that what I see under the lever in the photo? It looks like white translucent plastic. Or does that BELONG there?

 

[MichaelMc]

This thread may help.
Scubapro R108 High Performance -manual

On terminology/features.
The 108 is non-adjustable (by diver) and unbalanced.
The 109 is adjustable (by diver) and unbalanced. Your 109 is the "Adjustable Second".
The 156 is adjustable and balanced. A 156 is the "Balanced Adjustable"

Scubapro 2nd stage - R108 or R109 or something else?

 

[ams511]

Here is another thread that may be helpful: Sp 108

When I looked at the diagram posted, I noticed that it is 30 years old. I wondered if Scubapro made some changes and the washer was no longer needed so I checked some newer regs like a R190, R195, and R380 and all the diagrams showed a washer between the nut and the lever. However, in the 108 diagram the nut is kept and the washer is replaced while in the latter models the washer is kept and the nut is replaced. I wonder if the tech got confused and discarded the washer because the diagram said to but there was not a new one in the service kit to replace.

 

[herman]

I have never seen a similar second stage of any make that did not have a washer between the lever and nut and all the SP literature I have shows a washer between the lever and nut, including the service training manual. Looking at the photos, that may be the washer under the lever or it could be the insert. No way to tell without removing the lever. In any case, the order should be - insert (if it has one, some older models did not), lever, washer then nut.

I agree with ams511, this may be a tech wanna-be not realizing that the drawing was incorrect and simply not reinstalling it because it was not in the package.

 

[halocline]

I think it should go: Nylon tabbed insert, lever, flat metal washer, nyloc nut. In your photos it looks like the flat metal washer is missing.

 

[vintageair]

THANKS FOR ALL THE FEEDBACK and REFERENCES (I had seen DAs detailed assembly instructions and setup, so I had some solid info to start). There is plenty to discuss in the previous comments, but in this post I want to share what I have learned so far about the initial problem.

When I started the process this reg had a much higher cracking resistance than I remembered before the latest LDS overhaul.
I also noticed the washer that should be under the Nyloc nut appeared to be missing. (thx for confirming that) I thought before I disassembled the reg, I ought to try to restore the low cracking resistance. (The reason I opened it up in the first place) The lever seemed to work as intended and I couldn't see why adding a metal washer would make it breathe better. A plastic washer maybe would reduce friction, but not a metal one.

Setting Lever Height and Spring Preload

First thing I noticed was the lever took a lot of force to move. So I thought about what would minimize the amount of preload on the poppet spring, yet still allow enough spring pressure to prevent free flow.

My wife happily dives for an hour in 30 feet with her vintage 47 Cu ft LP steel tanks. So I set the 2nd stage using 2400 PSI.

This should be done at the highest IP pressure the 2nd stage would ever see coming from our unbalanced MK2 1st stage. (approx 2400 Primary pressure) I set the lever nut to allow viewing the rise (upward movement) of the lever as primary pressure dropped to zero. (the lever has always behaved this way) Each time I reduced the orifice pressure (CCW), the “under pressure” height of the lever rose higher. (I always depressed the lever while adjusting the orifice.)

Temporarily installing the diaphragm assembly allowed me to check for free flow (at the highest IP pressure) caused by setting the lever too high. If it free flowed with the diaphragm installed, I lowered the lever height by loosening the nut (CCW) 1/6th of a turn. After doing that, I re-set the orifice adjustment for minimal inhalation resistance. This resulted in reducing the spring preload but at the same time the lever re-rose to contact the diaphragm and caused some free flow. So I had to repeat the process again to prevent free flow when the diaphragm was installed. After a few iterations I found I had backed the nut to the point that one thread was showing above the nylon and I had backed the orifice about ¾ turn from where the LDS tech had set it. When I assembled the diaphragm I had found that (at highest IP) the lever had a very small gap (less than a mm) between it and the diaphragm. As the primary pressure dropped toward 1000 the gap would disappear. I left it adjusted this way, assuming normal water pressure would reduce the gap to zero. I left the rig under pressure (2300) overnight, with the tank valve off. No pressure loss was observed.

The result of this was to restore the low cracking effort that we had come to expect from this regulator.
(And a happy wife.)

I examined the used Nyloc nut that was returned to me after the last overhaul and with the help of a 10x eye loupe (it was really hard to see) I saw the faint telltale groove or scratch that the lever wore into the back side of the nut when purging. This could only have happened if the washer was missing for some time.

If I were to install the missing washer under the Nyloc nut, and repeat the process, then I would not have the required exposed threads when I was done. Perhaps sometime in the distant past a knowledgeable tech removed the washer to allow for the reduced spring preload, and thus the great performance she historically experienced from her reg.

In setting-up the reg have I done anything wrong?

 

[vintageair]

I know I should replace the missing washer. I don't want to make a "newbie" mistake, so advice is welcome.

There are 2 parts diagrams that I have found for the R108.
One says: Washer, Plastic # 01-060-107 (this washer is included in some 1st stage kits: MK11,11T,16/18,17/19)
The other says: Demand Valve Washer #108-58 (obviously an older part number)
Has anyone seen a plastic washer used here? I'm game to try it.
(Or maybe ScubaPro switched to metal because plastic wore quickly, this should be mentioned in a tech bulletin)

Since this is a 5-40 thread, can I just find any SS washer that will fit? (what grade?)
If someone can measure the correct washer (ID, OD, Thickness) , I will find a suitable substitute.

Can I just source the Nyloc nut from anywhere or is it "special" ? (I don't want galvanic issues)
(the original vintage nut looked like chrome plated brass)

Likewise, if this is a "special" washer, where can I source it?

The 11-080-41 Kit (from 1990s) includes a plastic washer, is this the required washer?

 

[herman]

Try contacting Bryan at Vintage Double hose, he likely has the parts on hand.