..K 11 AND MK 12 C02 SCRUBBER DEVELOPMENT. (U),UG 8O R W DOWBUL

UNCLASSIFIED NCSC-TR3 53-6ON

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MICROCOPY RESOLUTION TEST CIART

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.. MK If AND MK 12 C6 SCRUBBER DEVELOPMENT / TechnicaIlprt _

S. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(e) S. CONTRACT ON GRANT NUMNEIR()

, 1 R. W. Dowgul

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IS. SUPPLEMENTARY NOTES

I9. KEY WORDS (Cont Ine an severeg side finecesomy and dmatltp blok ridmbet)

Canisters Absorbers (Materials)Gas ScrubbersGas MixturesSwimmer Diver

20. ABSTRACT (Continue an feersi e It i meeae07 end IdS liy by bloe nber)

- Empirical testing is a major development tool in the design of COscrubbers used in diving systems. Suitable analytical models for predictingCO. scrubber behavior are currently under consideration. This report documents2

the development of CO2 scrubbers for the MK 11 and MK 12 diving systems. Plotsof various temperatures, pressures, flows, and system efficiencies are pre-sented. For specific details Hydrospace notes and/or NEDU manned test reportsare reference4 where applicable.

DD I FORS 173 EDITION OF I NOV 65 IS OBSIETE lS - -CUA4TY CLASSIFICATION OF THIS PAO1O2 .LbM P4"446

ABSTRACT

Empirical testing is a major development tool in the design of CO2 scrubbersused in diving systems. Suitable analytical models for predicting CO2 scrubberbehavior are currently under consideration. This report documents the develop-ment of CO2 scrubbers for the H4K 11 and MK 12 diving systems. Plots of varioustemperatures, pressures, flows, and system efficiencies are presented. Forspecific details Hydrospace laboratory notes and/or NEDU manned test reportsare referenced where applicable.

IITI

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GLOSSARY

ACFM Actual cubic feet per minute. A measure of the volume ofgas at operating temperature and pressure.

ALPM Actual litres per minute. A measure of gas equal to 0.001cubic metre per minute.

ATM Atmosphere. A unit of pressure equal to 1.013250 x 106

dynes/cm2, which is the air pressure at mean sea level(also known as standard atmosphere).

Baralyme Granules that are used as a CO2 absorbent.

BPM Breaths per minute.

Cap Regulator Constant absolute pressure regulator.

Cardiod Exhaust Attitude sensitive exhaust valve.Valve

CDP Constant Differential Pressure.

FSW Feet of seawater.

Heliox A mixture of helium and a small percent of oxygen usedfor breathing during deep dives.

High Performance A mixture of sodium hydroxide with calcium oxide; granulesSodasorb are used to absorb water vapor and carbon dioxide gas.

LPM Litres per minute.

PO2 Partial pressure of oxygen.

PSID Pounds per square inch differential. The difference inpressure between two points in a fluid flow system,measured in pounds per square inch (PSI).

PSIG Pounds per square inch gauge. The gauge pressure,measured by the number of pounds/force exerted on anarea of one square inch.

RMV Respiratory minute volume.

SLE Sea level equivalent. The equivalent level of the sur-face of the ocean; especially, the mean level halfwaybetween high and low tide, used as a standard in deter-mining sea depths.

STP Standard temperature and pressure.

UBA Underwater breathing apparatus.

WATTS The unit of power in the metre-kilogram-second systemof units, equal to 1 joule per second.

(Reverse Page ii Blank)

"S r

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TABLE OF CONTENTS

Page No.

INTRODUCTION ........... ... ............................ 1

General .......... ............................... I

Background ........... .. .......................... 1

MK 11 CO SCRUBBER DEVELOPMENT ......... ................... 2

MK 11 System Description ......... ................... 2

Background . . .. ....... ... ....................... 4

Initial Testing Summary .......... .................... 4

System Flow Analysis of MK 11 ........ ................. 7

Canister Modifications ....... .................... ... 21

MK 12 CO SCRUBBER DEVELOPMENT ...... ................... .... 32

MK 12 Mixed-Gas Recirculator System Description .......... ... 32

Developmental Testing ....... ..................... .... 36

REFERENCES ........... ............................. .... 61

APPENDIX A -MK 11 SYSTEM FLOW ANALYSIS ..... .............. ... A-i

APPENDIX B - MK 12 CO2 SCRUBBER DEVELOPMENT ANALYSIS ........... ... B-i

APPENDIX C - MK 12 SSDS MANNED HOT WATER HEATER RECIRCULATORDURATION TEST RESULTS ..... ................. .... C-I

L i

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LIST OF ILLUSTRATIONS

Figure No. Page No.

1 NK 11 Breathing Subsystem 3

2 Gas Flow Diagram in Each Operating Mode 5

3 Canister Efficiency Versus Depth (Manned/Unmanned) 6

4 Scrubber Instrumentation Piagram 8

5 Typical Unmanned 4K 11 Canisted Bed Temperatures 9

6 Typical Unmanned MK 11 Canister CO2 Signatures 10

7 Typical Manned M4K 11 Canister Bed Temperatures 11

8a MK 11 Manned CO2 Signature 12

8b Mean Canister Breakthrough Curves at 310, 350, and450 FSW, with 18 Percent High Performance Sodasorbat 350F Wet Pot Temperature 13

9a M4K 11 Reverse Flow Test (1 ATA) 14

9b MK 11 Reverse Flow Test (305 FSW) 15

10a HK 11 System Flow Tests at 50 FSW 17

l0b MK 11 System Flow Tests at 300 FSW 18

11 Exhalation Bag Pressure at 50 FSW and 300 FSW 20

12 Breathing Resistance Comparisons 25

13 Modified MK 11 Canister Heat Exchanger Instrumentation 29

14a Typical Unmanned Canister Duration Temperatures 30

lhb Typical Unmanned modified Canister DurationCO2 Level Profiles 31

15 MK 12 Mixed-Gas Configuration 33

16 Recirculator Assembly/Helmet Flow (Semi-Closed Mode) 34

17 Recirculator Assembly with Helmet Interface(Rear View) 35

IV

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LIST OF ILLUSTRATIONS (CONT'D)

Figure No. Page No.

18 MK 12 System Differential Pressure (Koegle Valves) 37

19 Ejector Configuration Identification 38

20 Performance Characteristics of MK 12 Final Design 41

21 Canister Condition at CO2 Breakthrough 45

22 MK 12 Manned Canister CO Signature, 32 FSW WaterTemperature 40°F (80/20 AeO2) 49

2

23 MK 12 Canister CO Signature, 400-450 PSW WaterTemperature 40°F f95/5 HeO2) 50

24 Kinergetics Gas Heater Installed (Inlet and Exhaust) 54

25 Canister Top Hot Water Port Configurations 55

26 MK 12 Carbon Dioxide Absorbent Canister 58

27 Final MK 12 Manned Canister CO2 Signatures, 390 FSW

and 40°0 Water Temperature (84/16 HeO2) 59

LIST OF TABLES

Table No. Page No.

1 Calculated Gas Flows for 50 FSW and 300 FSW 19

2 Initial Canister Configurations Tested Unmanned 22

3 Results of Alternative Changes to the Canister 26

4 Selected Ejector Test Data 39

5 MK 12 Diagnostic CO2 Scrubber Tests 43

6 Canister Bed Temperature Comparisons 46

7 Relative Humidity (RH) Percent of Gas in MK 12 CO2Scrubber 47

8 Summary Test Results 52

9 MK 12 Canister Efficiency 60

(Reverse Page vi Blank)

v

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INTRODUCTION

GENERAL

Carbon dioxide is a natural by-product of the respiration of animals andhumans (among other sources) formed by the oxidation of carbon in the body toproduce energy. It forms approximately 0.03 percent of the total atmosphere.For divers, the two major concerns with CO2 are control of the quantity inthe breathing supply, and removal of the "exhaust" after breathing.

In high concentrations the gas can be extremely toxic. Severe problemsmay arise for divers who use closed circuit and semi-closed circuit breathingsystems, if the system fails to dispose of the excess CO2.

The Navy has continuously worked on designing and improving techniques toeliminate carbon dioxide from the diver's gas supply.

The intent of the MK 11 and MK 12 C02 scrubber development is to maximizethe efficiency of the C02 absorbent canisters. The flow of gas in these sys-tems is through an absorbent canister where the carbon dioxide is removed. Aconstant flow of fresh C02-free gas ventilates the helmet or facemask for thediver to rebreathe. Since only the oxygen in the mix is consumed, assuminghis oxygen is replenished, the diver can remain at depth for an extendedperiod of time on relatively small amounts of inert gas. The inert gas isbreathed and rebreathed repeatedly by the diver instead of exhausting from thehelmet or facemask at the end of each exhaled breath.

The various systems, testing methods, and procedures of the C02 scrubberduring empirical development are described in this report.

BACKGROUND

Mixed gas diving is differentiated from other techniques in that thebreathing medium is a closely controlled mixture of oxygen and an inert gas suchas helium. Helium-oxygen mixtures (Heliox) are preferred over other gas mixturesdue to physiological and physical safety factors; however, helium is quite expen-sive, and methods to conserve helium usage are constantly being explored. C02scrubbers permit rebreathing of the inert gas by removing the carbon dioxidefrom the breathing mix and circulating the gas freshened with 02 back to thediver. This in turn reduces the expensive helium consumption and increases theapability to dive to deeper depths for a longer period of time,

Current development techniques for C02 scrubbers used in modern divingsystems do not include suitable analytical models, therefore empirical testingis a major development tool.

I"

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MK 11 CO2 Scrubber Development Results

The MK 11 C02 scrubber development terminated in a system that was man-tested at 450 feet (137.2 metres) of seawater (FSW) and 350F (1.70C) by theNavy Experimental Diving Unit (NEDU), Panama City, Florida. This resultedin a mean duration of 308(±42) minutes.

MK 12 C02 Scrubber Development Results

The MK 12 C02 scrubber development resulted in a system duration inexcess of 10 hours at 390 FSW (118.9 metres) and 400F (4.40 C). At a durationof 9 hours, the mean C02 level of the existing gas for three canisters was 0.2percent sea level equivalent (SLE). One canister test was continued to 0.5percent SLE which occurred at 10 hours.

MK 11 CO2 SCRUBBER DEVELOPMENT

MK 11 SYSTEM DESCRIPTION

The MK 11 semi-closed mixed gas underwater breathing apparatus (UBA)and associated equipment was intended to provide the complete life supportand thermal protection required for saturation divers to operate for up to4 hours in 280F (-2.2°C) water to depths of 850 FSW (259 metres). The HK 11diver is tethered to a diver support facility by an umbilical which suppliesbreathing gas, hot water, and electrical connections. Hot water is routedthrough a breathing subsystem (Figure 1) where it warms a canister con-taining a carbon dioxide absorbent bed, and then is routed to a diver ther-mal protection garment (the MK 16 hot water suit).

During normal semi-closed circuit, umbilical-supplied operation, thebreathing gas passes through an absolute pressure regulator block and sonicorifice into an inhalation bag, and then through a hose connection to anoral-nasal facemask. Exhaled gas passes from the oral-nasal mask via ahose to an exhalation bag. From the exhalation bag, most of the exhaledgas flows through the C02 scrubber to the inhalation bag where it ismixed with incoming gas from the umbilical, and subsequently, rebreathed.A portion of the exhaled gas does not pass through the canister but is exhaustedinto the water through an attitude-sensitive exhaust valve (cardioid valve).

Diver safety features include two-way communication equipment, a P02 sen-sor, and switchover indication equipment. If umbilical gas supply pressuredrops to a low level, the absolute pressure regulator admits breathing gasfrom a small emergency supply in the backpack activating the switchover indi-cator. If the breathing bags or canister should flood, the diver can switchto open circuit on umbilical; or for a short time, the diver may use the

2

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NCSC TR 353-80

emergency gas supply. Therefore, a normal operating mode (semi-closed cir-cuit, umbilical supply) and three backup modes (semi-closed circuit, emergencysupply; open circuit, umbilical supply; and open circuit, emergency supply)are available to the diver (see Figure 2).

BACKGROUND

As a result of NEDU manned dives conducted during the week of 3 July 1978,it was found that the MK 11 C02 scrubber packed with baralme was time-limitedto approximately 1.5 hours at 305 FSW (92.9 metres) and 35 F (1.7 C). Theseshort durations were revealed under NEDU work requirements utilizing repetitive10 minute cycles consisting of 4 minutes at rest and 6 minutes of work at 50watts as measured on an ergometer. Unmanned testing of various concepts andtechniques to improve the C02 scrubber duration were conducted as a result ofthese short duration NEDU manned tests.

NOTE

Canister upstream CO2 levels were recorded on subjects at depthin the MK 11 during rest and while registering 50 watts on anergometer during manned dives. These CO2 levels were then usedas control parameters during unmanned testing.

Rest 50 Watts

% C02 SLE 3.45 4.69

(Recorded) 22 RMV 40 RMV These were directUnmanned 0.7 LPM 1.8 LPM readings to giveUnmuaned 0.the percentage bySimulation C02 Injected C02 Injected volume. This is

not a true tempera-ture correctedflow at STP.

INITIAL TESTING SUMMARY

A total of 31 tests were conducted in the Hydrospace Laboratory(1).Results of these tests indicate that use of high performance sodasorb (specialfactory certified 18 ercent water by weight), tightly packed in the canisterwhile operating in 30 F (-1.1 C) water, resulted in an average run time of 3hours and 51 minutes to reach a C02 level of 0.5 percent SLE. The absorbentwas tightly packed by constantly tapping on the canister while slowly filling.

(1)Hydrospace Laboratory Note 11-78, Index No. 64, Underwater Breathing

Apparatus - MK 11 Scrubber Test, by G. H. Noble, August 1978.

4

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CANVSTE E.O_ FMASKFACILITY t. UMBILIC AL .,._ PRESSURE ZIN A TON

BREATHING GA [AHOSE ( REGULAtOR INH AL-TION

GAS BLOCK INTO ASUPPLY -,WATER C0 O A

C EXHALATION

1 REGULATOR VAV SAGAUSVALVE

A. SEMICLOSE0 -CIRCUIT, UMBILICAL-SUPPLIED OPERATION

uB, M K, 11 MOD 0 (BACKPA' CK) 02 __

MANIFOLD- ~ACE IFER FAASMAS

OCYLINDER AATERASSEMBLY J ]PRESSURE

REN REGULATOR REGULATOR AN HALATION

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OFPRICO ESR E CO HELETAE NLEXHALATIONREGUATOR REGULATOR VALVE DEAND MSqA N

REGULATO VIT

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[ S ITH (ELECTRICAL) - r__.A.S--B.Y

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B. SEMICLOSED- CIRCUIT, EMERGENCY MANIFOLD-SUPPLIED OPERATIONDIVERUBA MK fl MOD 0 (BACKPACK) (FACEMASK

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SUPPLY J VALVE

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ON-OF HANDLEI

C. OPEN -CIRCUIT, UM BILICA- SUPPLIED OPERATION

U 8A MK IH MOD 0 (BACKPACK) FACEMASK

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15

NSSEMo.. PRESSURE J.. OP* J HELMET[ STAGE ASiL- ..EX

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ON- SWT H SW[HO

OFF Wf REON-OFF HANDLE S iCOE

HANDLE (ELECTRICAL) INDICATOR

| -0 ASSEMBLY

. OPEN -CIRCUIT, EMERGENCY MANIFOLD- SUPPLIED OPERATION

•CONSTANT DIFFERENTIAL PRE33URE

FIGURE 2. GAS FLOW DIAGRAM IN EACH OPERATING MODE

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The test series began with little baseline data available other than thefact that the canister life was not adequate to meet test requirements duringmanned test dives. The test program was conducted in an attempt to provide aninterim solution to the immediate problem and to build a file of baseline data.Preliminary indications were that the reduced canister life at depth resultedfrom a combination of system design shortcomings.

General Observations

Unmanned test results were bracketed by manned test results. Adequate cor-relation was obtained between the two types of tests (Figure 3).

PVC pipe was used to tap the canister during the filling process at the 1/3,2/3, and full points. As an alternative, two hand-type electric massagers werestrapped on the canister to provide vibration during the filling process in anattempt to improve packing of the bed and to reduce the sharp impact fromtapping with a plastic pipe. The vibration resulted in a heavy accumulation ofdust in the center of the bed. The absorbent particle distribution was believedto be caused by pulverizing of the grains and shifting of the larger grains tothe perimeter. This method of packing was abandoned due to dust generated inthe breathing loop.

LEGEND60-

ORIGINAL MKII CANISTER MANDDATAHIGH PERFORMANCE SOOASOR9350F 1ATH TEMP.

50- UNMANNED DATA

A40Aw

30-

IOE20-

0 100 200 300 400 500 oo 700

DEPTH (FSW)

FIGURE 3. CANISTER EFFICIENCY VERSUS DEPTH (MANNED/UNMANNED)

6

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The scrubber instrumentation diagram is shown in Figure 4. Figure 5 de-picts typical unmanned canister bed temperatures of the MK 11 in the originalconfiguration for baralyme and high performance sodasorb 92.9 MSW (305 FSW,35°F (1.7°C) bath temperature). Figure 6 shows typical unmanned canister CO2signatures for baralyme and high performance sodasorb. Figure 7 presents typi-cal manned canister bed temperatures of the MK 11 in the original configuration.Figure 8a presents the MK 11 manned C02 signature, and 8b shows the mean canisterbreakthrough curves at various depths using high performance sodasorb.

SYSTEM FLOW ANALYSIS OF MK 11

Background

Manned testing of the MK 11 at depth (2) and at 6 MSW (20 FSW)3 re-vealed a marked difference in canister life (canister life was reduced at depthby over 85 percent). In an attempt to find the cause of this difference, aseries of MK 11 system dynamic flow measurements were made at various depthsand breathing rates.

Objective

The objective of this test series was to compare system flow at depthsfrom 0 to 259 MSW (0 to 850 FSW)4 .

Approach

Figures 9a and 9b are dynamic plots of actual flow through the canisterduring unmanned testing. An EMV of 40 LPM (1.4 ACFM) was used in both testsas shown in Figures 9a (0 FSW) and 9b (305 FSW) (92.9 MSW).

The normal direction of system flow is from the exhalation bag throughthe canister and into the inhalation bag. Simultaneously, fresh gas is beinginjected through the sonic orifice and into the inhalation bag. During unmannedtesting of the MK 11, it was observed that at specific times in the breathingcycle system flow direction reverses. This flow reversal is presented inFigures 9a and 9b as negative flow.

The duration of the C02 scrubber is directly proportional to the amount(mass) of C02 it absorbs. During reverse flow in this system the canister isbeing presented with C02-free gas; i.e., the gas in the inhalation bag con-sists of fresh make-up gas and gas previously scrubbed of C02. Using sine wave

( )Navy Experimental Diving Unit Report No. .18-78, Life Support Characteris-

tics of the MK 11 Semi-Closed Mixed Gas UBA at Intermediate Depths, byC. A. Piantadosi and W. H. Spaur, November 1978.

(3)Navy Experimental Diving Unit Report No. 10-78, Evaluation of the MK 11,Mod-O UBA in Cold Water, by R. K. O'Bryan, R. L. Clinton, and R. A.Vendetto, May 1978.

"4)Hydrospace Laboratory Note 6-79, Index No. 71, MK 11 Flow Test, by G. W.Noble, April 1979.

7

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1. Co Sample Line 6. Mid-Outer BED (YSI 701)2

2. 0.5 PSID Transducer 7. Inlet-Outer BED (YSI 701)

3. Outlet-Center BED (YSI 701) 8. Inlet-Outer BED (YSI 701)

4. Outlet-Outer BED (YSI 701) 9. UBA MK 11 Canister

5. Mid-Center Outer BED (YSI 701) 10. Scrubber Gas in Temp. (YSI 731)

FIGURE 4. SCRUBBER INSTRUMENTATION DIAGRAM

8

I i 1

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115

Baralyme

105 - 305 FSW ........... Inlet Mean Bed Temp

350F Bath ---- Mid Mean Bed Temp

95 - Temperature -- Outlet Mean Bed Temp

44 -- % -^ Scrubber Gas in Temp

85 1q. '%

• •\ %%

&j*Ij751 %-4

65

55

45 -

35 I I I I I I I I I I a I I I I I I I I I

0 1 2 3 4 5115 Time in Hours

MK 11 Scrubber Test

105 High Performance ......... Inlet Mean Bed Temp

Sodasorb305 FSW Mid Mean Bed Temp

95 350 F Bath Temperature -- Outlet Mean Bed Temp

,. -- Scrubber Gas in Temp

v 85 \''VV

0' ".'.,, .

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0 65

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Time in HoursFIGURE 5. TYPTCAL UNMANNED MK 11 CANISTER BED TrPEMTURES

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L.0 -HK 11 Scrubber Test

Baralyme

305 7SW350F Bath Temperature

0.8 -

0.7

0.6U

0.5

0.4;>.j 0.3 _

0.2 _

0.1 _

0.00 2 3 4 5

Time in Hours

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0.9 High Performance Sodasorb

0.8 305 FSW350F Bath Temperature

0.7

0.6

- 0.5

0.4

0.4

0.3

C)o 0.2

0.1

0.00 1 2 3 4 5

Time in Hours

FIGURE 6. TYPICAL UNMANlW HK 11 CANISTK CO2 S ATURJS

lo2

10R

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Inlet Hot Water Temp110

Outer Inlet Temp

Center Inlet Temp90

Outer Middle Temp

S704J OSF Manned Dive 7/7/78

Barlym0350F Wet Pot Temperature

30 -L L

O 1 2 3 4 5 6 7Time (Hours)

110Center Middle Temp

Outer Outlet Temp

go 9Center Outlet Temp

OSF Manned Dive 7/7/78S70 Baralyme

35*F Wet Pot Temperature13) 390 FSW

50

50

O 1 2 3 4 5 6 7Time (Hours)

FIGURE 7. TYPICAL MANNED MK 11 CANISTER BED TEMPERATURES

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11.

Original MK 11 Canister

1.1 7/78 OSF Manned Dive

Baralyme35*F Wet Pot Temperature

1.0 390 FSW, 4 Divers

Plotted Means of MK 11 Canister Effluent

9 at The End of 50-Watt Work Periods

| ~ ~Canister Breakthrough _

.3

.2

0 10 20 30 40 50 60 70 80 90 100

Minutes

FIGURE 8a. mK 11 MANNED CO 2 SIGNATURE

12

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approximations for the curves recorded on Figures 9a and 9b permits a calculatedestimate of actual flow in either direction through the canister per eachbreath. Comparing the calculated volume system flow through the canisterand respective CO2 level at 305 FSW (92.9 metres) with those at 1 ATA indicatesthat 55 percent more CO is being presented to the scrubber at 305 FSW (92.9 MSW)than at 0 FSW (refer to Appendix A for calculations).

Results

As shown in the analysis of flow signatures (I ATA, 40 RMV, and 305 FSW(93.0 MSW)), the MK 11 system has significant changes in system flow patternsto produce significant changes in quantities of CO in the absorbent canister

2(Appendix A). Calculations indicate that approximitely 55 percent more CO2flows into the canister at depth than at 1 ATA. This change in system flowis attributed to the minimum acceptable facility regulator setting beingincompatible with present system sonic orifice selection. The minimum settingis a resultant of the constant absolute pressure (CAP) regulator minimum allow-able setting. The flow reversal phenomenon is characteristic of the NK 11 atall tested breathing rates and depths.

Summation of total scrubber flow calculations (in both directions) indi-cates 1.02 actual litre/breath of gas is being dumped out the exhaust valve at1 ATA and 0.14 actual litre/breath of gas is being exhausted at 305 FSW (93.0MSW).

General Observations

Comparing Figures lOa and 10b reveals approximately the same ambient systemflow at depth and surface; however, both the breathing signature and orifice flowreveal differences. The orifice flow is approximately 6.8 actual litres perminute (ALPM) at 50 FSW (15.2 1MSW) and approximately 2.7 ALPM at 300 FSW (91.4MSW) with the breathing signature showing a more positive pressure in the systemat 50 FSW (15.2 MSW) than at 300 FSW (91.4 NSW). Table 1 shows the calculatedflows (per the 14K 11 Manual) for 50 FSW and 300 FSW, respectively, which com-pare favorably with the measured orifice flows of Figures 10a and lob.

Figure 11 presents a dynamic plot of the pressure inside the exhalationbag at 50 FSW (15.2 MSW) and 300 FSW (91.4 NSW). The greater system positivepressure can be observed on the 50 FSW plot.

Conclusions

Based on the analysis of the system flow tests, it is apparent that thecanister life is extended at depths of less than approximately 200 FSW (60.4MSW) due to reductions in CO2 presented to the canister. The reduction ofCO2 in the canister affleunt gas stream is a function of increased reverseflow which is the result of an incompatibility between the sonice orifice sizein use and facility regulator setting available at shallow depths. This resultsin excessive flow of make-up gas at shallow depths.

16

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20 PRESSURE in Cm H 20

4) I15

oJ -14 0

-1

0.0 0.5 1.0 1.5 2.0 2.5 3.0Volume in Litres

70 _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _-H 7 SYSTEM FLOW in ALPM60

o 50

0 30

10 20

'~10

*~-10

- 20 I-~ 0 50 100 150 2002530

No. of Data Points25 0

8ORIFICE FLOW in ALPM

00

wU-4 H

~ 60 50 100 150 200 250 300

No. of Data PointsFIGURE 10a. MK 11 SYSTEM FLOW TESTS AT 5O FSW

17

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11 0 0

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J*o -10-0PRESSURE in Cm H 20

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0.0 0.5 1.0 1.5 2.0 2.5 3.0Volume in Litres

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S -20 FSYS TEM FLOW i n ALPM

-400 50 100 150 200 250 300

No. of Data Points

3

2.72

-4M%

IIORIFICE FLOWinAP

tu 0 0 50 100 150 200 250 300No. of Data Points

FIGURE 10b. MK 11 SYSTEM FLOW TESTS AT 300 PSW

18

-oi

NCSC TR-353-80

TABLE 1

CALCULATED GAS FLOWS FOR 50 FSW AND 300 FSW

Emergency Bottle Pressure at 1 Atmosphere = 3000.0 psigEmergency Bottle Temperature at 1 Atmosphere - 70.0FWater Temperature - 70.0*F

50 FSW

Oxygen Consumption Rate 1.60 (alpm)Bag Level 0.1590CAP Setting 265.00 (psia)FR Setting 365.00 (psia)Plug Gauge at Sat Depth (CAP) 213.33 (psia)Plug Gauge at Sat Depth (FR) 313.33 (psia)

Umbilical Emergency

Oxygen Percent 40.00 ( % ) 40.00 ( % )Maximum Depth (O/C) 99.00 (ft) 132.00 (ft)Minimum Depth (O/C) 0.00 (ft) 0.00 (ft)Minimum Requirement Flow 5.58 (alpm) 5.58 (alpm)Actual Gas Flow 6.36 (alpm) 16.00 (alpm) 11.62 (alpm)B/L Minimum Depth PO 0.8384 (atma) 0.7650 (atm)B/L Maximum Depth PO2 0.8384 (atma) 0.7650 (atm)Orifice Size 9.00

Switchover Setting 2677.78 (psig)

300 FSW

Oxygen Consumption Rate 1.60 (alpm)Bag Level 0.0396CAP Setting 340.00 (psia)FR Setting 440.00 (psia)Plug Gauge at Sat Depth (CAP) 176.96 (psia)Plug Gauge at Sat Depth (FR) 276.96 (psia)

- I Umbilical Emergency

Oxygen Percent 15.00 ( % ) 19.00 ( % )Maximum Depth (O/C) 319.00 (ft) 314.37 (ft)Minimum Depth (O/C) 55.00 (ft) 36.47 (ft)Minimum Requirement Flow 13.92 (alpm) 10.22 (alpm)Actual Gas Flow 2.63 (alpm) 26.54 (alpm) 19.20 (alpm)B/L Minimum Depth PO 0.9633 (atma) 1.1741 (atm)B/L Maximum Depth PO2 0.9633 (atma) 1.1741 (atm)Orifice Size 9.00

Switchover Setting 2566.67 (psig)

19r.

NCSC TR-353-80

o16S14

S12

S10

S6-

S4-

0

-2

0 50 100 150 200 250 300N o , f D a t a P o i n t s5 0 F W 4 0 R V

c~j20

r~15-

S10

rh 5-

r.0

0

" -5

-10

0 50 100 150 200 250 300No, of Data Points

300 FSW, 40 RMV

FIGURE 11, EXHALATION BAG PRESSURE AT 50 FSW AND 300 FSW

20

NCSC TR-353-80

CANISTER MODIFICATIONS

Initial Modifications

Objective. Initially, a series of modifications were intended to identifythe cause of the poor canister efficiency at depth and indicate an appropriatecorrective design were tested"b).

Approach. The initial unmanned canister configurations tested at 650 FStJ(198.1 MSW) are shown in Table 2. Attempts were made to adjust the wall sur-face area and gas velocity to maximize the time required to reach 0.5 percentSLE of carbon dioxide and minimize the work of breathing rate.

Results. Visual inspection of used canister beds led to the hypothesisthat the gas was following the heated walls of the canister and not being dis-tributed evenly across the absorbent bed. The results of Table 2, CanisterConfiguration II, Radial Flow Coaxial (Figure 2), indicate that during workcycles the higher respiratory rates and resultant higher gas velocities createdbetter utilization of the absorbent bed in this configuration. The use of finsand additional wall surface appeared to improve the canister performance; how-ever, the elongated bed increased the system work of breathing.

During the initial unmanned testing of the canister configurations, it wasnot known that a pressure drop greater than that of the original MK 11 canistercould not be tolerated. Manned testing revealed that the MK 11 was already atthe maximum tolerable work of breathing"6). Figure 12 compares the breathingresistance of the MK 11 with other systems.

Alternative Mod if icat ions

Objective. Using the standard MK 11 canister shell, the objective was toproduce a modified canister with greater efficiency and no additional breathingresistance. (At this point in the canister development, new non-return valves(Koegle) with less resistance than standard MK 11 non-return valves wereadapted to fit the MK 11 facemask.)

Approach. Various internal changes to the MK 11 canister were attempted.Several heat exchanger modifications were tested. It was found that the opti-mum configuration for this depth and temperature range consisted of a 12-turncoil with a 2-inch outer diameter stainless steel sleeve and a hot water jacket.A production model of this design was fabricated and further testing was con-ducted with both the #9 and #13 sonic gas orifices. Configurations and resultsof alternative changes to the canister are shown in Table 3.

(6)Hydrospace Laboratory Note 3-79, Index No. 68, MK 11 Scrubber Test, Sequence3 at 650 FSW, by G. W. Noble, April 1979.

(6)Navy Experimental Diving Unit Letter, Manined Testing off the MK 11 UBA at 650

FSW and 350F (1.70C), Serial No. 62, dated 9 February 1979.

21

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TABLE 2. INITIAL CANISTER CONFIGURATIONS TESTED U5

(Sheet I of 3)

CANISTERCONFIGURATION DESIGN FLOW PATH REMARKS

I BASELINE TEST- A - Bath at 350

S.T_-ANDARD CANIS- B Bath at 350_TER WITH HOTWATER JACKET __

BATH AT 30(4 TESTS)

BATH AT 33014 TESTS) ATER JACKET

Partially successful atfl. RADIAL FLOW forcing even flow distrib-

COAXIAL __ __ution. Scrubbed better onSwork cycle.

SPERFORATED METAL WALLSON CENTRAL CORE

LINED INNER CORE WITH TWOLAYERS OF FILTER MATERIAL HOT WATER JACKET

Attempted to induce great-1.VERTICAL FLOW ---- er pressure drop to re-7__ distribute flow --- still

TWO LAYERS FILTER MAT'L- I unsatisfactory.

INLET, ONE LAYER-OUTLETTHREE LAYERS FILTER MAT-ERIAL ON INLET, ONE LAYERON OUTLET Q HOT WATER JACKET

Reduced wall area and in-u SYMMETRIC creased gas velocity bySEGMENTS inf | 5X. Wall channelirg

i N (down) appears to be the signifi-

..J cant factor in the lowdnf I, flow situation.

\HOT WATER JACKET

5ibid.

22

NCSC TR-353-80

TABLE 2. INITIAL CANISTER CONFIGURATIONS TESTED UNMANNED-CONTINUED

(Sheet 2 of 3)

Shortened perforated

3. MODIFIED. 7 section of 11 to increaseCOAXIAL • ----- p across bed.

NOT? AT __CE

~.EXTENDED Increased wall area & bedlength and Increased gas

LENGTH velocity. Work of breath-COAXIAL ing increased with time.

® ALL PASSAGES FILLEDWITH HPS$ HOT WATER JACKE-T

~ Center section was wet onA. Test confirmed centerof bed is being utilized

M.0 ABS~ORIENJ in CO2 absorption.i SCREErN MOVED TO INLErT O WAER

OF CENTER SECTION ANDCENTER FILLED W/ O HOTW R JACKE T - MW

ABSORBENT MATERIALIINSTEAD OF HPSS) i Trying to keep AP at a

1 DECREASEDrIANDr2AND minimum.

NO HPS 3IN CENTER NO Qi7 0 PSSPASSAGEHTWAR

_0TWATER JCKET-

23

I I

NCSC TR1-353-80

TA)BLE 2, INITIAL CONISTER CONFIGURATIONS TESTED UNMANNED-CONTINUED

(Sheet 3 of 3)

____ ____________ No physical bridgeEXENDED More efficient particular-

CO0AXIAL ly out of center sections.Performance same as

WITH EXTA ___ A- before.

WALL AREARWAEKTJ Fins add more wall

3 .FINNED 3-PASS surface.COAXIAL ( )

HOT WAEJAKET

Fins improved bothQ. DOBLE FINNED performance and workTHREE PASS of breathing.

COAXIAL ---

INNER FN UE

NOT WATER JAcKETT FINS

24

NCSC TR-.353-80

Results. The canister design combined with the new non-return valvesproduced a MK 11 diving system with acceptable canister life and decreasedbreathing resistance. Although it has not been confirmed, the canister haspossibly increased diver inspired gas temperature by a few degrees.

Figure 13 depicts the modified instrumentation location for the heatexchanger canister design.

Figures 14a and 14b show canister temperatures and modified canister CO2level profiles for a typical unmanned duration test at 450 FSW (137.2 MSW) and35*F (1.7*C) bath temperature. Manned testing of this canister configurationat 450 FSW (137.2 MSW) and 35*F (1.7°C) bath temperature resulted in a meancanister duration of 308 (+42) minutes and a breathing resistance lower thanthe original configuration.

Comparison of Breathing Resistanceof the MK 11 at 650 FSW With EX-17MK 14, and MK 1 MOD-S At Depths of

1Q00 FSW

50-

MK 11 at 650 FSW (Modified Coniaer)

40-/ BANDMASK

/ 1100 FSW

//MK 11a 65 FSW (Unmifed Corster)30 -*Mark 14

30 .- . -- EX- I?. of , - 1 05ao 4 FSW

.,96..- . ' °

oo

25 50 75 100 125 ISOWORK RATE (WATTS)

FIGURE 12. BREATHING RESISTANCE COMPARISONS

25

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i7TABLE 3. RESULTS OF ALTERNATIVE CHANGES TO THE CANISTEX

7

(Sheet 1 of 3)

CANISTERCONFIGURATION DESIGN FLOW PATH REMARKS

1INCREASED WALL SURFACEAREA- MAINTAINING SAME

ANNULAR LENGTH.

(COAXIAL STRAIGHT j ------THROUGH)

TEST NO. 42

NOT WATER 6F INSJACKET

11. BASELINE STAND- STANDARD CANISTER WITH

HoTIWATER JACKET ONLY TOARD CANISTER REESTABLISH BASELINE.

TESTS NO. 43 44

m.PO TED PENINCREASE WALL SURFACE ARCAM. PORTED OPWEHN WHILE MAKING OUTER SEGMENT

BOTTOM PATH LENGTH LONGER THAN CEN-( TER. (INCREASE &P ON OUTER(MODIFIE SRGHFIS WALL TO DISTRIBUTE GAS INTO

THROUGH) jJ _FN.....,/,., CENTER SECTION)TESTS NO. 45 8 46 -6FNS j

IS 7EQUALLY

SPACED HOLES, .25"

.INTERNAL HEAT -EXPLOR EFFECTS OF DIRECT

EXCHANGER WITH IIHEATINGWATER JACKE---A,

TEST 47: HPSS

TEST_49 BARALYME AT 450FSW AND36 NW URETHANE WBATH,. .3VIDC H.W. P K- HW.

-....... ... .-IN" JAC , T __r

7Hydrospace Laboratory Note 4-79

26

-- ,-- - - - - - -

N(";( TR--353-PO

TABLE 3. RESULTS OF ALTERNATIVE CHANCES TO THE CANISTER

CANISTER(Sheet 2 of '3)

CNIURTO DESIGN FLOWPATHI REMARKS

3Z.SIMULATE BAG- SAME AS 3 ASDBThEP O$0FT___ -SIMUL AT[ HEATED SAGOVCR

NA.1LE EAT ER- fFREE STANDING INNER COIL

NAL HET EX-BED FLOODED

i~ Al TEMPTED TO UTILIZE CENTERTESTS NO. 50, NOM 51 6 000. 5 OF CANISTER THROUGH HEATING

375"VD DCIY- HW. URET HANE HW,IN' PACKED "OUT"

JACKET

~.CE TER EAT30OD ALUMINUM SLEEVE

-EXCHANGER TO DETERMINE EFFECTS OFADDITIONAL HEATED WALL

TEj~ST,!!~z_ TWETJ 1100NOL 5? NOT WAT ER T, I 17

PO.54 HOT WATER T. 13iNo. 55 HOT WATER 4iO 16(9TRiNDU1IEOMK.IIMAK HOT WATER(SUR

JACKET -- !IW .colt. HA

=.MODIFIED CEN- ISIMPLIFIED ASSEMBLY OF HEATEDWAL L B Y REMOVING CENTER F IN S.

TER HEAT EX-

TIEST NO 56 SAME AS TESTk655EXCEPT NOFiNf.

(3*AL INNER SLEEVE ONLY)

27

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TABLE 3. RESULTS OF INTERNAL CHANGES TO THE CANISTER

(Sheet 3 of 3)

CANISTERCONFIGURATION DESIGN FLOW PATH REMARKS

1]. 12 TURN COIL___ IIITH 2"1D STAIN - ."O.D. STAILESS STL. SLEEVE

LESS STL SL!kEEVE OPIMIZE NO TEMPERATURES

TESTS NO. 57 AND 5S6W

WATER IN. *OiUTJACKET (I'TURN COIL)

X. 12 TURN COILWITH SAME AS IX EXCEPT WITH_1if0.D. STAIN- 2LO-D. SLEEVELESS STL SLEEVE TESTPIO. 60,WITHOUT HOT WATER ORIFICE ATTEMPTED TO FORCE EVENHEAT DISTRIBUTION THITESTI NIWITH h0T WATER ORIFICE THE CANISTER

28

NCSC TR-353-80

FLOW

LEGEND

1. Scrubber Gas Inlet Temperature

2. Canister Inlet Temperature

3. Canister Center Temperature

4. Canister Outlet Temperature

5. CO 2 Sample Line

FIGURE 13. MODITIED MK 11 CANISTER HEAT EXCHANGER INSTRUMENTTION

29

NCSC TR1-353-80

04~ F4

300

NCSC TR-353-80

BiflEoA Aq ZU80ioa UT TOAOJ ZO:)

0

100oU

H

-r-44.11

(7 G P %0L

j Sa aean9ada

31H

NCSC TR-353-80

MK 12 CO2 SCRUBBER DEVELOPMENT

MK 12 MIXED-GAS RECIRCULATOR SYSTEM DESCRIPTION

The MK 12 Surface Supported Diving System (SSDS) mixed-gas mode (Fig-ure 15) was designed and developed to serve as the United States Navy's basictethered system for use in nonsaturated mixed-gas diving operations. The U.S.Navy conducted a commercial diving equipment survey in 1971; development ofthe MK 12 began in 1972 to satisfy SOR 46-54 requirements. The mixed-gasrecirculator was under development at NCSC from November 1976 to October 1978and successfully completed technical evaluation (TECHEVAL) in December 1978.

Recirculator Assembly

Four operating configurations are available with the MK 12 mixed-gas recir-culator. In order of preferred use, they are: umbilical supply, semi-closedcircuit; umbilical supply, open circuit; emergency supply, semi-closed circuit;and emergency supply, open circuit. Figures 16 and 17 depict the MK 12 recircu-lator assembly.

During normal (umbilical, semi-closed) operations, surface supplied gasenters the recirculator low-pressure manifold and passes through the ejectornozzle. As this gas passes through the ejector throat, it creates a venturi

effect which draws the gas to be recirculated through the canister where it isscrubbed of carbon dioxide. This mixture of surface supplied and scrubbed gasenters the helmet through the supply (inlet) hose and mixed-gas, one-way valve.While approximately 10 percent of the gas in the helmet is exhausted through theadjustable exhaust valve, 90 percent is pulled into the canister via the return

(outlet) hose to complete the recirculation circuit.

Umbilical supply, open circuit, is used in the event of a recirculatorfailure when surface supplied gas can be fed directly to the helmet, bypassingthe recirculator. This configuration is also used when ventilating the diveron 02.

Two mixed-gas emergency configurations use the emergency bottle locatedin the recirculator. Emergency, semi-closed circuit, is utilized when surfacesupplied gas is lost or becomes contaminated and the recirculator remains opera-tional. Emergency, open circuit, is used if the surface supplied gas is lostand the recirculator fails. High pressure mixed gas from the emergency bottle

is regulated at 30 pounds per square inch gauge (psig) overbottom pressure andis fed through a bypass whip to the helmet.

32

NC(_SC TIZ-353-80

FIGURE 15. MlK 12 MIXED-GAS CONFIGURATION

33

NCSC TR-353-80

Mixed-Gas

Inlet Duct

Return Duct

DiffuserAdjustableEhaust

Helmet Open Circuit Valve

Supply Valve

Inlet SupplyHose Outlet Hose

Shroud . (Return)

Open Circuit Whip

Ejector Muffler

Ejector Throat

Emergency Bottle Surface Supply Whip

___----Absorbent Canister

Emergency BottleValve Hot Water Whip

Ejector Supply Valve

Low Pressure ManifoldHigh PressureManifold Pressure Regulator

FIGURE 16. RECIRCULATOR ASSEMBLY/HELMET FLOW (SEMI-CLOSED MODE)

34

r- - T ," I' m 'l t

. . . .. . . . ." ' : '

NCSC TR-353-80

A-Helmet Shell

Adjus table _One Way Valves

Exhaust ValveSupply Valve

Communications J2

Adapter and Whip Shroud HoseShroudedrnou doe Open Circuit Whip

Return Hose(Outlet)

_Gas Supply Hose

(Inlet)

Canister

EmergencyBottle

NeopreneInsulation

Fixed

Condensers

-Ejector Throat

Suirface Supply-4whip

Ejector Nozzle

•~. ----------------- -

- -4" Emergency BottlePressure Gauge

Ejector Emergency BottleValve, ~Supply -

Valve

FIGURE 17. RECIRCULATOR ASSEMBLY WITH HELMET INTERFACE (REAR VIEW)

35

NCSC TR-353-80

DEVELOPMENTAL TESTING

Total System and Component Pressure Drops

The purpose of this test series was to identify and minimize the system/component pressure drops" s) . The most significant results of these tests were:a) the utilization of conical design (Koegle) non-return valves in lieu of morecommonly used "Mushroom-Flapper" non-return valves (Figure 18 illustrates thereduction in system resistance due to these valves); and b) breathing hoseswere optimized with an 1 -inch inside diameter (ID).

Ejector Development

The purpose of this test series was to develop an ejector assembly that willsupply a recirculator system flow of 6 actual cubic feet per minute (ACFM)I(l70litres/per min (ALPM)) against the MK 12 optimized total system losses with anozzle flow of 0.4 to 0.5 acfm (11.3 to 14.2 ALPM) (at the diver depth) at a

maximum ejector supply pressure of 135 pounds per square inch (9.49 kg persquare cm) differential (psid) overbottom pressure9 10.

Figure 19 shows the ejector configuration identification method for the MK12 system. Table 4 lists the performance characteristics of some of theejectors tested. Empirical testing culminated in an ejector for MK 12 applica-tion which met all design requirements. Figure 20 shows performance characteris-tics of the final MK 12 design.

MK 12 Scrubber Development

Background. During manned and unmanned testing of an early scrubber proto-type in the period of December 1976 to January 1977, it was determined that theduration of effective CO2 scrubbing was not adequate(11)(12)(13).

Diagnostic Tqst Objective. In an early attempt to better understand theoperating phenomena of this CO2 scrubber, a series of diagnostic tests wereconducted.

(8)Hydrospace Laboratory Note 1-77, Index No. 14, Mk 12 SSDS Mixed-Gas Mode

and Total System and Component Pressure Drop Test, by G. W. Noble, May 1977.

C9)Hydrospace Laboratory Note 2-77, Index No. 15, MK 12 SSDS Ejector Develop-ment Test, by G. W. Noble, February 1977.

(1O)Hydrospace Laboratory Note 3-77, Index No. 16, Recirculator System flow

Test (Smooth Bore Nozzle), by G. W. Noble, February 1977.(")Hydrospace Laboratory Note 13-76, Index No. 13, Recirculator Duration Test,

by G. W. Noble, June 1976.(12)Hydrospace Laboratory Note 23-77, Index No. 34, MK 12 SSDS Recirculator

Canister Test, by G. W. Noble, August 1977.(13)Navy Experimental Diving Unit Report No. 10-77, Manned Evaluation of the

Prototype MK 12 SSDS Helium-Oxygen Mode, by R. K. O'Bryan, September 1977.

36

NCSC TR-353-80

M r-4 -

> -4 $4

0

I Z Z or. z

z = c

'00

G 0 Gn

0

0

s-I4

ccj

-4

a.)

'44

q P-4-4

z' -H% 'kD) aisodjTulj

I37

NCSC TR-353-80

TROAT

,,,REIRC LAED GASf NOZZLE

T ~-FRESH GAS

774 77777 -DEPTH OF ORIFICE BORE

Legend:

0 - Orifice

0.028 - Diameter of Orifice OpeningTT - Nozzle Configuration (Smooth Internal and External Taper)22 - Depth of Orifice Bore (Thousandths of an Inch)T - ThroatST - Short Throat

0.312 - Diameter of Ejector Throat Staright Section (Inches)F - 25 Milcron Filter Assembly Installed

Example: 0 =0.28TT22/T = ST.312FC/G 0.156

FIGURE 19. EJECTOR CONFIGURATION IDENTIFICATION

38

NCSC TR-353-80

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NCSC TR-353-80

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NCSC TR-353-80

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NCSC TR-353-80

A pp roac h. Table 5 is an outline of the diagnostic CO 2scrubber tests.\1 cainisters had absorbent material samples taken for chemical analysisOfpercent reactivity and percent water content by weight; Figure 21 com-

pares the residual chemical activity/moisture analyses at three locationsin a spent canister (14).

Table 6 compares canister bed temperatures of selected tests. Also shownis manned test data depicting gas percent relative humidity (RH) readings atthe canister inlet hose.

Results. In the 55 0 F(12. A) temperature range of the bath it becameapparent that the midsection of the absorbent bed was being excessivelydried. This drying is the result of the temperature gradient between theinlet gas and active-bed temperatures. (NOTE: The absorption of CO2 is an0exothermic reaction.) As the cool inlet gas (typically 100 percent RH at 590F(15.0 C) enters the active zone of the absorbent bed it is heated by the re-action and passes through the remainder of the bed absorbing moisture in itspath. Eventually, when the reaction starts migrating downward, the unusedreagent below the preliminary active zone is too dry to support the necessaryreaction and C02 absorption diminishes. Table 7 is a comparison of canisterswith different bed temperatures/durations. Appendix B contains a more detailedanalyses of the MK 12 C02 scrubber development.

Canister Modification Objective. An attempt was made to reduce the tempera-ture gradient between the inlet gas and mid-bed of the canister.

Approach. The insulation was removed from the canister and tests were runwith and without condensers installed in the bed. A slight improvement in can-ister performance was achieved after some modification to the condensers whicheliminated channeling problems. However, further testing indicated that theremoval of the insulation caused a second problem. The outer approximatelyi-inch (2.54 cm) of the bed closest to the canister wall was absorbing morecondensate than the center of the bed. This resulted in the center core ofthe bed having less flow resistance and therefore even higher gas flow. This"snowballing" of the flow through the center of the absorbent bed practicallycancelled out the benefits of reducing the temperature gradient.

The entire canister assembly was inverted in Test No. 12 of Table 5;i .e. , system f low directed f rom the bottom towards top, which indicated asubstantial increase in performance. System interface requirements prohib-ited incorporating this system flow direction reversal into the MK 12 C02scrubber design. It is speculated that the gas flow direction and opposedgravitational forces balanced each other to some degree in maintainingsome of the free water in the active portion of the absorbent bed. Taskschedules prohibited further investigation of this phenomena.

(''IHydrospace Laboratory Note 25-77, Index No. 35, MK 12 SSDS RecirculatorFunctional Characteristics Test, by G. W. Noble, July 1977.

42

NCSc TR-353-80

TABLE 5

MX 12 DIAGNOSTIC CO2 SCRUBBER TESTS

(Sheet I of 2)

TESTI TEST OBJECTIVES DURATION TEST RESULTSNO. (HOU RS)

I p i it,, , vcic c( f i itc t in, rits t-. t t ~t,: -8~eiiof i~Minned Iiv',-. i i teddiv.

rAt, sijit'ihi fur us' in thii test. I '.'I.sii tsmnn-d div,

3 (hjn arahiti vmr 1(its-r-fduce pi55 ihilIit\' .7, T'iir.-liit.,)t dtefect iv. htr i vmw c,itis ing sirt Iiir..

ju-n - ics, Test %', '~ icdt,

v4 \iIit, -i-h ,r w it i., t I mrIiii i (I iiiiliriv,-melt"ml itig. Okett jfle if itiWtlii,

cfimrutt I i lg.

C hinge ha rt IvnwI, liits- r-Iic. JsIhI it 2 4 irwrr v.-innt.,,f d-ihi,- i fai r-- illis in 1 ', short -fir-it ii-its- Tt-st No. 4 p n i-

6i Simutlate inriixint-d test of l'/?6.l4 Niiirvi, i

7 Th i -- n i ii,uitt i-ni .i,ii minis- h i 4i nli--i -- I. di-s ir-i d ijr.3-ti--rripe t itr, t ti~ - I tt,- .fLt,(Itif i o,'hor 1,p-tir -w nilte ridded ti clicck -- iI f)w.

I~ lv ijiitt- it ti-it tr 1'-1i - f,itI tiqp,-rai- 1 5.1rJ5, -ii l t i n.tiire (5h"F) 'ITT 11st NOi. 7 c')nfigiirat in.

t r temp t ti nIi fit tIi 'I 'i i Ow ,r is t.-mp,-r~i- 3. 4 'j 1i- :11 T1, r, is mi te ipritir..tui, with .,fufit i--.i! i ns,I.it in w if 115 1 TiZ i-i luiratiun.

p) i-it 1- it 'o,iui~f i,r fic timijin 3.4 tI,; i in -a i i n- i h iii d i f i or t im-1Irait ,-

N s t wn F f lqir ti- r 'i-i

I I 1vilua,i .- f t i)f r,--ivi1 F ifiiidii- 3. 17 N. LinfiTr frim the svst--i.

I., iviileitv ipi-rat iii with, r-iirciii,itr is- 5.42 \ 1 j-,h~t 1, In-is- inst-i I v inive rt-i ; Iin-jul d ft j r re, ins taI iTd. ew i r r i t ii

I I lv-ailiit tp 4rat imi wi th r(-i rctili tor is t .in

I ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ i r i vi- , i I ,its-r 11ctI) f qc ib - nft m - 4.i1 1,1 it t-1.

-ri tir,- iv r-muintv i i mis tt-r ITi,i ii t ion.

43

NCSC TR-353-80

TABLE 5

(Aheet 2 9f 2)

EST TEST OBJECTIVES DURATION TEST RESULTSNO (HOURS)

1:,.t l "-"I I, I!, i'l r 1 ,'i- - Inconclu ivv - apparatus mal-

, J i11: ; , , r],]. I - funci tione d - test stopped.

p,t 4.51 Approximately 30% increase in

canister duration.

tr , , fi t il: ., tw,.Tl in- 2.55 1*satisfactorv - condenser pro-, it it . dulo chann, Iing action.

. r, , is., r: '-r + ,, h ,hliing q.0 (oid durat inrt - erratic perform-. t W t I. i1C

I ,.d - p "t , .I -lnt htwen ill- ?.25 No imnprovcitlint in duration;It ],"t a -! ni t lto. sl isht improvement In bed

cod i t ion.

il t t It tltl ,'t ti 'prl ing) 2.5 No improvement.,r ,!,im

", + r, i ,tr t,, be~d.

i' it , t r it i i. :i. i-watier con- 4.25 Approximately 30/' improvement inrto w - i i , r b' we ilgbt) durit ion.

,I, ,' h.ir,ilvmL, 1.50 Mark-d decrease in scrubberSt i i ' 1 ,lP t L in., gAys d r,ition.

, o, .. ,t -- , . -, r- in ii:Ih 3.75 N(, improvement in duration.St+ r , trlt - i. 0-

". IXceSSive condensate noted near

clistor wAll. High gas flow in

tih canister hed.

t, , t, r t, , low 7.0 rnistr ,dartit ion increased1, t, low 1itrih ition.

.~ ~ ~ ~ ~ ~ 1 11 ' , 1t IT) ... , >. ' i ' at ,n

' , , , ' i 3.5) Rar tivri, durat iot 5W0 less than' [ . ... r " i ph wter sodilsorb.

. i i .- . . ' n- . 1(1.) Cli-at lv i:Icreisod durat ion -, I'.," ., t "\N . co ? I. , 'it ill I.cceptable

i tt I t IlI hours oIf oeration.

44

S

NCSC TR-353-80

Location of sample in canister

28% 26% Residual Chemical Activity*23% 21.5% Moisture Analyses

18% 26% Residual Chemical Activity1% 1% Moisture Analyses

11% 14% Residual Chemical Activity25% 26% Moisture Analyses

_ _ _*AlI values to nearest .5%

L. Center of Canister

* All Values to Nearest 0.5%

FIGURE 21. CANISTER CONDITION AT CO2 BREAKTHROUGH

45

NCSC TR-353-80

44'

WI4-i

5 mj 01 '.-14OI W 00_ _0

Lr) 44~

ZE--

41-6 41a

00 Lroa

Lnf Cfl0)Wn Ln 4-w

w1g 4'O

I-

r- LL ma

1.4 1.4- 0

Im_ ZW - '0 -H~1.~

CL -i ~ ~ LII ON1 LI~ m -4C1- m4-4u- Lr r ) cN0 0 c o 0 mJ O 00

'0 0- w-j N .

0 -0

ILI

NCSC TR-353-80

TABLE 7

RELATIVE HUMIDITY (RH) PERCENT OF GAS IN MK 12 CO 2SCRUBBER

Inlet Bed Bed* Duration

T~mperature Gas Temperature Gas of TestTest Data (F) ('C) (% RH) (0 F (0 C) (% RH) - (Hours)

4/28/77 64 17.8 100 High 42 2.9

(#13) (Estimated) 91 32.8560 F ahLow 60

13.3C Bat 79 26.1

Avg. 50

85 29.4

3/30/77 76 24.4 100 High 65 9

(#7) (Estimated) 91 32.8

76 0 F **Low 80

2 4 .4 C Bat 83 28.3

Avg. 72

87 30.6

12 18/76 50 10.0 100 High 70 940 F 59 15.0

4.4 0 Bath Low 95

51 10.6

Avg. 90

12'1/7674 3.3 10055 12.8

621/6 74 2. 0 High 59 970 F 92 33.3

21.1 0 Bath Low 85

79 26.1

Avg. 6986 30.0

,LHelmet Inside Temperature 680F (20.00 C*Based on NCSL Report 122-72, June 1972, Universal Humidity Chart**Helmet Inside Temperature 770F (25.0OC

47

NCSC TR-353-80

The final approach was to re-insulate the canister to maintain betterflow distribution and to use a high-water content C02 absorbent in conjunc-L ion with condensers in the canister to regulate the moisture in the bed.

Results. Further manned testing at NEDU revealed another shortcoming ofthe MK 12 CO2 canister. Earlier manned tests, and therefore unmanned simula-tion, had been conducted using a chill bath temperature of 50 0F (10.0 0C).0Manned dive protocol was changed to specify a chill bath temperature of 4Q0F(4.40C). The following excerpt is from NEDU Report 2-78(15):

"..The mean of all canister studies at depth was 255+55 minutes. Itis apparent from the above results that the capability of the prototype1K 12 SSDS is inadequate to support a diver performing prolonged moderatework during an operational dive which could easily last more than sixhours. The results do, hwever, lend insight into a basic problem ofcarbon dioxide absorption in cold water.

"Two findings of interest that emerged from the canister breakthroughstudies were the increased duration of action of the absorbent bed inwarmer water, and a return to higher efficiency during diver turn-overin two of the canister studies. The first finding came as no surpriseand is well supported in the literature. The second finding, however, wasa surprise during data collection, but upon reflection made sense. Ineach canister study, absorbent activity began in 29.40C chamber for severalminutes prior to being immersed in cold water. If degradation of canisterfunction occurred as a result of absorbent bed cooling rather than bychemical exahustion, one would expect that a return to 29.4%C chamber andcontinued scrubbing activity would restore bed activity. This is whatwas observed, and the conclusion is that the degradation of canisterfunction is not only secondary to chemical exhaustion, but also due toslow cooling of the absorbent bed.

SUMMARY

"The Prototype MK 12 SSDS helium-oxygen recirculating mode was evaluatedat its operational depth. The results clearly demonstrated that whilethe system can support a diver performing heavy work, it cannot supporta diver in cold water for sufficient time to complete an operationaldive at normal working depths. Since the results support the conclusionthat the degradation of canister bed efficiency is due in part to a slowcooling of the absorbent bed, improvements in the canister shouldinclude improved thermal protection of the canister and possible gasheating."

Figures 22 and 23 represent typical canister C02 signatures during these~inned tests. In Figure 23, the second breakthrough curve shows the recoveryJ the canister duni.. jiver change-over. The process of placing a fresh sub-,,-, (diver) in the system being tested (M4K 12) took place in the OSF "trunk"

('"Navy Experimental Diving Unit Report 2-78, Second Manned Evaluation ofthe Prototype M1K 12 SSDS Helium-Oxygen Mode, by R. K. O'Bryan, March1978.

48

NCSC TR-353-80

cqj

Ce'J

4CoM

:I

14 0HEn

(N4

-E-

w cm

0

N 4

0 ~ a) C4

co -

4~3

NCSC TR-353-80

U)wI--

4 r-

0 0

x CI)

w >

w~04

en4

cr -4\ 0

x-CNw-4 C

co E-

oI C'4

C14

rz w

000

- uanTMJ iaSTuVO UT (nS-) Zoowole

50

NCSC TR-353-80

0 0which was approximately 80 F (26.7°C) and required about 10 minutes to accom-plish. The area of canister thermal protection was addressed based on theresult9 of the tests.

Thermal Protection Objective. The objective of these tests was to opti-mize the thermal protection of the MK 12 CO2 scrubber.

Approach. Continued unmanned testing indicated a severe decrease in ab-sorbent material efficiency below a chill bath of 450F (7.20 C)(14). A seriesof manned pool dives were conducted to evaluate methods of heating the canisterand gas. The results of these tests are summarized in Table 8; dive profilesare provided in Appendix C.

Figures 24 and 25 show the gas heater, canister lid, and final configura-tions, respectively (also refer to Figure 17). Canister gas-out CO2 levels andtemperatures inside the backpack and recirculator were recorded. See Appen-dix C, Figure C-l, for location of thermistors and recorded data.

Results. During the early test dives (Test No. 71 to No. 76), severaldifferent gas and canister heating techniques were tested, but the desireddive duration was not reached (Table 8). A 9-hour dive was first achieved inTest No. 77. The configuration consisted of a hot water heated canister top,similar to that shown in Figure 25, shrouds on the helmet inlet and outlethoses, and a 12-pound canister. In subsequent test dives, the canister topwas used at both lower and higher temperatures. Eight of 11 dives met orexceeded the 9-hour requirement. All dives are summarized in Table 8; diveprofiles are provided in Appendix C.

Almost all of the 9-hour duration dives were made using high performancesodasorb as the C02 absorbent, although a 9-hour dive was also accomplishedusing medical-grade sodasorb.

Heating the canister top and the interior of the recirculator case was aneffective means of ensuring that the CO2 absorbent chemical reaction continuedfor the dive duration.

Because of the excellent life results at water temperatures between 350F(1.7°C) and 40 F (4.4°C), an unscheduled life dive in 29 F (-1.7°C) water at10 FSW (3.0 MSW) was conducted. Duration of this dive (Table 8, Test No. 91)was 9 hours with no trace of C02 at dive completion; however, the water bathtemperature increased to 390F (390C) over the 9 hours because of pool size andeffect of adding hot water for both recirculator and diver heating.

During this test period, a single MK 12 recirculator made 88 dives for atotal of 155.2 hours without a MK 12 system abort. In addition, the sameequipment was used for 10 brief training dives.

(14)ibid.

51

NCSC TR-353-80

00

V 34 u , 0 w44 w) $wC') 4, 4, > m4 *4 0

* 0 0 '.0

oo E~ C X a43 a'v4 0 4~ ))~'

-c4 4-..'44 0)' .0

c, cu 0 .0 u 4 00 4 .004 4- o 4 , * 0

0 : m , W 3 4 c 0 0 ' ~' A-~3~.H w . .0 -4 4-043 a 434 0

0~ Q)3 0o (v 4, 000 0 *-40 04-44,40 w V

4, ~~- 03,4 0) o n a0 -14 .443 r.4. C.4 r. 0J c. ca '

w.4 wE . 0 , 4 . Q)0 r 'a 0 - 0) .0co 4- 0

10 v 433 - 40 )- z 4) L 0

co (A. 43 3 H -4 4)0 m .4 0. 0WV0 ~0 0 91. 000 *H4 4 0'

*H) -(D =44 m0 0 a3 0, 0

r, u0 0 4)H u c4 or, )

Cy o r- C,4 r= -H.)~ a.. 4-- r_ 0- r ~ N

cu . .C V CU) U) E

'44.- 0.3 0 03 ) 00 4)

4)0 4 0 to ) w , Q ,. w -4, r_ c DI 4, 4) w) ) 4,0-43 m03 Q, Fa a m 3 00 cn k-ci 0 W43. I1n W04 U1- -~4 4 ) 31) (/3 L/3. I

*eZ w o 0 -t 00 0) M m m0 c 0

0.. 0~ w Q) 0- .0 -43 w-- a) w' ' ' 0' 0

- - -- r-r

0. 0 a la -H o 0. m 0 0

a' ,d 0 4. -n (A 00 w ) 4-t - 0 ' .0 0n U) V0 'n

D- 0' - 0 40 r 0 0 0 CD 0 0

00 Go C 00 al

'P,3 C) 0. 0. CD 0. 0. 0

4.13 CL 0. cw A

430 4) 1- 1 . 0 N 00 a, -4 C1 e

M40 I 3I I I I ITh~~e -q -4 -e4 .

52

NCSC TR-353-80

0 0

00

A*02 CO -a4 1

r C.

40 0

0 'T 4

w OD 2 0 co 0 0 0

U) (n U) LO

0 E' E0 I0 E0 2

04 '0- 4

cc 00 0 0 0 0 CD0 4.

-. 4 -4 0

w 2 0 (2 (2.0 In

0 e

0 10 000a00 (2 co co 0 co co 00 C

.- (. o 7 7

in 24 24 2 1

2 H H H H H53

NCSC TR-353-8O

(a),

Ejector Heater

(b)

Hlea ter

FIGURE 24. KINERGETICS GAS HEATER INSTALLED (INLET AND EXHAUST)

54

NCSC TR-353-80

A. 1/4" Copper Tube Hot WaterFlow Through Ten 1/16" DiameterHoles Around and Over CanisterTop. Used in Test No. 77

Hot Water

B. Flanged Plate DirectingHot Water. Used in AllTests After Test No. 77

Hot Water

FIGURE 25. CANISTER TOP HOT WATER PORT CONFIGURATIONS

55

NCSC TR-353-80

Conclusions. The recirculator configuration used in Test No. 78

(Table 8) and subsequent dives demonstrated consistent, long canister life.In this configuration, a hot water flow was directed at the recirculatorinlet/outlet hoses and then was exhausted into the recirculator case/shrouds.This flow path and temperature distribution inside the case produced condi-tions conducive to desired CO2 scrubbing action in the recirculator at thetest temperatures. On 6 February 1978, the recirculator design was frozenon this concept. A schematic illustration of the canister top is shown inFigure 25. Figure 6 illustrates the final recirculator design concept. Themodified recirculator demonstrated the required 9-hour duration in waterabove 50OF (10.00 C) without hot water heating.

High performance and medical-grade sodasorb provided longer canisterdurations than baralyme under the same test conditions. However, thetests of both medical-grade sodasorb and baralyme are inconclusive, sinceonly one test of each material was conducted. Past unmanned tests indicatethat medical-grade sodasorb has demonstrated a 9-hour canister life capa-

bility in a water temperature of 50F (10.0 0 C), and this absorbent should besatisfactory for the MK 12 recirculator. It may be concluded that baralymeis suitable for use in the MK 12 recirculator in dives of less than 6 hoursduration.

Breathing Gas Heater Evaluation

Objective. The objective of this test phase was to evaluate direct gasheating as a means to extend canister duration in cold water diving; i.e.,below 50°F (lO.O°C), in lieu of flooding the backpack with hot water.

Approach. Kinergetics gas heater, HEX-5 Model 3330, was used for theevaluation. The heater was inserted in place of the ejector muffler for TestNo. 72 and No. 74 (Figure 24a). For Test No. 73, the heater was placed on topof the canister (Figure 24b). In addition, the number of heating elementsused in the heater on the canister top configuration was varied in Test No. 75

and No. 76.

Results. Use of the gas heater in any of the configurations and in con-junction with the large canister did not obtain the required canister life of9 hours. When the gas heater was used in place of the ejector muffler, thetemperature drop across the recirculator inlet and outlet hoses and the helmetresulted in previously heated gas re-entering the canister at ambient tempera-ture. When the gas heater was tested on top of the canister, the heated gasdried out the absorbent bed and forced the bed moisture through the ejectorinto the helmet. As the absorbent bed dried, canister efficiency was reduced.

As testing progressed, use of hot water heating on the canister inlet andoutlet hoses and inside the recirculator case versus direct heating produced

better life results for the MK 12 system configuration.

Conclusions. A gas heater of the general type tested does not produce

the necessary conditions in the MK 12 system configuration to develop thedesired canister durations.

56

NCSC TR-353-80

Comments. Figures 15, 16, and 17 show the final design of the corrugated

shroud hoses. Figure 26 depicts the MK 12 carbon dioxide absorbent canister.

In July 1978 the MK 12 prototype CO2 scrubber underwent manned testingin the OSF. The results are described in Reference 16.

"Testing of previous prototype MK 12 SSDS carbon dioxide absorbentcanisters indicated that initial cooling of exhaled gas with sub-sequent gas rewarming within the CO2 absorbent bed led to dryingof the absorbent material and deterioration in performance. Thefirst two prototypes tested in manned dives had shorter CO2 scrub-bing durations than desired. The recirculator assembly was modifiedby incorporation of two moisture retaining condensors within thebody of the canister and hot water heating of the canister. Threecanister studies were performed in 400F water at 390 FSW. The diversperformed 6-minute work periods, separated by 4 minutes of rest, ata work rate of 50 watts on a pedal ergometer. The work-rest sequencewas selected to approximate an average metabolic production of 1.5liters of CO2 per minute and simulate a hard working dive. The work-rest sequence proceeded until canister effluent reached 0.5 percentSea Level Equivalent (SLE) (3.8 mmHg). The mean CO2 value of thethree canisters at 9 hours was 0.2 percent SLE. One study was con-tinued until breakthrough, 0.5 percent SLE, which occurred at 10hours. It is unlikely that any operational dive would involve con-tinuous, moderate work for 9 hours.

"Therefore, the results clearly demonstrated that the MK 12 SSDShelium-oxygen mode would support a diver for the design goal of9 hours."

Figure 27 shows the canister breakthrough curves for the final canisterCO signature tests. Based on the one canister life that was terminated at1.6 percent SLE, the efficiency of the absorbent bed is indicated in Table 9.

Canister degradation as a function of depth cannot be plotted due tothe lack of data points. Three test configurations were identical or veryclose to the final design (see Table 8, Test No. 77, No. 78, and No. 83).Comparing test results of the manned pool tests conducted during Januaryand February 1978 to the OSF test dives(16) yields the following comparisons:

Pool Tests OSF Tests

10 FSW @ 40'F 390 FSW @ 40°F(3.0 MSW @ 4.4°C) (118.9 MSW @ 4.4 C)

SLE CO2 reading at 9 hours SLE CO2 reading at 9 hoursX = 0.03% X = 0.2%

This would indicate a 15 percent degradation between 10 FSW (3.0 MSW) and

390 FSW (118.9 MSW).

(16)Navy Experimental Diving Unit Report 20-78, Carbon Dioxide Absorbent

Canister Studies of Hot Water Heated Helium-Oxygen Mode, by W. H.Spaur, E. D. Thalmann, and R. C. Maulbeck, December 1978.

57

-. -

NCSC TR-353-80

Aro lApprxinatln 12.5 Pounds High Pressure Sodasorb

- - Active Length 14 3/4 Inches

" f7 1

,IJ I

1/2 - Inch Thickness

BtIRubber

-;. -'i I I

6.0) InchIInside

)iameter(ID)

I IIS

FTGU,1IE 26. CARBON DIOXIDE ABSORBENT CANISTER

$8

NCSC TR-353-80

0

00x 0

o p

J-j C.

CC.w

04 C0

00 -- rr

(j) C;

aso~oqZuaq a~v Ae uaqun~jgaesuv u ZOHI qaoa

59p.

NCSC TR-353-80

TABLE 9

MK 12 CANISTER EFFICIENCY

CO. ltvels into canister 2. Weight of high performance(mean values) based on 2/77 Sodasorb in MK-12 canisterNEDU dive. is approximately 12.46

lbs. (5.65 kg)

% CO2 (SLE)

R s t 50 watts

o.33 0.75

3. Determining the total amount of CO2 produced by the. diver.

Q = 6 ACFM (169.9 ALPM) Flow

= upstream % CO 2 (SLE) 1 -- During rest

P2 -- During work

= Density of CO2 at 1 ATA and 300 F (-1.1C)

= 0.12393 lb/ft 3 (1.98469 kg/m 3 )

A test duration of 11 hrs* with 10 min. cycles of 4 min.rest and 6 min. of work yields

264 min. of rest

396 min. of work

This implies a total mass of CO2 produced:

,) L (264) + 2Q6 (396) = 12.46 lbs (5.65 kg)

.liwrc iWa ILy, high performance Sodasorb should absorb 50 percent of its own.,:iLt in C0), cr 6.23 lb (2.83 kg) of CO2 . The MK 12 canister efficiencyir, tLh)r.t--,-prUximately 45.8 percent (amount of CO2 absorbed/theoretical

, i c l it y).

, i , - t 1..), ((o SLE.

60

,,,---- ;- z ;- ;.-: 7- i _ 7 . ... -NOWl ~ lu l l l~ alX -. . .. . .. ..

NCSC TR-353-80

REFERENCES

1. Hydrospace Laboratory Note 11-78, Index No. 64, Underwater BreathingApparatus - MK 11 Scrubber Test, by G. W. Noble, August 1978.

2. Navy Experimental Diving Unit Report No. 18-78, Life Support Characteris-tics of the MK 11 Semi-Closed Mixed Gas UBA at Intermediate Depths, byC. A. Piantadosi and W. H. Spaur, November 1978.

3. Navy Experimental Diving Unit Report No. 10-78, Evaluation of the MK 11,Mod-O UBA in Cold Water, by R. K. O'Bryan, R. L. Clinton, and R. A.Vendetto, May 1978.

4. Hydrospace Laboratory Note 6-79, Index No. 71, MX 11 Flow Test, by G. W.Noble, April 1979.

5. Hydrospace Laboratory Note 3-79, Index No. 68, MK 11 Scrubber Test,Sequence 3 at 650 FSW, by G. W. Noble, April 1979.

6. Navy Experimental Diving Unit letter, Manned Testing of the MK 11 UBAat 650 FSW and 35*F (1.70C), Serial No. 62, dated 9 February 1979.

7. Hydrospace Laboratory Note 4-79, Index No. 69, MK 11 Scrubber Test,Sequence 4 at 450 FSW, by G. W. Noble, May 1979.

8. Hydrospace Laboratory Note 1-77, Index No. 14, MK 12 SSDS Mixed-GasMode and Total System and Component Pressure Drop Test, by G. W. Noble,May 1977.

9. Hydrospace Laboratory Note 2-77, Index No. 15, MK 12 SSDS EjectorDevelopment Test, by G. W. Noble, February 1977.

10. Hydrospace Laboratory Note 3-77, Index No. 16, Recirculator System FlowTest (Smooth Bore Nozzle), by G. W. Noble, February 1977.

11. Hydrospace Laboratory Note 13-76, Index No. 13, Recirculator DurationTest, by G. W. Noble, June 1976.

12. Hydrospace Laboratory Note 23-77, Index No. 34, MK 12 SSDS RecirculatorCanister Test, by G. W. Noble, August 1977.

13. Navy Experimental Diving Unit Report No. 10-77, Manned Evaluation ofthe Prototype MK 12 SSDS Heliwn-Oygen Mode, by R. K. O'Bryan, September1977.

14. Hydrospace Laboratory Note 25-77, Index No. 35, MK 12 SSDS RecirculatorFunctional Characteristics Test, by G. W. Noble, July 1977.

15. Navy Experimental Diving Unit Report 2-78, Second Manned Evaluation ofthe Prototype MK 12 SSDS Helium-Oxygen Mode, by R. K. O'Bryan, March1978.

16. Navy Experimental Diving Unit Report 20-78, Carbon Dioxide AbsorbentCanister Studies of Hot Water Heated Helium-Oxygen Mode, by W. H. Spaur,E. D. Thalmann, and R. C. Maulbeck, December 1978.

61

NCSC TR-353-80

APPENDIX A

MK 11 SYSTEM FLOW ANALYSIS

Ihe normal direction of system flow is from the exhalation bag throughthcL canister and into the inhalation bag. Simultaneously, fresh gas is beinginjected through the sonic orifice and into the inhalation bag. During un-manned testing of the MK 11, it was observed that at specific times in thebreathing cycle system flow direction reversed. The flow reversal process isdepicted in Figures A-I and A-2 as a negative flow.

The duration of the CO2 scrubber is directly proportional to the amount(mass) of CO? it absorbs. During reverse flow in this system the canister isbeing presented with gas free of C02 ; i.e., the gas in the inhalation bag con-sists of fresh make-up gas and gas previously scrubbed of CO2. Using sine waveapproximations for the curves recorded in Figures A-I and A-2 permits a calcu-lated estimate of actual flow in either direction through the canister per eachbreath.

Conpider an apparent greater amount of reverse flow on the surface as com-pared to the 305 FSW (93.0 MSW), approximating the curves in question by asine wave (refer to the dynamic flow plots of Figures Al and A2).

ym-

m = max. amplitude

wt = 21w - 2ir

t/2 Ym t/2area=ly sin wt dt --- cos wtara=0 m w 0

and

1 breath = 100 data pointsat 1 BPM, 1 data point - 0.03 second

which yields:

A-i

k .....-=7=

NCSC TR-353-80

0

z>z Z

-4

rznIn-

--

000-44

'-4

r-4 P-4 V-WC17V U MOTA

enwI-'nL

0- a

00 0C1 C

-I- I

NCSC TR-353-80

000

-0 0

0 4

Q03 -0

~ 03 0

0~ CA

-H-

41 0

A4~ e'-4

Cu1

4

4 -4

m, c'4L

03c 03 '0I

-A-

rf

NCSC TR-353-80

at surface at 305 FSW (93.0 MSW)

ym = 21.37 ALPM (0.755 ACFM) Ym = 6.41 ALPM (0.2263 ACFM)

t/2 = 0.597 sec. t/2 = 0.174 sec.

t/2 = 0.00995 min. t/2 = 0.0029 min.

actual litre actual litre0.1.35 breath 0.0018 breath

REVERSE FLOW REVERSE FLOW 3'000477 actual ft3 actual ft

(0047- - ) (0.0000636breath breath

During exhalation atthe end of each ex-haled breath and thebeginning of eachinhaled breath

To fill in some estimates on the CO2 curve: the first 0.150 litre (0.0053 ft )

of the tidal volume is from dead space in the trachea and contains no CO . AllCO2 is contained in the tidal volume less the dead space.

(2 litres - 0.15 litre) = 1.85 litres(0.0706 ft3 - 0.0053 ft3 - 0.0653 ft3)

For 40 RMV

-- Theoretical Breathing Curve = 125.66 ltre/min

Actual Flow Thru Cani*ter (4.44 ft /mn)@ 1 ATA Curve wt = 125.66

2 7

t

tl t t = 0.05

t = 0.025 in

, approximate the CO2 signature by a square wave, then between tI and t2i,,,J a total of 1.85 litre (0.0653 ft 3 ) of CO2 laden gas.1 2

, ine wave approximation for the breathing signature, solve for t

t = 0.025

It ,, ln = 1.85 - { cos wtwtI

A- 4

NCC R 353-80

S-TART oSTAhRT

AIO1N TRbcvHE

APPRO)('MATINOF CC Str"TR

SUtAE~ ALPt

I= 0.020 O.o238 #CTUAL Y

0c.0118 ACTUPL LTRFI

.o042 XCTUALIT

NC(' TR V5 3-5 0

2 u21. 85 - L-) (cos 0.05 0.25 - cos t !

t- = 0.1766

0.05 min

L, = 0.0044 min

>.Iw ,stsiwate thte iroa tinder the curve representing canister flow I ATA:

EXIALATION

52= 52 ALPM (1.84 A(;FI)52 A IPM nI . o

1.84 ACFM t 2 ;

- ----- = 57.1o.04 0.02

t = 0 t = 0.020

t = 0.020 y 0.020 52 0.020

y sin ,it dt = -- cos wt = (-.) cos ( - t)IIIe w Y51 W o 0.04

0 0t0

- (0.331) (cos (0.04 (0.020) _ cos (2.04 (0))0.04 0- 0-.0

area = 0.662 actual litre (0.0234 ft 3 ) per exhaled breath

4 .7 INHALATTON m 41.7 AIP'. (1.47 ACT-7)~~wt =2'

Wt 2 'T

w 0.04 - 157.1

t=04.005 ;min

0.020- .2 (024 t) = -(0.265) (-2) 0.531

1WI.1 /0.005

3- ' I , ttla] litre (0.01875 ft ) per iilha lod breath

6(, + 0.5 3 1 .193 actual itres breath. + (.()1,8i5 0.0423 ft )

A-6

NCSC 'FR 353-80

This implies that 1.193 actual liters (0.0423 ft 3 ) of CO2 laden gas passesthrough the canister during each breath at I ATA and 40 RMV.

Now estimate the area under the curve representing canister flow at (10.2 ATA).

EXHALED68.8

For simolicity, consider this

curve a sine wave above a constant

14.6 flow of 14.6 ALPM (.5155 ACFM)

t = 0.025

t=0

The area of this portion is:

-54.2-- )(-2) = 0.8626 actual litre

68.8-1566 (0.0305 ft3)

54. The area of this sortion is:

{0.365 actual litre (.01289 ft3)

Ym = 54.2

t = 0.025 wt = 27

t 02 = 125.660.05

Total area = 0.8626 + 0.365 = 1.228 litre (0.0305 + 0.01289 = 0.0434 ft3

1.228 actual litre (0.0434 ft3 ) per exhaled breath.

A-7

_A

NCSC TR 353-80

INHALED The area of this portion is:

-- )(-2) - 0.4390 litre. ...*15 (.0155 ft 3 )

J1.2The area of this portion is:

14.6 0.3227 actual litre (0.01139 ft3)

(v) n -n (,'yM 31.2t (0.025 - 0.0024) m

t = 0 t 0.0221 min wt= 227T 142.15

Total area 0.4390 + 0.3227 = 0.762 actuai litre (0.0155 + 0.01139 =

nw0,sq ft0)

0.762 actual litre (0.0269 ft3) per exhaled breath

1.288 + 0.762 = ].989 actual litres/breath

(0.0434 + 0.0269 = 0.0703 ft3 )Thlis implies that 1.989 actual litres (0.0703 ft3 ) Of C02 laden gas

passes through the canister during each breath at 305 'FSW (93 MSW) and40 RMV.

Comparing the flow of make-up gas at 0 MSW (0 FSW) (6.85 ALPM orifice flow)(0.2419 ACFM) and the gas flow at 305 FSW (93 MSW) (2.72 ALPM orifice flow)(0.0960 ACFM):

the total ul-, ,it f s removed is as follows:

at 40 RMV the (,)taL amount of gas moved is

(20 K.,L,/iin.) (2 litres (0.0706 ft 3 ) tidal volume) +make -up1) gas

at I ATA

(40 + b.8)) litres = 46.85 litres ((1.41 + 0.24) ft = 1.65 ft )

at 305 FSW

(40 - 2.2 litrp: = 42.72 litres ((1.141 f .09(j) It = 1.51 ft )

which ni ip ,:

42 6, i .( 1 0966 lADy,4-5. > 1 ,Z - -I ""

A-8

-

NCSC TR-353-80

The concentration of CO2 will be 10 percent greater at depth thanat the surface (assuming similar mixing of gases).

Combining this information with the canister flow comparisons yields:

1.193 0.5469(1.10) (1.989)

or approximately 55 percent more CO2 being presented to the canister at depththan at I ATA, which implies that:

where the total flow through the canister is forward andreverse flow

at 1 ATA

4685 - (1.193 actual litres/breath) 1.149

1 65 3 3- 0.042 actual ft3 0.0406 ft3)

1.15 actual litres/breath are tented out of the

cardiod exhaust valve (0.04 ft ).

at 305 FSW

42.7220--) - 1.989 actual litres/breath = 0.147

1I 51. 3((L ) - 0.070 actual ft3/breath - 0.0052

20i

0.15 actual litre/breath is venied out of thecardiod exhaust valve (0.005 ft ).

A-9

,- . .. .. •

NCSC TR-353-80

APPENDIX b

MK 12 CO2 SCRUBBER DEVELOPMENT ANALYSIS

Empirical test results of the MK 12 CO2 scrubber indicated that the mid-section of the absorbent bed was being dried excessively. This drying is theresult of the temperature gradient between the inlet gas and active-bed tempera-tures. (NOTE: The absorption of C02 is an exothermic reaction.) As the coolinlet gas (typically 100 percent RH @59 F (15.0 C)) enters the active zoneof the absorbent bed it is heated by the reaction and passes through theremainder of the bed absorbing moisture in its path. Eventually, when thereaction starts migrating downward, the unused reagent below the preliminaryactive zone is too dry to support the necessary reaction and CO2 absorptiondiminishes.

Consider 100 percent relative humidity (RH) at an inlet temperature of600F (15.60C) and 100 percent RH in zone of canister which is at 800F (26.70C:

80°F 0.0014(81)lb H 20/ft3 (26.7°C 0.0224 gm/litre)

600 0.0007 lb H 20/ft 3 (15.6°C 0.0112 gm/litre)

0.0007 lb H 20/ft 3 (0.01112 gm/litre)

0 0 3Therefore, the 80 F (26.7 C) zone must provide 0.0007 lb H20/ft , which at6 ACFM (169.9 ALPM) (ft3/min) is:

(6 ft 3/min.) (0.0007 lb H20/ft3) 3 0.0042 lb H20/min

(0.0112 gm/litre) (169.9 gm/litre) = 1.903 gm/min

Absorbent material in the 800F (26.7 0C) zone is being dried at a rateof 0.0042 lb H20/min (1.903 gm/min).

Absorbent Materials

8% bonded H2 0

Baralyme n, 12% water4% free H 0

2

,Assume that the absorbent material becomes inactive at< 8% H20

High Pressure (HP) Sodasorb, (S/S) " 17% water - none bonded.

(81)Naval Coastal Systems Ldboratory Report 122-72, Universal Humidity Chart,

by P. G. Sexton, June 1972.

This is not actually a step function.

B-1

NCSC TR-353-80

Estimates of Allowable H 0 Losses2

lbH20 gm H2 0

Baralyme 0.04 2 0.04 gm H 20

lb absorbent gm absorbent

ibH20 gm H2 0

HP Sodasorb 0.09 2 0 0.09 gmH20

lb absorbent gm absorbent

Therefore, the respective absorbent material is becoming inactive at arate of:

Baralyme

(0.0042 lb H20/min)/(0.04 lb H20/lb) = 1.05 lb absorbentmin

(1.903 gm H90/min)/(0.04 gm/gm) = 47.6 gm absorbentmin

U I

mini mai9.5 mn (0.021 mi

lb absorbent gm absorbent

HP Sodasorb

(0.0042 lb H20/min)/(0.09 lb H20/1b) = 0.0467 lb absorbentmin

(1.903 gm H20/min)/(0.09 gm/gm) = 21.18 absorbentmin

or

21.42 mi (0.047 milb absorbent gm absorbent

Approximate CO2 Absorption Rates

From unpublished NCSC testing, Code 712, using canister gas vel ' 9.2 in/sec (, 23.37 cm/sec), amount of CO2 absorbed at 0.5% SLE:

500F (10.O°C) and I ATA

3 litres (105 ft 3) of 1% CO2 in He per gram (0.0022 ib) HP Sodasorb3380°F (26.7°C) and 1 ATA

6 litres (0.212 ft 3) of 1% CO2 in He per gram (0.0022 ib) Sodasorb

B-2

NCSC TR-353-80

Ignoring what is absorbed in the first cold layer of absorbent material,consider the usage rate of the 80 F (26.7 0 C) zone to be approximated by:

6 litres (0.212 ft 3) of 1% CO2

3 o 00.06 litre (0.0021186 ft ) of CO at 80 F (26.7 C)where p = 0.11224 lb/ft3 (p = 0.01798 gm/cm 3)

or,

3 30.0021186 ft3 (60 cm,) yields

lb CO2 gm CO2

0.1081 2 0.10788lb LIP S/S gm HP S/S

From OSF manned tests, upstream CO2 levels are approximated by

at 50'F (10.00C) Work: 0.75% SLE CO2

inlet temperature Rest: 0.33% SLE CO2

Using the higher work rate at 1 ATA:

(6 ACFM) (0.75%)->(6 ft3/min)(0.0075) 0.045 ft3C02 min.((169.92 LPM) (0.75%) (169.92) (0.0075) = 1.274 litre CO2/min)

where at 50°F (10.00C) and 1 ATA for CO2

p = 0.11897 lb C02/ft3 yields 0.00535 lb C02/min.

p = 1.9057 gm/litre yields 24.286 gm CO2 min.

or

0.1081 lb C02/lb HP S/S / 0.00535 lb CO 2/min

(0.10788 gm C02/gm HP S/S / 2.4286 gm C02/min) =

20.21 min/lb HP S/S or 0.0495 lb HP S/S/min

(0.004442 min/gm HP S/S or 22.51 gm HP S/S/min)

Consumption Rate

For lack of a better approximation, consider baralyme and high pressuresodasorb to have the same consumption rates (0.0495 lb. absorbent/min) (22.5gm absorbent/min). From empirical tests, the real rate for baralyme shouldreflect shorter durations.

B-3

NCSC TR-353-80

1. Rate at which absorbent material is being used by absorbing

CO2 : 0.0495 lb/min (22.51 gm/min)

2. Rate at which absorbent material is being dried beyond auseable level:

a. Baralyme 0.104 lb/min (47.63 gm/min)

b. HP Sodasorb 0.0467 lb/min (21.18 gm/min)

Lone lus ions

1. Comparing the usage rate (1 above) and the drying rate for baralyme(2 above) indicates that the absorbent is becoming too dry to react

faster than it is being used. This comparison correlates withexperiments.

2. The usage rate with high pressure sodasorb (2 above) is higher thanthe drying rate (I above) indicating that the drying rate will notdirectly terminate the reaction; however, a possible reduction inabsorption efficiency is still possible due to excessive moisturein the lower canister towards the end of its duration.

B-4

NCSC TR-353-80

APPENDIX C

MK 12 SSDS MANNED HOT WATER HEATEDRECIRCULATOR DURATION TEST RESULTS

As described in the section on M12 scrubber development, the MK 12recirculator demonstrated consistent, long canister duration. In this con-figuration, a hot water flow was directed at the recirculator inlet/outlethoses and then exhausted into the recirculator case/shrouds (Figure C-1 forthermistor placement). This flow path and temperature distribution producedconditions conducive to desired CO2 scrubbing action using high performance,medical-grade sodasorb and baralyme at various temperatures. The modifiedrecirculator demonstrated the required 9-hour duration in water temperaturesabove 50 F (10.0°C) without hot water heating. A summary of backpack tempera-tures for the MK 12 test series is shown in Table Cl.

Dive profiles of the manned canister life tests are contained in this'Appendix. Each plot shows time versus CO2 level (%SLE). Refer to Table 8in the report for a summary of the test results.

C-1

NCSC TR-353-80

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Backpack A

Gas Out ofLid into Bed

Outer Bed

Center Bed

H-otWater -

Inlet

Backpack B

FIGURE Cl. THERMSTOR. PLACEMENT, M4K 12 SSDS MIXED-GAS RECIRCULATOR

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