Marginal Reg Testing Results After Service?

[Marek K]

I recently sent out the family's four regulators for annual service by a very reputable dive shop. One old Sherwood 3300 Magnum, one newer Sherwood SRB5900 Magnum, and two entry-level Mares Axis R2.

The shop was good enough to report back the test results. I'm comparing them now to the published specs, and it appears that the tested values are marginal or just outside tolerances. I don't know enough about the technical aspects of regulators to know whether I should be worried at all or not.

Both Sherwoods should have an IP between 135 and 150 psi. Both tested right at 135.

Both Sherwood second stages are supposed to have a cracking pressure of about 1". The 5900 tested at 1.2" and there was no result for the 3300.

I can only find metric specs for the Mares -- IP should be 9.8 to 10.2 bar. (The latter is just a bit less than 150 psi, isn't it?) One reg tested at 151 psi, and the other at 152 psi.

Second stage cracking pressures for both Mares were 1.2".

I'm not so worried about the cracking pressures. That would mean slightly higher cracking effort, but less tendency to free-flow, right? All four seemed to breathe fine in a pool test.

But the IP's...?

OBTW, all four alternates are Mares Vipers. Cracking pressure on three was 1.7", and the fourth was 1.2". I'd expect it to be set a bit high on an alternate, yes?

 

[scubafanatic]

...none of your 2nd-stages are diver-adjustable, so it doesn't amaze me the cracking pressures were set a bit on the high side, as you can't dial them down to reduce free flow sensitivity...which is one reason I prefer adjustable 2nd-stage regs. (although I do own some nice older Mares regs which are back up regs these days) Personally I don't like to have to have a high cracking pressure to offset the lack of 2nd-stage adjustability though. 1.7" on the Vipers is a bit 'high', at least in my book, but again, it's not uncommon to be on the high side as it's both non-adjustable and an octo. The IP's on the Mares is a touch 'high' but they're barely 'out of spec' there so I really don't see a problem, as long as the IP is steady and doesn't creep higher...'creep' does signal a problem. Also, make sure your Mares regs received the modern 'tri-material' HP seat...the older Mares seats wore out quickly, and while Mares upgraded to the 'new' seats a while back, it's possible there might still be the old version seats in some shops inventory, so make sure you didn't get new 'old stock' seats installed.

 

[LeadTurn_SD]

Your Mares R2 is a piston first stage, spec'ed IP range is 142 - 152 psi.

It is at the high end of spec.... but fine as long as there is no "creep" after lockup.

Cracking effort of 1.2 on your Axis 2nd stages sounds fine... I believe 1.1 - 1.2 inches is as low as you can go on most Mares primary 2nd's without running into case geometry fault issues (and resulting tendancy to freeflow in face down position). For most regulators (adjustable or not), 1.2 is pretty good and will breath very well.

1.7 is "ballpark" for non-adjustable octos. You can of course go lower, but then they become more finicky if not handled carefully at the surface....

Best wishes.

 

[herman]

The exact IP pressure is really not a big deal. As long as your second stages are set up with the first stage they are attached to, everything is good. Tuning a second stage is a balancing act between forces, as long as you keep the starting IP constant, reguardless of its value- with in reason, the other components are adjusted to work with it. There are times when you need to tweek the IP one way or the other to accomplish the balancing act but that is the techs problem. The place where widely varied IP between different first stages will bite you is if you swap second stages around. If one reg has a high end IP and another a low end IP and you swap the second stages it's likely one will slightly freeflow and the other will be a tad harder breathing, assuming unbalanced second stages, balanced ones are a lot more tolerant of IP changes. For most divers this is not a problem, with my Frankenstine regs I never know what second will be connected to what first so I set everything as close to one value as I can. Anyone know where I can get a 1959/62/75/80 Scubapro/US Diver/Dacor/Voit reg serviced?

 

[Marek K]

The IP's on the Mares is a touch 'high' but they're barely 'out of spec' there so I really don't see a problem, as long as the IP is steady and doesn't creep higher

Your Mares R2 is a piston first stage, spec'ed IP range is 142 - 152 psi.

It is at the high end of spec.... but fine as long as there is no "creep" after lockup.

The exact IP pressure is really not a big deal. As long as your second stages are set up with the first stage they are attached to, everything is good.

Thank you, Gentlemen!

 

[muddiver]

The exact IP pressure is really not a big deal. As long as your second stages are set up with the first stage they are attached to, everything is good. Tuning a second stage is a balancing act between forces, as long as you keep the starting IP constant, reguardless of its value- with in reason, the other components are adjusted to work with it. There are times when you need to tweek the IP one way or the other to accomplish the balancing act but that is the techs problem. The place where widely varied IP between different first stages will bite you is if you swap second stages around. If one reg has a high end IP and another a low end IP and you swap the second stages it's likely one will slightly freeflow and the other will be a tad harder breathing, assuming unbalanced second stages, balanced ones are a lot more tolerant of IP changes. For most divers this is not a problem, with my Frankenstine regs I never know what second will be connected to what first so I set everything as close to one value as I can. Anyone know where I can get a 1959/62/75/80 Scubapro/US Diver/Dacor/Voit reg serviced?

I'm right there with you. My Sherwoods are not that old though. I swap my Kerby Morgan Superflow 350 second stages around from a Sherwood Magnum, a Sherwood Brut, a Poseidon Xtream Duration and a Poseidon Xtream Oxyegne. So the IP's all have to be around 135'ish.

 

[Marek K]

So the problem usually is when the IP is too high? And/or creeping higher?

I know IP creep is bad. Too lazy to research, but as long this thread is open, what does that eventually lead to? And any way to detect it short of a gauge?

On the other hand, what does a too-low IP lead to?

 

[Zung]

Herman said it all above, so let me make a terse reply:

1. The IP can be at the upper end of its range, no problem if it's stable and if the second is tuned to it. The flowrate is a bit better.
2. If the IP creeps, the second'll start freeflowing after a while, if it's tuned "soft". To detect it, an IP gauge is best, or you can leave it on for 10-15 minutes; if the creep is bad, the second'll freeflow.
3. The IP can be at the lower end of its range, no problem if it's stable and if the second is tuned to it. The flowrate is a bit worse.

 

[LeadTurn_SD]

So the problem usually is when the IP is too high? And/or creeping higher?

I know IP creep is bad. Too lazy to research, but as long this thread is open, what does that eventually lead to? And any way to detect it short of a gauge?

On the other hand, what does a too-low IP lead to?

The 1st and 2nd stages have springs and seats that are designed to work "optimally" within a range of IPs. They can operate "ok" outside that range, up to a certain point.

2nd stages can be tuned to match a 1st stage that is at a higher-than-spec IP, but at a certain point if the IP is too high it is going to overpower the spring on the 2nd stage demand valve, and a freeflow will occur.

Too low an IP can (if really low) result in poor performance, and possibly inadequate air delivery in an emergency if the demand suddenly rises (two stressed divers breathing from same first stage in OOA situation).

An IP that "locks-up" in normal range but then begins creeping slowly higher usually indicates a failing HP seat. Some creep is "ok", too much is not. How much is acceptable varies with the brand and model of 1st stage.

Best wishes.

 

[tfsails]

Lots of good answers here. Some makers allow as much as 15psi creep after initial lockup. Others don't allow much more than a pound or two. Depends on the manufacturer. I totally agree with the statement that tuning a second is a balancing act between several forces. I deal with that every day.