Oil Skimming Facts Tutorial Handbook (PDF 262 KB)

www.abanaki.com1-800-358-SKIM (7546) www.abanaki.com 1-800-358-SKIM (7546) www.abanaki.com 1-800-358-SKIM (7546) www.abanaki.com 1-800-358-SKIM (7546)Oil and WaterDon’t MixThe relationship between oil and water in a mix-ture is well-known and governed by two physicalproperties:Specific Gravity: Most hydrocarbons have a lowerspecific gravity than water. Without agitation, oilseparates 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 gravityand are known as DNAPL’s, Dense Non-AqueousPhase Liquid.Surface Tension and Affinity: Normally, oil bondsmore tightly to itself and other materials than towater. This affinity, and differences in surface ten-sion between oil and water, cause oils to adhere toa skimming medium.Oil SkimmingAlthough designs vary, all oil skimmers rely on spe-cific gravity, surface tension and a moving mediumto remove floating oil from a fluid’s surface.Floating oil and grease cling to skimming mediamore readily than water, and water has little affin-ity for the media. This allows skimming media inthe shape of a belt, disk, drum, etc. to passthrough a fluid surface to pick up floating oil andgrease with very little water. This oily material issubsequently removed from the media with wiperblades or pinch rollers.Oil skimmers are simple,dependable and effectivetools for removing oil,grease and other hydrocar-bons from water. Often, askimmer by itself canachieve the desired level ofwater purity. In moredemanding situations,skimming is a cost-effectivemeans of removing most ofthe oil before using morecomplicated and costlytreatments such as coa-lescers, membrane filtersand chemical processes.Grease skimming involveshigher viscosity hydrocar-bons. Skimmers must beequipped with heaterspowerful enough to keepgrease fluid for discharge.The patented AbanakiGrease Grabber® is fittedwith heating elements tohandle these applications.If the floating grease hasformed into solid clumps ormats, a spray bar, aerator or mechanical apparatuscan be used to break up grease mats and facilitateremoval.Typical Applications forIndustrial Oil SkimmersWastewater SumpsMost manufacturing orprocessing facilities have cir-culating water systems. Thiswater collects in a centraltank or sump. Removingfloating hydrocarbon con-tamination with little watercontent can reduce the costof disposal and lower thecontingent liabilities of wastewater discharge.Coolants and Cutting FluidsWhen machine coolantsbecome contaminated withtramp oils, four things usu-ally occur: 1.) coolant life isreduced; 2.) quality ofmachined parts is reduced;3.) in many cases, a smokewill begin to appear in the shop, causing irritationto the workers on the job; and 4.) the fluid takeson a “rotten egg” odor. Skimmers that removetramp oils solve these problems and typically payfor themselves within a few months.Heat TreatingQuench oils that must beremoved from heat treatedparts can be captured forre-use or disposal. Theresults are lower quench oilcosts, prolonged washwater life and lower dispos-al costs.Parts WashersFloating oils re-contaminateparts as they are removedfrom a wash tank. Oilskimmers can remove thisoil. The benefits of using an oil skimmer are oil-freeparts and extended fluid life.Food ProcessingFacilitiesRemoval of vegetable oils,greases, and animal fatsfrom a plant’s wastewaterstream reduces the costs ofprocessing and disposal.Parking Lots, Garagesand Service FacilitiesWaste oil from leaks, spillsand other sources must beretrieved from sumpsbefore water can be dis-charged to storm or sanitarysewers.Outdoor Ponds,Lakes, Basins, Etc.Where floating oils arepresent, skimmers provideinexpensive and effectiveremoval, solving a seriousenvironmental problem.Recovery/Monitoring WellsRemoving oil, fuel andother hydrocarbon liq-uid from wells can bemore cost-effectiveusing a belt skimmerinstead of a down wellpump. Skimmers don’thave nearly the main-tenance issues and canreach depths of 200feet or more, removingproduct despite fluctu-ating water tables. Skimmers can handle very thickfluids effortlessly and some (like the AbanakiPetroXtractor®) can separate some DNAPL’s such ascoal tar and creosote from water.Choosing AnAppropriate SkimmerThere are several types of industrial oil skimmers.Choosing one best suited for your application willmaximize oil removal while minimizing capitaloutlay and skimmer operating costs. First, definethe application in terms of the following charac-teristics:Operating ConditionsAll skimmers have a moving medium, and possiblyother parts, immersed in the liquid. The perform-ance and life of the pick-up medium, wiper blades,pulleys, etc. are affected by different conditions.These conditions include temperatures in and outof the liquid, pH of the solution, and the presenceof solvents or other reactive chemicals.Hazardous Materials:Applications involving flam-mable materials or explosivevapors require the use ofexplosion proof (or air driv-en) motors and controls.Temperature/Viscosity: Allskimmers require floating oilto be in a liquid, free-flow-ing state. If the oil congealsor solidifies at ambient tem-peratures, the tank and/orskimmer will require heatersto maintain fluid flow. Thisis especially true at tempera-tures low enough to freezewater. A heater option is amust if a skimmer is to beused outdoors in freezingtemperatures.Removal CapacityRating: Skimmers usuallyhave an oil removal rateexpressed in gallons perhour. The rate varies with oilviscosity, so Abanaki andmost manufacturers rateskimmers using SAE 30weight motor oil at 65°F(18°C.) If a manufacturerdoesn’t specify the test oilfor its rating, or your appli-cation involves a much dif-ferent viscosity, it is wise to ask for additional testdata. When specifying removal capacity, it is betterto err on the high side to allow for peaks in the oilinflux. (See “Comparing Different Types of OilSkimmers.”)Water Content: All oil skimmers pick up somewater with the oil they remove. Some designs,particularly suction skimmers, pick up more waterthan others. High watercontent increases oil recy-cling and disposal costs.Generally, the ratio ofwater-to-oil decreases withthicker films of floating oiland slower moving pick-upmedia. An Oil Concentrator®or decanter installed at theskimmer discharge port pro-vides secondary oil/water separation that canreduce water content to nearly zero.Residual Oil: A skimmer continues to remove oilsas long as they are present. Depending on oilinflux rate and the skimmer’sremoval rate, residual oil inthe water may be as low as afew parts per million. Whenresidual oil reaches this leveland further reduction isrequired, it may be more prac-tical to use a secondaryremoval method followingskimming, such as membranefiltration.Portability: Skimmer portabili-ty is a plus in some applica-tions. For example, in plants,mobile equipment serviceshops, and at remediationsites, a portable skimmer cansometimes service multiplemachines, sumps, or wells.Tank or Sump CharacteristicsThe location, shape, and capacity of a tank orwater impoundment are major factors in choosingthe right skimmer. Also consider fluctuations inwater level, turbulence and possible emulsions.Although skimmers do not cause emulsions, theycan have trouble removing certain types.Size/Design: Oil and watercan emulsify when subjectedto turbulence and othermechanical agitation. Avoidthis by having water returnto the tank below the liquidsurface at as low a velocityas practical. Make sure yourtank or sump provides quietareas, weirs, and sufficientvolume to allow adequatetime for oil/water separa-tion.Shape: Tanks without nooksand crannies for oil to accu-mulate in are best. If youhave an irregular shape, putthe skimmer where thelargest amount of oil accu-mulates. Consider a meansof directing oil towards theskimmer such as a floatingboom or baffle plate.Location/Installation: Thephysical location and charac-teristics of the tank and col-lection container are impor-tant. Does skimmed materialneed to be pumped fromthe skimmer to the contain-er? Will skimmer access forperiodic maintenance be aproblem? How much mount-ing space is available? Aretank or container modifica-tions required? Cheap sys-tems quickly lose appealwhen costs for additionalcomponents, increased maintenance and expensivetank modifications are involved.Different Types ofOil SkimmersFor industrial oil skimming,there are six basic designscommonly used:Belt Skimmers: Belt-typeskimmers use an endless beltof stainless steel, elastomeror poly medium, which islowered into the tank orvessel to be skimmed. Thebelt passes through resilientwiper blades where the oil isremoved from both sides ofthe medium.Disk Skimmers: These skim-mers rotate a disk shapedmedium through the liquid.Oil is wiped off and dis-charged into a collectioncontainer in a manner simi-lar to belt skimmers. It isimportant to consider reach,the portion of the disk thatactually gets immersed,when looking at a disk skimmer. Less disk in thefluid, means less oil removed. Obviously, fluctuat-ing fluids can be a real problem for disk skimmers.Also, it is important to look at how much of thedisk the wipers are actually wiping. If the wipersonly wipe 2? from the edge, then any reach intothe fluid beyond 2? is wasted. As a result, removalcapacities for disks can be relatively low.Drum/Barrel Styles: Theseare similar to the disk type,but use a rotating drumshaped medium. Comparedto disk types, they are usual-ly more rugged and havehigher removal capacity.These units can also be ren-dered ineffective by fluctu-ating fluid levels.Mop Skimmers: These skim-mers use an endless mediumshaped like a rope and hav-ing mop-like tendrils thatpick up the oil. As the medi-um leaves the liquid andenters the drive unit, it ispressed and wrung out withpinch rollers. For higher vis-cosity oils, the medium tendsto mat down and lose effec-tiveness. A decant system is a must for these units,as water pickup can be very high. Also, replace-ment mops can be very expensive, so check priceson replacements before purchasing.Large Tube Skimmers: Tube skim-mers use a floating plastic hose thatsnakes out over the surface of theliquid and is then drawn backthrough the drive unit where oil isremoved. This design requires a rel-atively large amount of surface areafor proper operation.Abanaki Grease GrabberAbanaki PetroXtractor withstand and Oil ConcentratorAbanaki Mighty MiniSST w/integratedtimerAbanaki Model 82w/Oil Concentratorand standAbanaki Model 82Skimmerman™www.abanaki.com1-800-358-SKIM (7546) www.abanaki.com 1-800-358-SKIM (7546) www.abanaki.com 1-800-358-SKIM (7546) 1-800-358-SKIM (7546)Mini Tube Skimmers: Very similar to the large tubeunits, but use either a 3/16? or a 5/16? tube insteadof 1?. The pickup rate varies from 1 quart/hour to1.5 gph depending on the diameter of the tube.These units are fairly compact, and can fit in tightspots. The better units will have the motor mount-ed underneath, to bring room required over thelip of the tank down to near zero. The 5/16? diam-eter is preferable as it has enough stiffness to notdrag on the housing and prematurely wipe off oilwhen being drawn into the unit.Floating Suction Skimmers: These come in severalforms, but all have a floating intake. They aremost suitable for relatively thick layers of oil (1/4inch), otherwise they tend to ingest large amountsof water. Some machines will actually emulsify oildue to churning as it passes through the suctionpump. This type of skimmer requires a coalescingor at least a decanting unit to be at all effective.Specifying an AbanakiSkimmer for YourApplicationRemoval CapacityCapacity should be based on the maximumamount of oil to be removed within the shortestavailable time. For instance, total oil influx may be200 gallons in a 24 hour period, which averagesabout 8.3 gallons per hour. But if most of it comesduring a single eight hour plant shift, you willprobably need a removal rate that is three timesas high, especially if you are trying to prevent anunwanted discharge of contaminated water to asewer system. As a rule-of-thumb, specify approxi-mately twice the maximum capacity you anticipateneeding for normal conditions.Abanaki ModelsBelt and Tube Length: Removal capacity is notaffected by length. Choose a length that: assurescontact with the liquid at its lowest level; allowseasy mounting of the skimmer where oil dischargeis convenient; and has good access for routineservice. Abanaki’s ability to supply skimmers withlong belts, and lift skimmed material well over 100feet with no loss in capacity or efficiency, is impor-tant to many users.Disk Diameter: The disk must always be touchingthe fluid. Size the diameter accordingly.Choosing the RightBelt Material for yourAbanaki Belt SkimmerAbanaki offers 6 different belt materials. The chartindicates which material is most suitable for com-mon situations. However, belt performance anddurability depends on the nature of the liquid, itschemical composition, temperature, etc. Forinstance, high temperature increases a belt’s sensi-tivity to pH levels. To make sure the belt performssatisfactorily in your application, Abanaki offersfree samples of belt material for test purposes.Wiper BladesAbanaki offers 4 wiper blade materials for a vari-ety of operating environments. The standard isNitrile (also known as Buna-N), which is appropri-ate for about 80% of all applications. Optionalmaterials are designed for applications with harshoperating conditions. The materials include: CRV(very high chemical resistance), ceramic hybrid(excellent lubricity and moderate chemical resist-ance), and ceramic (high chemical, heat, and gritresistance).Motor TypesAll Abanaki skimmers are designed with standard,industrially rated, continuous duty motors andfully enclosed speed reducing drives. Most of theseskimmers can be specified with the followingmotor options:• Any common voltage or electrical requirement• Explosion proof• Drip proof• Tropicalized• Dirty duty• Food service• Wash down dutyContact Abanaki regarding availability of specialmotors, controls, and drive components to satisfyunusual requirements.Optional EquipmentAbanaki accessories make it easy to customizeyour system for quick installation and optimal per-formance. Listed below are the most commonlyrequested items. More specialized accessories areavailable on request.Mounting Stands and AdaptersChoose from several pre-engineered mounting standsfor easier installation.Models are available for pits,walls, and free-standingunits. Handy storage standsare available for portableunits. All stands are shippedfully painted and ready forquick assembly.Shelters/ EnclosuresReinforced poly-shelters,and below-grade enclo-sures are available forselected Abanaki modelsto provide protection fromthe elements.Solving Oil RemovalProblems forOver ThirtyYearsOilSkimmerFactsBelt CapabilitiesMaterials Stain-lessSteelElasto-mer PolyXP-PolyHT-Poly FuzzyTemperatureRange<220°F(104°C)<120°F(49°C)140°F(60°C)<180°F(82°C)<220°F(104°C)<160°F(71°C)pH Range 2-13* Yes Yes Yes Yes Yes YesOperates in thepresence of gritfines and othersuspendedparticlesNo Yes Yes Yes Yes NoRemoves certainDNAPL’s andsome emulsifiedoilsNo No Yes No No YesEffective forvery light oils No No No No No Yes*At ambient temperatures.FeaturesAbanaki(All Types) Belts Mops TubesMiniTubes Drums DisksNumber of Models 16 1-2 1 2 1 2 3Stainless Steel Pick Up Media Yes No No No No Yes YesChoice of Wiper Materials Yes No No No No No NoExplosion Proof Motors & Controls Yes Yes Yes Yes No No NoSingle & Three-Phase Motors & Controls Yes Yes Yes Yes No Yes NoOptional Heaters Yes No No Yes No No NoTurnkey Systems Available Yes No No No No No NoStainless Steel Housings Yes No Yes No No No NoLife Expectancy (Average Years) 20 3 5–10 10–12 2–4 5–10 0–1Required Operating Area (Sq. Ft.) 1/2–1 1–5 5+ 4+ 1 5+ 1/2–1Optional Mounting Arrangements & Stands Yes No No Yes No No NoRemoval Capacity GPH (SAE 30) 1–200 2–150 100+ <1 25 10–100 2–3Skimming Lift Distance (Ft.) 100+ 5–10 30–50 60 5’ 0.5 0.5Handles Fluctuating Fluid Levels Yes Yes Yes Yes Yes No NoWorks in Shallow Tanks (= 6 in.) Yes No Yes Yes Yes No NoSuitable for Streams & Ponds Yes No Yes Yes No No NoMaximum Fluid Temperature (°F) 212°+ 150° 130° 180° 120° 180° 130°Requires Modifications to Tank No No No No No Yes NoServiceability Good Fair Messy Messy Messy Fair PoorEase of Installation Easy Moderate Moderate Moderate Easy Difficult EasyComparing Different Types of Oil SkimmersInformation in this table was collected from sales and technical literature available for various types and manufacturers of oil skimmers. It rep-resents manufacturers’ data only at the time of collection and is merely a guide to general characteristics and capabilities. Not all manufactur-ers provide complete data and some may change specifications without notice. Contact the manufacturers for their latest product literature.Desired Removal RateMighty Disk™SkimmerTubeTastic™or Coolescer™Mighty MiniBelt Skimmer1? or 2?Tote-It &PetroXtractor1, 2 or 4? beltModel 4 w/ 4? beltModel 82w/ 8? beltGreaseGrabber w/ 8? beltModel MB w/ 2x, 3x, 4xor 5x 8? belts1 GPH (3.8 LPH) ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦2 gph (7.6 LPH) ¦ ¦ ¦ ¦ ¦ ¦6 GPH (23 LPH) ¦ ¦ ¦ ¦ ¦12 GPH (45 LPH) ¦ ¦ ¦ ¦ ¦20 GPH (60 LPH) ¦ ¦ ¦ ¦40 GPH (240 LPH) ¦ ¦ ¦80 GPH (360 LPH) ¦ ¦120 GPH (454 LPH) ¦ ¦160 GPH (600 LPH) ¦ ¦200 GPH (757 LPH) ¦* Grease Grabber capacity is based on use of Brooks Technology Plexelene 725 grease.¦ Indicates skimmer models normally appropriate for the desired removal rate.¦ Indicates skimming capacity well above the desired level.Removal Capacity with SAE 30 Motor Oil, Except Grease Grabber* Controls/AccessoriesAbanaki offers a float switch and warning light to monitor fluid level in the oil collection drum,which helps prevent overflow. Other electricaloptions include: timer, control panel, variablespeed drive, generator sets (for portable power at remote sites), solar power packs and completeturnkey systems.Concentrators: Abanaki Oil Concentrators® providea secondary separation step after skimming tovirtually eliminate water from skimmed product.Units are available for easy installation on mostAbanaki skimmers.Heaters: Most of Abanaki’smodels can be ordered withheating devices to keepskimmed product fluid incold temperature applica-tions. This maintains effi-cient removal and dischargefrom the skimmer beltand/or Oil Concentrator.Special Tail Pulleys, Yokesand Tethers: Tail pulley(idler) options include:1. High Capacity Pulley avail-able with Oil Grabbers®increases removal ratesapproximately 20%.2. Yoke and Tether assemblyprevents pulley loss due tohuman error or beltbreakage.3. Cage assembly for yokeand tether further prevents loss of pulley or beltin turbulent applications.Abanaki Model 82w/stand and drumswitchAbanaki Model 82w/heaterAbanaki Poly ShelterAbanaki Oil ConcentratorSkimmerman™050310KGW