Info Scubapro Announces the new updated MK17 first stage, the MK17 EVO 2!!

[RobPNW]

As a no neck guy I may consider one. With it upside down it looks low profile for us head bangers

 

[Umuntu]

The Mark 11 has nearly triple the open flow (195cfm) of the AL Conshelf------Legend (65-70 cfm) so not like it is a compromise on performance.

I have never considered the high flow characteristics of Scubapro’s first stages to be an advantage. I will never have 100 divers trying to breathe on my regulator.

In fact I consider it a disadvantage: if an LP hose fails or a second stage goes into free flow on a high flow first stage, it will empty your tank much quicker.

The real world test is does it provide enough air, and perform reliably, for two divers at depth ?

The fact is that all the regulators that have passed the very demanding Norsok tests are diaphragm regulators with much lower flow rates; and none of them are by Scubapro. They are Poseidon, Apeks and Mares models if I recall correctly.

 

[Nemrod]

I have never considered the high flow characteristics of Scubapro’s first stages to be an advantage. I will never have 100 divers trying to breathe on my regulator.

In fact I consider it a disadvantage: if an LP hose fails or a second stage goes into free flow on a high flow first stage, it will empty your tank much quicker.

The real world test is does it provide enough air, and perform reliably, for two divers at depth ?

The fact is that all the regulators that have passed the very demanding Norsok tests are diaphragm regulators with much lower flow rates; and none of them are by Scubapro. They are Poseidon, Apeks and Mares models if I recall correctly.

I do not disagree. But what little real data we have on any of these is often average flow rates, no info on responsiveness to follow peak instantaneous demand or IP lag and MTTF. And, have seen precious little info and data on diver demand. I still occasionally will do a triathlon if feeling up to it (rarely) but many years ago I was almost pro, well, yeah, another story about the almost part, but I was put on a machine to test my VO2 Max. It was interesting. Mixing apples and oranges, I know. Anyways average inspiration over a given time is not the same as instantaneous inspiration rate. Instataneous can be many times higher than average. Graphed it is a (sharp) saw tooth line, not straight. Not describing it well right now, kind of distracted today. But I can definitely tell when my breathing is being restricted, both on inhalation and exhalation and either causes me to become very anxious for my next breath. Call it a phobia but I will take the one that has more than adequate flow and response and the least drop under demand.

I need to get a copy of 250A, but to sustain two divers at 100 feet, what rates are being considered pass/fail? I would really like to see more information on all of this other than this regulator has a pretty cover and can be color coordinated with your wetsuit so it is a good one . I would like to see ANSTI test published yearly. On the other hand, I suppose such data has become irrelevant like computer clock speeds used to be bragging rights and now all exceed what is needed in practicality that color coordinating with our wetsuits is the important thing to the user.

 

[Tanks A Lot]

[...]I need to get a copy of 250A, but to sustain two divers at 100 feet, what rates are being considered pass/fail?[...]

To pass EN250, the regulator must pass:

• Breathing test at 62.5L per minute with 25 cycles per minute at a 2.5L tidal volume at 6bar absolute pressure.
• Work of breathing not exceeding 2.5J/l.
• Peak respiratory pressure of 25mbar on inhalation and exhalation.
• Positive work during inhalation not exceeding 0.3J/l.
• Pressure spikes with no measurable positive work of breathing no higher than 10mbar.
• Pressure peaks with measurable positive work of breathing no higher than 5mbar.

To pass what is commonly called EN250a, although EN250A is also the above, the cold water tests, it has to additionally pass:

• Immersed in 2°C to 4°C water and at least 0.2m depth, for at least 5 minutes at 6bar absolute pressure.

Somewhat disingenuous, the above only applies to to a first stage with a single second stage. If a alternate second stage is attached, it only has to pass Annex B of EN250, which includes:

• Maximum pressure of 4bar, instead of the 6bar from above. Otherwise the exact same data from above applies.
• The use of an auxiliary emergency breathing system in temperature less than 10 °C is not a preferred configuration and alternative fully independent systems are advised.

An extra test the system with two second stages has to endure is:

An intermediate pressure outlet on the first stage regulator shall be connected to a flowmeter on the outside of the test chamber. The volume of the intermediate pressure system pipe work shall be minimised and not exceed 200 ml. The first stage regulator shall be supplied with a constant pressure of 50 bar. After the chamber is pressurized to the test pressure, the test sequence shall be as follows:

• Set a constant flow rate of 560 l/min STP on the flowmeter;
• Start the breathing simulator attached to the demand valve under test;
• During the simulated breathing the flow rate will fall and shall not be re-adjusted;
• Record the inhale and exhale respiratory pressures and calculate the work of breathing;
• Stop the breathing simulator after a period of 2 min;
• Stop the constant flow.

No free-flow shall be observed during the test.

There is a ton more things the regulator has to fulfill to pass EN250, like several temperature related tests, hose burst tests and so on. It is a pretty exhaustive list.

 

[rsingler]

I have never considered the high flow characteristics of Scubapro’s first stages to be an advantage. I will never have 100 divers trying to breathe on my regulator.

I must beg to differ.
If you have a SAC of 0.5 SCFM, what is the peak gas flow from your second stage? Well actually, you are inhaling ~80% of your 0.5 CF in about half of the inspiratory portion of your breath, or in about 25% of a breath cycle. In other words, a SAC of 0.5 equates to a peak flow of 2 SCFM for a fraction of each breath.

Now add heavy work in current...
Your SAC might jump briefly to 2 SCFM, which yields a peak flow of 8 SCFM for a portion of each breath.

Now put your emergency at 100 feet (4 atm). Your peak flow is now 32 SCFM worth of air molecules.

Now add (briefly) a second panicked OOA diver.
64 SCFM peak flow.

What is your first stage's dynamic intermediate pressure during that flow? Is it enough to supply your second stage with easy breathing at max gas density?

Peak flow can matter, if only once in your life.

 

[Umuntu]

I must beg to differ.
If you have a SAC of 0.5 SCFM, what is the peak gas flow from your second stage? Well actually, you are inhaling ~80% of your 0.5 CF in about half of the inspiratory portion of your breath, or in about 25% of a breath cycle. In other words, a SAC of 0.5 equates to a peak flow of 2 SCFM for a fraction of each breath.

Now add heavy work in current...
Your SAC might jump briefly to 2 SCFM, which yields a peak flow of 8 SCFM for a portion of each breath.

Now put your emergency at 100 feet (4 atm). Your peak flow is now 32 SCFM worth of air molecules.

Now add (briefly) a second panicked OOA diver.
64 SCFM peak flow.

What is your first stage's dynamic intermediate pressure during that flow? Is it enough to supply your second stage with easy breathing at max gas density?

Peak flow can matter, if only once in your life.

I do not disagree that peak flow matters, but to meet the demand required does not require the very high flow rates that Scubapro uses as central to the marketing of their regulators.

Regulators that provide flow rates that exceed the demand imposed by two divers working (and so with higher rates of breathing) by a significant margin, with high rates of responsiveness and recovery of IP from the drop induced by initial inhalation are more important than just the basic high flow numbers advertised by Scubapro.

There’s a point above which any additional flow rate from the first stage does not provide any advantage.

An oversimplistic analogy would be a car manufacturer advertising a car only on the basis of it having a top speed of 400mph – who cares about that? None of us are going to drive anywhere near a quarter of that speed. But we would care about having good acceleration, safety, steering etc. too.

EDIT: I recall that in one of your YouTube videos - I think it was discussing the Mk19Evo - you remarked that the Poseidon (300??) diaphragm regulator did not have Scubapro’s high flow rates and yet performed so well that it was amongst the first to pass Norsok’s tests, which are more demanding than EN250A.

 

[scubadada]

I have been diving versions of Scubapro MK25 since 2002 with G250HP or S600 seconds. I have never noticed the WOB on inhalation at any work level. I have noticed the WOB on exhalation at my highest work loads. On a few occasions, I have taken ahold and stopped diving to recover somewhat from the effort of diving. I think this is perfectly consistent with the WOB curves obtained with ANSTI testing.

 

[Nemrod]

I must beg to differ.
If you have a SAC of 0.5 SCFM, what is the peak gas flow from your second stage? Well actually, you are inhaling ~80% of your 0.5 CF in about half of the inspiratory portion of your breath, or in about 25% of a breath cycle. In other words, a SAC of 0.5 equates to a peak flow of 2 SCFM for a fraction of each breath.

Now add heavy work in current...
Your SAC might jump briefly to 2 SCFM, which yields a peak flow of 8 SCFM for a portion of each breath.

Now put your emergency at 100 feet (4 atm). Your peak flow is now 32 SCFM worth of air molecules.

Now add (briefly) a second panicked OOA diver.
64 SCFM peak flow.

What is your first stage's dynamic intermediate pressure during that flow? Is it enough to supply your second stage with easy breathing at max gas density?

Peak flow can matter, if only once in your life.

Thanks for this, this is what I was getting to. The peak flow rates at the limits of human exertion during a breath cycle (and possibly more so with a fit person capable of sustained high demand) as opposed to an average.