Help with Regulator Age and ID

[halocline]

In the MK5 there's a turret, meaning air from the piston goes through a hollow bolt just to get to the LP ports. In the MK1, there's no turret bolt. That could affect flow easily as much as the direction of the flow out of the LP port, probably more.

But none of it really matters, the bottom line is that the 2nd stage can't flow anywhere near as much gas as the first stage can flow. It looks like the 2nd stage in the Navy tests was unbalanced, meaning much more sensitive to changes in IP. A balanced 2nd stage, especially a center-balanced valve like the D series with very little downstream bias, will tolerate much higher variances in IP with less cracking effort change. I think I've made this comment before on your thread about feeding a single 2nd stage from two tanks with two first stages.

Bottom line, I agree with the others. Unless the 1st stage is really lacking in flow capacity, at anything even close to recreational diving depths, with a single diver breathing off a regulator, the 2nd stage determines the breathing characteristics.

 

[Couv]

.....So Luis, this confirms your position.....

Agree; and if my estimations are close, at > 23 SCFM it's pretty much a moot point.

(106/1080 = 0.098 cu ft per psi X 120 X 2)

John, thank you for your efforts.

.......................................

OK, Halo is the early bird and got the worm, but I was busy calculating.

 

[herman]

John, if you take a good look at the graphs what you will find the data points are all over the place and there is not enough information to make any conclusions with. I printed out all 4 “wet with valve open” test so I could really compare them and several things immediately jumped out at me. First, assuming the test parameters are the same….and if they are not the test are invalid, the exhaust pressures shown on the graphs should be very close to the same for all test, in fact, they are considerably different. Both regs in 69 came in at around 19 cmWC and one would expect that they would be close to the same, however in 70 they both came in at around 14 cmWC. Roughly a 5 cmWC (25%) improvement, this means that the seconds on the 69 test were different from the ones in the 70 test (or had been adjusted) OR the test were somehow conducted differently. This could simply be differences in individual regulators but to be meaningful test, a lot more samples must be done to average out the variations between the regulators. To evaluate the performance differences in the first stages the second stages must remain the same and have the same flow characteristics, obviously these do not. I understand that the exhaust has nothing at all to do with the possible flow rates of the first stage but it does show the test did not include enough test samples to make conclusions based on the finding of the test.
Moving on to the inhalation pressure, there are inconstancies here as well. I am going to just use the 200 ft endpoints to make things easy and use rough reading of the graphs since the numbers are not that close. The MK-1 in in 69 had a inhalation resistance (at 200ft) of 6 cmWC however in 70 it had one of 15 cmWC. An increase of 9 cmWC (250%) …. Even accounting for individual reg variances, this number should have remained a lot closer, something is way off here. On the other hand, the MK-5 increased from 10 cmWC in 69 to 11-12 in 70, a reasonable variance between regs. What is interesting is both the 69 and 70 MK-5 data is much better than the 70 MK-1.
Even with all this widely ranging data, there is an even simpler reason these test are useless for evaluating the first stage. To be able to evaluate the maximum flow rate of a first stage you must have some way of allowing it to flow to it’s maximum potential with no external flow restrictions and one of the biggest in a scuba reg is the second stage. No second stage is capable of flowing anywhere near the max flow of any first stage so as soon as you attach one, you can not draw any conclusions about the flow capabilities of the first stage since all you are measuring at that point is the flow rate of the second stage. Which brings me to the main point, regardless of whether the MK-1 has a higher flow potential than the MK-5, the second stage is going to be the limiting factor so it makes no difference at all even if the MK-1 does have a slightly higher max flow rate. No diver, or machine for that matter, is going to be able to push any first stage to it’s flow limits as long as it is doing so through a second stage.

 

[John C. Ratliff]

Couv,

Here's the math on that problem. The tanks are old USD 1800 psi rated steel tanks, for 52 cubic feet/tank, or 104 cubic feet total when full. I replaced my twin AL 50s with them a few years back, and they float so I need to add about 6 pounds of weight to them to get down.

Test 2

104 ft3 / 1800 psi = 0.058 ft3/psi

200 psi/min x 0.058 ft3/psi = 11.6 ft3/min

It's not quite the output you showed, but it is respectable for the purge valve.

Herman,

Looking again at the graphs, the exhalation resistance you are seeing compares the regulator breathed wet and dry, and that could account for some of the differences you are seeing on exhalation resistance.

SeaRat

 

[herman]

Couv,

Here's the math on that problem. The tanks are old USD 1800 psi rated steel tanks, for 52 cubic feet/tank, or 104 cubic feet total when full. I replaced my twin AL 50s with them a few years back, and they float so I need to add about 6 pounds of weight to them to get down.

Test 2

104 ft3 / 1800 psi = 0.058 ft3/psi

200 psi/min x 0.058 ft3/psi = 11.6 ft3/min

It's not quite the output you showed, but it is respectable for the purge valve.

Herman,

Looking again at the graphs, the exhalation resistance you are seeing compares the regulator breathed wet and dry, and that could account for some of the differences you are seeing on exhalation resistance.

SeaRat
View attachment 170041

That is not the case John. I have them printed in front of me and the 4 that I am using are clearly marked" wet, valve open". I was careful to make sure I was comparing the same conditions. As it happens, I also printed the “dry, open valve” graphs as well. Looking at the 70 dry graphs, they farther illustrate the point. The exhaust values for it both the MK-1 and 5 are vastly different, with the MK-1 at about 3 cmWC as opposed to about 8 cmWC for the MK-5, this should not be. Even allowing for individual regs, the values should be close to the same. Unless you use equal test conditions, you can not use the results to make any conclusion. These second stages are clearly not equal.

 

[John C. Ratliff]

Herman, I just learned how to switch views on the screen to see these in horizontal format. (I know...ol' guy syndrome!) So I see what you mean on this. I have one other question: when did Scubapro switch to silicone exhaust valves?

I have a few questions about this report myself. The NEDU's reason for rejecting these regulators has to do with the adjustment factor that the diver can make on his own. It can, under certain circumstances cause it to be hard to breath; this is the point of that adjustment, so that in high current a diver can prevent free-flow. I'm curious why the NEDU would think a diver cannot do that adjustment and then adjust it back when needed? So I have questions about this report too. The NEDU did not think too highly of the intelligence of their own divers.

I did find the NEUD report from 1980 which covered the Four- and Five-port versions of the combination Mk V/AIR I regulator. They did work of breathing and interstage pressure decreases, both of which showed the Five-Port version of the Mk V/AIR I regulator better at extremely high work rates and depths. There is a lot of other information in this study, which seems better done than the previous one. I have copied some of these charts, and present them below.

Evaluation of Commercially Available Open Circuit Scuba Regulators.
These differences only occur at extremely high work rates at depth, and most will never see or feel any differences. But there are differences, from what I can see.

Luis, I would like to see the tests that you mentioned which show no differences between the Four-Port Mk V and the Five-Port Mk V with the regulator second stage mounted in-line to the top port of the first stage.

SeaRat

 

[ams511]

Guys, at this point the OP is probably shaking his head asking what on earth did he start.

OP, in my opinion the MK-1 is not worth upgrading because even if you can find the parts it will probably cost more than a late model MK-5 (heavy yoke and 5 ports) from eBay or Couv.

 

[Couv]

Couv,

Here's the math on that problem. The tanks are old USD 1800 psi rated steel tanks, for 52 cubic feet/tank, or 104 cubic feet total when full.

I see; the tanks were not full when you started. I thought 1080 was a rather odd service pressure.

But again, I think you have confirmed Luis' contention re l/p port position. One mustn't forget that the pressure in the hose at the second stage is the important detail; and that pressure is at (or near) the IP regardless of path the gas took.

Perhaps a straight on port might be more efficient if you were attempting to use your gear as leaf blower with the second stage removed.

 

[CaptainK]

Hey ams511,

You just kind of took the words/regulator right out of my mouth. I never ever expected such a complete and thorough explanation. It's been fun though.
I guess at this point I'd just like to proceed with hooking up a SPG to the MK-1 so I don't have to rely on the J-valve to see how much air I have remaining.
If I just continue to use my old steel 72's is there still a reasonable need to upgrade to a heavier yoke?

Thanks guys

 

[Couv]

Hi CaptainK,

he, he....that's the way we do things here.

I don’t want to talk myself out of a sale-if you are still interested in the MK 5 as a backup, have a look at the pictures I've sent you and let me know.

At any rate, your MK 1 with an adapter and SPG should work just fine especially if you are using 2475psi tanks.

Couv