CPI / TPI Corrugated Plate Interceptor

Corrugated Plate Interceptors (CPI) and Tilted Plate Interceptors (TPI) are gravity-based, plate-assisted oil-water separation systems that achieve significantly finer oil droplet removal than conventional API separators. By incorporating angled plate packs within the separation vessel, these units multiply the effective settling area while maintaining a compact footprint — enabling higher throughput capacity or finer separation in a smaller space than a plain open-channel API separator.

The inclined plates — typically positioned at 45 to 60 degrees to the horizontal — create a short settling distance for oil droplets and a large effective coalescing surface. As oily wastewater flows through the plate pack, oil droplets contact the inclined surfaces, coalesce into larger droplets, and rise along the underside of the plates to be collected at the surface. Settled solids slide down the plate surfaces to the tank sump for periodic removal.

A single-stage TPI or CPI removes free oil globules of 50 microns and larger, while a two-stage configuration achieves removal of droplets down to 20 microns — approaching the performance of dissolved air flotation without chemical addition or aeration energy. After installation, these units operate entirely on gravity with no power consumption, making them an exceptionally low-cost secondary oil removal stage downstream of an API separator.