U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-060• Specific recovery systems found in the Navy’s inventory.• Oil recovery equipment in the ESSM System.In situ burning, dispersing, bioremediation and other viable means of oil control and removal arediscussed in Chapter 6. NOSC contingency plans address alternative abatement methods and listthe primary skimmers available to salvors.5-2 OIL RECOVERY SYSTEMS AND PRINCIPLESRecovery devices vary widely in size and the principles employed to remove oil from the water.In general, oil recovery devices can be grouped in five basic groups:• Mechanical devices using oleophilic materials (belts, ropes, drums, disks or brushes).• Suction devices.• Induction devices (weirs and inclined planes).• Oleophilic materials (sorbents) placed on the water surface or oil-fouled shore andrecovered by manual or mechanical means.• Devices using other principles (nets, screw pumps, vortex skimmers, mechanical grabs,manual recovery).Recovery systems that remove oil from the water surface in an essentially continuous process arecalled skimmers. Skimmers may be built into self-propelled or towed vessels or configured asportable equipment to be operated from shore, pier or vessel of opportunity.Some skimmer systems have semirigid short boom sweeps attached to the side of the skimmercraft and supported by outriggers or kept taut by towboats and span wires. The boom directs theoil flow into the skimmer mouth or vessel side openings for pick up by belt, disc, bristles ordecanting recovery systems.Recovery rate is generally taken as the rate at which the oil-water mixture is recovered by thedevice or system, regardless of the relative oil and water proportions. Recovery efficiency is theratio of oil to water in the recovered oil-water mixture.Recovery efficiency depends on oil viscosity, water and air temperature, sea and wave conditions,the degree of oil weathering and operator skill. Many mechanical recovery systems do not operatewell through the entire range of environmental conditions. This is especially true of weir systemsoperating in heavy weather; too much mixing at the oil-water interface reduces recovery efficiency.The range of oil properties and sea conditions in which a skimmer operates effectively iscommonly called the skimmer’s recovery window.5-2