OXYGEN CONCENTRATOR FILTER RE-DESIGN & TESTING
Michael Madea Biomedical Engineering Wyatt Albert
Eleventh Annual School of Science, Engineering, and Health Symposium May 2, 2014 CLIENT f Macha Mission Hospital f Dr. John Spurrier f Mr. Melvin Mabeta f DeVilbiss Healthcare- partnering organization OXYGEN CONCENTRATORS f Purpose: Delivering concentrated oxygen for patients
f Elderly with respiratory issues
f Infants and children with bronchiolitis PROJECT IDENTIFICATION f Problem: Premature concentrator failure f Average life is 43% lower than expected f Non-ideal conditions- humidity and dust f Irregular maintenance f Goal: To sustain oxygen concentrator function f Increase longevity of machine f Maintain adequate oxygen output f Simplify maintenance procedures WHAT ARE OXYGEN CONCENTRATORS? f Oxygen concentrators vs. oxygen tanks f Access f Sieve beds-filter out Nitrogen f Mode of failure
21% Oxygen 95% Oxygen 78% Nitrogen 5% Other gases 1% Other gases HOW IT WORKS To the Patient
Natural Air Depressurizes Oxygen Gas Nitrogen Purge
Pressurizes
Photo: Devilbiss Healthcare WHAT IS ZEOLITE? f Zeolite f Separates gasses f Crystal structure f Cage-like resemblance f Molecular exclusion
Photo: molecularsive.org WHY IS PRESSURE IMPORTANT? f Adsorption vs. Absorption
f Adsorption = Physical bond High Temperature (weak) f Absorption = Chemical Bond (strong) f Pressure Swing Adsorption f High pressure = High adsorption Adsorption Low Temperature f Low pressure = Low adsorption Increasing FIRST SOLUTION f Desiccant based filter f Removes humidity f Preserves zeolite functionality f Chose Silica Gel as desiccant PAST WORK f Designed Dehumidifying Filter f Desiccant based f Site team trip May 2013 f Evaluated prototype on site f Provided aid with repairs
George Mono and Steven Bandstra 2013 RESEARCH
f Desiccant vs. Membrane
f Desiccant f Cost effective f Effective over short time f Requires periodic maintenance f Regenerative
f Membrane f No maintenance required f Long lifespan f Expensive - $150/ft2 f Requires dry air source NAFION MEMBRANE f Tetrafluroethylene – AKA Teflon f Bonded with Sulfonic Acids f Transports water across f Acid Groups form channels f Blocks all non polar molecules
f O2, N 2, ect. f Passive transport f Requires difference in water Credit: Eric Listor concentration MEMBRANE FILTER
Membrane HOUSING DESIGN f Decided on a design based on cost, durability and manufacturability f 3D printed f Extruded ABS plastic f 2 Halves sealed with rubber gasket
Photo: Makerbot.com HOUSING MANUFACTURING TESTING OF DESIGN f Questions to answer f Will design reduce humidity? f How much membrane material is needed? TESTING APPARATUS Humidity Chamber Oxygen Concentrator HUMIDITY CONTROL SYSTEM
www.arduino.com RECORDING DATA
Pressure, Temperature, Humidity sensors
Membrane Housing Humidity Chamber Dry O2
Data Logging Oxygen Concentrator INITIAL RESULTS
f Encountered Sensor Error f Not calibrated for varying pressure
f Relative Humidity = Function of pressure and temperature f Sensors not compensated for pressure CONCLUSIONS f Initial tests indicate membrane does work f Membrane filter can provide a self-sustaining solution f Testing procedure adequate to benchmark prototype f Need better procedure for collecting humidity data FUTURE WORK
´ Test membrane material in multiple conditions
´ Rework data collection
´ Revise filter design
´ Site team trip in January ACKNOWLEDGEMENTS
fDr Brian Swartz, Advisor fDr. John Spurrier, Client fMr. Mabeta, Client fMark Cole, Professional Correspondent fJilean Schutz fEric Listor fChris Scheib fBarbara Ressler, Former Advisor QUESTIONS
DRYING AGENT COMPARISON CHART
Power Solution Cost Size Implementation Availability requirements Transportation Maintenance Fairly Aftercooler High Intermediate Hard Common Large Varies Minimal Mechanical Water Separator Low Small Easy Common None Simple Daily Deliquescent Not Dryer Fairly Low Large Hard Common Varies Difficult Weekly Fairly Condenser High Large Hard Common Varies Difficult Monthly Membrane Fairly Air Dryer High Small Easy Common None Easy Minimal
Desiccant Low Small Easy Common None Easy Moderate DETERMINATION OF FAILURE MODE
Temperature Humidity Altitude Dust Level
DeVilbiss specifications 50 to 96 F 50 to 90% 10,000ft Minimal
Conditions in Zambia 43 to 104F 60 to 95% 3000 to 10,000ft High
² Analysis and collaboration with DeVilbiss led us to conclude cause of failure is contamination of the sieve beds-through dust and humidity f The humidity in Macha is typically below 80% relative humidity so as long as we are able to reduce the humidity by 30% we believe we will not have problems with reduced concentrator lifetime