Enhancement to the ET-35N Oil Content Monitor: A Model Based on Mie Scattering Theory.

Abstract : A theoretical model to calculate the turbidity of oil-in-water emulsions formed in the Navy's ET-35N Oil Content Monitor (OCM) has been developed. The model predicts that the turbidity measurements of the ET-35N will be dependent on the oil droplet size, the wavelength of the light used to illuminate the sample, and on the angle at which the light is scattered. It also shows that the turbidity is a linear function of oil concentration from 0 to 15 ppm but that the slope of the turbidity concentration curve is oil droplet diameter dependent. The model also predicts that the turbidity decreases drnmatically for oil droplets less than 0.2 micron in size implying that the ET-35N is not very sensitive to oil-in-water emulsions containing droplets of this diameter or less. The model suggests modifications to the ET-35N which should increase its sensitivity by a factor of three and a modification that will reduce the turbidity's dependence on the diameter of the oil droplets being analyzed thus improving the accuracy of the turbidity measurements.