APHA COLOR MONITORING

INTRODUCTION

The detection of color changes in a liquid process stream is often a good indication of other process parameters that might affect the intermediate or final product. Some of these parameters may include overheating, dilution ratios, distillate carryover, blending, interface detection, etc.

APPLICATION

There is a need in many processes to immediately detect color changes in a liquid. These changes may be due to color addition, color removal or unwanted discoloration. Changes in color can be an indication of a decrease in process efficiency, heat exchanger leakage, overheating, upsets in distillation splits, inefficiencies in decolorization filters, etc. The detection of color changes has historically been done in the laboratory using human vision or the spectrophotometer. Visual comparisons of a liquid sample are made against standards established by each company or by APHA (American Public Health Association). Like all visual color tests, APHA color is limited by human subjectivity. This limitation is more pronounced in applications where the color changes are barely visible to the human eye, such as dark oils or apparent colorless fluids. When the spectrophotometer is used to detect color changes, it is often found that the color changes are naturally occurring yellows and browns and thus do not have a specific wavelength associated with their presence. Since broad band measurements are too time consuming to perform in an industrial environment, usually a single “optimum” wavelength is chosen for measurement. Attempting to correlate the results to AHPA is usually unsatisfactory.

SOLUTION

Monitek provides a broadband wavelength instrument that can be installed in-line to continuously detect color changes in the liquid stream. Both the low color and medium to high color models provide high sensitivity and repeatability.

ADDITIONAL COMMENTS

The Monitek unit can also be correlated to other standard color units such as ASTM and Saybolt. APPLICATIONS: Some standard applications include: sugar color, potable water color, heat exchanger leak detector, overhead streams off distillation columns, polymer discolorants, vegetable oil color, pipeline interface detector.

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