API separator is a generic term used to refer to the gravity-type rectangular channeled oil-water separator that is designed based on “API421 guidelines for design and operation of oil-water separators”. K-pack follows the first edition published in February 1990. This OWS [Oil-water separator] is designed for the separation of free-floating oil globules from the waste-water stream. The design is relayed on the density difference between oil globules to that of effluent water and is defined by ‘Stokes’s Law’ and is applied to the laminar flow condition.
Oil globule sizes of 150 microns and above are removed with closer to 90% design efficiency. When designed using API421 design criteria, the API channel leads to oil globule coalescing and rises due to buoyant forces to form an oil layer on top of the API channel. This layer is then scrapped off using a chain skimmer mechanism which also runs down to scrape off the heavier sludge which is collected at the bottom of the API separator.
Applications: The design is majorly used in refinery applications where a shock load of oil is expected which needs a larger area of separation. Also, the design is limited to the removal of free-floating oil of 150 microns and above only.
