Piston 1st IP adjuments simplified

[raftingtigger]

20 PSI creep over several minutes would be totally unacceptable to me. If you were diving a single tank, and as such cycling the first stage every few seconds, it doesn't really matter, but with doubles you are allowing one of the first stages to sit closed for several minutes, so the slow creep could really cause problems.

20 psi creep (then stop and go no higher overnight) is about what I'm getting. That is clearly out of standards, but the IP is stopping at 150 (or below). I'm more comfortable with 2 completely independent 1sts even if one is sitting pressurized and static for more than 20 min (closer to 40 min the way I dive). There are a lot of ways to get around leaving one 1st on standby for a long time - none of which I think is acceptable (eg. close the tank valve, periodically purge the 2nd).

What I did find quite interesting is that the IP would creep to 150 over 20 min then stop. When leaving pressurized with an open tank valve for >12 hours the IP would go DOWN to 140-145. I certainly can't explain that, but is reassuring. This happened both times I have left it pressurized for a long time.

 

[rsingler]

20 psi creep (then stop and go no higher overnight) is about what I'm getting.
What I did find quite interesting is that the IP would creep to 150 over 20 min then stop. When leaving pressurized with an open tank valve for >12 hours the IP would go DOWN to 140-145. I certainly can't explain that, but is reassuring. This happened both times I have left it pressurized for a long time.

I've seen the same thing, tigger. I think what is happening is that you're eventually (e.g., 20 min) getting good lockup. Then as it sits overnight, microscopic leak from the second stage allows IP to drift down, but not enough to trigger valve opening. The 1st "wanted" to seal at a lower IP (early lockup), but couldn't. Once the seat/piston DID seal after drift, the valve wouldn't reopen until it dropped to some lower IP than the place the drift finally sealed it.

Sounds to me like you're really close. It might improve over time, though I'd understand your bagging it and going back to plain 10's since the drift is so large.

 

[raftingtigger]

Rsingler, Guess what I need to do is dive more often

 

[rsingler]

Rsingler, Guess what I need to do is dive more often

Isn't that our problem? Every single one of us?
Just paid the balance yesterday on my August trip to Grand Cayman!!!!
Can. Not. Wait.

 

[rhwestfall]

It would be interesting to get it on one of the cycling machines to see if it would aid in taking a set....

 

[raftingtigger]

This is what I have right now.

Firsts:
MK10+ with yoke, Lock 135, drift to 152, difference 17 psi No SPEC boot yet
MK10+ with DIN, lock 140, drift to 151, difference 11 psi, SPEC boot OEM, not yet installed or packed
MK10 with DIN, Lock 135, drift to 139, difference 4 psi, SPEC and packed
XS Scuba DIN, Lock 130, drift to 138, difference 8 psi, Not SPEC capable
MK5 DIN, 4 port, Lock 130, drift 132, difference 2 psi, Not SPEC capable

The last 3 regulators are certainly within specifications. I have an old MK5 2 port not listed.

 

[halocline]

Notice how the MK5 doesn't creep?

They do tend to lock up better than MK10s. But what you're listing, 17 and 11 PSI of creep, is awful.

BTW, I would not use the term "drfit", that's more about IP moving around unpredictably. When IP slowly increases after a breathing cycle, that's definitely creep. "Lock" is where the reg finally stops creeping. So your first MK10+ is locking up at 152, way too high IMO. The problem with it not immediately rebounding to that pressure when you breathe is that your IP during demand is much lower than your final lock up IP, and that makes it impossible to accurately tune the 2nd stage.

You can try a couple of things. 1) Make sure you are using a 90 duro HP o-ring, maybe try polyurethane, and use PTFE grease (Christolube) to really lubricate it. If there's any glaze on the piston shaft, you could remove it with micromesh. Those steps might lower friction on the piston shaft and help get a better lock up. 2) Get out the loupe and very carefully inspect the piston edge, and really clean it with micromesh, so there are absolutely no flaws even under 10-15X magnification.

I suspect that no matter what you do, you'll still have some creep in the MK10+. I just don't think SP really got the rounded piston right until the composite piston in the MK25. Although, I do have a MK20 with the first, all SS piston, and it locks up great.

Hopefully it will be a fun project! If you want to convert them to regular MK10s, I have plenty of NOS pistons.

 

[halocline]

An industrious little birdie reminded me that SP uses the term "drift" to describe creep in some of their bulletins, so there it is. But I personally still wouldn't describe it that way, because there is a different thing that happens on some regulators, where after each purge or breath, the IP locks up at a slightly different pressure, sometimes higher, sometimes lower. I would call that 'drfit' because it's moving around ion no particular direction. I found this to happen with my old DA aquamaster until I replaced the mainspring.

Anyhow, raftingtigger, please feel free to use whatever term you like, and if you do try some of the suggestions I made, hopefully they'll help. 11 psi of IP movement (drift or creep or sashay or crawl) is quite a bit.

 

[raftingtigger]

halocine,

Thanks for the offer. My MK10+s have been swapped with MK10s which are much better behaved. Once I get the DIN adapters all on I'll have a consistent fleet of MK10/109As.

 

[Bryan@Vintage Double Hose]

It would be interesting to get it on one of the cycling machines to see if it would aid in taking a set....

It's a very beneficial tool that helps insure there are no surprises when a customer gets their regulator back.