Mine Clearance CUMA Rebreather

RonMicjan · 26th June 2006, 06:06

Just finished an article on the Canadian Forces CUMA mine clearance rebreather, see the article on my website www.tmishop.com/CUMA.htm
neat rig. discuss it here.

Loubylou, feel free to slurp up the article and post it on Rebreather World when you have time. thx.

gathan · 26th June 2006, 13:00

Hi Ron,

I would like to say thank you for the work you did putting together the article on the CUMA. It is indeed quite a unique kind of rebreather. As I read through the information that you provided, I did notice some innacuracies. I hope you won't mind my helping you correct them.

1. The scrubber capacity is rated to 2.5Kg vs 2.2Kg. We use sofnolime SL 812.

2. You stated that the CUMA works as an oxygen rebreather in less than 20FSW. The ratio regulator portion of the assembly delivers gas to the diluent metering valve sub-assembly at an output pressure equal to approximately 1.9 times the ambiant gauge pressure, less 0.4 bar (6psig) offset for helium. Basically what this means is that the ratio regulator will not allow helium to flow through until the diver reaches 13FSW. After leaving the surface, we send a signal - before we reach 20FSW - to the surface crew to let them know that a green light was achieved, indicating that the unit is delivering a heliox mixture that fall within established parameters. So, if all works well, the unit starts to deliver heliox at 13FSW, not 20FSW.

3. The by-pass valve does not supply pure oxygen on the surface, it delivers a mixture of 18-22% oxygen at a flow rate of 185slm, increasing to 290slm and 13% oxygen at 273FSW. In fact, the diver always flushes the loop by using the by-pass, before he/she submerges in order to reduce the PO2. Starting the dive with pure oxygen in the loop would not be a good thing.

4. The part about using the bailout in an OC mode of sort... given that the flow through the fixed orifice of the bailout assembly regulator is 16slm, using it in an OC way is out of the question, what I'm saying is that if the loop is not usable, you don't have a bailout. We will soon be able to deliver what we call an Auxilliary Gas System or AGS. We've completed all in house and field testing and hopefully the first units will be delivered to the operational teams soon. The AGS is a self contained gas delivery system that gets lowered into the water column, usually at the first decompression stop depth. We're looking to see whether it is feasible to deploy it deeper. The AGS will supply deco gas to 2 divers at once through the use of QD hoses that are fitted on the CUMA sets. In this mode, the AGS basically works as an offboard gas delivery system of sort. The AGS can aslo be used as a "bailout rebreather" and can support one diver in this fashion. I know some will question why we simply don't carry OC bailout with us. You have to keep in mind that these units are designed for a very specific purpose which is to get a diver very close to smart influence mines. Carrying noise making bailout cylinders is one sure way to cut short a Clearance Diver's career.

5. One of your pictures shows a counterlung relief valve or (CRV) which is used to protect the loop from overpressurization. It also serves as a means to accelerate gas bleed off during flushing drills. The pic is not of a buoyancy control valve (BCV) & bubble diffuser, as you state.

I, by no means, aim to critique your article Ron, in fact I thank you again for enabling information on the CUMA to reach the members of this fine forum.

Andre Fortin
Chief Diver (Clearance Diver)
Defense Research & Development Centre Toronto, Canada
Experimental Diving and Undersea Group (formerly DCIEM)

onetime · 26th June 2006, 13:00

Interesting. Thanks for the write up. Do you have any info on how the CCDA differs or is that an article that you have in the works?

gathan · 26th June 2006, 13:20

The CCDA or Canadian Clearance Diving Apparatus is not much diffrent than other, off the shelf SCRs except for being made to military specifications which include the use of non-ferrous materials in it's construction. As Ron correctly stated, it shares many components with the CUMA, including the loop. It typically uses premixed NATO standard nitrox mixtures, but can also be configured as an oxygen rebreather, for training purposes, using pure oxygen as a gas source. Flow settings are set by the diver through the use of a micro-metering valve. Flows and max operating depths are as follows:

O2 - 1.5slm / 8msw
60EAN - 6slm - 24msw
40EAN - 12slm - 42msw

We also used to use EAN 32.5 to a depth of 54msw. This is no longer the case. CUMA is used deeper than 42msw.

Andre

diverrob · 26th June 2006, 13:58

Nice article Ron! Glad you enjoyed the visit, make sure you give me a ring next time you are in town. To answer your question about the diapers/depends, YES CUMA can be issued with them!

Rob

Crazyduck · 26th June 2006, 14:47

Ron thanks for the write up and great pictures.

Very interesting machine and thanks to the guys that use the machine in hostile conditions.

Andre- thank you for your additions, footnotes, and thoughts- very interesting sir.

Regards, Andrew

RonMicjan · 27th June 2006, 05:18

Quote: (Originally Posted by gathan)

Hi Ron,

I would like to say thank you for the work you did putting together the article on the CUMA. It is indeed quite a unique kind of rebreather. As I read through the information that you provided, I did notice some innacuracies. I hope you won't mind my helping you correct them.

1. The scrubber capacity is rated to 2.5Kg vs 2.2Kg. We use sofnolime SL 812.

2. You stated that the CUMA works as an oxygen rebreather in less than 20FSW. The ratio regulator portion of the assembly delivers gas to the diluent metering valve sub-assembly at an output pressure equal to approximately 1.9 times the ambiant gauge pressure, less 0.4 bar (6psig) offset for helium. Basically what this means is that the ratio regulator will not allow helium to flow through until the diver reaches 13FSW. After leaving the surface, we send a signal - before we reach 20FSW - to the surface crew to let them know that a green light was achieved, indicating that the unit is delivering a heliox mixture that fall within established parameters. So, if all works well, the unit starts to deliver heliox at 13FSW, not 20FSW.

3. The by-pass valve does not supply pure oxygen on the surface, it delivers a mixture of 18-22% oxygen at a flow rate of 185slm, increasing to 290slm and 13% oxygen at 273FSW. In fact, the diver always flushes the loop by using the by-pass, before he/she submerges in order to reduce the PO2. Starting the dive with pure oxygen in the loop would not be a good thing.

4. The part about using the bailout in an OC mode of sort... given that the flow through the fixed orifice of the bailout assembly regulator is 16slm, using it in an OC way is out of the question, what I'm saying is that if the loop is not usable, you don't have a bailout. We will soon be able to deliver what we call an Auxilliary Gas System or AGS. We've completed all in house and field testing and hopefully the first units will be delivered to the operational teams soon. The AGS is a self contained gas delivery system that gets lowered into the water column, usually at the first decompression stop depth. We're looking to see whether it is feasible to deploy it deeper. The AGS will supply deco gas to 2 divers at once through the use of QD hoses that are fitted on the CUMA sets. In this mode, the AGS basically works as an offboard gas delivery system of sort. The AGS can aslo be used as a "bailout rebreather" and can support one diver in this fashion. I know some will question why we simply don't carry OC bailout with us. You have to keep in mind that these units are designed for a very specific purpose which is to get a diver very close to smart influence mines. Carrying noise making bailout cylinders is one sure way to cut short a Clearance Diver's career.

5. One of your pictures shows a counterlung relief valve or (CRV) which is used to protect the loop from overpressurization. It also serves as a means to accelerate gas bleed off during flushing drills. The pic is not of a buoyancy control valve (BCV) & bubble diffuser, as you state.

I, by no means, aim to critique your article Ron, in fact I thank you again for enabling information on the CUMA to reach the members of this fine forum.

Andre Fortin
Chief Diver (Clearance Diver)
Defense Research & Development Centre Toronto, Canada
Experimental Diving and Undersea Group (formerly DCIEM)

Thanks for the careful read Chief, I always stick in a couple small errors just so I know folks are paying attention, good catch!

Yup, scrubber is 2.5kg or 5.5lbs, but measured by volume.

13fsw it is, by gosh, wondering where I got 20? I read the procedure where the diver is not to leave the surface with a green light, so what tolerance specifies green light and red light? does the sensor need to see some diluent before it changes? So somewhere between 13 and 20 you will get the green? A green light at the surface would mean a poor calibration??

If the bypass valve blows a mix that could drop your po2 to .18, with tolerance stacking going against you worse case, what would the diver do if he needed to increase the loop volume at the surface, just wait out the 3.6lpm O2 injection, or bump the bypass a bit?

does the diver bump the bypass on the descent to maintain loop volume? Wouldnt this skew the decompression with a loop that lean for the first few minutes of the dive?

I got the part about OC breathing from the bypass from Page 5-2-13, article 5217, Emergency use of bypass, it seemed a difficult scenario, but what else would you do in the event of a flood?

So as i understand it, there are two different exaust type valves, one in each counterlung, one is a CRV or counterlung relief valve with quick dump and is meant to be shut down in the proximity of ordance, the other is a buoyancy control device and has the bubble diffuser, can you clarify which is where please? I may have mixed up the pics.

thanks for the info

diverrob · 28th June 2006, 00:40

Quote: (Originally Posted by RonMicjan)

Thanks for the careful read Chief, I always stick in a couple small errors just so I know folks are paying attention, good catch!

Yup, scrubber is 2.5kg or 5.5lbs, but measured by volume.

13fsw it is, by gosh, wondering where I got 20? I read the procedure where the diver is not to leave the surface with a green light, so what tolerance specifies green light and red light? does the sensor need to see some diluent before it changes? So somewhere between 13 and 20 you will get the green? A green light at the surface would mean a poor calibration??

If the bypass valve blows a mix that could drop your po2 to .18, with tolerance stacking going against you worse case, what would the diver do if he needed to increase the loop volume at the surface, just wait out the 3.6lpm O2 injection, or bump the bypass a bit?

does the diver bump the bypass on the descent to maintain loop volume? Wouldnt this skew the decompression with a loop that lean for the first few minutes of the dive?

I got the part about OC breathing from the bypass from Page 5-2-13, article 5217, Emergency use of bypass, it seemed a difficult scenario, but what else would you do in the event of a flood?

So as i understand it, there are two different exaust type valves, one in each counterlung, one is a CRV or counterlung relief valve with quick dump and is meant to be shut down in the proximity of ordance, the other is a buoyancy control device and has the bubble diffuser, can you clarify which is where please? I may have mixed up the pics.

thanks for the info

I think I can shed some light on your questions...........

1. A green light indicates that the set is delivering the gas within the alarm set points (1.2-1.8). The set is tested and calibrated to deliver gas at 1.5-1.7. So if the diver gets a red light it indicates that the set is outside the alarm settings (either too high or too low) the diver does not know which. at the surface the PO2 is max 1.0 which would give you a red light (good to go). Before the diver dives he flushes the CL using the bypass (18-22% O2) diver still has a red light. The set will always supply 3.6SLM of O2 so as the diver descends the PO2 increases and around 13FSW the dil starts to flow at this point the diver should get a green light indicating that the PO2 is above 1.2, he then signals and proceeds on with his dive. The 20FSW you were told comes from the fact that the life line is sometimes tied around the divers waist and that in a current the markings on the line will not accurately indicate the correct depth due to the angle of the line. Yes a green light at the surface would indicate a poor calibration or more likely a problem in the electronic side of the Rebreather either way the diver would not dive the set.

2. If the diver needs to increase his CL volume at any depth he does so with the Bypass Valve.

3. Yes the diver does use the Bypass to add to the CL volume on decent. As for skewing the deco profile I am here to tell you I have done most of the profiles we have and so far no problems. The guy with the big head seems to know what he is doing. Andre would probably have the technical info on that question if you would like it.

4. As for the exhaust valves on the CL yes there are two different valves and they do different jobs. The CRV (Counterlung Relief Valve) is located on the divers left side and is just that a relief valve (OPV). It is also used to preform flushes. The BCV (buoyancy Control Valve) is located on the divers right side and is used to control the buoyancy of the diver (helps maintain CL volume). Remember that we are diving a SCR and the gas flow never stops during the dive so if we did not have this we would have out CL full at all times. The BCV also is designed to keep the escaping bubbles small enough that the acoustic signature meets the design specification which will keep the diver safe when around a acoustic mine. The CRV should never be operated around live mines as the noise of the larger bubbles "could" set the mine off (or at least piss it off a little)

***Louby Lou*** · 14th July 2006, 19:37

Quote: (Originally Posted by RonMicjan)

Loubylou, feel free to slurp up the article and post it on Rebreather World when you have time. thx.

Hi Ron

Sorry for the delay... moving house!

Thanks again for the article; its now all up and running in all its glory HERE

Cheers

Lou

AD_ward9 · 6th December 2007, 15:09

I notice from the pictures, http://www.rebreatherworld.com/photo...php?photo=2729 in particular, that the electronics is abysmal.

Use of electrolytic capacitors, and clearly no redundancy (just two chips, one of which seems to be doing all the work), 5 trim pots. This is the sort of thing a pre-university hobby builder might make for his science project. It definitely does not compy with US or UK safety standards for electronics.

Astonishing! I was expecting something much more professional.

Anyone know who did the electronics?

Alex

26th June 2006, 06:06	#1 (permalink)
RonMicjan Cap Ron scourge of the NW Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Cape Disapointment, The Graveyard of the Pacific Posts: 1,100	Mine Clearance CUMA Rebreather Just finished an article on the Canadian Forces CUMA mine clearance rebreather, see the article on my website www.tmishop.com/CUMA.htm neat rig. discuss it here. Loubylou, feel free to slurp up the article and post it on Rebreather World when you have time. thx. __________________ Marine rescue, towing and salvage. Interfering with natural selection since 1983. www.tmishop.com Diving bits etc. www.seatowpdx.com The Summer Job
(Offline)

26th June 2006, 13:00	#2 (permalink)
gathan MixedGas Current Rebreather/s: Classic Kiss Other SCR Other Rebreather/s: Other SCR Join Date: Sep 2005 Location: Tottenham, Ontario, Canada Posts: 194	Re: Mine Clearance CUMA Rebreather Hi Ron, I would like to say thank you for the work you did putting together the article on the CUMA. It is indeed quite a unique kind of rebreather. As I read through the information that you provided, I did notice some innacuracies. I hope you won't mind my helping you correct them. 1. The scrubber capacity is rated to 2.5Kg vs 2.2Kg. We use sofnolime SL 812. 2. You stated that the CUMA works as an oxygen rebreather in less than 20FSW. The ratio regulator portion of the assembly delivers gas to the diluent metering valve sub-assembly at an output pressure equal to approximately 1.9 times the ambiant gauge pressure, less 0.4 bar (6psig) offset for helium. Basically what this means is that the ratio regulator will not allow helium to flow through until the diver reaches 13FSW. After leaving the surface, we send a signal - before we reach 20FSW - to the surface crew to let them know that a green light was achieved, indicating that the unit is delivering a heliox mixture that fall within established parameters. So, if all works well, the unit starts to deliver heliox at 13FSW, not 20FSW. 3. The by-pass valve does not supply pure oxygen on the surface, it delivers a mixture of 18-22% oxygen at a flow rate of 185slm, increasing to 290slm and 13% oxygen at 273FSW. In fact, the diver always flushes the loop by using the by-pass, before he/she submerges in order to reduce the PO2. Starting the dive with pure oxygen in the loop would not be a good thing. 4. The part about using the bailout in an OC mode of sort... given that the flow through the fixed orifice of the bailout assembly regulator is 16slm, using it in an OC way is out of the question, what I'm saying is that if the loop is not usable, you don't have a bailout. We will soon be able to deliver what we call an Auxilliary Gas System or AGS. We've completed all in house and field testing and hopefully the first units will be delivered to the operational teams soon. The AGS is a self contained gas delivery system that gets lowered into the water column, usually at the first decompression stop depth. We're looking to see whether it is feasible to deploy it deeper. The AGS will supply deco gas to 2 divers at once through the use of QD hoses that are fitted on the CUMA sets. In this mode, the AGS basically works as an offboard gas delivery system of sort. The AGS can aslo be used as a "bailout rebreather" and can support one diver in this fashion. I know some will question why we simply don't carry OC bailout with us. You have to keep in mind that these units are designed for a very specific purpose which is to get a diver very close to smart influence mines. Carrying noise making bailout cylinders is one sure way to cut short a Clearance Diver's career. 5. One of your pictures shows a counterlung relief valve or (CRV) which is used to protect the loop from overpressurization. It also serves as a means to accelerate gas bleed off during flushing drills. The pic is not of a buoyancy control valve (BCV) & bubble diffuser, as you state. I, by no means, aim to critique your article Ron, in fact I thank you again for enabling information on the CUMA to reach the members of this fine forum. Andre Fortin Chief Diver (Clearance Diver) Defense Research & Development Centre Toronto, Canada Experimental Diving and Undersea Group (formerly DCIEM) Last edited by gathan : 26th June 2006 at 13:24.
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26th June 2006, 13:00	#3 (permalink)
onetime Classic KISSer #138 Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Mar 2005 Location: US, NJ Posts: 673	Re: Mine Clearance CUMA Rebreather Interesting. Thanks for the write up. Do you have any info on how the CCDA differs or is that an article that you have in the works?
(Offline)

26th June 2006, 13:20	#4 (permalink)
gathan MixedGas Current Rebreather/s: Classic Kiss Other SCR Other Rebreather/s: Other SCR Join Date: Sep 2005 Location: Tottenham, Ontario, Canada Posts: 194	Re: Mine Clearance CUMA Rebreather The CCDA or Canadian Clearance Diving Apparatus is not much diffrent than other, off the shelf SCRs except for being made to military specifications which include the use of non-ferrous materials in it's construction. As Ron correctly stated, it shares many components with the CUMA, including the loop. It typically uses premixed NATO standard nitrox mixtures, but can also be configured as an oxygen rebreather, for training purposes, using pure oxygen as a gas source. Flow settings are set by the diver through the use of a micro-metering valve. Flows and max operating depths are as follows: O2 - 1.5slm / 8msw 60EAN - 6slm - 24msw 40EAN - 12slm - 42msw We also used to use EAN 32.5 to a depth of 54msw. This is no longer the case. CUMA is used deeper than 42msw. Andre Last edited by gathan : 26th June 2006 at 13:27.
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26th June 2006, 13:58	#5 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 336	Re: Mine Clearance CUMA Rebreather Nice article Ron! Glad you enjoyed the visit, make sure you give me a ring next time you are in town. To answer your question about the diapers/depends, YES CUMA can be issued with them! Rob
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26th June 2006, 14:47	#6 (permalink)
Crazyduck Underwater Mechanic Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Mar 2005 Location: TEXAS, Dallas/ Ft.Worth Posts: 711	Re: Mine Clearance CUMA Rebreather Ron thanks for the write up and great pictures. Very interesting machine and thanks to the guys that use the machine in hostile conditions. Andre- thank you for your additions, footnotes, and thoughts- very interesting sir. Regards, Andrew __________________ Howdy Senor- What’s Happening! Rob Davie April 2005- Presently in a state of transition from Open Circuit to Closed Circuit. "You will not be punished for your anger; you will be punished by it." - Buddha.
(Online)

27th June 2006, 05:18	#7 (permalink)
RonMicjan Cap Ron scourge of the NW Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Cape Disapointment, The Graveyard of the Pacific Posts: 1,100	Re: Mine Clearance CUMA Rebreather Quote: (Originally Posted by gathan) Hi Ron, I would like to say thank you for the work you did putting together the article on the CUMA. It is indeed quite a unique kind of rebreather. As I read through the information that you provided, I did notice some innacuracies. I hope you won't mind my helping you correct them. 1. The scrubber capacity is rated to 2.5Kg vs 2.2Kg. We use sofnolime SL 812. 2. You stated that the CUMA works as an oxygen rebreather in less than 20FSW. The ratio regulator portion of the assembly delivers gas to the diluent metering valve sub-assembly at an output pressure equal to approximately 1.9 times the ambiant gauge pressure, less 0.4 bar (6psig) offset for helium. Basically what this means is that the ratio regulator will not allow helium to flow through until the diver reaches 13FSW. After leaving the surface, we send a signal - before we reach 20FSW - to the surface crew to let them know that a green light was achieved, indicating that the unit is delivering a heliox mixture that fall within established parameters. So, if all works well, the unit starts to deliver heliox at 13FSW, not 20FSW. 3. The by-pass valve does not supply pure oxygen on the surface, it delivers a mixture of 18-22% oxygen at a flow rate of 185slm, increasing to 290slm and 13% oxygen at 273FSW. In fact, the diver always flushes the loop by using the by-pass, before he/she submerges in order to reduce the PO2. Starting the dive with pure oxygen in the loop would not be a good thing. 4. The part about using the bailout in an OC mode of sort... given that the flow through the fixed orifice of the bailout assembly regulator is 16slm, using it in an OC way is out of the question, what I'm saying is that if the loop is not usable, you don't have a bailout. We will soon be able to deliver what we call an Auxilliary Gas System or AGS. We've completed all in house and field testing and hopefully the first units will be delivered to the operational teams soon. The AGS is a self contained gas delivery system that gets lowered into the water column, usually at the first decompression stop depth. We're looking to see whether it is feasible to deploy it deeper. The AGS will supply deco gas to 2 divers at once through the use of QD hoses that are fitted on the CUMA sets. In this mode, the AGS basically works as an offboard gas delivery system of sort. The AGS can aslo be used as a "bailout rebreather" and can support one diver in this fashion. I know some will question why we simply don't carry OC bailout with us. You have to keep in mind that these units are designed for a very specific purpose which is to get a diver very close to smart influence mines. Carrying noise making bailout cylinders is one sure way to cut short a Clearance Diver's career. 5. One of your pictures shows a counterlung relief valve or (CRV) which is used to protect the loop from overpressurization. It also serves as a means to accelerate gas bleed off during flushing drills. The pic is not of a buoyancy control valve (BCV) & bubble diffuser, as you state. I, by no means, aim to critique your article Ron, in fact I thank you again for enabling information on the CUMA to reach the members of this fine forum. Andre Fortin Chief Diver (Clearance Diver) Defense Research & Development Centre Toronto, Canada Experimental Diving and Undersea Group (formerly DCIEM) Thanks for the careful read Chief, I always stick in a couple small errors just so I know folks are paying attention, good catch! Yup, scrubber is 2.5kg or 5.5lbs, but measured by volume. 13fsw it is, by gosh, wondering where I got 20? I read the procedure where the diver is not to leave the surface with a green light, so what tolerance specifies green light and red light? does the sensor need to see some diluent before it changes? So somewhere between 13 and 20 you will get the green? A green light at the surface would mean a poor calibration?? If the bypass valve blows a mix that could drop your po2 to .18, with tolerance stacking going against you worse case, what would the diver do if he needed to increase the loop volume at the surface, just wait out the 3.6lpm O2 injection, or bump the bypass a bit? does the diver bump the bypass on the descent to maintain loop volume? Wouldnt this skew the decompression with a loop that lean for the first few minutes of the dive? I got the part about OC breathing from the bypass from Page 5-2-13, article 5217, Emergency use of bypass, it seemed a difficult scenario, but what else would you do in the event of a flood? So as i understand it, there are two different exaust type valves, one in each counterlung, one is a CRV or counterlung relief valve with quick dump and is meant to be shut down in the proximity of ordance, the other is a buoyancy control device and has the bubble diffuser, can you clarify which is where please? I may have mixed up the pics. thanks for the info __________________ Marine rescue, towing and salvage. Interfering with natural selection since 1983. www.tmishop.com Diving bits etc. www.seatowpdx.com The Summer Job
(Offline)

28th June 2006, 00:40	#8 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 336	Re: Mine Clearance CUMA Rebreather Quote: (Originally Posted by RonMicjan) Thanks for the careful read Chief, I always stick in a couple small errors just so I know folks are paying attention, good catch! Yup, scrubber is 2.5kg or 5.5lbs, but measured by volume. 13fsw it is, by gosh, wondering where I got 20? I read the procedure where the diver is not to leave the surface with a green light, so what tolerance specifies green light and red light? does the sensor need to see some diluent before it changes? So somewhere between 13 and 20 you will get the green? A green light at the surface would mean a poor calibration?? If the bypass valve blows a mix that could drop your po2 to .18, with tolerance stacking going against you worse case, what would the diver do if he needed to increase the loop volume at the surface, just wait out the 3.6lpm O2 injection, or bump the bypass a bit? does the diver bump the bypass on the descent to maintain loop volume? Wouldnt this skew the decompression with a loop that lean for the first few minutes of the dive? I got the part about OC breathing from the bypass from Page 5-2-13, article 5217, Emergency use of bypass, it seemed a difficult scenario, but what else would you do in the event of a flood? So as i understand it, there are two different exaust type valves, one in each counterlung, one is a CRV or counterlung relief valve with quick dump and is meant to be shut down in the proximity of ordance, the other is a buoyancy control device and has the bubble diffuser, can you clarify which is where please? I may have mixed up the pics. thanks for the info I think I can shed some light on your questions........... 1. A green light indicates that the set is delivering the gas within the alarm set points (1.2-1.8). The set is tested and calibrated to deliver gas at 1.5-1.7. So if the diver gets a red light it indicates that the set is outside the alarm settings (either too high or too low) the diver does not know which. at the surface the PO2 is max 1.0 which would give you a red light (good to go). Before the diver dives he flushes the CL using the bypass (18-22% O2) diver still has a red light. The set will always supply 3.6SLM of O2 so as the diver descends the PO2 increases and around 13FSW the dil starts to flow at this point the diver should get a green light indicating that the PO2 is above 1.2, he then signals and proceeds on with his dive. The 20FSW you were told comes from the fact that the life line is sometimes tied around the divers waist and that in a current the markings on the line will not accurately indicate the correct depth due to the angle of the line. Yes a green light at the surface would indicate a poor calibration or more likely a problem in the electronic side of the Rebreather either way the diver would not dive the set. 2. If the diver needs to increase his CL volume at any depth he does so with the Bypass Valve. 3. Yes the diver does use the Bypass to add to the CL volume on decent. As for skewing the deco profile I am here to tell you I have done most of the profiles we have and so far no problems. The guy with the big head seems to know what he is doing. Andre would probably have the technical info on that question if you would like it. 4. As for the exhaust valves on the CL yes there are two different valves and they do different jobs. The CRV (Counterlung Relief Valve) is located on the divers left side and is just that a relief valve (OPV). It is also used to preform flushes. The BCV (buoyancy Control Valve) is located on the divers right side and is used to control the buoyancy of the diver (helps maintain CL volume). Remember that we are diving a SCR and the gas flow never stops during the dive so if we did not have this we would have out CL full at all times. The BCV also is designed to keep the escaping bubbles small enough that the acoustic signature meets the design specification which will keep the diver safe when around a acoustic mine. The CRV should never be operated around live mines as the noise of the larger bubbles "could" set the mine off (or at least piss it off a little)
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14th July 2006, 19:37	#9 (permalink)
*Louby Lou* XLVI WC! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Roman Corinium! Posts: 1,019	Re: Mine Clearance CUMA Rebreather Quote: (Originally Posted by RonMicjan) Loubylou, feel free to slurp up the article and post it on Rebreather World when you have time. thx. Hi Ron Sorry for the delay... moving house! Thanks again for the article; its now all up and running in all its glory HERE Cheers Lou __________________ Miss Lou x Use of Rebreather World is subject to the Rebreatherworld Terms and Conditions - Please read! Outlaw Divers - Sssh we're diving! You heff vays uff dealink vis zem, oh Miss Rebreather World Admin! - Rob Davie Feb 06
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6th December 2007, 15:09	#10 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,864	Re: Mine Clearance CUMA Rebreather I notice from the pictures, http://www.rebreatherworld.com/photo...php?photo=2729 in particular, that the electronics is abysmal. Use of electrolytic capacitors, and clearly no redundancy (just two chips, one of which seems to be doing all the work), 5 trim pots. This is the sort of thing a pre-university hobby builder might make for his science project. It definitely does not compy with US or UK safety standards for electronics. Astonishing! I was expecting something much more professional. Anyone know who did the electronics? Alex
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