Overview to the DL Open Revolution Submission

AD_ward9 · 18th November 2005, 21:10

Here are the same questions as Kevin Gurr´s excellent list for the Ouroboros: "Why Design It That Way?"

(Questions that are not applicable, eg cylinder size, are omitted, others are adjusted to make them relevant)

Why use xxx mounted counterlungs?
We make no assumption on counterlungs except they must be located parallel with the lungs, and not more than 200mm from the lungs. Back-mounted, shoulder mounted, over-shoulder or chest mounted, must all pass.

Why are the hoses so big?
To allow for deep diving and the increased gas density at depth. This design of hose also contains an armoured spring system to prevent accidental collapse and provide abrasion protection.

Can I adjust the mouthpiece and hoses for comfort?
To reduce failure points, the hose and mouthpiece are clamped together. Adjustment needs a multi-tool.

Why is there no manual backup PO2 system?
Three batteries are provided: only one needs to operate. If all batteries fail, then the O2 sensors are also out of order. This means the user should not be trying to run the unit in closed loop, so there is no manual PO2 system. Instead, the user should be operating the unit as a semi-closed rebreather.

How long will the batteries last?
There are three batteries fitted: one in the handset and two in the scrubber cap. The system can operate for 30 hours on any one battery. Any two batteries can fail and the system operates normally. The batteries are Lithium Ion rechargeable, using a standard Nokia phone socket mounted next to the O2 sensors.

Why not just use an active (constant flow) addition?
Tracking of required PO2 is often not as accurate as an electronic control system. Also if the flow jet blocks or fails there may be no alarm indication as to the fall or rise in PO2.

Why use small bore pipe work?
If a valve or addition system fails, a limited amount of gas (potentially oxygen) will be released into the loop and in the event of a failure to atmosphere, a limited amount will be lost before a shut down procedure can be activated. Larger bore gas lines also tend to make the rebreather's PO2 fluctuate considerably during ascents and descents.

Why use stainless steel pipe work?
All pipework is eliminated, because pipework means fittings, and fittings fail. The user simply plumbs in intermediate pressure gas directly to the injector, which pierces the wall of the scrubber to allow connection. This also means there is no intermediate pressure O2 or DIL in the breathing loop.

Why is no vibrating alarm fitted?
Vibrating alarms can escalate panic. Instead a voice annunciation system is used, telling the user the problem and what action they should take. This is accompanies by a suitable music during gaps in the speech (continuous speech is ignored in an emergency, as if it were noise).

Can I recover from a partial flood or mouthpiece loss?
Yes, a water removal pump is fitted to the exhale breathing bag.

What happens if I sever a cable?
If the handset is lost totally, the system still operates normally, using voice annunciation and the HUD, as the O2 injectors are intelligent.

All cable systems are flood proof, screened and double armoured. All cables carrying electrical signals are filled with a silicone oil compatible with the hose material.

What happens if I flood or damage a display?
The other displays will continue to function independently.

Why use a ‘wet turn-on’ system?
An analysis of accidents has shown a high proportion of users forgetting to turn their units on prior to entering the water. Some even forgot to turn their gas on. The system not only automatically turns on when immersed, it will always maintain a minimum PO2 of 0.4 and will alarm if HP gas is turned off.

What happens if the wet turn on system fails?
The unit can also be turned on by touching a button on the Primary display it will also automatically turn on at approximately 1m or can be dived manually using the Backup oxygen display. If dive checks are not carried out, below 10m the unit shuts off the breathing loop.

What happens if the oxygen solenoid or automatic diluent addition valve fails?
Firstly alarms will be activated and then you have the option to manually isolate the failed valve and continue diving.

Will the computer system lock out for a decompression violation or any other alarm?
Never, the user is always given the option to make the final decision.
Will the unit keep up its PO2 on fast ascents?
The unit has a virtually optimal closed loop injector which keeps track with variable ascent rates up to 200ft/min.

How do I calibrate when diving at altitude?
The rebreather automatically senses altitude and with a known gas will automatically calibrate.

Some units have a solenoid fire light, why is the Ouroboros different?
The system checks the injector, which is not solenoid based, and calculates if it has injected the correct amount of gas. There is full closed loop control on the injector.

Changes in injector setting cause a synthesised sound to be produced, simulating the sound of gas flow through a valve being openned or closed.

Injector failures will show as alarms in the HUD, Voice and on the displays.

Can I complete a decompression dive on the HUD only?
Yes, there is enough information for PO2, decompression, general alarms and solenoid fire status. You can also complete on voice annunciation only.

Will the dive computer track an open circuit bailout decompression?
Yes, tell it you are now on open circuit and it will track. If you recover the rebreather and switch back to it you can put the computer back into closed circuit mode.

What happens if all four cells are reading wrong?
The injector can still control PPO2 for 25 minutes, as the injector is calibrated during pre-dive checks, and the system monitors how much gas is injected, or flushed, or lost.

Why keep active electronics and batteries outside the breathing loop?
Electronics of any sort are a fire hazard in an oxygen enriched environment. Major failures of oxygen valves and pipe work in the loop will create a rapid rise in PO2.The Ouroboros has no active electronics or batteries in the breathing loop.

How does the system protect against valve failures?
All valves are protected by 15 micron in-line filters which can be replaced if required.

Is the injector valve affected by varying first stage pressures?
The injectors can even withstand and operate with high pressure gas (no first stage), being connected.

Why is the auto diluent addition valve not adjustable?
It has a balanced design, sufficient to withstand a firehose without freeflow, whilst making breathing easily, within EN250, but with enough resistance as not to inject when gas is flowing normally around the loop.

What items in the unit can be stripped down or removed without tools?
The case
The mouthpiece
There are no gas blocks
The hose ends
The counterlungs
The absorbent canister
The oxygen sensors
There is no battery compartment
All major O rings

If you cannot crush the hoses how do you monitor a negative test?
EN14143 requires that the hoses are not crushable.
The system runs the neg pressure test: it only asks the user to apply neg pressure and then checks the user has done so. It uses the pressure sensors to monitor the pressure. It does the same for positive pressure, but uses the O2 injector to create the pos pressure.

Can the handset implode?
The handset is filled with silicone oil, so should be able to withstand 12,000ft.
All cables carrying electrical signals are filled with silicone oil. The hermetic chamber for the electronics is filled with silicone oil.

What is the depth limit?
440ft, set by the pressure sensors that are used. Beyond that means a factory change of the pressure sensors.

Why use both optical and electrical communication with the handset and base?
To withstand different failure modes (electrical interference, sharp bends, LED MTBFs etc).

Connectors look like P connectors: will they fail?
The connector is similar to the Draeger P connector, but with the following important changes:
a. The top face is fixed on with a pin, so it will not fall off.
b. There are two O rings, and two springs and two spring grooves. This gives the sequence: retain, seal, positive retain and loud click. This means they should never come off accidentally.
This compares to the single spring, single O ring, and single groove in the Draeger version.
c. The inner diameter is increased from 24mm to 35mm to reduce WOB

AD_ward9 · 18th November 2005, 21:13

The following link provides a series of pdf files, giving an overview of DL´s Open Revolution submission, and where we are coming from: http://www.deeplife.co.uk/or.php

18th November 2005, 21:10	#1 (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: 1,862	Overview to the DL Open Revolution Submission Here are the same questions as Kevin Gurr´s excellent list for the Ouroboros: "Why Design It That Way?" (Questions that are not applicable, eg cylinder size, are omitted, others are adjusted to make them relevant) Why use xxx mounted counterlungs? We make no assumption on counterlungs except they must be located parallel with the lungs, and not more than 200mm from the lungs. Back-mounted, shoulder mounted, over-shoulder or chest mounted, must all pass. Why are the hoses so big? To allow for deep diving and the increased gas density at depth. This design of hose also contains an armoured spring system to prevent accidental collapse and provide abrasion protection. Can I adjust the mouthpiece and hoses for comfort? To reduce failure points, the hose and mouthpiece are clamped together. Adjustment needs a multi-tool. Why is there no manual backup PO2 system? Three batteries are provided: only one needs to operate. If all batteries fail, then the O2 sensors are also out of order. This means the user should not be trying to run the unit in closed loop, so there is no manual PO2 system. Instead, the user should be operating the unit as a semi-closed rebreather. How long will the batteries last? There are three batteries fitted: one in the handset and two in the scrubber cap. The system can operate for 30 hours on any one battery. Any two batteries can fail and the system operates normally. The batteries are Lithium Ion rechargeable, using a standard Nokia phone socket mounted next to the O2 sensors. Why not just use an active (constant flow) addition? Tracking of required PO2 is often not as accurate as an electronic control system. Also if the flow jet blocks or fails there may be no alarm indication as to the fall or rise in PO2. Why use small bore pipe work? If a valve or addition system fails, a limited amount of gas (potentially oxygen) will be released into the loop and in the event of a failure to atmosphere, a limited amount will be lost before a shut down procedure can be activated. Larger bore gas lines also tend to make the rebreather's PO2 fluctuate considerably during ascents and descents. Why use stainless steel pipe work? All pipework is eliminated, because pipework means fittings, and fittings fail. The user simply plumbs in intermediate pressure gas directly to the injector, which pierces the wall of the scrubber to allow connection. This also means there is no intermediate pressure O2 or DIL in the breathing loop. Why is no vibrating alarm fitted? Vibrating alarms can escalate panic. Instead a voice annunciation system is used, telling the user the problem and what action they should take. This is accompanies by a suitable music during gaps in the speech (continuous speech is ignored in an emergency, as if it were noise). Can I recover from a partial flood or mouthpiece loss? Yes, a water removal pump is fitted to the exhale breathing bag. What happens if I sever a cable? If the handset is lost totally, the system still operates normally, using voice annunciation and the HUD, as the O2 injectors are intelligent. All cable systems are flood proof, screened and double armoured. All cables carrying electrical signals are filled with a silicone oil compatible with the hose material. What happens if I flood or damage a display? The other displays will continue to function independently. Why use a ‘wet turn-on’ system? An analysis of accidents has shown a high proportion of users forgetting to turn their units on prior to entering the water. Some even forgot to turn their gas on. The system not only automatically turns on when immersed, it will always maintain a minimum PO2 of 0.4 and will alarm if HP gas is turned off. What happens if the wet turn on system fails? The unit can also be turned on by touching a button on the Primary display it will also automatically turn on at approximately 1m or can be dived manually using the Backup oxygen display. If dive checks are not carried out, below 10m the unit shuts off the breathing loop. What happens if the oxygen solenoid or automatic diluent addition valve fails? Firstly alarms will be activated and then you have the option to manually isolate the failed valve and continue diving. Will the computer system lock out for a decompression violation or any other alarm? Never, the user is always given the option to make the final decision. Will the unit keep up its PO2 on fast ascents? The unit has a virtually optimal closed loop injector which keeps track with variable ascent rates up to 200ft/min. How do I calibrate when diving at altitude? The rebreather automatically senses altitude and with a known gas will automatically calibrate. Some units have a solenoid fire light, why is the Ouroboros different? The system checks the injector, which is not solenoid based, and calculates if it has injected the correct amount of gas. There is full closed loop control on the injector. Changes in injector setting cause a synthesised sound to be produced, simulating the sound of gas flow through a valve being openned or closed. Injector failures will show as alarms in the HUD, Voice and on the displays. Can I complete a decompression dive on the HUD only? Yes, there is enough information for PO2, decompression, general alarms and solenoid fire status. You can also complete on voice annunciation only. Will the dive computer track an open circuit bailout decompression? Yes, tell it you are now on open circuit and it will track. If you recover the rebreather and switch back to it you can put the computer back into closed circuit mode. What happens if all four cells are reading wrong? The injector can still control PPO2 for 25 minutes, as the injector is calibrated during pre-dive checks, and the system monitors how much gas is injected, or flushed, or lost. Why keep active electronics and batteries outside the breathing loop? Electronics of any sort are a fire hazard in an oxygen enriched environment. Major failures of oxygen valves and pipe work in the loop will create a rapid rise in PO2.The Ouroboros has no active electronics or batteries in the breathing loop. How does the system protect against valve failures? All valves are protected by 15 micron in-line filters which can be replaced if required. Is the injector valve affected by varying first stage pressures? The injectors can even withstand and operate with high pressure gas (no first stage), being connected. Why is the auto diluent addition valve not adjustable? It has a balanced design, sufficient to withstand a firehose without freeflow, whilst making breathing easily, within EN250, but with enough resistance as not to inject when gas is flowing normally around the loop. What items in the unit can be stripped down or removed without tools? The case The mouthpiece There are no gas blocks The hose ends The counterlungs The absorbent canister The oxygen sensors There is no battery compartment All major O rings If you cannot crush the hoses how do you monitor a negative test? EN14143 requires that the hoses are not crushable. The system runs the neg pressure test: it only asks the user to apply neg pressure and then checks the user has done so. It uses the pressure sensors to monitor the pressure. It does the same for positive pressure, but uses the O2 injector to create the pos pressure. Can the handset implode? The handset is filled with silicone oil, so should be able to withstand 12,000ft. All cables carrying electrical signals are filled with silicone oil. The hermetic chamber for the electronics is filled with silicone oil. What is the depth limit? 440ft, set by the pressure sensors that are used. Beyond that means a factory change of the pressure sensors. Why use both optical and electrical communication with the handset and base? To withstand different failure modes (electrical interference, sharp bends, LED MTBFs etc). Connectors look like P connectors: will they fail? The connector is similar to the Draeger P connector, but with the following important changes: a. The top face is fixed on with a pin, so it will not fall off. b. There are two O rings, and two springs and two spring grooves. This gives the sequence: retain, seal, positive retain and loud click. This means they should never come off accidentally. This compares to the single spring, single O ring, and single groove in the Draeger version. c. The inner diameter is increased from 24mm to 35mm to reduce WOB
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18th November 2005, 21:13	#2 (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: 1,862	Re: Overview to the DL Open Revolution Submission The following link provides a series of pdf files, giving an overview of DL´s Open Revolution submission, and where we are coming from: http://www.deeplife.co.uk/or.php
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