Performance Tests of Off-The-Shelf Oil Skimmers

Abstract

ABSTRACT Five advancing-type commercially available oil skimmers were tested at the EPA's OHMSETT facility. Four were found to be low speed devices, with very low thruput efficiency at speeds greater than 1.25 kt to 1.5 kt. One device, the Cyclonet, recovered oil best at speeds of 4 kt to 6 kt. Typical oil recovery rates were 10 gpm to 20 gpm. Improvements in the design, use, and testing procedures for these types of skimmers are suggested. INTRODUCTION During July 1975 the U. S. Coast Guard Office-of Research and Development sponsored tests of five off-the-shelf oil- recovery devices at the EPA's OHMSETT facility. The tests had four objectives:to develop a standard test procedure for testing oil recovery devices,to familiarize Coast Guard Strike Teams with the devices tested,to assist in the evaluation of these skimmers for purchase as operational equipment, andto evaluate these skimmers for use in fast currents. The oil skimmers tested are considered representative not only of each manufacturer's products but of different generic types of skimmers. Interpretation of the test results, then, enables one to evaluate each particular device, to consider design advantages or disadvantages (or possible improvements) of each type, and to criticize and improve the test procedures. A complete evaluation of a device must involve additional considerations besides oil recovery performance. Testing the full scale, prototype devices in a large-tank such as OHMSETT also allows a qualitative evaluation of practical problems encountered when using a skimmer, such as set-up time, ease of operating, demobilization and cleaning problems, and support equipment, manpower, storage, and maintenance requirements. A comprehensive report with test details will be released soon by the Coast Guard and will be available through NTIS. TEST PROCEDURE AND RATIONALE The test plan was basically the same for each device, with oil distribution rate, tow speed, etc. adjusted to suitable values. Each plan began with an investigation of the effects of speed on performance and determination of the "optimum speed" followed by investigation of the effects of encounter rate, waves, and oil type. In each test an attempt was made to achieve "steady state" conditions, defined as the average operating conditions during several hours of continuous skimming. In general this meant establishing a stable slick in front of the device and filling basins, sumps, pumps, and hoses with fluid recovered under such conditions. Three measures of-performance were of general concern: (oil) recovery rate; recovery efficiency, defined as that percent of the recovered fluid which is oil; and thruput efficiency, defined as that percent of the oil encountered which is recovered. A lube oil and ½ fuel oil were selected for testing. The oils were reused repeatedly during the four week test period with gravity separation of the water between uses. The following were the average properties over the period:(Available in full paper)