When many kinds of petroleum products of various companies aresent serially through a pipe, the most serious problem is contamination.
In order to reduce the amount of contamination two methods are used; one is a turbulent flow, the other is to use a mechanical separator like a sphere.
Where the method of “a turbulent flow” is used contamination is caused by axial mixing which may be considered as a diffusion mechanism governed by Fick's Law. On the other hand, where the method of “using a sphere” is used, contamination is caused by the “flow back” across a sphere.
The amount of the “flow back” must be about 0.02-0.04 percent of the total volume displaced.
According to the above assumption, this report presents the amount of contamination which is expected to occur in real pipelines, comparison of the two methods, the relation between the final amount of contamination and the number of spheres, their spacing and initial contamination which has occurred at a starting station.