ScupaPro Mk10+ IP creep

[Zung]

Yes, with mattmagic.

 

[elan]

Thanks Zung, you guys are awesome

I cannot wait for my second MK5 to come in for rebuild, these things are addictive
I think I have enough regs now to assemble a DIR rig and piss my DIR buddies off

 

[Couv]

I can only imagine the technical difficulties involved with machining substances ethereal.

.....and metric on top of that!

I just crawled out of the "WABAC Machine" WABAC machine - Wikipedia, the free encyclopedia and located THE thread- http://www.scubaboard.com/forums/regulators/335230-mk-5-turret-retainer.html Can you believe we had approx 60 of them made yet there are none to be had‽

 

[mahjong]

Thanks, Halocline. I'm certainly sold on your explanation. My understanding of regs is very basic. I couldn't help but think that proper spring tension mattered, but couldn't quite draw the distinction between IP drift and creep.

Just an added clarification question: Is there the possibility that an old spring that's lost proper tension could lead to piston action that could in turn lead to the seat going bad? So the bad seat is causing IP creep, while the bad spring was a contributing factor in the seat going bad?

I've never seen a mainspring cause a problem in a balanced piston 1st stage. It certainly wouldn't cause creep. I've had a few MK5s with low IP, like 120 with the shortest seat and no shims, I switched the spring, little effect. Someone sent me a NOS spring for a MK15, tried it at the next rebuild, no effect. These springs are pretty beefy and they're relaxed when the reg is not pressurized, so they last a really long time. I've read that sometimes they can stiffen up over time, resulting in high or drifting IP, but I've never personally experienced that. Drifting means they lock up at a slightly different IP every time you cycle them, and is not creep where the IP rises when the reg is closed.

There was an issue with mainsprings in some old US Divers doublehose regs; one of the vintage fans (maybe herman?) found some new springs that worked well. With those, the IP would drift down, usually you'd want to set it pretty high and it would hold for a while, but after a couple of dives it would be back down to under 125. I guess the springs were losing strength and causing IP to drop, which is more intuitive to me than a bad spring causing high IP.

This is a really simply problem, either the seat is bad or the piston edge (much more likely IMO) is bad.

 

[oncor23]

Picked up my regulator. The head tech adjusted both 2nd stages with me there to okay everything. They both seem to be working the way I want...less likely to free flow. The 1st stage was "adjusted"; they told me they lowered the IP. I was told it is now locking up. So, I dove it...without issues. After I got home, I did check it with my IP gauge. Here's what I got:

Starting pressure after a purge or breathe: 122 psi
45 secs: 127
60 secs: 128
5 minutes: 137

I will continue to check it after every dive to see if the IP creep is stable or getting wider. Who knows what they actually did to the 1st stage. I doubt that the piston was changed. Maybe a new HP seat. Did they change the number of shims to get lower initial pressure?

So...it ain't perfect. It is considerably better than it was. We will see how it goes.

 

[elan]

Picked up my regulator. The head tech adjusted both 2nd stages with me there to okay everything. They both seem to be working the way I want...less likely to free flow. The 1st stage was "adjusted"; they told me they lowered the IP. I was told it is now locking up. So, I dove it...without issues. After I got home, I did check it with my IP gauge. Here's what I got:

Starting pressure after a purge or breathe: 122 psi
45 secs: 127
60 secs: 128
5 minutes: 137

I will continue to check it after every dive to see if the IP creep is stable or getting wider. Who knows what they actually did to the 1st stage. I doubt that the piston was changed. Maybe a new HP seat. Did they change the number of shims to get lower initial pressure?

So...it ain't perfect. It is considerably better than it was. We will see how it goes.

I have a similar situation with one Mk5 that I have got recently, it stops at 125 after the purge and creeps to 135. Not ideal. Upon examining the piston I have found that the piston edge is a bit scratched. Careless handling by a tech I bet. So it takes more of the IP swing to make it lock.

In your case it likely is the same cause. But I might be wrong. They might have replaced the seat with a thicker one or removed a shim to reduce the IP. Its not really a fix but rather a bandaid. I guess the permanent solution would be replacing a piston or doing some polishing using the link provided by Monseur Zung.
In my case I have left the piston alone as it locks properly and I might try to do the procedure during th next service.
In your case watch it for a while, as the seat takes a set it might improve as it will greate the groove

 

[Couv]

Picked up my regulator. The head tech adjusted both 2nd stages with me there to okay everything. They both seem to be working the way I want...less likely to free flow. The 1st stage was "adjusted"; they told me they lowered the IP. I was told it is now locking up. So, I dove it...without issues. After I got home, I did check it with my IP gauge. Here's what I got:

Starting pressure after a purge or breathe: 122 psi
45 secs: 127
60 secs: 128
5 minutes: 137

I will continue to check it after every dive to see if the IP creep is stable or getting wider. Who knows what they actually did to the 1st stage. I doubt that the piston was changed. Maybe a new HP seat. Did they change the number of shims to get lower initial pressure?

So...it ain't perfect. It is considerably better than it was. We will see how it goes.

Personally, I think 10psi is too much creep. But if it definitely stops at 137 then probably no harm can come from it. However, it would be a PIA to tune the second stage, especially an unbalanced one.

With the MK10+ the intermediate pressure can be adjusted with shims under the hp seat cap or on either side of the spring. I don't know if the + has a series of hp seats (like a real MK10) that can be used to adjust IP. I do like the shim under the cap idea though.

 

[Zung]

Bro, the MK10+ uses the same seats as the MK20/25 and there's only 1 single size. The IP has to be adjusted with shims, and they go only on 1 side of the spring opposite of the piston crown, and the seat retainer. That's because of the plastic piece built in the piston just below the crown.

 

[halocline]

Starting pressure after a purge or breathe: 122 psi
45 secs: 127
60 secs: 128
5 minutes: 137

That's not even close to acceptable IP creep to me. Chances are it will get worse, too. You can try leaving it pressurized overnight, maybe that will help, but probably it won't do much. Assuming the guy changed the seat when you brought it back, meaning this piston has creeped with two different new seats, you need a new piston or possibly yours could be re-surfaced. What I don't understand is how a supposed professional tech would not know this, or let a regulator out of the shop with that much IP creep.

 

[Zung]

"... they told me they lowered the IP..."

I think the only thing they did was to remove a shim. I can understand it from a business point of vue: they did something and collected some money against it; whatever extra they have to do is pure loss. If they had to throw in a new seat, that'd be another extra loss, worth at least $2. Whether or not this is ethical, or even professional, is usually not relevent.

OTOH, I know for sure SP would replace the piston under warranty: a LDS over here confirmed it. But since this can't be a warranty case, and the specs are nearly borderline, your LDS thought they could get away with it. That's sadly common: I have 1 MK20 and 1 MK25 that were freshly serviced before I bought them, and they had a similar case of creep.