The first form of a plate coalescer was the parallel plate interceptor (PPI). This involved installing a series of plates parallel to the longitudinal axis of an API separator (a horizontal rectangular cross section skimmer) as shown in Figure 7-5. The plates form a “V” when viewed along the axis of flow so that the oil sheet migrates up the underside of the coalescing plate and to the sides. Sediments migrate towards the middle and down to the bottom of the separator, where they are removed.
