axxel57
Contributor
Strange that SP came up with the top port on the MK5 so late.
The MK1 had been already for long time on the market.
The MK1 had been already for long time on the market.
Mk5 possible devil spring?
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I can confirm also this.
I actually saw a prototype of Air-1 with Pilot internals.
SP Italy was never very happy of the Pilot servicing, they received a lot of complaints by their customers (including my friend Marco, who bought one of the first Pilots sold, with two hoses: he was initially enthusiast of the performances, but after two years he attempted to service it, never managing to restore it properly, despite bringing it back to the factory a couple of times - he still owns it).
So the history went the way around, many Pilots were converted with Air-1 internal parts.
Slightly worse performances below 70m, but much easier to service.
A second stage demand regulator will never deliver more volume than the diver attached to it demands. The A700 can deliver, open flow, upwards of 2,000 l/m and the G260 something like 1,800 l/m. No human diver will ever demand that much flow volume, what is your SAC? Yes, hose position on some (first stage) regulators can affect the absolute open flow rate, so can the diameter and length of the hoses and any adapters along the way. But all of these things are normally below the signal to noise threshold, the human diver will not perceive them because the diver's needs/demand can never approach the performance limits of these regulators.
I just did a search on Google Scholar, and found this document:
U.S.N. PROCEDURES FOR TESTING THE BREATHING CHARACTERISTICS OF OPEN
CIRCUIT SCUBA REGULATORS Stephen D. Reimers
Navy Experimental Diving Unit Washington, D. C.
11 December 1973
The tests are explained in this document, including the terms. The term, "RVM" is defined:
What this shows is that the regulator can be tested at higher Respiratory Minute Volume, and that the regulator can be taxed and not perform to the needs of a diver under very heavy stress. Is this normal? No. But it really cannot be said that "...the human diver will not perceive them because the diver's needs/demand can never approach the performance limits of these regulators..." (Nemrod quote, above) Because, the diver's requirements can under very high workloads and depth exceed the performance limits of almost any regulator, as shown by the Navy tests.
SeaRat
U.S.N. PROCEDURES FOR TESTING THE BREATHING CHARACTERISTICS OF OPEN
CIRCUIT SCUBA REGULATORS Stephen D. Reimers
Navy Experimental Diving Unit Washington, D. C.
11 December 1973
The tests are explained in this document, including the terms. The term, "RVM" is defined:
So this is why the U.S. Navy tested to 62.5 R/M/V, 75 R/M/V and 90 R/M/V. Note that the 4-port Scubapro Pilot did not meet specs at 62.5 R/M/V at 132 feet. The 5-port Scubapro Pilot met that spec down to about 170 feet.
What this shows is that the regulator can be tested at higher Respiratory Minute Volume, and that the regulator can be taxed and not perform to the needs of a diver under very heavy stress. Is this normal? No. But it really cannot be said that "...the human diver will not perceive them because the diver's needs/demand can never approach the performance limits of these regulators..." (Nemrod quote, above) Because, the diver's requirements can under very high workloads and depth exceed the performance limits of almost any regulator, as shown by the Navy tests.
SeaRat
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L13
Contributor
@Nemrod were you taking into account high workload, fast breaths with high peak flow rate (Peak flow >> average flow rate during the breathing cycle) and great depth (some deep air divers were going > 10 ATA)?
a 2 L breath at 40 BPM is a flow rate of >160 LPM during the inhale cycle. at 10 ATA, that is >1600 LPM of air. (160 LPM assumed constant flow during the inhale cycle, reality is a significantly higher peak).
a 2 L breath at 40 BPM is a flow rate of >160 LPM during the inhale cycle. at 10 ATA, that is >1600 LPM of air. (160 LPM assumed constant flow during the inhale cycle, reality is a significantly higher peak).
I am considering sport diver depths to 165 feet and conventional open circuit scuba gear.
That is not exactly correct. The volume does not change with depth. Density of course does but your lungs hold the same volume at 5 atmospheres as they do at the surface. The demand flow through the regulator remains the same, the density increases, but the lpm is the same as at the surface.
Peak inspiration flow is an interesting point as a diver's SAC or RMV is an average over time but at the moment of peak inspiration the flow could be instantaneously much higher. And there is enough volume in the system to compensate at sport diving depths. You guys diving at 10 atm on open circuit, at that point I want to be in a submersible (a good one) or on a CCR. So, no, I am not considering esoteric possibilities at great depths.
axxel57
Contributor
The OP asked if the 7,9bar IP he measured at 30bar tank pressure would be okay or if he should shim the spring or do something else.
Some here wrote that that is okay and he shouldn’t do anything, okay.
I assumed he was a Solo Diver using the reg for recreational fun dives, but I mentioned that if not, that I think he should shim the spring or higher the IP by using Dow111 as lube for the piston o-rings, because in an exhausting situation with higher air demand and at low tank pressure the dynamic IP could probably drop to a level where the cracking effort (CE) is effecting even balanced 2nds ( is his Octo also balanced?).
I still believe that.
I did years ago tests on my Flow Bench to find out the correlation between dynamic IP drop and raising CE with balanced and unbalanced 2nds.
The result was, if I remember right, that a drop in dyn. or static IP of about 3-5psi IP translated in a higher CE of 0,1-0,2 inch/h2o with unbalanced 2nds.
With balanced 2nds one needed a 5-8psi drop to have the same result, means that a balanced 2nd compensates something, but if you have for whatever reason a real higher air demand at low tank pressure, you will get the air, but it will cost you quite sure a higher CE and WOB.
If the OP measured at full tank an IP of 9,2bar IP and at low tank 7,9bar, then one can hardly call that a balanced 1st ( specs ask for an IP in the range from 128psi-140psi at 2000psi and almost empty tank).
The 5 port MK5 flows at 2000psi tank pressure 2464 l/min, but at 300psi only 1359 l/min.
Seems that some here consider that per se as sufficient air flow, but for me it depends also on the situation.
I would have to test it on my bench, but an old spring can get stiffer with time or softer, means it could show a higher or not so high dynamic IP drop. In any case it will show a dyn. IP drop.
If my 2nd was adjusted at 9,2bar IP (balanced or unbalanced) and I get in a situation where the IP could drop to almost 2bars lower IP than the one where I adjusted the 2nd, then it will higher the CE and WOB in my primary and my Octo and will not be helpful in an emergency situation for example.
When I didn’t work with customers or students I used to be a relaxed Solo Diver, so I wouldn’t worry too much about an IP that is a bit below the specs, I could rely on myself, but if I don’t dive alone, I always would want to be prepared for that one f..k up dive in 500.
I that case I would look for another spring.
Some here wrote that that is okay and he shouldn’t do anything, okay.
I assumed he was a Solo Diver using the reg for recreational fun dives, but I mentioned that if not, that I think he should shim the spring or higher the IP by using Dow111 as lube for the piston o-rings, because in an exhausting situation with higher air demand and at low tank pressure the dynamic IP could probably drop to a level where the cracking effort (CE) is effecting even balanced 2nds ( is his Octo also balanced?).
I still believe that.
I did years ago tests on my Flow Bench to find out the correlation between dynamic IP drop and raising CE with balanced and unbalanced 2nds.
The result was, if I remember right, that a drop in dyn. or static IP of about 3-5psi IP translated in a higher CE of 0,1-0,2 inch/h2o with unbalanced 2nds.
With balanced 2nds one needed a 5-8psi drop to have the same result, means that a balanced 2nd compensates something, but if you have for whatever reason a real higher air demand at low tank pressure, you will get the air, but it will cost you quite sure a higher CE and WOB.
If the OP measured at full tank an IP of 9,2bar IP and at low tank 7,9bar, then one can hardly call that a balanced 1st ( specs ask for an IP in the range from 128psi-140psi at 2000psi and almost empty tank).
The 5 port MK5 flows at 2000psi tank pressure 2464 l/min, but at 300psi only 1359 l/min.
Seems that some here consider that per se as sufficient air flow, but for me it depends also on the situation.
I would have to test it on my bench, but an old spring can get stiffer with time or softer, means it could show a higher or not so high dynamic IP drop. In any case it will show a dyn. IP drop.
If my 2nd was adjusted at 9,2bar IP (balanced or unbalanced) and I get in a situation where the IP could drop to almost 2bars lower IP than the one where I adjusted the 2nd, then it will higher the CE and WOB in my primary and my Octo and will not be helpful in an emergency situation for example.
When I didn’t work with customers or students I used to be a relaxed Solo Diver, so I wouldn’t worry too much about an IP that is a bit below the specs, I could rely on myself, but if I don’t dive alone, I always would want to be prepared for that one f..k up dive in 500.
I that case I would look for another spring.
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