constant IP regs, piston vs diaphragm

Shas · 20th February 2007, 18:22

Quote: (Originally Posted by Dave Sutton)

Changing the *brand of the supply regulator* has a potential to upset the P02 control? Really. Do please tell us why.
I must have missed that part of my fluid dynamics class and would love to have my engineering deficiencies corrected.

(x) PSI suppled at (y) LPM is all that is required to serve the downstream system.

Can the physics of the equation read a brand name on the regulator?

Your sarcasm aside Dave this is not a brand name issue but due diligence on our behalf.

Here's why it's not that simple,
To obtain a Mass flow of x lt/min as stated in the previous post we need to maintain sonic flow or choked flow thorough the orifice. Roughly that means we need 2.0 times the upstream pressure to the down stream after the restriction. This is a very accurate "Mass flow " device if you have a fixed upstream pressure.(Drager) On the Prism the regulator adjusts for over bottom like most diving regs so we can still have choked flow conditions at a given fixed depth but the flow will increase with an increase in depth and increase in upstream pressure. This gave us a window to work with so I could size the orifice in the solenoid and adjust the band width for the solenoid for a large depth range. The restrictor up stream also gives you a time peroid to shut the oxygen off in the event of the solenoid failing open or hose failure not to mention the metering effect on solenoid opening.

OR quoted from the web site.

"mass flow rate is primarily dependent on the cross-sectional area A of the hole and the supply pressure P, and only weakly dependent on the temperature T. The rate does not depend on the downstream pressure at all. All other terms are constants that depend only on the composition of the material in the flow".

So the reasons changing the regulator may be a problem are,

1. Solenoid max operating pressure is 150 psi.
2. Oxygen relief valve set to 200 psi
3. As above calcs and testing done for Mk2 not done for others.
4. Not all regs are good for oxygen service even though they may be oxygen clean.

Again I would like to point out that in the PRISM, "the regulators, restrictor, solenoid and associated pipe work are designed to be part of a system"

Pete

**Dave Sutton** · 20th February 2007, 18:55

Quote: (Originally Posted by Shas)

1. Solenoid max operating pressure is 150 psi.
2. Oxygen relief valve set to 200 psi
3. As above calcs and testing done for Mk2 not done for others.
4. Not all regs are good for oxygen service even though they may be oxygen clean.

Again I would like to point out that in the PRISM, "the regulators, restrictor, solenoid and associated pipe work are designed to be part of a system"

So, Pete: Let's get this straight:

What you are saying in an obscured way is that basically any cheap 02 clean regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any sort of reasonable flow would do fine for the 02 side since all the system needs is >2x ambient to run your restricting orifice (so you do not need to time the solenoid as carefully or use the old fashoned 50cc accumulator beloved by the Mark-15), and any cheap first stage regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any reasonable flow would do fine for the diluent. So, the old piece of junk Sherwoods out of a Mark-15 would do nicely, and anything else would be better.

Not surprised. Just checking to make sure my understanding is clear..

And forgive my sarcasm, but I've heard way too many fairy tales abut "special sensors" and "special regulators" and "special 'sorb" and "special epoxy" and "special this and that" to believe too much from OEM's. Not addressed to you, but to the industry at large (well... a *little* to you too, don't want you to feel left out......

)

Dave

Shas · 20th February 2007, 23:19

Quote: (Originally Posted by Dave Sutton)

Last edited by Dave Sutton : Today at 14:01. Reason: Removed extra-snide comment as I felt bad to poke additional fun at Peter

Right - BS - what you originally posted was;

Quote: (Originally Posted by Dave Sutton)

So, Pete: Let's get this straight:

What you are saying in an obscured way is that basically any cheap 02 clean regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any sort of reasonable flow would do fine for the 02 side and any cheap first stage regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any reasonable flow would do fine for the diluent. So, the old piece of junk Sherwoods out of a Mark-15 would do nicely, and anything else would be better.

Not surprised. Just checking to make sure my understanding is clear..

Removing material???? - looks like you added more crap to cover-your-ass to me and as ever, its the typical cheap shot I've come to expect from you, resorting to personal attacks because you can't dispute the facts.

You can stop trying to put words in my mouth though - read my posts - I have not made any insistence on "brand names" (your term) or suggested "cheap" or "junk" alternatives (you again), they are hardly phrases I would consider appropriate when it comes to designing or putting together an oxygen control for a life support system.

I put together an accurate post describing the design criteria in order to assist you with your "engineering deficiencies" and to inform others why it may be a bad idea to slap any regulator on the system without the considerations listed.

I also posted to clarify why we use the components we do and what the results MAY be of changing them without a through understanding of the engineering involved in selecting them, which given the question that was asked, seemed an appropriate and prudent thing to do at the time.

I can't speak for other manufacturers, but I can confirm that the PRISM oxygen system was designed to be a complete assembly - all the components are chosen and matched because they meet criteria 3 & 4 of my second post and we tested them to prove their functionality and reliable performance.

Quote:

(so you do not need to time the solenoid as carefully or use the old fashoned 50cc accumulator beloved by the Mark-15),

Wrong again Dave, timing is critical when matched to the flow, or the Po2 would be all over the map. Obviously you never looked at a PRISM carefully or you would know that yes, the hose acts as an accumulator because the restrictor is at the regulator.

Quote:

And forgive my sarcasm, but I've heard way too many fairy tales abut "special sensors" and "special regulators" and "special 'sorb" and "special epoxy" and "special this and that" to believe too much from OEM's. Not addressed to you, but to the industry at large (well... a *little* to you too, don't want you to feel left out......

)

More digs - lets address them once and for all ;

"Special sensors" - Yes true, matched to the electronics and displays...
"special regulators" - No same Scubapro mk2 plus DIN.
"special 'sorb" - No, standard Sodasorb
"special epoxy" - Yes blended in house, non-off gassing and is moldable. Delrin which we use sparingly off-gasses Formaldehyde, as well as being unsuitable for strong alkaline's. See link http://www.matweb.com/SpecificMaterial.asp?bassnum=P1SM03&group=General

Pete

**Dave Sutton** · 21st February 2007, 00:41

Must have hit a sore spot... I added a LOT more and then removed half of it. I pointed out a bunch of other things that in retrospect seemed just mean (albeit true), and I'm just not a mean guy. You deserve to make a living selling your rig. With that said, Ya'll can BS some of the folks, but ya'll can't BS me. I've been around way too long. As long as you, in fact. And there are plenty of "facts" you have cited over the years that are just plain bogus, but it's too wearying to recite them and why bother anyway? The bottom line is that I respect you as an engineer (sometimes at least) but I just don't like your style. You should feel special: You're the only one of the OEM's that I have a visceral distrust of from a personality standpoint.

So, uh....now that we have that all sorted: Pete: Is the Prism sensitive to a change of the first stage? Could one, for example, use the *milspec and obviously top-notch quality* unbalanced Sherwood Mark-15 first stages for example? (on second thought, don't bother, because I already know the answer)

Use of the hose as an accumulator *is* pretty clever though. Takes all the fun out of doing solenoid timing with software. Cheaper than the 50cc accumulator, and functional. High marks for simplicity. See, I *can* give a complement when needed....

(And the epoxy I'm thinking of is smeared on the cracked heads... because, I *have* actually studied a Prism carefully a few times...

)

La La La.....

Dave

"Somewhere, in some place in the outback, a village is missing it's banjo player..."

OceanOpportunity · 21st February 2007, 01:06

To all,

seems this happens all to often on these forums...i.e. valuable 'opinions' from varying credible sources end up in conflict...clearly not my intention in starting this thread.

This, and others I've started have all been in an effort to arrive at concrete data to support the varying principles of designs out there from rig to rig...and they vary tremendously at that. With such small markets, its no wonder that 'what works, works' is the general perspective taken out there. To any of those interested (perhaps a subject for another thread), I am keen to compile as much empirical data as possible on various scrubber designs, o2 injection systems, etc, and hopefully arrive at some publishable compilation of this information..be it a paper or series of papers in an MTS Journal, or the like. There is all too little concrete published data (for mass consumption) out there on CCRs (at least for the recreational/technical/scientific community), which is a function of R&D $ available due to the limited market segements. I'm not referring to performance data here (although that would be nice too), rather hard evidence supporting the different principles of design. Standard physics surely, but invaluable for the homebuilder/limited production house that jsut plain won't, for whatever reason, crunch the #'s for themselves.

So, to anyone with hard data, and interested in collaborating to get it out there for the masses to chomp on productively..please give me a shout.

Safe Diving
ML

Gobfish1 · 21st February 2007, 01:25

Something for the Interlude

YouTube - Advanced Nitrox & Deco

Mike · 21st February 2007, 01:37

Quote: (Originally Posted by Dave Sutton)

"Somewhere, in some place in the outback, a village is missing it's banjo player..."

- cruel and somewhat apt

I don't see that there is an issue here.
Pete has said that he has tested the Prism O2 add as a complete system, using the Mk2. He knows that it works.

Other regs will most likely work just as well, but Pete hasn't bothered testing them. He has a system that is simple, cheap, and works. Performance of the rebreather is not going to improve by adding a better reg, so why bother?
Pete isn't saying it won't work, just that it's on your head if you decide to swap - so make sure you have a good think about it first.

I was initially keen to replace the regs on my prism, as I'd managed to swap all my other regs out to Apeks for ease of service. (and the TX100 firsts route really neatly on the rebreather). But then I figured I can just buy new MK2s every couple of years for the same as it costs me to service Apeks myself, so why mess with it?
(But the Tx100s do route neatly... and the 200 bar DIN wheel on the O2 side was a pain in the butt

)

Mike

**Dave Sutton** · 21st February 2007, 01:47

I just hate the use of scare tactics to sell equipment, and there is a *certain* sort of OEM who use those tactics. I've just been around way too long and have heard way too much.... trust me on this.

That's the short story. Long story is not worth bothering about. Only we old timers care and we're outnumbered now.

Dave

"They traded him for an idiot, and they thought they got a fair deal....."

AD_ward9 · 21st February 2007, 11:42

Quote: (Originally Posted by OceanOpportunity)

So, to anyone with hard data, and interested in collaborating to get it out there for the masses to chomp on productively..please give me a shout.

Have a look at the Design Verification Report on a variable orifice injector in the list HERE. It gives the detailed Matlab model of an orifice, their control, flow curves for different sizes, depths etc. Really, all the meat you should need.

We are having a distributed Denial Of Service attack from SPAMMERs just now, who might be objecting to our SPAM filter, so the site will be slower to respond than usual. Just have patience: it is up and running with a huge bandwidth.

There is another related report on the risk of the flow being wrong. I will try and get that published later this week. It will be in the same place, when it comes out.

Just for clarity, in the above report, we refer to Compensated and Uncompensated first stages. A compensated first stage has an intermediate pressure which is equal to ambient plus 10 bar in absolute terms. A non-compensated first stage has an intermediate pressure which is fixed in absolute terms.

As regards the off topic debate, my 2p worth, is that Pete is absolutely correct in the points he made. Equipment is verified with a particular configuration. No manufacture I know of guarantees their kit if you go and change things left right and centre. Dave made some good comments earlier on, then got a bee in his bonnet introducing things off topic. We should keep the debate clean here and value the input people make rather than try to bully them. If Dave is saying he has never made a mistake in his life, then it would be a confession that he has not learnt anything. I am sure this is not the impression Dave wants to give, so let us keep this forum a pleasant place to exchange information and learn from each other.

Alex

**Dave Sutton** · 21st February 2007, 13:12

Quote: (Originally Posted by AD_ward9)

As regards the off topic debate, my 2p worth, is that Pete is absolutely correct in the points he made. Equipment is verified with a particular configuration. No manufacture I know of guarantees their kit if you go and change things left right and centre. Dave made some good comments earlier on, then got a bee in his bonnet introducing things off topic.

I would simply say that there is a difference between not supporting changes and using active scare tactics. Yes, I am sure that AP Valves prefers that you use their "special" cell but there's no doubt that many others are suitable. Ditto their first stages, cylinders, etc. Their attitude is just a matter of "you change it, you deal with the results". That's an entirely different matter than actively using scare tactics to keep people "in your flock". That's all I am going to post here. There is a VERY long (10+ years) backstory, and that's what triggers the bees to fly in my bonnet. Just cannot help it. My blood pressure rises every time I hear the familiar strains of the fiddle music from "Deliverance" being played from the Woods of Appalachia......

Dave

"At least the idiot played quietly in the corner and never tried to frighten anyone....."

20th February 2007, 18:22	#41 (permalink)
Shas New Member Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Mar 2005 Location: Lebanon, TN Posts: 11	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Dave Sutton) Changing the brand of the supply regulator has a potential to upset the P02 control? Really. Do please tell us why. I must have missed that part of my fluid dynamics class and would love to have my engineering deficiencies corrected. (x) PSI suppled at (y) LPM is all that is required to serve the downstream system. Can the physics of the equation read a brand name on the regulator? Your sarcasm aside Dave this is not a brand name issue but due diligence on our behalf. Here's why it's not that simple, To obtain a Mass flow of x lt/min as stated in the previous post we need to maintain sonic flow or choked flow thorough the orifice. Roughly that means we need 2.0 times the upstream pressure to the down stream after the restriction. This is a very accurate "Mass flow " device if you have a fixed upstream pressure.(Drager) On the Prism the regulator adjusts for over bottom like most diving regs so we can still have choked flow conditions at a given fixed depth but the flow will increase with an increase in depth and increase in upstream pressure. This gave us a window to work with so I could size the orifice in the solenoid and adjust the band width for the solenoid for a large depth range. The restrictor up stream also gives you a time peroid to shut the oxygen off in the event of the solenoid failing open or hose failure not to mention the metering effect on solenoid opening. OR quoted from the web site. "mass flow rate is primarily dependent on the cross-sectional area A of the hole and the supply pressure P, and only weakly dependent on the temperature T. The rate does not depend on the downstream pressure at all. All other terms are constants that depend only on the composition of the material in the flow". So the reasons changing the regulator may be a problem are, 1. Solenoid max operating pressure is 150 psi. 2. Oxygen relief valve set to 200 psi 3. As above calcs and testing done for Mk2 not done for others. 4. Not all regs are good for oxygen service even though they may be oxygen clean. Again I would like to point out that in the PRISM, "the regulators, restrictor, solenoid and associated pipe work are designed to be part of a system" Pete
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20th February 2007, 18:55	#42 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,913	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Shas) 1. Solenoid max operating pressure is 150 psi. 2. Oxygen relief valve set to 200 psi 3. As above calcs and testing done for Mk2 not done for others. 4. Not all regs are good for oxygen service even though they may be oxygen clean. Again I would like to point out that in the PRISM, "the regulators, restrictor, solenoid and associated pipe work are designed to be part of a system" So, Pete: Let's get this straight: What you are saying in an obscured way is that basically any cheap 02 clean regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any sort of reasonable flow would do fine for the 02 side since all the system needs is >2x ambient to run your restricting orifice (so you do not need to time the solenoid as carefully or use the old fashoned 50cc accumulator beloved by the Mark-15), and any cheap first stage regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any reasonable flow would do fine for the diluent. So, the old piece of junk Sherwoods out of a Mark-15 would do nicely, and anything else would be better. Not surprised. Just checking to make sure my understanding is clear.. And forgive my sarcasm, but I've heard way too many fairy tales abut "special sensors" and "special regulators" and "special 'sorb" and "special epoxy" and "special this and that" to believe too much from OEM's. Not addressed to you, but to the industry at large (well... a little to you too, don't want you to feel left out...... ) Dave __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 20th February 2007 at 20:01. Reason: Removed extra-snide comment as I felt bad to poke additional fun at Peter
(Offline)

20th February 2007, 23:19	#43 (permalink)
Shas New Member Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Mar 2005 Location: Lebanon, TN Posts: 11	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Dave Sutton) Last edited by Dave Sutton : Today at 14:01. Reason: Removed extra-snide comment as I felt bad to poke additional fun at Peter Right - BS - what you originally posted was; Quote: (Originally Posted by Dave Sutton) So, Pete: Let's get this straight: What you are saying in an obscured way is that basically any cheap 02 clean regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any sort of reasonable flow would do fine for the 02 side and any cheap first stage regulator serving up the basic old household intermediate pressure of 140PSIG and able to do so at any reasonable flow would do fine for the diluent. So, the old piece of junk Sherwoods out of a Mark-15 would do nicely, and anything else would be better. Not surprised. Just checking to make sure my understanding is clear.. Removing material???? - looks like you added more crap to cover-your-ass to me and as ever, its the typical cheap shot I've come to expect from you, resorting to personal attacks because you can't dispute the facts. You can stop trying to put words in my mouth though - read my posts - I have not made any insistence on "brand names" (your term) or suggested "cheap" or "junk" alternatives (you again), they are hardly phrases I would consider appropriate when it comes to designing or putting together an oxygen control for a life support system. I put together an accurate post describing the design criteria in order to assist you with your "engineering deficiencies" and to inform others why it may be a bad idea to slap any regulator on the system without the considerations listed. I also posted to clarify why we use the components we do and what the results MAY be of changing them without a through understanding of the engineering involved in selecting them, which given the question that was asked, seemed an appropriate and prudent thing to do at the time. I can't speak for other manufacturers, but I can confirm that the PRISM oxygen system was designed to be a complete assembly - all the components are chosen and matched because they meet criteria 3 & 4 of my second post and we tested them to prove their functionality and reliable performance. Quote: (so you do not need to time the solenoid as carefully or use the old fashoned 50cc accumulator beloved by the Mark-15), Wrong again Dave, timing is critical when matched to the flow, or the Po2 would be all over the map. Obviously you never looked at a PRISM carefully or you would know that yes, the hose acts as an accumulator because the restrictor is at the regulator. Quote: And forgive my sarcasm, but I've heard way too many fairy tales abut "special sensors" and "special regulators" and "special 'sorb" and "special epoxy" and "special this and that" to believe too much from OEM's. Not addressed to you, but to the industry at large (well... a little to you too, don't want you to feel left out...... ) More digs - lets address them once and for all ; "Special sensors" - Yes true, matched to the electronics and displays... "special regulators" - No same Scubapro mk2 plus DIN. "special 'sorb" - No, standard Sodasorb "special epoxy" - Yes blended in house, non-off gassing and is moldable. Delrin which we use sparingly off-gasses Formaldehyde, as well as being unsuitable for strong alkaline's. See link http://www.matweb.com/SpecificMaterial.asp?bassnum=P1SM03&group=General Pete
(Offline)

21st February 2007, 00:41	#44 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,913	Re: constant IP regs, piston vs diaphragm Must have hit a sore spot... I added a LOT more and then removed half of it. I pointed out a bunch of other things that in retrospect seemed just mean (albeit true), and I'm just not a mean guy. You deserve to make a living selling your rig. With that said, Ya'll can BS some of the folks, but ya'll can't BS me. I've been around way too long. As long as you, in fact. And there are plenty of "facts" you have cited over the years that are just plain bogus, but it's too wearying to recite them and why bother anyway? The bottom line is that I respect you as an engineer (sometimes at least) but I just don't like your style. You should feel special: You're the only one of the OEM's that I have a visceral distrust of from a personality standpoint. So, uh....now that we have that all sorted: Pete: Is the Prism sensitive to a change of the first stage? Could one, for example, use the milspec and obviously top-notch quality unbalanced Sherwood Mark-15 first stages for example? (on second thought, don't bother, because I already know the answer) Use of the hose as an accumulator is pretty clever though. Takes all the fun out of doing solenoid timing with software. Cheaper than the 50cc accumulator, and functional. High marks for simplicity. See, I can give a complement when needed.... (And the epoxy I'm thinking of is smeared on the cracked heads... because, I have actually studied a Prism carefully a few times... ) La La La..... Dave "Somewhere, in some place in the outback, a village is missing it's banjo player..." __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 21st February 2007 at 01:06.
(Offline)

21st February 2007, 01:06	#45 (permalink)
OceanOpportunity for a world of water Current Rebreather/s: Other CCR Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Other CCR Dolphin Home Build Join Date: Nov 2006 Location: Providence, RI USA Posts: 598	Re: constant IP regs, piston vs diaphragm To all, seems this happens all to often on these forums...i.e. valuable 'opinions' from varying credible sources end up in conflict...clearly not my intention in starting this thread. This, and others I've started have all been in an effort to arrive at concrete data to support the varying principles of designs out there from rig to rig...and they vary tremendously at that. With such small markets, its no wonder that 'what works, works' is the general perspective taken out there. To any of those interested (perhaps a subject for another thread), I am keen to compile as much empirical data as possible on various scrubber designs, o2 injection systems, etc, and hopefully arrive at some publishable compilation of this information..be it a paper or series of papers in an MTS Journal, or the like. There is all too little concrete published data (for mass consumption) out there on CCRs (at least for the recreational/technical/scientific community), which is a function of R&D $ available due to the limited market segements. I'm not referring to performance data here (although that would be nice too), rather hard evidence supporting the different principles of design. Standard physics surely, but invaluable for the homebuilder/limited production house that jsut plain won't, for whatever reason, crunch the #'s for themselves. So, to anyone with hard data, and interested in collaborating to get it out there for the masses to chomp on productively..please give me a shout. Safe Diving ML __________________ Michael Lombardi Oceans of Opportunity www.oceanopportunity.com Elected Director, Society for Human Performance in Extreme Environments MN'07, The Explorers Club Project Manager, Diving a Dream
(Offline)

21st February 2007, 01:37	#47 (permalink)
Mike Prism 'prentice Current Rebreather/s: Prism Topaz Other Rebreather/s: Inspiration Classic Evolution Join Date: Feb 2005 Location: Melbourne Posts: 332	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Dave Sutton) "Somewhere, in some place in the outback, a village is missing it's banjo player..." - cruel and somewhat apt I don't see that there is an issue here. Pete has said that he has tested the Prism O2 add as a complete system, using the Mk2. He knows that it works. Other regs will most likely work just as well, but Pete hasn't bothered testing them. He has a system that is simple, cheap, and works. Performance of the rebreather is not going to improve by adding a better reg, so why bother? Pete isn't saying it won't work, just that it's on your head if you decide to swap - so make sure you have a good think about it first. I was initially keen to replace the regs on my prism, as I'd managed to swap all my other regs out to Apeks for ease of service. (and the TX100 firsts route really neatly on the rebreather). But then I figured I can just buy new MK2s every couple of years for the same as it costs me to service Apeks myself, so why mess with it? (But the Tx100s do route neatly... and the 200 bar DIN wheel on the O2 side was a pain in the butt ) Mike __________________ Open ....... Closed Mind ........ Loop
(Offline)

21st February 2007, 01:47	#48 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,913	Re: constant IP regs, piston vs diaphragm I just hate the use of scare tactics to sell equipment, and there is a certain sort of OEM who use those tactics. I've just been around way too long and have heard way too much.... trust me on this. That's the short story. Long story is not worth bothering about. Only we old timers care and we're outnumbered now. Dave "They traded him for an idiot, and they thought they got a fair deal....." __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 21st February 2007 at 01:52.
(Offline)

21st February 2007, 11:42	#49 (permalink)
AD_ward9 RBW Member Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,016	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by OceanOpportunity) So, to anyone with hard data, and interested in collaborating to get it out there for the masses to chomp on productively..please give me a shout. Have a look at the Design Verification Report on a variable orifice injector in the list HERE. It gives the detailed Matlab model of an orifice, their control, flow curves for different sizes, depths etc. Really, all the meat you should need. We are having a distributed Denial Of Service attack from SPAMMERs just now, who might be objecting to our SPAM filter, so the site will be slower to respond than usual. Just have patience: it is up and running with a huge bandwidth. There is another related report on the risk of the flow being wrong. I will try and get that published later this week. It will be in the same place, when it comes out. Just for clarity, in the above report, we refer to Compensated and Uncompensated first stages. A compensated first stage has an intermediate pressure which is equal to ambient plus 10 bar in absolute terms. A non-compensated first stage has an intermediate pressure which is fixed in absolute terms. As regards the off topic debate, my 2p worth, is that Pete is absolutely correct in the points he made. Equipment is verified with a particular configuration. No manufacture I know of guarantees their kit if you go and change things left right and centre. Dave made some good comments earlier on, then got a bee in his bonnet introducing things off topic. We should keep the debate clean here and value the input people make rather than try to bully them. If Dave is saying he has never made a mistake in his life, then it would be a confession that he has not learnt anything. I am sure this is not the impression Dave wants to give, so let us keep this forum a pleasant place to exchange information and learn from each other. Alex Last edited by AD_ward9 : 21st February 2007 at 12:40.
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21st February 2007, 13:12	#50 (permalink)
Dave Sutton Diveshop of Horrors Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Evolution Megalodon rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,913	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by AD_ward9) As regards the off topic debate, my 2p worth, is that Pete is absolutely correct in the points he made. Equipment is verified with a particular configuration. No manufacture I know of guarantees their kit if you go and change things left right and centre. Dave made some good comments earlier on, then got a bee in his bonnet introducing things off topic. I would simply say that there is a difference between not supporting changes and using active scare tactics. Yes, I am sure that AP Valves prefers that you use their "special" cell but there's no doubt that many others are suitable. Ditto their first stages, cylinders, etc. Their attitude is just a matter of "you change it, you deal with the results". That's an entirely different matter than actively using scare tactics to keep people "in your flock". That's all I am going to post here. There is a VERY long (10+ years) backstory, and that's what triggers the bees to fly in my bonnet. Just cannot help it. My blood pressure rises every time I hear the familiar strains of the fiddle music from "Deliverance" being played from the Woods of Appalachia...... Dave "At least the idiot played quietly in the corner and never tried to frighten anyone....." __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com Last edited by Dave Sutton : 21st February 2007 at 13:19.
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