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SKIMMERS
A.
GENERAL
After the oil is contained, it must be recovered from the water. Depending on the circumstances, three different approaches might be used: Use of mechanical skimmers; Use of sorbents; or Use of manual labor. A skimmer is a mechanical recovery device designed to remove the oil from the water's surface without causing major alterations in its physical or chemical properties. All skimmers work best in calm waters with little or no wave action. The two major categories of skimmers are: Suction Skimmers and Adhesion Skimmers. Viscosity of the spilled oil determines the most appropriate skimmer and pump types for a particular incident. Viscosity is the measure of a fluid's internal friction or its resistance to flow; a fluid's surface tension. Lower viscosity substances are lighter and when spilled spread out over a greater area. Higher viscosity oils do not spread out as much and remain thicker. A weir skimmer is an example of a suction skimmer. A rope mop skimmer is an example of an adhesion skimmer. Viscosity of the oil being recovered is a major determinant of skimmer effectiveness. Most skimmers have a range of viscosities in which they work best:
B. TYPES OF SKIMMERS
There are basically five different types of skimmers: The Weir Skimmer: This type of skimmer utilizes an adjustable dam (weir) to take a cut of the oil on the water's surface. The oil flows over the top of the weir and into the skimmer where it collects. The recovered oil/water mixture is then either pumped or sucked from the skimmer. The GT-185 Skimmer shown below and the Desmi Ocean Skimmer shown deployed from a vessel are examples of weir skimmers.
GT-185
Skimmer A
special type of weir skimmer is the weir-boom skimmer in which
weirs are built into the floating boom. Oil enters the weirs and
is pumped from the weirs via an oil tube to recovery tanks The Suction Skimmer: Suction skimmers are similar to weir skimmers. Like weir skimmers they float on the water but use an external vaccum pump system and are adjusted to float at the oil/water interface. Sometimes the skimmer simply consists of a simple suction head attached to the end of a vacuum hose. To view a drawing of a Vacuum System click here. You can also view a picture of a vacuum truck.
Suction
Skimmer The Centrifugal Skimmer This
type of skimmer is also called a weir-vortex skimmer. It operates
by the creation of a water vortex or whirlpool, which draws the
oil into a collection area where it is then pumped out. The Walosep W-4 Skimmer is an example of this type. Submersion Skimmers Submersion skimmers are usually mounted on or incorporated in a powered vessel. Oil in the path of the skimmer is forced beneath the water surface by a moving inclined belt. The belt forces the oil down toward the mouth of a collection well where it rises to the surface. Water collected with the oil passes under the collection well. The JBF (DIP) Dynamic Inclined Plane skimmer is a submersion belt skimmer. The skimmer's belt is not oleophilic and does not rely on oil sticking to the belt for recovery. The system is based totally on the hydrodynamic of oil and water. JBF's home page has complete information about the DIP. Sorbent Surface Skimmers This type of skimmer has a surface to which oil adheres. The sorbent (or oleophilic) surface can be in the form of a drum, disc, belt, or rope which is continuously moved through the oil film. The collected oil is removed from the sorbent surface by a wiper or roller and is then held in a storage tank.
Illustrations of some Sorbent Surface Skimmers View a file drawing of the WP-1 helical drum skimmer
How a Drum Brush skimmer works
How a Rotating Disc skimmer works View a file drawing of a Disc Skimmer.
View a file drawing of a Sorbent Lifting Belt skimmer
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