Summer 2010 CDC Detailed Task List

I. Validation Test I - Precision (1-2 weeks)

Test precision of orifice. Will drilling technique play a roll in dosing reliability? Will Korifice change with different materials, or for that matter, different drilling techniques? Determine the precision of our manufacturing process by running a series of tests as outlined:

Procedural Outline:

• Test 3 different sized orifices, selecting a representative low, mid and high diameter. Although the upper and lower diameter will be dictated by drill bit size and float valve size, the actual sizes selected will be arbitrarily. We are testing manufacturing precision
• Push-connect caps manufactured by Legris, made of polyamide will be used for these tests.
• For each of the three sizes, 5 caps will be drilled. Each of the five caps in each group will be labeled with their size and a letter designation
• Each cap will be tested on the prototype chemical doser. The lever arm and float will not be used but instead a simple linear bar with specific h-values marked. Each cap will be tested throughout the range of 0 - 40 cm. The first 4 cm will be in 1 cm increments and afterwards in 4 cm increments.
• Each cap will be tested through this 0-40 cm range in a random -fashion to better replicate possible field operation.
• Each cap will be tested 5 times through the 0-40 cm range as described above so that we may gain confidence in our data. The orifice tube will be unclipped between each test set to better replicate real world operations and see if error of any significance could be originating from our method of attachment.
• All tests will be run with water.
• Results will be logged on an Excel spreadsheet. This spreadsheet has been set up to calculate standard deviation and confidence intervals. A standard error exceeding 5% will be considered cause for alarm and demonstrate the need to further evaluate our manufacturing technique.

II. Validation Test II - Accuracy (1 week)

Comparing the data collected from precision testing, make a judgment based claim using calculated Q values. An outline of the testing method is shown below:

Procedural Outline

• No additional data need be collected for this experiment, this is only data processing
• Using average flow values from Validation Test I, compare calculated values of flow for each orifice size.
• Graph data over range of delta h 0 - 40 cm, with possible sub graphs showing problem areas.
• It is expected that errors resulting from surface tension will be demonstrated here.
• Additionally, our manufacturing technique may create a Vena Contracta Coefficient, Kvc, that differs from .62. Develop a new Kvc if proven necessary.

III. Validation Test III - Surface Tension

•Validation Test II will show inaccuracies in the low range that we attribute to surface tension. The current solution to this problem is to add yet another scale and orifice to the system. Evaluate whether or not this is the best solution.
•Understand and accommodate surface tension issue. Is the triple scale the solution? Is there are simpler solution available? Perform literature survey of alum and chlorine to see if these fluids would have a different effect.

IV. Validation Test IV - Clogging

•At this point, we will postpone clogging experiments. I have discussed this issue with the engineers in Honduras and it appears this problem has been reduced with the addition of a sedimentation tap. Additional clogging results from precipitant forming along the walls of the tubes, which builds up until a small piece breaks off and leads to clogging. They will be playing with a preventative maintenance program that may improve or eliminate this problem.

V. Validation Test V - Moment Errors

•The above experiments will be performed without using the float and lever arm. This will allow us to keep any possible errors isolated. The sixth validation test will be done using the lever arm and float to ensure that no other errors are incorporated into the chemical doser. Use aquarium to simulate water level changes in entrance tank. Compare readings with those from previous Validation Test I and from calculated values
•Analyze any possible error caused by moving the slider to higher or lower concentrations. This movement shifts the moment around the pivot point and effects dosing

VI. Research Items - Materials

•Convert as practically as possible to locally available materials
•Eliminate components that have small pieces that can easily be lost (i.e. no more compression fittings)
•Convert to materials that are suitable for both alum and chlorine dosing
•What can't be obtained locally to be made of high quality, reliable components that will reduce down time / lead time resulting from component failure
•Modify administering tube so that a positive visual indication of flow can be seen

Material Selection Process:

Survey peer-reviewed articles or manufacturer data sheets of the materials listed below to determine their suitability for use with alum and chlorine. Please note that although Wikipedia is a great source for initial information gathering, it is generally not considered peer-reviewed.
Components:
• PVC and CPVC
• Acetal
• Polypropylene
• Polyamide (Legris)
• PVDF (Kynar)
Piping / Tubing:
• PVC rigid piping
• PVC soft flex tubing
• Vinyl tubing
• Pex tubing

Materials suitable for our application will then be analyzed for cost and ease of availability. We will not be able to readily determine which materials are available in Honduras but we do have two people in Honduras who can suss- out materials for us. In addition to material selection, we will discuss different fitting styles and select the most appropriate:
• Barbed
• Compression
• Quick-Connect

Once material and component selection is made, we will create a standardized material list for installation of the chemical doser.

Future Objectives (Fall 2010 and beyond):

• Automate selection of orifice and design of scale. From a given plant flow rate, we should be able to produce the two (or three) orifice sizes and the two (or three) scales.
• Incorporate rotometers in design between stock tank and constant head tank to allow quick and accurate visual indication of dosages. Determine the effect on the location of the stock tanks. Note that this will require the stock tanks to be elevated to accommodate head loss in the rotometers.
• Generate a parts list of all components. Work with engineers in Honduras to determine which components need to be compromised to allow local material access.
• Work with the design team to create a float valve database of the Kerick valves that we will use for larger plants. Also, find different fittings for valve so that we are using a barbed connection instead of compression Create the design algorithm that will choose the correct float valve
• Create a poster and presentation to display P3 competition and award
• A second acrylic model plant needs to be constructed. Also modifications need to be made to the first one: a larger manifold in the bottom of the sed. tank.