Flow Control Module

Linearization and Calibration

Introduction

Presently, the flow control module is being utilized to create a constant head tank, where the water level in a tank remains constant, being refilled by a stock tank. This constant head tank is the measuring point for the head loss which governs the flow rate of Alum into the plant. However when implemented in the field, it has become increasingly apparent that there are one or more, possibly yet unidentified, confounding variables that are rendering our equations inaccurate, causing for miss-dosing in the plant, reducing efficiency and at times creating wasteful and dangerous situations for the communities.

Specifically, in tests that have been conducted in Honduras and the United States, flow rates at greater head losses are expirimentally producing lower flow rates that those calculated, indidcating that the flow control module is not functioning linearly. This section of the Flow Control Module Team is conducting tests to identify confounding variables to more accurately render the equations to provide for more efficient flocculation in the plant.

Goals

This project section is attempting to resolve the mystery of where inconsistencies arise that cause deviations from the standardized equations that relate head loss and flow rates which are used to dose the flow of the water treatment plant. There are a few variables that we hope to test. First we need to assure our selves that the flow control module is actually operating within the laminar flow range, rather than prematurely transitioning to the turbulent flow range. After this, we will look into the affect of tube length on the flow, as well as evaluating the possible affect that the length of the tube in question has on the dosing flow that is being modeled. After this, the question of additional sources of head loss will be considered, the possiblity of manufacturing in acuracies or possible the inclusion of constants based on the mechanism. Lastly, we will look into the possiblity that highly concentrated solutions of alum are causing unintending consequences that need to be factored in.

Linearization and Calibration team goals and meeting minutes.

Methods and Results from Specific Experiments

Float valve corrosion test

• A simple test where float valve parts were left in alum and chlorine for extended periods of time to determine corrosion effects

Flow controller body design and selection

• Includes notes on the brainstorming that went into FCM parts selection and design

Flow versus head loss data collection in the turbulent range

• Experiments were conducted to establish a model for the relationship between FCM outflow and headloss associated with outflow tube position

Determining the maximum inlet shut-off pressure

• The maximum inlet pressure that the float valve can shut off was investigated in order to determine how much head there can be between the chemical stock tanks and the flow controllers

Fall 2007 Final Report

• Background on previous research

Conclusions

Based on the research that has been done, it may be concluded that the flow control module is prematurely transitioning into turbulent flow, causing inaccuracies in the calculated flows. We hope to continue testing, modifying different variables to find the source of the inaccuracy.