About Oil Skimming:

• Oil and Water Don't Mix
• Oil Skimming
• Typical Applications for Industrial Oil Skimmers
• Choosing An Appropriate Skimmer
• Different Types of Oil Skimmers
• Specifying an Abanaki Skimmer
• Optional Equipment

Oil Skimming Facts Tutorial Handbook It is the industry's most complete handbook on how to select and size an oil skimmer for your application. This handbook contains information on all aspects of oil skimmer application. Request this handbook now in PDF format for printing

The relationship between oil and water in a mixture is well-known and governed by two physical properties:

Specific Gravity: Most hydrocarbons have a lower specific gravity than water. Without agitation, oil separates from the water and floats to the surface. These oils are known as LNAPL's, Light Non-Aqueous Phase Liquid. Oils (and other compounds) that sink in water have a higher specific gravity and are known as DNAPL's, Dense Non-AqueousPhase Liquid.

Surface Tension and Affinity: Normally, oil bonds more tightly to itself and other materials than to water. This affinity, and differences in surface tension between oil and water, cause oils to adhere to a skimming medium.

Oil Skimming	Back to Top
Although designs vary, all oil skimmers rely on specific gravity, surface tension and a moving medium to remove floating oil from a fluid's surface. Floating or sinking oil and grease cling to skimming media more readily than water, and water has little affinity for the media. This allows skimming media in the shape of a belt, disk, drum, etc. to pass through a fluid surface to pick up oil and grease with very little water. This oily material is subsequently removed from the media with wiper blades or pinch rollers. Oil skimmers are simple, dependable and effective tools for removing oil, grease and other hydrocarbons from water. Often, a skimmer by itself can achieve the desired level of water purity. In more demanding situations, skimming is a cost-effective means of removing most of the oil before using more complicated and costly treatments such as coalescers, membrane filters and chemical processes. Grease skimming involves higher viscosity hydrocarbons. Skimmers must be equipped with heaters powerful enough to keep grease fluid for discharge. The patented Abanaki Grease Grabber® is fitted with heating elements to handle these applications. If the floating grease has formed into solid clumps or mats, a spray bar, aerator or mechanical apparatus can be used to break up grease mats and facilitate removal.
	Abanaki Grease Grabber

Wastewater Sumps Most manufacturing or processing facilities have circulating water systems. This water collects in a central tank or sump. Removing floating hydrocarbon contamination with little water content can reduce the cost of disposal and lower the contingent liabilities of wastewater discharge.
Coolants and Cutting Fluids When machine coolants become contaminated with tramp oils, three things usually occur: 1) coolant life is reduced 2) quality of machined parts is reduced 3) in many cases, smoke will begin to appear in the shop, causing irritation to workers on the job 4) the fluid takes on a "rotten egg" odor Skimmers that remove tramp oils solve these problems and typically pay for themselves within a few months.
Heat Treating Quench oils that must be removed from heat treated parts can be captured for re-use or disposal. The results are lower quench oil costs, prolonged wash water life and lower disposal costs.
Parts Washers Floating oils re-contaminate parts as they are removed from a wash tank. Oil skimmers can remove this oil. The benefits of using an oil skimmer are oil-free parts and extended fluid life.
Food Processing Facilities Removal of vegetable oils, greases and animal fats from a plant's wastewater stream reduces the costs of processing and disposal.
Parking Lots, Garages and Service Facilities Waste oil from leaks, spills and other sources must be retrieved from sumps before water can be discharged to storm or sanitary sewers.
Outdoor Ponds, Lakes, Basins, Etc. Where floating oils are present, skimmers provide inexpensive and effective removal, solving a serious environmental problem.
Recovery/Monitoring Wells Removing oil, fuel and other hydrocarbon liquid from wells, can be more cost effective using a belt skimmer instead of a down well pump. Skimmers don't have nearly the maintenance issues and can reach depths of 200 feet or more, removing product despite fluctuating water tables.  Skimmers can handle very think fluids effortlessly and some (like the Abanaki PetroXtractor®) can separate some DNAPL's such as coal tar and creosote from water.	Abanaki PetroXtractor  with stand and Oil Concentrator

There are several types of industrial oil skimmers. Choosing one best suited for your application will maximize oil removal while minimizing capital outlay and skimmer operating costs. First, define the application in terms of the following characteristics:

Operating Conditions
All skimmers have a moving medium, and possibly other parts, immersed in the liquid. The performance and life of the pick-up medium, wiper blades, pulleys, etc. are affected by different conditions. These conditions include temperatures in and out of the liquid, pH of the solution and the presence of solvents or other reactive chemicals.

Hazardous Materials: Applications involving flammable materials or explosive vapors require the use of explosion proof (or air driven) motors and controls.
Temperature/Viscosity: All skimmers require floating oil to be in a liquid, free-flowing state. If the oil congeals or solidifies at ambient temperatures, the tank and/or skimmer will require heaters to maintain fluid flow. This is especially true at temperatures low enough to freeze water. A heater option is a must if a skimmer is to be used outdoors in freezing temperatures.

Removal Capacity

Rating: Skimmers usually have an oil removal rate expressed in gallons per hour. The rate varies with oil viscosity, so Abanaki and most manufacturers rate skimmers using SAE 30 weight motor oil at 65° F (18°C.) If a manufacturer doesn't specify the test oil for its rating, or your application involves a much different viscosity, it is wise to ask for additional test data. When specifying removal capacity, it is better to err on the high side to allow for peaks in the oil influx.
Water Content: All oil skimmers pick up some water with the oil they remove. Some designs, particularly suction skimmers, pick up more water than others. High water content increases oil recycling and disposal costs. Generally, the ratio of water-to-oil decreases with thicker films of floating oil and slower moving pick-up media. An Oil Concentrator® or decanter installed at the skimmer discharge port provides secondary oil/water separation that can reduce water content to nearly zero.
Residual Oil: A skimmer continues to remove oils as long as they are present. Depending on oil influx rate and the skimmer's removal rate, residual oil in the water may be as low as a few parts per million. When residual oil reaches this level and further reduction is required, it may be more practical to use a secondary removal method following skimming, such as membrane filtration.	Abanaki  Mighty Mini SST w/integrated timer
Portability: Skimmer portability is a plus in some applications. For example, in plants, mobile equipment service shops, and at remediation sites, a portable skimmer can sometimes service multiple machines, sumps, or wells.

Tank or Sump Characteristics
The location, shape, and capacity of a tank or water impoundment are major factors in choosing the right skimmer. Also consider fluctuations in water level, turbulence and possible emulsions (the mixing of oil and water). Although skimmers do not cause emulsions, they can have trouble removing certain types.

Size/Design: Oil and water can emulsify when subjected to turbulence and other mechanical agitation. Avoid this by having water return to the tank below the liquid surface at as low a velocity as practical. Make sure your tank or sump provides quiet areas, weirs, and sufficient volume to allow adequate time for oil/water separation.
Shape: Tanks without nooks and crannies for oil to accumulate in are best. If you have an irregular shape, put the skimmer where the largest amount of oil accumulates. Consider a means of directing oil towards the skimmer such as a floating boom or baffle plate.
Location/Installation: The physical location and characteristics of the tank and collection container are important. Does the skimmed material need to be pumped from the skimmer to the container? Will skimmer access for periodic maintenance be a problem? How much mounting space is available? Are tank or container modifications required? Cheap systems quickly lose appeal when costs for additional components, increased maintenance and expensive tank modifications are involved.	Abanaki Model 82 w/ Oil Concentrator and stand

For industrial oil skimming, there are six basic designs commonly used:

Belt Skimmers: Belt-type skimmers use an endless belt of stainless steel, elastomer or poly medium, which is lowered into the tank or vessel to be skimmed. The belt passes though resilient wiper blades where the oil is removed from both sides of the medium.	Abanaki Model 82
Disk Skimmers: These skimmers rotate a disk shaped medium through the liquid. Oil is wiped off and discharged into a collection container in a manner similar to belt skimmers. It is important to consider reach, the portion that actually gets immersed, when looking at a disk skimmer. Less disk in the fluid, means less oil removed. Obviously, fluctuating fluids can be a real problem for disk skimmers.  Also, it is important to look at how much of the disk the wipers are actually wiping. If the wipers only wipe 2" from the edge, then they reach into the fluid beyond 2" is wasted. As a result, removal capacities for the disks can be relatively low.
Drum/Barrel Styles: These are similar to the disk type, but use a rotating drum shaped medium. Compared to disk types, they are usually more rugged and have higher removal capacity. These units can also be rendered ineffective by fluctuating fluid levels.
Mop Skimmers: These skimmers use an endless medium shaped like a rope and having mop-like tendrils that pick up the oil. As the medium leaves the liquid and enters the drive unit, it is pressed and wrung out with pinch rollers. For higher viscosity oils, the medium tends to mat down and lose effectiveness. a Decant system is a must for these units, as water pickup can be very high. Also, replacement mops can be very expensive so check prices on replacements before purchasing.
Large Tube Skimmers: Tube skimmers use a floating plastic hose that snakes out over the surface of the liquid and is then drawn back through the drive unit where oil is removed. This design requires a relatively large amount of surface area for proper operation.
Mini Tube Skimmers: Very similar to the large tube units, but use either a 3/16" or a 5/16" tube instead of 1". The pickup rate varies from 1 quart/hour to 1.5 gph depending on the diameter of the tube. These units are fairly compact, and can fit in tight spots. The better units will have the motor mounted underneath, to bring room required over the lip of the tank down to near zero. The 5/16" diameter is preferable as it has enough stiffness to not drag on the housing and prematurely wipe off oil when being drawn into the unit.

Floating Suction Skimmers: These come in several forms, but all have a floating intake. They are most suitable for relatively thick layers of oil (1/4 inch), otherwise they tend to ingest large amounts of water. Some machines will actually emulsify oil due to churning as it passes through the suction pump. This type of skimmer requires a coalescing or at least a decanting unit to be at all effective.

* Information in this table was collected from sales and technical literature available for various types and manufacturers of oil skimmers. It represents manufacturers' data only at the time of collection and is merely a guide to general characteristics and capabilities . Not all manufacturers provide complete data and some may change specifications without notice. Contact the manufacturers for their latest product literature.

Removal Capacity
Capacity should be based on the maximum amount of oil to be removed within the shortest available time. For instance, total oil influx may be 200 gallons in a 24 hour period, which averages about 8.3 gallons per hour. But if most of it comes during a single eight hour plant shift, you will probably need a removal rate that is three times as high, especially if you are trying to prevent an unwanted discharge of contaminated water to a sewer system. As a rule-of-thumb, specify approximately twice the maximum capacity you anticipate needing for normal conditions.

* Grease Grabber capacity is based on use of Brooks Technology Plexelene 750 grease.
X Indicates skimmer models normally appropriate for the desired removal rate.
+ Indicates skimming capacity well above the desired level.

Belt and Tube Length: Removal capacity is not affected by length. Choose a length that assures contact with the liquid at its lowest level; allows easy mounting of the skimmer where oil discharge is convenient; and has good access for routine service. Abanaki's ability to supply skimmers with long belts, and lift skimmed material well over 100-feet with no loss in capacity or efficiency, is important to many users.

Disk Diameter: The disk must always be touching the fluid. Size the diameter accordingly.

Choosing the Right Belt Material for your Abanaki Belt Skimmer
Abanaki offers 6 different belt materials. The chart below indicates which material is most suitable for common situations. However belt performance and durability depends on the nature of the liquid, its chemical composition, temperature, etc. For instance, high temperature increases a belt's sensitivity to pH levels. To make sure the belt performs satisfactorily in your application, Abanaki offers free samples of belt material al for test purposes.

Wiper Blades
Abanaki offers three 4 wiper blades materials for a variety of operating environments. The standard material is Nitrile (also known as Buna-N), which is appropriate for about 80% of all applications. Optional materials are designed for applications with harsh operating conditions. The materials include: CRV (very high chemical resistance), ceramic hybrid (excellent lubricity and moderate chemical resistance), and ceramic (high chemical, heat and grit resistance).

Motor Types
All Abanaki skimmers are designed with standard, industrially rated, continuous duty motors and fully enclosed speed reducing drives. Most of these skimmers can be specified with the following motor options:

• Any Common Voltage or Electrical Requirement
• Explosion Proof, Drip Proof, Tropicalized
• Dirty Duty, Food Service, Wash down duty

Contact Abanaki regarding availability of special motors, controls and drive components to satisfy unusual requirements.

Abanaki accessories make it easy to customize your system for quick installation and optimal performance. Listed below are the most commonly requested items. More specialized accessories are available on request.

Mounting Stands and Adapters: Choose from several pre-engineered mounting stands for easier installation. Models are available for pits, walls, and free-standing units. Handy storage stands are available for portable units. All stands are shipped fully painted and ready for quick assembly.	Abanaki Model 82 w/stand and drum switch
Shelters/Enclosures Reinforced poly-shelters, fiberglass utility sheds and below-grade enclosures are available for selected Abanaki models to provide protection from the elements.	Abanaki Poly Shelter

Controls/Accessories
Abanaki offers a float switch and warning light to monitor fluid level in the oil collection drum, which helps prevent overflow. Other electrical options include timers, control panels, variable speed drives, generator sets (for portable power at remote sites), solar power packs and complete turnkey systems.

Concentrators: Abanaki Oil Concentrators® provide a secondary separation step after skimming to virtually eliminate water from skimmed product. Units are available for easy installation on most Abanaki skimmers.
Abanaki Oil Concentrator
Heaters: Most of Abanaki's models can be ordered with heating devices to keep skimmed product fluid in cold temperature applications. This maintains efficient removal and discharge from the skimmer belt and/or Oil Concentrator.	Abanaki Model 82 w/heater
Special Tail Pulleys, Yokes and Tethers: Tail pulley (idler) options include: High Capacity Pulley available with Oil Grabbers® increases removal rates approximately 20%. Yoke and Tether assembly prevents pulley loss due to human error or belt breakage. Cage assembly for yoke and tether prevents further loss of belt or pulley in turbulent applications.