Zeyu Yao's Individual Contribution Page

Spring '14 Contributions

I worked on the design team this semester, and our team's focus was on Chemical Dose Controller modifications

Stock Tank function

In order to simplify the stock solution mixing process, a function was created to solve for the stock tank volume and water depth or "fill line" iteratively. The inputs for the function are the coagulant stock tank flow rate, the time between refills, and the supplier chemical tank volume, and the outputs are the stock tank volume and the number of coagulant bags to be added. It was written in a way that the dose selected by the CDC algorithm can continue to be used, and the dimensions of the tank can be calculated using existing functions. It also allows for more accurate stock concentration since the plan operator is no longer required to weigh the proper amount of coagulant in order to achieve the set concentration. 

Dosing components redundancy and entrance tank height adjustment

While the existing dosing tube function was written to generate an extra dosing tube when there is only one dosing tube designed, the goal this semester was to modify the code so that an extra dosing tube would be generated at all times, and the manifold code was modified to match the changes to the dosing tubes. Since the added redundancy presented a problem with the fitting of the manifold system on the entrance tank wall when the plant flow rate is below 35 L/s, a temporary solution was to raise the height of the entrance tank wall by 0.4m. While the added height would not hinder maintenance as the raised wall height would be about the same as that of a 60 L/s plant, we recommended the future team to seek a solution that doesn't require an increase in construction costs.

Flexible Tubing Function

Another task that I focused on towards the end of the semester was the error checking and updating of the FlexTubeF, which was used to draw the flexible tubing in order to better represent the CDC system. An initial attempt of using the existing FlexTubeF resulted in an irregular shaped polyline that didn't represent at all a flexible tubing. Since I noticed that it was the sweep function that was failing each time I tested the FlexTubeF and FlexCylinderF, I found out that the names of the inlet and outlet points were the origin of the errors. I tried to shorten the names but still abide by the AguaClara naming conventions, however the flexible tubing failed to be drawn each time unless I changed the names to simple words such as "Inlet1" and "Outlet1". I recommend future teams to further investigate to find out the source of this error. Another error that I discovered was with the "mirror" function embedded in the FlexCylinderF, which was generating a mirror image of the tubing at its correct position while keeping the one originally drawn. The "mirror" function was fixed so that the tubing could be reversed to the correct direction after it was drawn. I also noticed that there was an discrepancy in the inner and outer tube curvatures of the tubing, but future teams would need to discover whether this was due to errors in the calculation of points of parabola or mirroring of the image.

Lever arm modification

The CDC team laster semester started to work on the design of a single lever, and we would like to reflect the changes in the CDC drawings. I asked the CDC team this semester to explain to us their design and provide us the design drawings. Since there will be four type of lever arms: double full sized, double half sized, single full sized and single half sized, in order to accommodate the demand of the plant, I think the best way to incorporate the changes is to create a function that can help easily switch among the four types of design. 

Fall '13 Contributions

Chlorinator packaging for India

Prepared a setup manual for local personnel who are not familiar with chemical dose controller to aid the system assembling process. I also started to prepare a packaging spreadsheet because a large of the components need to be pre-assembled in lab since they cannot be locally sourced as well as easily assembled. This spreadsheet will be complete once Mathcad codes are embedded. 

Improving CDC design

Calculated using Mathcad the number and length of dosing tube for a low flow plant (plant flow rate = 2.4 L/s), and modified the manifold design based on the calculations. Changes I made to the setup include cutting the manifold to only two pairs, and eliminating or shortening unnecessary tubings and pipes. I also tested drop tube calibration and found that a ball valve can be attached so solution volume can be directly measured in drop tube. The added weight of ball valve may offset the balance of lever arm, but errors are negligible.

Researched on different types of constant head tank to replace the one that is not chlorine resistant. I found a Nalgene bottle and cap made of chlorine resistant materials, and also a chlorine resistant bottle with a regular cap with Teflon cap liner added. 

Designed a single lever for dosing one chemical, and made Sketchup drawings for the lever arm and drop tube group.