EFFECT OF SMALL VARIATIONS IN TEST CONDITIONS ON THE CO2 SCRUBBER ENDURANCE TO EN14143:2003 AND NORSOK U-101 DOCUMENT NUMBER: [Filename]

Transcription

1 DL OPEN REVOLUTION REBREATHER FAMILY OF PRODUCTS EFFECT OF SMALL VARIATIONS IN TEST CONDITIONS ON THE CO SCRUBBER ENDURANCE TO EN44:00 AND NORSOK U-0 DOCUMENT NUMBER: [Filename] DV_OR_ScrubberEndurance_084.doc CONTRIBUTORS: Dr. Bob Davidov, Dr. Oleg Zagrebelny, Mihael Soloviev, Viktor Sudakov, Dr. Alex Deas DEPARTMENT: Engineering LAST REVISED: 4 th Nov 008 REVISION: C APPROVALS Project Manager Quality Officer Controlled Document Revision History Revision Date Description A th May 008 Document assembled from other files Date Date B th May 008 Calibration information moved to DV report Classified Document DO NOT COPY. C 4 th Nov 008 Horizontal cases added. Correlation with results at Micropore facility. Copyright 008 Deep Life Ltd All patents, patent applications, design and topographical rights reserved. No circuit may be reproduced without a licence for the topographical rights contained therein from Deep Life Ltd. This document does not constitute a licence to use and patent, patent application or topographical right of Deep Life Ltd. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

2 Table of Contents PURPOSE AND SCOPE... TEST STRUCTURE AND PARAMETERS... CALIBRATION AND EQUIPMENT TEST RESULTS Standard conditions: Vertical, Gas temperature C, water 4C Colder water: Vertical, C exhale, but ambient water just C, test scrubbers First scrubber sample Second scrubber sample Third scrubber sample Colder water: Vertical, C exhale, but ambient water just C, short interrupt of CO injection Effect of using a scrubber for two dives in very cold conditions Reducing the exhaled gas temperature from C to C Horizontal Position: C exhale, C water, test three scrubbers First scrubber cartridge sample Second scrubber sample Third scrubber sample... 7 MAXIMUM INHALED CO LIMITS CORRELATION WITH THIRD PARTY TEST RESULTS CONCLUSION...9 DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

3 PURPOSE AND SCOPE This document describes the test method and results of scrubber endurance trials carried out by Deep Life Limited to assess the effect of small variations in temperature on the scrubber endurance. The variations considered are:. Reference test under standard conditions defined in EN44 and NORSOK U-0. Effect of reducing the ambient water temperature from 4C to C. Effect of reducing the exhaled gas temperature from C to C 4. Effect of performing two dives with an interval of 8 hours without changing the scrubber rotation, and assuming the dives have a low exhaled gas temperature.. Effect of adopting a horizontal position instead of a vertical position in very cold ambient water (C) All tests were done at 40msw, using the.6 lpm flow rate specified as one of the tests in NORSOK U-0 and the only test condition in EN44:00. Tests were stopped at a PPCO corrected to surface pressure of at least kpa: the NORSOK U-0 maximum permitted CO level, to ensure the curve is gradual and continuous. DL generally rate scrubbers to the kpa limit permitted in NORSOK U-0, as this limit is free of symptoms for normal diving over the short duration this spike occurs. The scrubbers are tested inside the single scrubber Open Revolution rebreather (Sample ). TEST STRUCTURE AND PARAMETERS The tests use the following equipment:. Single scrubber Open Revolution rebreather, fitted with scrubber health monitor ( temperatures measured axially along the scrubber) and RH sensor immediately prior to scrubber.. Deep Life Breathing Machine A, fitted with humidifier. Matlab data capture system mm diameter chamber working pressure to 000msw, with refrigeration. 60mm diameter chamber rated to 00msw for calibration purposes. 6. Chamber refrigeration cooling system, computer controlled. 7. Supply of compressed gases including air, pure carbon dioxide and nitrogen. 8. Pressure, CO, temperature and humidity sensors 9. Mass flow control valve 0. Fresh Micropore EAC scrubbers are required for each test run. The scrubbers were the mm Micropore EACs, with large internal bore, of a batch marked Use by February Scales to weigh the CO cylinder before and after each test to confirm that the correct amount of CO is injected. The smallest cylinder that can provide sufficient CO for the test is a 0 litre cylinder for a single cartridge: the test requires 9. litre calculated as (.6lpm_of_MR x (0min_of_test+0_min_of_reserve)) / (4bar_of_start_pressure 0bar_of_end_pressure). The weight of a 0 litre cylinder is kg. The weight of the gas used for the 0 min test is 47 g (as.6l/m x 0 DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

4 min x.97 g/l). This check is only a gross check: it is not a calibration check because it would require a balance with 0 kg range and g or 0.0% accuracy to measure the amount of CO weigh with % accuracy. Note: the pressure of the remaining CO is monitored, with correction for temperature. The maximum pressure of CO against temperature is shown in Figure -. This plot is derived from the CO pressure temperature phase diagram shown in Figure - 6 Pressure - Temperature phase diagram for CO 60 Pressure, atm formula table data Figure -. Gas liquid phase diagram of CO (detail). Figure -. Gas liquid phase diagram of CO. DV_OR_ScrubberEndurance_084.doc Rev C Page 4 of 4

5 The CE EN44:00 and the comparable NORSOK U-0 test, specify the following test conditions:. Depth/ambient pressure is 40 msw / bar. Water temperature is 4+/-C or less. Diluent gas is Nitrogen 4. Carbon dioxide injection rate is.6 lpm. Breathing simulator rate is 40 lpm 6. Breathing frequency is 0 min- As for EN44:00, NORSOK U-0 the scrubber endurance is stated for the PPCO being less than mbar shown in Figure - and less than the warning levels of 8 mbar and 0 mbar shown in Figure -4. PPCO, mbar Endurance Time Figure -. Scrubber endurance as defined in EN44:00. The 0. kpa is a very low level. DL generally uses the NORSOK limits which are compared below. PPCO mbar kpa 0 Warning level: < 0 mbar (< kpa) Warning level: +/- mbar (0.+/- 0. kpa) EN44:00 NORSOK U-0 Standard Figure -4. PPCO warning levels for EN44 and NORSOK U-0. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

6 Exhale flow is separated from the breathing cycle by sampling the gas line at the diver s lips (using a dummy mouthpiece bite), and switching it using a solenoid which is open during exhale cycles. The exhale cycle is synchronized with the breathing machine without any delay. Before testing the mass flow control valve used for CO injection has been set for.6 lpm flow rate under the valve input pressure of 0 bar, which has been calibrated: a DV report is available. A flow metre provides a further measure to monitor flow levels. The test fixture used for scrubber endurance tests is shown in Figure -. All operations of the test fixture other than connecting gases, are computer controlled and logged. DV_OR_ScrubberEndurance_084.doc Rev C Page 6 of 4

7 CO cylinder N cylinder Single UNIT < 0.6 l/min.6 l/min Breathing control < 0.6 l/min CO sensor Scrubber canister Figure -. Deep Life s scrubber endurance test fixture. DV_OR_ScrubberEndurance_084.doc Rev C Page 7 of 4

8 CALIBRATION AND EQUIPMENT The calibration of the response of the CO sensor was a complex process, as it involved confirming that it can provide a 0ms response. Due to the extensive nature of those calibrations, a detailed calibration report and equipment description has been produced for these tests, in DV_CO_Cal_080.pdf This report is summarised below. This calibration process forms the bulk of the separate calibration report. It is noted that the mixing that occurs in the sampling line will reduce the effective response time. The calibration of the instruments used in the tests are managed within the normal QA controls, except for the flow and CO sensors, which are critical to the scrubber endurance tests, so is quad checked using the process describe below and then further audited using a fifth method, as well as having tests carried out at an independent laboratory. The volume of CO injected from the cylinder is verified by the use of four methods (that is, by using all four methods each time to ensure there is no significant error):. By the change in the weight of the CO cylinder,. By the cylinder pressure. As a reference the temperature of CO inside the cylinder is calculated using the measured pressure and the pressure-temperature phase diagram shown in Figure -.. By oxygen trace gases. The CO is mixed with air, such that a bleed measurement gas can be taken from the device under test without reducing the pressure in the chamber. The bleed causes a reduction in PPO which should be compensated almost exactly by the injected O, if the injection rate is correct. To check this, the PPO of the loop is monitored. The flow from the bleed line is monitored: this should be between 0.08 and 0. lpm. 4. By the period during which there is a CO flow at a constant rate: this is the primary method used to set the amount of CO dosed into the scrubber. The accuracy this method depends on the accuracy of the CO flow through the mass flow controller. The controller is calibrated using a.6 lpm test flow at STPD (7ºK, i.e. 0ºC, and atm). At room temperature a temperature correction must be used as shown in Figure -. Figure -. CO flow calibration. DV_OR_ScrubberEndurance_084.doc Rev C Page 8 of 4

9 The flow sensor output is checked by filling a known volume with gas, by displacement of water. The flow rate is proportional to the change in volume over a fixed time interval. The calibration of the flow sensor found it had a different reading if vertical compared to horizontal. It was calibrated in the position used for the appropriate test. Calibration data is held on SVN. A post-test audit was carried out by requesting the reading from the CO sensor immediately prior to the scrubber, and confirming that the sum of the inhaled PPCO and the injected PPCO is shown on that sensor. All sensor data was stored for the entire sequence of these tests. 4 TEST RESULTS 4. Standard conditions: Vertical, Gas temperature C, water 4C The power of the breathing gas heating was set to 08W as 4V^/ohm..(V^/ohm)*97%, to achieve an exhaled gas temperature of C. During the temperature stabilisation period of 0 minutes, the power was 06W. The test includes the following steps.. Run Re-Br. Close chamber. Fill chamber via the breathing loop by air up to bar absolute pressure (40 msw) 4. Apply CO of.6 lpm via the mass control valve to BM. Open CO measuring channel to set the flow rate of ~0.6 lpm. Flow is checked using the flow sensor 6. Apply the external air flow into the breathing loop to compensate the gas flows from the breathing loop into the CO measuring channel. 7. Testing until measured CO surface corrected, exceeds 4% 8. Stop Re-Br 9. Stop CO injection. 0. Decrease chamber pressure down to atmospheric pressure.. Stop test data recording.. Open chamber DV_OR_ScrubberEndurance_084.doc Rev C Page 9 of 4

10 Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-. Ambient pressure against time. CO against Time 4 CO, % Figure 4-.. CO in the breathing loop against time. SCRB time life (mbar PPCO) = 77 min; SCRB time life (mbar PPCO) = 08 min or hour 48 min; SCRB time life (0mbar PPCO) = 6 min or hour 4 min; DV_OR_ScrubberEndurance_084.doc Rev C Page 0 of 4

11 Heater, BM and water temperature against Time 0 Heater BM Water Figure 4-. Temperature water, heater, and inside BM. Temperature against Time BL temp SCRB temp Figure 4-4. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

12 7 Humidity against Time 00 Humidity inside the membrane bell against Time Humidity, % 0 Humidity, % Humidity in the breathing machine Humidity immediately prior to the scrubber. Figure 4-. Humidity in the breathing machine and the rebreather against time. The average humidity in the breathing machine is %. 0. Gas flow in measuring channel against Time Flow, lpm Figure 4-6. Gas flow from the breathing loop exhale into the CO measuring channel against time. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

13 4. Colder water: Vertical, C exhale, but ambient water just C, test scrubbers The exhale gas temperature was set to C (power to the breathing gas heating was set to 0W as V^/ohm*99). The water was cooled to C - there was some lag at the start of the test. Three scrubber samples were tested. The test includes the following steps.. Run Re-Br. Close chamber. Fill chamber via the breathing loop by air up to bar absolute pressure (approx 40 msw) 4. Apply CO of.6 lpm via the mass control valve to BM. Open CO measuring channel to set the flow rate of ~0.6 lpm. Flow is checked using the flow sensor. 6. Apply the external air flow into the breathing loop to compensate the gas flows from the breathing loop into the CO measuring channel. 7. Testing until measured CO surface corrected, exceeds 4% 8. Stop Re-Br 9. Stop CO injection. 0. Decrease chamber pressure down to atmospheric pressure.. Stop test data recording.. Open chamber 4.. First scrubber sample Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-7. Ambient pressure against time. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

14 4. CO against Time 4.. CO, % Figure CO in the breathing loop against time. SCRB time life (mbar PPCO) = 8 min; SCRB time life (mbar PPCO) = 8 min or hour min; SCRB time life (0mbar PPCO) = 44 min or hour 4 min; DV_OR_ScrubberEndurance_084.doc Rev C Page 4 of 4

15 Heater, BM and water temperature against Time 0 0 Heater BM Water Figure 4-9. Temperature water, heater, and inside B Temperature against Time BL temp SCRB temp Figure 4-0. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

16 8 Humidity against Time 00 Humidity inside the membrane bell against Time Humidity, % 70 6 Humidity, % Humidity in the breathing machine Humidity inside the rebreather immediately before the scrubber. Figure 4-. Humidity in the breathing machine and the rebreather against time. The average humidity in the breathing machine during the scrubber endurance is 7%. 0.8 Gas flow in measuring channel against Time Flow, lpm Figure 4-. Gas flow from the breathing loop exhale into the CO measuring channel against time. 4.. Second scrubber sample Note: The test is terminated on this run when the CO reaches gets. mbar. DV_OR_ScrubberEndurance_084.doc Rev C Page 6 of 4

17 Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-. Ambient pressure against time. 0.7 CO against Time CO, % Figure CO in the breathing loop against time. CO injection starts at. min SCRB time life (mbar PPCO) = 6 min or hour min; SCRB time life (mbar PPCO) = 04 min or hour 44 min; DV_OR_ScrubberEndurance_084.doc Rev C Page 7 of 4

18 Heater, BM and water temperature against Time Heater BM Water Figure 4-. Temperature water, heater, and inside BM. Temperature against Time BL temp SCRB temp Figure 4-6. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page 8 of 4

19 Humidity against Time Humidity inside the membrane bell against Time Humidity, % 6 60 Humidity, % Humidity in the breathing machine (~7%) Humidity inside the membrane bell (~9%). Figure 4-7. Humidity in the breathing machine (~7%) and the rebreather against time. 0. Gas flow in measuring channel against Time Flow, lpm Figure 4-8. Gas flow from the breathing loop exhale into the CO measuring channel against time. DV_OR_ScrubberEndurance_084.doc Rev C Page 9 of 4

20 4.. Third scrubber sample Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-9. Ambient pressure against time. CO against Time. CO, % Figure CO in the breathing loop against time. CO injection starts at 4 min SCRB time life (mbar PPCO) = 6 min or hour min; SCRB time life (mbar PPCO) = 96 min or hour 6 min; SCRB time life (0mbar PPCO) = 88 min or hour 8 min; DV_OR_ScrubberEndurance_084.doc Rev C Page 0 of 4

21 Heater, BM and water temperature against Time Heater BM Water Figure 4-. Temperature water, heater, and inside BM. Temperature against Time BL temp SCRB temp DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

22 4. Colder water: Vertical, C exhale, but ambient water just C, short interrupt of CO injection The CO injection is interrupted at 67 min for 4 min to calibrate the CO response in measurement channel. Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-. Ambient pressure against time.. CO against Time. CO, % Figure 4-.. CO in the breathing loop against time. CO injection starts at 8 min SCRB time life (mbar PPCO) = 47 min; SCRB time life (mbar PPCO) = 77 min or hour 7 min; SCRB time life (0mbar PPCO) = 9 min or hour 8 min; DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

23 Heater, BM and water temperature against Time 0 0 Heater BM Water Figure 4-4. Temperature water, heater, and inside BM Temperature against Time 0 0 BL temp SCRB temp Figure 4-. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

24 80 Humidity against Time Humidity inside the membrane bell against Time Humidity, % 6 Humidity, % Humidity in the breathing machine (~7%) Humidity inside the membrane bell (~8%). Figure 4-6. Humidity in the breathing machine (~7%) and the rebreather against time. 4.4 Effect of using a scrubber for two dives in very cold conditions This test considered the effects of two ice dives, in very cold conditions. From other testing, DL know that interrupting the test seems to extend the scrubber life. This is particularly the case if the scrubber is rotated about its axis by 80 degrees. This test in cold conditions did not rotate the scrubber, but simply ran two dives with an 8 hour interval between them. To recreate the worst possible diving conditions, the exhale gas temperature was reduced from the usual C to 7C for the first dive, and C for the second dive. During the first stage air is used as a diluent gas, the heater of the exhale gas is off. During the second stage the pure nitrogen fills the breathing loop to compensate the ambient pressure, the heater of the exhale gas is on. The power of the breathing gas heating is 6W as 4V^/ohm/ to achieve C. The first stage of the test includes the following steps.. Run Re-Br. Close chamber. Fill chamber via the breathing loop by air up to bar absolute pressure (40 msw) 4. Apply CO of.6 lpm via the mass control valve to BM. Open CO measuring channel to set the flow rate of ~0.6 lpm. Flow is checked using the flow sensor 6. Apply the external air flow into the breathing loop to compensate the gas flows from the breathing loop into the CO measuring channel. 7. Testing in one hour 8. Stop Re-Br 9. Stop CO flow input into the rebreather 0. Decrease chamber pressure down to atmospheric pressure.. Stop test data recording. DV_OR_ScrubberEndurance_084.doc Rev C Page 4 of 4

25 . Open chamber The second stage steps are. Run Re-Br 4. Close chamber. Fill chamber via the breathing loop by N up to bar absolute pressure (40 msw) 6. Apply CO of.6 lpm via Porter flow controller to BM 7. Open CO measuring channel with flow rate of ~0.6 lpm. Flow is checked using the flow sensor 8. Apply external N flow into the breathing loop to compensate flow into the CO measuring channel. 9. Testing until CO in the measuring channel exceeds 4%, surface corrected 0. Stop CO injected into the breathing loop. Drop the chamber pressure down to the atmospheric pressure. Stop Re-Br. Stop test data recording. 4. Open chamber 6 Ambient pressure against Time. Ambient and loop pressure against Time Pressure, bar 4. Pressure, bar..... Amb pressure Loop pressure First stage Second stage Figure 4-7. Ambient pressure against time. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

26 CO against Time 4 CO, % Figure 4-8..Second stage of the test. CO in the breathing loop against time. Reminding the scrubber endurance during the first stage of the test SCRB time life (mbar PPCO) = 9 min; SCRB time life (mbar PPCO) = 9 min or hour min; SCRB time life (0mbar PPCO) = 0. min or hour 0. min;. PPO against Time 0. PPO against Time PPO, ATA PPO, ATA Diluent gas is air Diluent gas is pure nitrogen Figure 4-9. PPO in the breathing loop DV_OR_ScrubberEndurance_084.doc Rev C Page 6 of 4

27 9 8 Heater, BM and water temperature against Time Heater BM Water 4 0 Heater, BM and water temperature against Time Heater BM Water Figure 4-0. Temperature water, heater, and inside BM. Temperature against Time Temperature against Time 4 0 BL temp SCRB temp BL temp SCRB temp Figure 4-. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page 7 of 4

28 00 Humidity inside the membrane bell against Time Humidity, % Figure 4-. Humidity in the rebreather. The humidity is below 80% for the beginning of the dive because the gas temperature is below the dew point. 4. Reducing the exhaled gas temperature from C to C The power of the breathing gas heating was set to W (4V^/ohm), to achieve a desired breathing gas temperature of C. This is to assess the effect of additional gas cooling from the diver, due to longer hoses, narrower hoses or stainless steel hoses. The test includes the following steps.. Run Re-Br. Close chamber. Fill chamber via the breathing loop by air up to bar absolute pressure (40 msw) 4. Apply CO of.6 lpm via the mass control valve to BM. Open CO measuring channel to set the flow rate of ~0.6 lpm. Flow is checked using the flow sensor 6. Apply the external air flow into the breathing loop to compensate the gas flows from the breathing loop into the CO measuring channel. 7. Testing until CO in the breathing loop exceeds 4%, surface corrected 8. Stop Re-Br 9. Stop injection of CO. 0. Decrease chamber pressure down to atmospheric pressure.. Stop test data recording.. Open chamber DV_OR_ScrubberEndurance_084.doc Rev C Page 8 of 4

29 Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure 4-. Ambient pressure against time. CO against Time 4 CO, % Figure CO in the breathing loop against time. SCRB time life (mbar PPCO) = 4 min; SCRB time life (mbar PPCO) = 69. min or hour 9. min; SCRB time life (0mbar PPCO) = 08.7 min or hour 48.7 min; DV_OR_ScrubberEndurance_084.doc Rev C Page 9 of 4

30 0 Heater, BM and water temperature against Time Heater BM Water Figure 4-. Temperature water, heater, and inside BM. Temperature against Time 0 BL temp SCRB temp Figure 4-6. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page 0 of 4

31 Humidity inside the membrane bell against Time Humidity, % Figure 4-7. Humidity in rebreather against time, measured immediately prior to the scrubber. 4.6 Horizontal Position: C exhale, C water, test three scrubbers The horizontal position was tested using three scrubbers, under as similar conditions as could be achieved in a reasonable time, to assess the effect of a horizontal attitude in the worst case diving conditions. The test depth and CO flow rate was otherwise set to be the same as for the test of the rebreather in the vertical position in C ambient water, with C exhale temperature. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

32 4.6. First scrubber cartridge sample Ambient and loop pressure against Time 4. 4 Pressure, bar.. Amb pressure Loop pressure Figure 4-8. Ambient pressure against time. CO against Time. CO, % Figure CO in the breathing loop against time. CO injection starts at 6 min. SCRB time life (mbar PPCO) = 4 min; SCRB time life (mbar PPCO) = 90 min or hour 0 min; SCRB time life (0mbar PPCO) = 69 min or hour 49 min; DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

33 Heater, BM and water temperature against Time 0 0 Heater BM Water Figure Temperature water, heater, and inside BM. Temperature against Time BL temp SCRB temp Figure 4-4. Temperature in rebreather and scrubber stick. DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

34 9 Humidity against Time Humidity inside the membrane bell against Time Humidity, % Humidity, % Humidity in the breathing machine (~80%) Humidity inside the membrane bell (~96%). Figure 4-4. Humidity in the breathing machine and the rebreather against time Gas flow in measuring channel against Time Flow, lpm Figure 4-4. Gas flow from the breathing loop exhale into the CO measuring channel against time: this is the measurement monitoring channel, not the CO injection channel. This is typical of that in the other tests and is provided here by way of illustration. DV_OR_ScrubberEndurance_084.doc Rev C Page 4 of 4

35 4.6. Second scrubber sample Ambient and loop pressure against Time 4. 4 Pressure, bar.. Amb pressure Loop pressure Figure Ambient pressure against time. CO against Time. CO, % Figure CO in the breathing loop against time. CO injection starts at min. SCRB time life (mbar PPCO) = 7 min or hour and min; SCRB time life (mbar PPCO) = min or hour min; SCRB time life (0mbar PPCO) = 96 min or hour 6 min; DV_OR_ScrubberEndurance_084.doc Rev C Page of 4

36 Temperature against Time BL temp SCRB temp Figure Temperature in rebreather and scrubber stick. 90 Humidity against Time 00 Humidity inside the membrane bell against Time Humidity, % 7 70 Humidity, % Humidity in the breathing machine (~77%) Humidity inside the membrane bell (~9%). Figure Humidity in the breathing machine and the rebreather against time.. DV_OR_ScrubberEndurance_084.doc Rev C Page 6 of 4

37 4.6. Third scrubber sample Ambient and loop pressure against Time 4. 4 Pressure, bar... Amb pressure Loop pressure Figure Ambient pressure against time. CO against Time. CO, % Figure CO in the breathing loop against time. SCRB time life (mbar PPCO) = 68 min or hour 8 min; SCRB time life (mbar PPCO) = 96 min or hour 6 min; SCRB time life (0mbar PPCO) = 8 min or hours min; DV_OR_ScrubberEndurance_084.doc Rev C Page 7 of 4

38 Humidity against Time 00 9 Humidity inside the membrane bell against Time Humidity, % 6 60 Humidity, % Humidity in the breathing machine (~6%) Humidity inside the membrane bell (~9%). Figure 4-0. Humidity in the breathing machine and the rebreather against time.. MAXIMUM INHALED CO LIMITS There is a problem that some standards define CO breakthrough at such a low level that there are no symptoms, so divers do not treat the figure seriously and go onto exceed scrubber durations without having any good data points on what the limit actually is. For example, EN44:00 defines a maximum inhaled CO limit of 0.kPa: the U.S. Occupational Safety and Health Administration advise that average exposure for healthy adults during an eight-hour work day should not exceed 0.kPa. As a scrubber breakthrough figure this is just not meaningful. For exposure up to 0 minutes, the U.S. National Institute for Occupational Safety and Health (NIOSH) and American Conference of Government Industrial Hygienists (ACGIH) limit is kpa. NORSOK U0:999 takes a more pragmatic and sensible approach, giving a limit of kpa generally, and for short periods kpa. A scrubber breakthrough event is a short period, so the limit on scrubber endurance of a kpa breakthrough should be one that divers can accept. The kpa limit is used by Deep Life Ltd. For certification purposes, the 0. kpa and.0 kpa 6 CORRELATION WITH THIRD PARTY TEST RESULTS Tests were carried out by Micropore at their Newark facility using a dumb head (i.e. single scrubber Open Safety Apocalypse version of the rebreather) and these correlate to within 4 minutes of the times measured by Deep Life at the 0. kpa calibration point used by Micropore, with 4C +/-.C water and the rebreather in the vertical position, at 0 fsw. Water Scrubber endurance, minutes Mean and SD of group at 0. kpa Inhale at DSV Exhale at DSV 0. kpa.0 kpa. kpa kpa DV_OR_ScrubberEndurance_084.doc Rev C Page 8 of 4

39 7 CONCLUSION The table below tablulates the test results. Using the NORSOK U-0 kpa limit, the scrubber life in 4C of hours 4 mins seems to be a reliable figure that is lost only if the exhale temperature reduces excessively. There is no loss in performance from an interrupt of 8 hours between two dives: in fact, it is in line with other test results showing the scrubber performance improves slightly. Table. Scrubber endurance test results Humidity, % CSCRB endurance, min Notes Water Breathing machine Exhale Breathing loop Scrubber Breathing machine 0. kpa 0. kpa kpa Standard vertical test conditions. hours 4 min endurance in NORSOK Standard vertical test conditions other than water is C. 7 7/ nd vertical C test 6. 7/ rd vertical C test 7 7/ Vertical C test interrupted at 67 min for 4 min Vertical very cold expired gas, but 8- hours-break between DV_OR_ScrubberEndurance_084.doc Rev C Page 9 of 4

40 two test stages Vertical reduced exhale temperature. 80/ Horizontal std to cold test (first test). 6 77/ nd std horizontal test / rd std horizontal test The NORSOK U-0 kpa limit that is a practical limit for divers, is hours 4 minutes. This is extended by around 0 minutes when the diver is horizontal. There is a small spread of results, so for conservatism, the manufacture will state the duration of the scrubber is hours minutes at 40msw, with a 40lpm RMV, using air as the diluent. The reduction of the water temperature to C does not cause a statistically significant change in the duration. A reduction in the exhale temperature does reduce the scrubber duration substantially. This underlines the importance of the biased counterlungs, and large bore diameters in the Open Revolution rebreathers to prevent gas cooling from the diver to the scrubber. From other tests, there is no difference in scrubber duration between the instrumented eccr head used for the Apollo Incursion and the dumb head used for the Open Safety Apocalypse rebreather product. The dual scrubber rebreather in the Open Revolution series used for the Bell Diver and Cave Diver products is the subject of a separate report. DV_OR_ScrubberEndurance_084.doc Rev C Page 40 of 4

41 DV_OR_ScrubberEndurance_084.doc Rev C Page 4 of 4