Marginal Reg Testing Results After Service?

[halocline]

It would not surprise me if the mares viper octos started freeflowing slightly with IP in the 150 range after a few dives. That's assuming you're talking about the old Dacor viper side exhaust octo. Maybe you'll get lucky, I didn't. If they do start flowing, you can take it as a good excuse to dump them and get better octos.

If the Mares 1st stages are unbalanced pistons, then having a high IP with a full tank is not such a bad thing; it will drop as the tank pressure does, so starting at 150 allows it to drop without falling below the manufacturers range. In general, though, with balanced 1st stages, I like to set the IP on the low side. It doesn't go down as the reg wears, that's for sure.

If I had a first stage creep 15 PSI I would not use it. To me, given the multitude of inexpensive, excellent regulators out there, that much creep is not acceptable.

 

[tfsails]

Mattboy--that 15psi creep (actually 1 bar) is totally acceptable in a Poseidon first stage. It's right in Poseidon's repair manual. Of course, that's part of what makes Poseidons unique...

 

[Marek K]

It would not surprise me if the mares viper octos started freeflowing slightly with IP in the 150 range after a few dives. That's assuming you're talking about the old Dacor viper side exhaust octo. Maybe you'll get lucky, I didn't. If they do start flowing, you can take it as a good excuse to dump them and get better octos.

Yes, they're the side-exhaust ones. Why would they in particular start to free-flow?

If the Mares 1st stages are unbalanced pistons, then having a high IP with a full tank is not such a bad thing; it will drop as the tank pressure does, so starting at 150 allows it to drop without falling below the manufacturers range.

Yes, both the Mares are unbalanced pistons. Does IP tend to drop with those, as tank pressure falls? Could that be why the IP was set so high?

In general, though, with balanced 1st stages, I like to set the IP on the low side.

OK, why? Yes, both the Sherwoods are balanced (IP = 135).

 

[halocline]

Yes, they're the side-exhaust ones. Why would they in particular start to free-flow?



Yes, both the Mares are unbalanced pistons. Does IP tend to drop with those, as tank pressure falls? Could that be why the IP was set so high?



OK, why? Yes, both the Sherwoods are balanced (IP = 135).

I found the Dacor viper that I had was horribly sensitive to changes in IP, especially as the seat wore down a little. This in combination with it's crappy breathing led me to give it away to a friend, then in a fit of guilt give the friend a proper octo.

In an unbalanced piston reg, the IP is influenced by the tank pressure, and drops as the tank empties. On my MK2 a full tank yields about 145 PSI, near empty about 125. If you checked yours with a full tank and it was near 150, fine. If it was that with a near empty tank, that's too high.

I set IP low on my balanced piston regs, although they are a different type than yours. Mine are flow through piston designs, which have very high flow and quick response, so they can easily supply a couple of 2nd stages all the air I could ever need at a low IP. Since IP will gradually rise as the seat wears, I set it low to start.

Your sherwoods are flow-by piston regs, and "balanced" not by equalizing air forces, but by moving the HP orifice on a set of cup washers; it's an ingenious and simple design. 135 is probably about an ideal IP for them; I don't consider that low at all.

 

[Marek K]

I found the Dacor viper that I had was horribly sensitive to changes in IP, especially as the seat wore down a little. [...] In an unbalanced piston reg, the IP is influenced by the tank pressure, and drops as the tank empties. On my MK2 a full tank yields about 145 PSI, near empty about 125. If you checked yours with a full tank and it was near 150, fine. If it was that with a near empty tank, that's too high.

I didn't measure the IP; the shop did. I have no idea how much tank pressure they used, but I'd assume near-full -- Sherwood, for one, specifies tank pressure between 2700 and 3500 psi.

Are you saying that a high IP might induce the Dacor Viper to free-flow? But then, if the IP falls so drastically as the tank empties...

In any case, we've used our Vipers for about three years now, with no problems other than the usual occasional free-flow at the surface that's easily remedied with turning the mouthpiece down. I agree with you, not the easiest-breathing second stages, but I do like the no-rightside-up feature...

 

[Marek K]

Interesting... I did ask the shop, and their tech sent me a very nice e-mail back.

He said that the IP for Sherwoods is supposed to be 130-140 psi, and for Mares 140-155 psi.

Um, every reference I've ever found for Sherwoods specifies 135-150 psi. And using a conversion factor of 14.7 psi/bar, the Mares metric specs of 9.8-10.2 bar would be about 144-150 psi.

OK, I'm assuming the difference isn't that significant. But where could his specs be coming from?

I did ask him back, but haven't received an answer yet.

 

[redacted]

Interesting... I did ask the shop, and their tech sent me a very nice e-mail back.

He said that the IP for Sherwoods is supposed to be 130-140 psi, and for Mares 140-155 psi.

Um, every reference I've ever found for Sherwoods specifies 135-150 psi. And using a conversion factor of 14.7 psi/bar, the Mares metric specs of 9.8-10.2 bar would be about 144-150 psi.

OK, I'm assuming the difference isn't that significant. But where could his specs be coming from?

I did ask him back, but haven't received an answer yet.

I have seen similar "spec" changes in some Scubapro documentation, usually related to torque specs. One problem we have is most of this documentation is bootlegged as the manufacturers do not usually make such information available to consumers. So it may well be that the tech is looking at different documentation, with different specs, than you have available. In any case, the differences you are citing are so small as to be negligible in their performance effects. (They could even be accounted for in gauge errors.)

But it might be interesting to send your questions to the manufacturers and see if they are willing to even address the issue.

 

[Marek K]

I have seen similar "spec" changes in some Scubapro documentation ... One problem we have is most of this documentation is bootlegged as the manufacturers do not usually make such information available to consumers.

Well, yeah... but "bootlegged" doesn't mean wrong.

I'm specifically getting these specs from the service manuals on frogkick.dk, but I've seen the same Sherwood manuals elsewhere.

I believe Sherwood also lists their IP specs in their user's manuals -- I'd have to check at home, though. Same IP range as in their service manual.

Sherwood hasn't changed these specs for their regulators in the past 25 years.

 

[halocline]

Interesting... I did ask the shop, and their tech sent me a very nice e-mail back.

He said that the IP for Sherwoods is supposed to be 130-140 psi, and for Mares 140-155 psi.

Um, every reference I've ever found for Sherwoods specifies 135-150 psi. And using a conversion factor of 14.7 psi/bar, the Mares metric specs of 9.8-10.2 bar would be about 144-150 psi.

OK, I'm assuming the difference isn't that significant. But where could his specs be coming from?

I did ask him back, but haven't received an answer yet.

SP specifies 125-150 for IP, a much wider range. The differences you're talking about are really minimal. I would just use the lower end of the scale for balanced 1sts (or somewhere in the middle) and the upper end for unbalanced pistons with a full tank. Otherwise, don't worry about it.

The important thing is the solid lock up of IP with no creep by the 1st stage. As seats wear, it usually requires more pressure to produce an airtight seal in the 1st stage, and this pushes IP up.