constant IP regs, piston vs diaphragm

**wedivebc** · 17th February 2007, 15:41

Quote: (Originally Posted by jmurba)

if you use an orifice as restrictor you would hav a problem, but if you use a needle valve you will b abl to adjust the flow rate using the regular 11 bars ip

If you are using an adjustable needle valve why do you even need constant IP?

O.C.Diver · 17th February 2007, 15:51

Quote: (Originally Posted by wedivebc)

If you are using an adjustable needle valve why do you even need constant IP?

You don't, but every time you change depth the absolute (including ambient) intermediate pressure will change, changing the liter flow rate, requiring you to adjust the needle valve.

Ted

**wedivebc** · 17th February 2007, 16:00

Quote: (Originally Posted by O.C.Diver)

You don't, but every time you change depth the absolute (including ambient) intermediate pressure will change, changing the liter flow rate, requiring you to adjust the needle valve.

Ted

Which is the whole point of using an adjustable needle valve. Orifice type leaky valve rebreathers are depth limited by the constant IP, adjustable needle valves aren't. Why use a needle valve then don't take advantage of that feature?

O.C.Diver · 17th February 2007, 16:01

An other good choice for 1st stage regulator is an Oceanic CDX5 cold water sealed. This reg requires no additional parts to convert to unbalanced. The reg uses a disc with a driver rod to transfer pressure from the water to the diaphragm. Removing the driver rod unbalances the reg.

Ted

O.C.Diver · 17th February 2007, 16:23

Quote: (Originally Posted by wedivebc)

Which is the whole point of using an adjustable needle valve. Orifice type leaky valve rebreathers are depth limited by the constant IP, adjustable needle valves aren't. Why use a needle valve then don't take advantage of that feature?

No, and here is why. The purpose of a needle valve over a fixed orifice is to allow you to set the intermediate pressure high enough to go to whatever depth you want. On my homebuilt, I set my Oceanic at 175 psi which will work to over 300'. The needle valve allows you to set your flow rate for whatever liter flow you need at depth. The advantage to the unbalanced reg is that as you change depths during your bottom time, the liter flow rate remains constant.

The other advantage to unbalanced is that at deeper depths (200'+) it is much easier to get the right setting on the needle valve when the absolute intermediate pressure is closer to ambient pressure. At 250' would you rather try to get a 1 liter flow rate with 140 psi or 65 psi?

Ted

Tom Rose · 17th February 2007, 23:22

[quote=O.C.Diver;96933]No, and here is why. The purpose of a needle valve over a fixed orifice is to allow you to set the intermediate pressure high enough to go to whatever depth you want. On my homebuilt, I set my Oceanic at 175 psi which will work to over 300'. The needle valve allows you to set your flow rate for whatever liter flow you need at depth. The advantage to the unbalanced reg is that as you change depths during your bottom time, the liter flow rate remains constant.

I've used fixed orifices and needle valves with fixed ip and non fixed ip....It depends upon the diving you plan to do. Remember in these discussions, compare apples to apples....

The real factor is the depth you dive to.

If you are going deep a fixed ip or a needle valve is necessary. However some of do not dive deep but dive rebreathers because of the convenience, lower weight, quiet long operation, and warm moist air. Selection of a proper orifice can allow a kiss system to simply use a oxygen cleaned regulator....this means to 100 feet..thats right...you can set up a kiss system that works just fine to 100 feet with an orifice and filter from McMaster Carr....just make sure you include an over pressure valve in one of the low pressure ports on the regulator....Last week in Bonaire I was diving a system as described and only had to add oxygen 4 times in a hour to keep it in acceptable range unless I was changing depth.

Tom Rose

O.C.Diver · 18th February 2007, 00:04

Quote: (Originally Posted by Tom Rose)

I've used fixed orifices and needle valves with fixed ip and non fixed ip....It depends upon the diving you plan to do. Remember in these discussions, compare apples to apples....

The real factor is the depth you dive to.

If you are going deep a fixed ip or a needle valve is necessary. However some of do not dive deep but dive rebreathers because of the convenience, lower weight, quiet long operation, and warm moist air. Selection of a proper orifice can allow a kiss system to simply use a oxygen cleaned regulator....this means to 100 feet..thats right...you can set up a kiss system that works just fine to 100 feet with an orifice and filter from McMaster Carr....just make sure you include an over pressure valve in one of the low pressure ports on the regulator....Last week in Bonaire I was diving a system as described and only had to add oxygen 4 times in a hour to keep it in acceptable range unless I was changing depth.

Tom Rose

Hi Tom,

Unless the homebuilder already owns a balanced regulator, I don't see your reasoning for choosing to use a balanced versus an unbalanced regulator. Please explain the performance advantage in an MCCR of a balanced regulator.

Ted

**Dave Sutton** · 18th February 2007, 01:58

Probably best to redefine terms:

Balanced Regulator: One which supplies a fixed intermediate pressure *even as INLET pressure from the high pressure source varies*. Most quality first stages these days are of this design.

Unbalanced Regulator: One which varies intermediate pressure as INLET pressure varies. Example is the old Poseidon 300 first stage that INCREASES the IP as cylinder pressure falls.

Constant Ambient Pressure Regulator: One which provides a fixed pressure in relationship to SENSED AMBIENT PRESSURE. This is the typical SCUBA first stage, producing, for example, 125PSI *over bottom pressure* at all times.

Constant Absolute Pressure Regulator: One which *does not sense external pressure* and as a result *provides a constant intermediate pressure expressed in PSI(A)* (PSI *absolute*, IE in reference to 1 atmosphere *absolute*). This is what we seek for fixed orifice bleed systems.

The term "Balanced" and "Unbalanced" are inaccurately used by many when talking about the latter two regulators. It would be best if we all standardized on the correct nomenclature in order to reduce confusion.

KISS system orifices require the last type, preferable of the BALANCED type so that they provide an ABSOLUTE pressure that is not affected by CYLINDER SUPPLY PRESSURE.

The reason that needle valves are not optimal is that the time-base of PP02 decay is WAY TOO LONG to allow "adjustment on the fly" for such a system. Fixed orifice systems are far simpler, and with a correctly sized orifice allow diving as deep as anyone would practically desire.

Dave Sutton

O.C.Diver · 18th February 2007, 03:15

Quote: (Originally Posted by Dave Sutton)

The reason that needle valves are not optimal is that the time-base of PP02 decay is WAY TOO LONG to allow "adjustment on the fly" for such a system. Fixed orifice systems are far simpler, and with a correctly sized orifice allow diving as deep as anyone would practically desire.

While in general terms I would agree with you, the needle valve in combination with a manual add valve allows the diver to set a liter flow rate on the surface relative to his nominal work rate for the particular dive, and then bring up the loop with the manual add button (like the KISS valve). As an example, if I'm going to scooter the whole dive at 250', I would set the flow to .5 lt.. If I plan to fin the whole dive at less than 80' (cave diving), I'm more likely to set the flow at .9 to 1.0 lt.. By using a needle valve and a manual add valve I can set the flow to whatever level I feel is most optimal for that particular dive, and not have to worry about a depth limitation do to a low intermediate pressure. Finally, if I not happy with my choice of flow rate, it's adjustable during the dive unlike a fixed orifice setup.

Ted

OceanOpportunity · 18th February 2007, 04:24

in the case of needle valves, are these being referred to as a device that also restricts flow within a certain range, or a means to control the full spectrum from 'on' to 'off' with the IP flow from the LP hose? In other words, is the needle valve being used in conjunction with an orifice that say offers a max flow of 1lpm or thereabouts on the high end, so it can be tuned down during the dive to adjust for the IP increase on descent?

17th February 2007, 15:41	#11 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,510	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by jmurba) if you use an orifice as restrictor you would hav a problem, but if you use a needle valve you will b abl to adjust the flow rate using the regular 11 bars ip If you are using an adjustable needle valve why do you even need constant IP? __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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17th February 2007, 15:51	#12 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 244	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by wedivebc) If you are using an adjustable needle valve why do you even need constant IP? You don't, but every time you change depth the absolute (including ambient) intermediate pressure will change, changing the liter flow rate, requiring you to adjust the needle valve. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
(Online)

17th February 2007, 16:00	#13 (permalink)
wedivebc Dave Tomblin Current Rebreather/s: Megalodon Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Other CCR Join Date: Feb 2005 Location: Vancouver Island BC Canada Posts: 1,510	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by O.C.Diver) You don't, but every time you change depth the absolute (including ambient) intermediate pressure will change, changing the liter flow rate, requiring you to adjust the needle valve. Ted Which is the whole point of using an adjustable needle valve. Orifice type leaky valve rebreathers are depth limited by the constant IP, adjustable needle valves aren't. Why use a needle valve then don't take advantage of that feature? __________________ Cheers, Dave.... Man is the only animal burdened with the knowledge he will eventually die
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17th February 2007, 16:01	#14 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 244	Re: constant IP regs, piston vs diaphragm An other good choice for 1st stage regulator is an Oceanic CDX5 cold water sealed. This reg requires no additional parts to convert to unbalanced. The reg uses a disc with a driver rod to transfer pressure from the water to the diaphragm. Removing the driver rod unbalances the reg. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
(Online)

17th February 2007, 16:23	#15 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 244	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by wedivebc) Which is the whole point of using an adjustable needle valve. Orifice type leaky valve rebreathers are depth limited by the constant IP, adjustable needle valves aren't. Why use a needle valve then don't take advantage of that feature? No, and here is why. The purpose of a needle valve over a fixed orifice is to allow you to set the intermediate pressure high enough to go to whatever depth you want. On my homebuilt, I set my Oceanic at 175 psi which will work to over 300'. The needle valve allows you to set your flow rate for whatever liter flow you need at depth. The advantage to the unbalanced reg is that as you change depths during your bottom time, the liter flow rate remains constant. The other advantage to unbalanced is that at deeper depths (200'+) it is much easier to get the right setting on the needle valve when the absolute intermediate pressure is closer to ambient pressure. At 250' would you rather try to get a 1 liter flow rate with 140 psi or 65 psi? Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
(Online)

17th February 2007, 23:22	#16 (permalink)
Tom Rose Still Learning Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Prism Topaz Other CCR Home Build Join Date: Oct 2005 Location: USA,North Carolina Posts: 331	Re: constant IP regs, piston vs diaphragm [quote=O.C.Diver;96933]No, and here is why. The purpose of a needle valve over a fixed orifice is to allow you to set the intermediate pressure high enough to go to whatever depth you want. On my homebuilt, I set my Oceanic at 175 psi which will work to over 300'. The needle valve allows you to set your flow rate for whatever liter flow you need at depth. The advantage to the unbalanced reg is that as you change depths during your bottom time, the liter flow rate remains constant. I've used fixed orifices and needle valves with fixed ip and non fixed ip....It depends upon the diving you plan to do. Remember in these discussions, compare apples to apples.... The real factor is the depth you dive to. If you are going deep a fixed ip or a needle valve is necessary. However some of do not dive deep but dive rebreathers because of the convenience, lower weight, quiet long operation, and warm moist air. Selection of a proper orifice can allow a kiss system to simply use a oxygen cleaned regulator....this means to 100 feet..thats right...you can set up a kiss system that works just fine to 100 feet with an orifice and filter from McMaster Carr....just make sure you include an over pressure valve in one of the low pressure ports on the regulator....Last week in Bonaire I was diving a system as described and only had to add oxygen 4 times in a hour to keep it in acceptable range unless I was changing depth. Tom Rose __________________ The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time. www.atlimp.com
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18th February 2007, 00:04	#17 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 244	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Tom Rose) I've used fixed orifices and needle valves with fixed ip and non fixed ip....It depends upon the diving you plan to do. Remember in these discussions, compare apples to apples.... The real factor is the depth you dive to. If you are going deep a fixed ip or a needle valve is necessary. However some of do not dive deep but dive rebreathers because of the convenience, lower weight, quiet long operation, and warm moist air. Selection of a proper orifice can allow a kiss system to simply use a oxygen cleaned regulator....this means to 100 feet..thats right...you can set up a kiss system that works just fine to 100 feet with an orifice and filter from McMaster Carr....just make sure you include an over pressure valve in one of the low pressure ports on the regulator....Last week in Bonaire I was diving a system as described and only had to add oxygen 4 times in a hour to keep it in acceptable range unless I was changing depth. Tom Rose Hi Tom, Unless the homebuilder already owns a balanced regulator, I don't see your reasoning for choosing to use a balanced versus an unbalanced regulator. Please explain the performance advantage in an MCCR of a balanced regulator. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
(Online)

18th February 2007, 01:58	#18 (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 Probably best to redefine terms: Balanced Regulator: One which supplies a fixed intermediate pressure even as INLET pressure from the high pressure source varies. Most quality first stages these days are of this design. Unbalanced Regulator: One which varies intermediate pressure as INLET pressure varies. Example is the old Poseidon 300 first stage that INCREASES the IP as cylinder pressure falls. Constant Ambient Pressure Regulator: One which provides a fixed pressure in relationship to SENSED AMBIENT PRESSURE. This is the typical SCUBA first stage, producing, for example, 125PSI over bottom pressure at all times. Constant Absolute Pressure Regulator: One which does not sense external pressure and as a result provides a constant intermediate pressure expressed in PSI(A) (PSI absolute, IE in reference to 1 atmosphere absolute). This is what we seek for fixed orifice bleed systems. The term "Balanced" and "Unbalanced" are inaccurately used by many when talking about the latter two regulators. It would be best if we all standardized on the correct nomenclature in order to reduce confusion. KISS system orifices require the last type, preferable of the BALANCED type so that they provide an ABSOLUTE pressure that is not affected by CYLINDER SUPPLY PRESSURE. The reason that needle valves are not optimal is that the time-base of PP02 decay is WAY TOO LONG to allow "adjustment on the fly" for such a system. Fixed orifice systems are far simpler, and with a correctly sized orifice allow diving as deep as anyone would practically desire. Dave Sutton __________________ "Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com
(Online)

18th February 2007, 03:15	#19 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 244	Re: constant IP regs, piston vs diaphragm Quote: (Originally Posted by Dave Sutton) The reason that needle valves are not optimal is that the time-base of PP02 decay is WAY TOO LONG to allow "adjustment on the fly" for such a system. Fixed orifice systems are far simpler, and with a correctly sized orifice allow diving as deep as anyone would practically desire. While in general terms I would agree with you, the needle valve in combination with a manual add valve allows the diver to set a liter flow rate on the surface relative to his nominal work rate for the particular dive, and then bring up the loop with the manual add button (like the KISS valve). As an example, if I'm going to scooter the whole dive at 250', I would set the flow to .5 lt.. If I plan to fin the whole dive at less than 80' (cave diving), I'm more likely to set the flow at .9 to 1.0 lt.. By using a needle valve and a manual add valve I can set the flow to whatever level I feel is most optimal for that particular dive, and not have to worry about a depth limitation do to a low intermediate pressure. Finally, if I not happy with my choice of flow rate, it's adjustable during the dive unlike a fixed orifice setup. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
(Online)

18th February 2007, 04:24	#20 (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 in the case of needle valves, are these being referred to as a device that also restricts flow within a certain range, or a means to control the full spectrum from 'on' to 'off' with the IP flow from the LP hose? In other words, is the needle valve being used in conjunction with an orifice that say offers a max flow of 1lpm or thereabouts on the high end, so it can be tuned down during the dive to adjust for the IP increase on descent? __________________ 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
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