March 12, 2009
Design Lab Presentation
Update on Status of the Solar Autoclave and Sterilization Indicator
On February 13th the new design team currently working on the solar autoclave system presented the status of the project to their sponsors. Among the attendees of the presentation were Executive Director Lori Hanna, myself (Director of Product Research, Daniel Hensel), longtime sponsor Dr. Margaret Pinnell, and the ETHOS field team accompanying me to Sabana Grande, Nicaragua this summer. The presentation provided a brief overview of the project, the status of what they are working on now, and their plans for the immediate future. The members of the design team, those who presented, are Staci Grey, Christopher McGuinness, Ryan Smolik, Corey Vossler and Kyle Zeller.
To begin with, Lori and I were impressed with how obvious it was that the design team had carefully read through our own team’s work the previous semester. They are carefully and constructively criticizing our work and finding ways to improve the product wherever possible. The design team has essentially split up into three teams: two working on testing and modifying the pressure vessel, two finalizing the sterilization indicator design, and one looking at improving the system as a whole including the solar box cooker.
The students working on the solar autoclave pressure vessel reported that they had repeated the pressure tests performed by our previous team. They noted that they had a similar problem as we did with hydraulic fluid leaking through an end cap, as well as showed that the butyl rubber seal broke at 10psi, ending the testing. After testing, the team reported noticeable deformation in the bottom of the coffee can used as the cylindrical pressure vessel. They plan to improve the seal of the solar autoclave pressure vessel, use aluminum end caps instead of wood, paint the can with the black paint that is already used in Sabana Grande, and use lock nuts on one stationary end of the pressure vessel to reduce handling and hassle.
The work on the sterilization indicator has produced a nifty hourglass design that utilizes Polywax 2000 to show whether or not the proper sterilizing conditions have been maintained, and thus whether or not the instruments are sterile. US Sterilization standards dictate that, to reach sterilization, 121 degrees Celsius (250 degrees Fahrenheit) and 15psi must be held for 15 minutes. Therefore, the design team has devised an hourglass device that will contain an appropriate amount of wax such that when all the wax heats up, turns to a liquid and falls to the bottom chamber, the time and temperature have been reached. The team is working on mass balancing the design to determine the size and amount of wax needed, then testing can begin.
The team is on task and plan to order the materials needed for the final design and conduct testing, as well as manufacture the final sterilization indicator design. Lori and I reminded them that it is pertinent that we have a final working design by the end of this semester that I may take to Nicaragua with me for final testing and production rollout. I am urging them to try testing with water as well as to come up with a plan for testing that I may use while in Sabana Grande.
The design team will present again at their 2nd oral presentation Friday, March 13th at 8am. They will provide us with more updates and their plans for the remainder of the semester, and another update will be provided here on saluddelsol.org. Until next time!
La Paz y Salud,
Daniel J. Hensel
Director of Product Research
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