EVALUATION OF OLEOPHILIC SKIMMER PERFORMANCE IN DIMINISHING OIL SLICK THICKNESSES

Abstract

ABSTRACT 2017-086 ASTM F2709-15 “Standard Test Method for Determining a Measured Nameplate Recovery Rate of Stationary Oil Skimmer Systems” has become the standard for testing the performance of stationary skimmers. This standard specifies testing the skimmer in “ideal conditions” in order to measure a skimming system’s maximum performance. These ideal conditions are created by testing the skimmer in calm conditions and allowing the skimmer to recover either in pure oil or in a thick layer of oil on water. When testing the skimmer in oil and water, the skimmer recovers oil in a starting oil thickness of 75mm and continues recovery until the oil thickness reaches 50mm. Performance values obtained from this test include measured nameplate recovery rate (NRR) which is the maximum rate at which the skimmer system can recover and process oil under ideal conditions, and the recovery efficiency (RE) which is the percentage of oil collected to total fluid collected. In actual oil spills it cannot be assumed that a skimmer will encounter enough oil to continuously conduct recovery operations in 50–75mm of oil. As these performance values are becoming a tool used by regulators to verify the capabilities of response equipment listed in oil spill response contingency plans, it is important to understand if and how a skimmer’s performance will vary as oil slick thickness changes. To explore this question, the Bureau of Safety and Environmental Enforcement (BSEE) and Ohmsett - The National Oil Spill Response Research and Renewable Energy Test Facility, recently conducted independent performance testing of two oleophilic skimming systems to better understand the relationship between oil recovery rate, recovery efficiency, and different oil slick thicknesses. Skimmers were tested in various oil slick thicknesses ranging from 75mm down to 6mm at the Ohmsett facility. Skimmers were tested in a type I refined test oil as defined by the ASTM F631-15 “Standard Guide for Collecting Skimmer Performance Data in Controlled Environments.” Testing results suggest that reduced oil thicknesses do indeed have a significant impact on the measured recovery capabilities of a skimmer. This paper outlines the final testing results, and discusses the potential implications of using ASTM F2709-15 performance values in conjunction with various oil spill response planning standards for mechanical oil recovery equipment.