WATER PASTEURIZATION INDICATOR (WAPI) MAKER REDESIGN
Victor Rodriguez
B.S., California State University, Sacramento, 2008
PROJECT
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
MECHANICAL ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
FALL
2011
WATER PASTEURIZATION INDICATOR (WAPI) MAKER REDESIGN
A Project
by
Victor Rodriguez
Approved by:
__________________________________, Committee Chair
Akihiko Kumagai, Ph.D.
____________________________
Date
ii
Student: Victor Rodriguez
I certify that this student has met the requirements format contained in the University format
manual, and that this project is suitable for shelving in the Library and credit is to be awarded for
the Project.
__________________________, Department Chair
Susan Holl, Ph.D.
Department of Mechanical Engineering
iii
________________
Date
Abstract
of
WATER PASTEURIZATION INDICATOR (WAPI) MAKER REDESIGN
by
Victor Rodriguez
Currently, the Biology Department at California State University,
Sacramento is involved with the manufacturing of Water Pasteurization Indicators
(WAPIs). These indicators are use to aid developing countries with their water cleaning
process. The current manufacturing process has some disadvantages that make the
manufacturing inefficient and unsafe. For example, the current devise used to
manufacture the WAPIs is very difficult to use because it requires lots of strength to press
the ends of the tubes. This devise also gets extremely hot and is very delicate to adjust the
temperature to the required range. If temperature is too low, the polycarbonate tube
would break. If temperature is too high, the polycarbonate tubes would melt and stick to
the clamping plates. In addition, the heating system is design with parts that are not
reliable. The current design is unsafe because part of the heating coil is exposed. Having
the heating coil expose might also reduce its life expectancy. In addition, the current
design is not easy to repair or maintained. To conclude, the device needed to be redesign
to make it more user-friendly, safer, more economical, and more reliable. To solve the
old device issues, the clamping and heating mechanism was redesign to a more reliable,
iv
economical, user-friendly and safer design. The new design was tested, and showed
positive results by producing good quality WAPIs.
_______________________, Committee Chair
Akihiko Kumagai, Ph.D.
_______________________
Date
v
ACKNOWLEDGMENTS
I want to thank professor Kumagai for given me the opportunity to work on this
project. Working on this project has given me the opportunity to grow as a person and as
an engineer as well. It has been an honor to work on a highly important project, which is
going to facilitate and improve the lives of many people around the world. This project
has provided me the opportunity to learn new ways in which an engineer can assist
communities in need.
In addition, I want to thank my family for their support and for been there every
step of the way, but more importantly I want to thank God for giving me strength to
design and build this device on the time given. Furthermore, I want to thank GNB
Corporation for donating the needed resources I used to fabricate the prototype. I want to
give special thanks to Edgardo Barrera for assisting me with welding skills for this
project.
vi
TABLE OF CONTENTS
Page
Acknowledgments.....................................................................................................................vi
List of Tables ........................................................................................................................ viii
Chapter
1. INTRODUCTION …………………… ………………………………………………… 1
2. CURRENT DESIGN .......................................................................................................... 3
3. REDESIGN ........................................................................................................................ 5
4. MANUFACTURING THE NEW WAPI MAKER ........................................................... 9
5. TEST AND RESULTS .................................................................................................... 11
6. CONCLUSION ................................................................................................................ 14
Appendix A. Figures ............................................................................................................. 15
Appendix B. Drawings and Work Instructions ...................................................................... 22
Bibliography ........................................................................................................................... 66
vii
LIST OF TABLES
Tables
Page
1.
Controlling Factors and Two Level Values……….………………………......13
2.
Testing Results…………………………………….…………………………..13
viii
ix
1
Chapter 1
INTRODUCTION
Many third world countries lack the basic resources that allow them to have
drinkable water, food, clothing, medicine, etc. Today 2.5 billion people in many parts of
the world do not have access to safe drinking water. In fact, every twenty seconds a child
dies because of low levels of sanitation in food, water, etc. (UN Water). Not having
clean water can affect not only people’s health, but it can also spread diseases and create
conflicts between villages. Furthermore, engineering can be use as a way to develop and
design systems that can assist third world countries to obtain basic resources in an
economical manner. To resolve this issue, Solar Cookers International (SCI) in
Sacramento, CA. developed a reflective solar cooker called “Cookit.” This system is use
to pasteurize water in third world countries. In addition, Dale Andreatta and the
Department of Biological Science at California State University, Sacramento developed a
device called Water Pasteurization Indicator (WAPI). This device is use together with the
Cookit to check if the water is above its pasteurization temperature, so that people can
drink it (Kumagai et al.).
For this project, I will concentrate on the WAPI. The Water Pasteurization
Indicator is made of carnauba wax in a polycarbonate tube. The tube is seal at both ends
and a washer is use as a weight to set the orientation of the WAPI. A fishing string is use
for pulling the WAPI out of water. Before the water is hot, the wax is at the top of the
tube, and after the water gets hot, the wax melts down. When the wax melts down it
2
means the water is pasteurize (Kumagai et al.). Figures 1 and 2 provide an illustration of
this system.
There are other types of pasteurization indicators; however, the WAPI has been
the easiest to understand and the cheapest to manufacture. Although the manufacturing is
cheap, this one has shown room for improvement. A few safety and reliability concerns
needed to be address to make the device, used to make the WAPIs, more user-friendly.
This project illustrates how the device was redesign to eliminate the concerns and
reliability problems.
3
Chapter 2
CURRENT DESIGN
Prof. Robert Metcalf in the Department of Biological Science at California State
University, Sacramento has worked with his students and other researchers to develop
WAPI. However, a manufacturing method to produce WAPIs had to be developed so that
WAPIs are used by a large number of people in developing countries beyond a proof of
concept in a lab environment. The task to tackle this challenge of manufacturing WAPIs
was initially given to a group of mechanical engineering students at CSUS, who produced
the first manufacturing process for making WAPIs. The design tool to manufacture
WAPIs, was build fallowing specific design requirements. One of the requirements was
to make a design based on technology that can be used in third world counties. In
addition, this one had to be productive, simple, economical, easy to operate, easy to
maintenance, and safe (Kumagai et al.).
The first design consisted on a pair of aluminum plates heated by heating
electrical wires. A variable autotransformer was use to control voltage for the heating
wires. K-thermocouples with digital thermometer were use to monitor the temperatures of
the heating plate. A vise was use to create the pressing force needed for crushing the
tubes (Kumagai et al.). A more detail manufacturing process for this design is shown on
figure 10.
This design has been producing WAPIs successfully for a few years. Throughout
this time, there have been many different operators using this devise and feedback on this
4
devise has shown that there is room for improvement. Operators say the device needs to
be more user-friendly and safer. For example, the device requires lots of strength to
clamp the plastic tubes, the body gets hot, and the device is unstable. The body being
unstable and hot can crate a dangerous environment, which can injure the operator. In
addition, the device seems to have a heating wire expose, which can also be a safety
concern.
Another opportunity for improvement, pointed by the operators, was the variable
transformer voltage adjustment. The variable transformer is very unreliable when trying
to obtain the desired temperature range needed for sealing the ends of polycarbonate
tubes. When the temperature is too low, the polycarbonate tube would break, and when
the temperature is too high, the polycarbonate tubes would melt and stick to the clamping
plates. Due to this problem, many polycarbonate tubes have been scraped.
The design of the heating system is another feature pointed out as a possible
opportunity for improvement. This one is currently design with a heating coil exposed to
the air. For this reason, the devise might not last long, making the design unreliable. It
was also pointed out the device was not easy to repair or to do any maintenance. Many of
the parts used by the device, such as the heating system, are parts that need to be
specifically order from a company. As mentioned above, there are opportunities for
improvement. In order to eliminate the operator’s safety and reliability concerns, this
device will be redesign to make it more reliable, economical and easier to operate which
would make the WAPIs manufacturing more efficient and accessible.
5
Chapter 3
REDESIGN
As mentioned, the existing WAPI Maker needs improvements. The operators
have safety concerns and believe the devise can be redesign to a more user-friendly,
reliable, and economical design. In order to obtain a good understanding of the problems
the operators were facing, I decided to test the tool by making a few sets of WAPIs.
I first decided to change the clamping mechanism. During my testing, pressing
the tubes was not a simple operation, especially when the part was unstable and too hot to
handle. I decided to replace the vise with a standard 1.5-ton scissor jack. These are
commonly use in cars. This scissor jack is strong, inexpensive, user-friendly, and reliable.
In order to use it, I needed to build a frame for it. I decided to make the frame out of 3inch (1/8 inch wall) mild steel square tube. I decided to use this tube because of its
strength, weight, reliability, low cost, and less conductive shape and properties. When
designing the frame, I added a mounting base to keep the tool stable. I also decided to
add holes throughout the body of the frame to make the assembly of the devise easier. A
picture of the frame is shown on figure 2. When making the frame I decided add a base
for the transformer. This helps to keep everything together and makes it easier to move
around if needed. Drawings and work instructions for modifications to the scissor jack,
and to build the frame are shown in Appendix B.
Once the frame was ready, it was painted with high temperature paint to prevent it
from corroding. This extends the life of the frame, because mild steel was use. In
6
addition, plastic caps were use to cover the ends of the square tubes to protect the
electrical wires and connections. To operate the scissor jack, I needed a user-friendly
handle. I decided to go with a 12-inch stainless steel float rod. These are threaded at both
ends and are widely available. At the ends of the rod, I used black phenolic ball knobs.
By combining, the phenolic knob and the float rod I was able too obtain a user-friendly,
economic, and reliable handle. A picture of the handle and modified jack is shown on
figure 3.
The next feature to redesign was the heating system of the devise. As mentioned
before, the existing heating system was unreliable and had safety concerns. I decided to
replace the existing heating design with 1-1/2” strip heaters. These are widely available,
reliable, and are easy to replace if they get damage. In addition, these can reach high
temperatures in a short period with low voltage. The only problem with these strips is the
middle of the strip gets hotter than the ends. This was a problem because a constant
temperature is needed throughout the heating system to make five WAPIs at a time. To
solve this problem, I use a ¼-nch copper plate to protect the strip heating plates. The
copper helped conduct the heat of the strip heating plate throughout the five tubes. In
addition, during my testing with the old device, I notice that the WAPIs were not
consistent after pressing the ends. The ends did not have established dimensions, as a
result, these could very on thickness and length. To solve this problem, I decided to give
it a length and thickness by adding a step on one of the copper plates. This step help
indicate how much the tube needed to be pressed. The step also eliminated the problem
of applying too much force when pressing the tube at higher temperatures.
7
Another problem encounter during the testing was the short temperature range
allowed to make the WAPIs. The temperature to operate the tool successfully ranges
from 300-315° F, which is not easy to maintain with the current device. When the
temperature is too high, the tube melts and sticks to the plate, and when the temperature
is low, the tube breaks. To solve this problem, I decided to use aluminum plates to hold
the tubes, while these were pressed. The aluminum plates bolt to the body of the heating
system. The body and the copper plates conduct heat to the aluminum plates. The
aluminum holder heats the plastic tubes, while the ends of the tubes are pressed. Heating
the tubes with the aluminum plates helps form the ends of the tubes to a shape that will
not break while also allowing the device to operate successfully at a wider temperature
range (315-350°F). The aluminum plates are also use to help align the scissor jack and
the heating system. This alignment was accomplished by using dowel pins as aligning
shafts. With this heating design, I was able to obtain a more consistent and bettor quality
seal on the ends of the tubes.
To reduce cost and to make the device more reliable, I changed the thermometer
used to read the heating system’s temperature. The existing device uses k-thermocouples
with the digital thermometer Model HH12 to read the temperature. The cost for this
devise is over $100 dollars while the cost for a digital cooking thermometer, TP3001
model, is $15 dollars or less. These cooking thermometers are widely available and can
be from any brand or model as long as withstands the temperature.
As we see above, the device was redesign with the purpose to eliminate the
concerns mentioned by the operators. The new design is more economical and reliable
8
due to the changes made to the clamping and heating system. By redesigning the heating
system, the safety concerns were eliminated. The device is now more user-friendly due to
the changes made to clamping mechanism. Overall, I believe this design can be use as a
base to develop an economical mass-producing WAPI facility.
9
Chapter 4
MANUFACTURING THE NEW WAPI MAKER
Once the redesign was completed, the next step was to manufacture the tool itself.
When redesigning the WAPI Maker, specific manufacturing requirements were taken in
to account. The requirements consisted in designing the individual components to a low
complexity where simple machining techniques could be use to fabricate them. The
purpose of having these requirements was to make the device simple enough so that it
can be build by people in developing countries with little machining experience and
machining resources. To ensure the device was design in accordance with these
guidelines, I decided to machine all the components using a Bridgeport manual milling
machine. This gives me a good understanding on what complexity level the components
were design. In addition, by doing the machining, I was able to make design changes to
make the machining step simpler.
To facilitate and organize the manufacturing of the WAPI Maker itself, a bill of
materials (BOM) was created. The BOM provides a clear description on the materials and
components needed to build the WAPI Maker. It also organizes the manufacturing
process by establishing assembly layers. The assembly layers allow the fabricator to
know the next fabrication step of a component after a certain operation. In addition, the
BOM designates work instruction numbers to components that need to be fabricated.
This helps identify the work instruction number needed to fabricate the part using the
BOM.
10
As mentioned, work instructions are designated to parts that need to go through
any fabrication or modification. The work instructions provide detail information on how
to fabricate the part. These give the stock material required, drawing number, and inform
the sequence of operations needed to complete the part. In addition, these are use to give
detail information such as procedures to the fabricator. The work instruction packages are
use by the fabricator to minimize possible manufacturing errors and to standardize the
manufacturing process of the part. The BOM, drawings, and work instructions for the
WAPI Maker are shown in Appendix B. Using work instructions to manufacture the
WAPI Maker will help reduce fabrication time by allowing the parts to smoothly flow
through a shop until successfully building the device.
11
Chapter 5
TEST AND RESULTS
After manufacturing and fully assembling the WAPI Maker, the devise was ready
for testing. I decided to perform similar tests the students who made the old design
performed. This provided a good illustration on the areas that were improved by
comparing the results to the previous data. During their testing, they experimented three
control parameters; temperature of the heating plates, clamping gap, and clamping time.
These parameters affected the quality of the WAPI produced (Kumagai et al.). On the
new design, the clamping gap control variation was eliminated. The clamping gap was set
at .08 inches by the new heating system. As a result, we end up with a two process factors
and their two level values.
After analyzing the old design results, I notice the higher the temperature the
higher the quality of the WAPI. This was until facing the limit temperature. With this
observation, I assumed that extending the operational temperature of the device, but not
damaging the tubes, would increase the probability of having a good quality WAPI,
regardless of a gap variation. The theory was proven following the tests of the new
device. Table 1 shows the two controlling factors and their two level values. Table 2
shows the results which indicate how more efficient the device works with the new
features and controlling parameters.
During the testing, the time the device took to get to the desired temperature was
nine minutes. After recording the time, the testing begun with the high temperature and
ten seconds clamping. All WAPIs were tested under hot water to ensure these were
12
operational. By reviewing the results, we see the device can successfully operate at a
range of 315-350 °F and with a clamping time that can be as low as ten seconds. Other
parameters were also tested to find out about the limits on temperature and clamping
time. Temperatures over 360° F would start damaging the material and a bad quality end
would form. Temperatures, below 300°F would not always seal and it would take more
clamping time to make it work. The clamping time of five seconds was good for
temperatures above 335° F. Below this temperature it did not always worked. The best
results were obtained at the 320-335° F range and a ten-second clamping time. With
these parameters, the WAPIs looked and wok the best.
13
Table 1) Controlling Factors and Two Level Values
Time to heat up to 300 F =
9 min
Table 1: Controlling Factors and Two Level Values
Middle Level
High Level
Factor A (Temperature)
315-330 F (A1) 335-350 F (A2)
Factor B (Clamping time)
10 sec (B1)
15 sec (B2)
Table 2) Testing Results
Table 2: Testing Results
Combination
Pass
Total
A1B2
9
10
A1B3
10
10
A2B2
10
10
A2B3
10
10
Totals
39
40
Percentage
90%
100%
100%
100%
98%
14
Chapter 6
CONCLUSION
To conclude, we can say the new improved design met the desired goal. The
devise was redesign following the given design specifications. The goal of eliminating
the operator’s safety and reliability concerns was reached by redesigning the heating
system. The new heating system produces consistent WAPIs and allows the device to
operate at a wider temperature range, which makes the devise easier to operate and
reduces the probability of error. The clamping system was also redesign. This helped the
device to be more compact and user-friendly. With this project, the old design was
improved by eliminating many of the operators concerns, but this is the first step to
eventually build a device or a manufacturing process that can be use to mass produce
WAPIs on a economical manner in third world countries. To be able to reach this goal, it
is necessary continuously improving this devise.
15
APPENDIX A
Figures
16
Figure 1) WAPI description figure
17
Figure 2) Frame
Figure 3) Modified Scissor Jack
18
Figure 4) Assembly Picture 1
Figure 5) Assembly Picture 2
19
Figure 6) Assembly Picture 3
Figure 7) Assembly Picture 4
20
Figure 8) Final Assembly
21
Figure 9) Cookit by solar Cookers International (SCI)
Figure 10) Old WAPI Maker
22
APPENDIX B
Drawings and Work Instructions
23
BILL OF MATERIALS (BOM)
24
25
LABOR HOURS SUMMARY
26
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BIBLIOGRAPHY
UN Water, Statistics Graphs and Maps: Drinking Water and Sanitation, 16 Nov. 2011,
<http://www.unwater.org/statistics_san.html>
Solar Cookers International, Water Pasteurization Indicator, 16 Nov. 2011,
<http://solarcooking.wikia.com/wiki/Water_Pasteurization_Indicator>
Kumagai, Akihiko, Tien I. Liu, Minhaj Khan, Scott Yu, Brian Wargala, Anthony Littke,
Robert Jhonson, Jeff Bear, “Manufacturing Methods For Producing Water
Pasteurization Indicators (WAPI).” ASME Mechanical Engineeirng Congress &
Exposition Nov. 5-10 2006.