Finding Attenuation Factor
Introduction
Until recently, the float valves used in the AguaClara's flow controllers were slightly flawed. The float valve connector included a compression nut, which was easily misplaced or misused, leading to leaks. A new float valve would preferably have pipe threads and be able to connect to a quick connect tube fitting. Furthermore, the float on the float valve was replaced in favor of another float, complicating post manufacturing assembly. A new float valve was found with pipe threads, quick connect tube fitting and had a more appropriate valve attached. However, before the new float valve was to be implemented, a study on the attenuation factor (change in pressure from stock tank over the change in pressure in the constant head tank) was to be conducted.
Procedure
We followed the procedure for finding attenuation factor found on the Flow Controller Theory page.
Results
The attenuation factors we found correspond to the slopes of our trials on the graph, therefore the average attenuation factor we found for the new float valve is 585.4.
The set up consisted of a stock tank of water, a peristaltic pump, a constant head tank (using the desired float valve), a 200 kPa sensor and a 7 kPa sensor. The change in the stock tank was controlled by the peristaltic pump, which pumped water through the float valve. The 200 kPa sensor was attached to the inlet at the float valve and the 7 kPa sensor was attached to the outlet (either open or not open).
Results
Valve | Outflow | Average Attenuation Factor |
|---|---|---|
New | No | 123.99 |
New | Yes | 397.865 |
Old | No | 242.7 |
Old | Yes | 712.16 |
Conclusion
The attenuation factor of the new floats are not as large as the attenuation factor of the old floats, which were approximately 900, but should still be sufficient for our usesfloat valve with an outflow is low and leads to an error of approximately 2.5 mm. This is an acceptable error for use in Honduras, however a valve with a greater surface area would be preferred.