GENCOAT Peabody andElectrostatics

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The present Peabody Division of GENCOAT began in 1947, handlingelectrostatic spray painting processes where paint particles are subjected to ahigh charge and attracted to the object to be painted.

In the late 1960's, Peabody Industrial developed an electrostatic bladeapplicator which was simpler than spray atomizer. The blade applicator hassubsequently been used for an increasing variety of applications where thesubstrate forms a continuous strip or separate items such as panel blanks.

Since 1979 Peabody Industrial has concentrated on industrial electrostaticoiling applications. Peabody Industrial subsequently became a Division ofSale Tilney Technology Ltd (STT), the industrial technology companywithin the Sale Tilney Group established in 1860.

In 1992 GFG, now known as GENCOAT, purchased the Peabody divisionand all rights to manufacture, with all existing patents. GENCOAT is aleading technology engineering company with sales of $20 million,exporting 60% of its production. It specializes not only in electrostatics butalso in Roll coaters, and Process lines.

GENCOAT Peabody electrostatic spray systems have been particularly wellaccepted in the steel, aluminum and automobile industries. Over 600installations have been provided in 40 countries world-wide, backed up by acomprehensive after-sales service.

Typical Blade Coater installationretrofitted to an inspection line at

Voest Alpine in Linz, machine featuresopen end “C” Frame to allow machine

to be driven on or off line with thestrip in position.

Contents

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Electrostatic Blade Coater on a rewindline in Hoesch Stahl's, Westfallenhuette,Germany, applying a uniform controlledcoating of oil prior to delivery.

The Blade Coater makes no mechanicalcontact with the strip, uses nocompressed air to atomize the oil andhas few moving parts. The uniformdistribution of oil is clearly evident.

The area around the oiler remains oilfree, and air pollution is alsominimized to provide an improvedworking environment.

4 Electrostatics

5 Features

6 Typical System

8 Applicators

10 Coatings

Electrostatics Explained

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The electrostatic principle is based on the law of physics which simplystates: 'like charges repel, unlike charges attract'. Thus, when a suitableliquid (oil) is formed into a thin film exposed to an intense electrostaticenergy field, it will separate almost immediately into a collection of veryuniform and equally charged particles.

The reason for this is that the electrostatic charge in a sprayed particle tendsto be forced to the outer surface, as all of the like-charged ions repel eachother. Because of factors like surface tension, resistively, etc., only so muchcharge (energy) can exist in a droplet before it spontaneously breaks up intosmaller droplets in order to increase its surface area, as the so-called"Rayleigh Limit" of the liquid is exceeded.

Each smaller droplet generated will thus carry a charge of the same valueand polarity and will therefore repel its neighbor. In consequence, thiscontrolled dispersion within the electrostatic field ensures excellentuniformity over the surface being coated: more drops for less coatingmaterial.

Electrostatics ensure that each charged particle of liquid is attracted stronglyto the target, which is grounded and hence seen by the particle as being ofopposite polarity. It then loses its charge and returns to its stable state.(Voltages as high as 120,000 volts are used, but at only 200 microamps).

Such intense electrostatic energy fields overcome gravity, enabling thesystem to work equally well "upside down" to ensure uniform application onboth sides of the target when presented horizontally. (For verticalpresentation of strip, the sprayers are positioned to discharge horizontally).

The electrostatic effect is seen in its purestform in the GENCOAT Peabody LinearAccelerator (L.A.) Blade, described later.However, for special applications,electrostatic systems from GENCOATcan also use air-assisted nozzles or highspeed Rotary Atomizer rotating cup(bowl), thus extending the range of liquidswhich can be sprayed electrostatically.

Left: Steel Linear Accelerator bladeshowing non conductive edge (which

multiplies the charge densityavailable), oil distribution manifold

and blade heating.

Right: Visual evidence of electrostaticenergy at work. Operating upwards in

this instance, opposing gravity, oil ispulled from the blade edge where there

is maximum electrostatic activity. Theoil particles then separate due to

mutual repulsion into a uniform patternwhich is itself strongly attracted to the

underside of the target surface.

Oil transfer efficiency is extremelyhigh. Oil particles, having attachedthemselves to the strip, remain there

with no loss to atmosphere.

Features and Benefits ofElectrostatics

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Uniform Coating: Electrostatics ensure that a uniform coatingof oil is applied to the item at a precisely-controlled coating weight - thus reducingreject rates and hence costs as well as beingbetter able to satisfy customer demands.

Significant Oil (Coating) Savings: Due to the high transfer efficienciesoccurring, electrostatics reduce significantlythe amount of oil/coating fluid needed forcomplete protection in comparison with non-electrostatic methods - therefore reducingcoating costs. This saving is considerable andcan result in the machine paying for itself inunder a year.

Coating Weight Flexibility: GENCOAT Peabody electrostatic applicatorsystems are capable of applying coating weightsfrom as low as 10 mg/m2 to more than 5Grams/m2, if required. Hence, a wide variety ofdifferent coating programs and oil (coating)types can be handled by a single machine. Ifcoating requirements change, the machine cannormally accommodate them.

No Mechanical Contact: There is no mechanical contact with thetarget surface. Thus, the risk of surfacedamage is negligible and wear in themachine is minimal. Also, intermittent orpatchy covering of, say, the strip, as can occur

with other systems using contact rollers, iseliminated. Further, roller bounce fromuneven strip surfaces is avoided, as is costlymaintenance of rollers and their bearings.

Coating Material Transfer Efficiency Near100 Per Cent:Any unused coating oil is confined withinthe machine and is recycled, giving an overalltransfer efficiency approaching 100 per cent.Thus, coating costs are further reduced.

Improved Environment: Improved Coil Shape Because excessive coating is eliminated,seepage from coils does not occur. Thus,there is no opportunity for coils to loseshape and hence the tension in the coilsremains stable. Further, capillary evacuationfrom high pressure points (which can causecircular dry patches) can not occur.

Oil spillage to floors and nearbymachinery and oil mist emissions areeffectively eliminated, thereby improving theworking environment and often allowing forreduced insurance costs.

Few Moving Parts/Low Maintenance Costs: The GENCOAT Peabody electrostaticcoating system achieves its objectives usingvery few moving parts. Hence, maintenanceis minimized so downtime of the line isreduced to the lowest possible level, givingfurther cost savings.

Top Left: Totally uniform oildistribution with needle sharp cuspsemanating from the high profile edgeof the LA Blade.

Top Right: Graphical analysis ofsavings achieved by Republic Steelwith their first GENCOAT Peabodyelectrostatic blade coater. The graphshows a saving of 70% in oilconsumption after the blade coaterwas installed.

Bottom: The before and after effectsof using electrostatic coating methodsshowing the virtual elimination of oilseepage from the coil.

Typical Peabody Bla

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Special design fully insulated oil tankfor storage of water base oils.

1. Solid State High voltagepower supplies mounted onthe cabin to minimize thelength of the connecting cable.

2. Linear Accelerator (L.A.)blades giving optimumatomization of oil under alloperating conditions.

3. Non conductive bladeSupports.

4. Telescopic blade mounts topand bottom to allow bladesto be completely withdrawnfrom the cabin for cleaningor maintenance.

5. Movable drip trough foroverhead blade to preventoil falling onto the stripduring line stop conditions.

6. "Table" type protection toprotect blades frommovement in the strip,particularly duringthreading operations.

Left: High quality conveyors used oncut to length applications to provide

total control of each sheet as theypass through the machine.

Right: Complete assembly for theautomobile industry, showing washer

and oiling unit coating cut sheetdirectly in front of a multi

axis transfer press.

7. Dedicated blade heating toensure oil in the blade isalways at the optimumtemperature for atomization,even when line is stoppedand no oil is flowing.

8. Strong steel cabin ruggedlyconstructed in 12 mm (1inch) thick plate.

9. Full length maintenancedoors at both ends of thecabin with safety securitylocks and gutters to ensureoil is kept inside the cabin.

ade Coating System

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Oiler installation on a continuousannealing line in Europe.

Left: Machine built to DIN standardsretrofitted neatly into existing colorcoating line in Germany.

Right: Typical machine awaitingshipment. This unit applies oil to steel strip.

10. Oil storage tanks, heatedwhere necessary, withautomatic oil changeovercontrol for multi oil types.

11. Precision metering pumpswith servo motors to preciselymeter oil to each blade.

12. Operators interface (MMI)with all necessary controland alarm functions (remotemounted where required).

13. Main electrical enclosurehousing PLC (ProgrammableLogic Controller), ServoMotor controllers, all relays,transformers, and overloadcircuits. Cabin available to avariety of different standardsincluding DIN

Types of Applicator

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Blade CoatersGENCOAT Peabody can offer several methods of spraying the various typesof coating oils, waxes or other materials, to give a quality and uniformity ofparticle size suitable for electrostatics. These are described below:

GENCOAT Peabody originally developedthe concept of electrostatic blade coaterssome 30 years ago. The latest form is theso-called L.A. (Linear Accelerator) bladeand it offers a wide range of coatingweights and product speeds.

Blade coaters utilizes a narrow slot todistribute the coating fluid. A naturalinteraction between the electrostaticallycharged particles after atomization ensurescomplete uniformity of coating fluid overthe entire target surface. The blade converts the fluid into a dense, well-definedpattern of electrostatically charged particles, which are strongly attracted to thetarget surfaces with a transfer efficiency approaching 100 per cent.

The latest L.A. blade embodies design features which increase the density ofthe atomized particles within the charged pattern almost six-fold over earlierblade types. The linear accelerator blade therefore uses less coating fluid and isable to operate over a much wider range of coating weights than earlier bladedesigns, generally from 50-5,000 mg/m2.

Rotary AtomizersRotary atomizers have been used for many years in industrial applications.In electrostatics, the coating fluid applied to the bowl of an atomizer is spunout to its edge and subjected to an intense electrostatic energy field.

The cup-shaped atomizer is rotated at high speeds (up to 40,000 rpm) usinga friction- free air turbine and utilizes a combination of centrifugal andelectrostatic energy to atomize anddistribute uniformly coating fluids downto low mg/m2 levels.

The resultant dense, uniformlydistributed pattern of charged fluidparticles is strongly attracted to thegrounded target, providing almost 100per cent transfer efficiency.

The particular advantage of the rotaryatomizer is its ability to maintain uniformdistribution down to extremely low coating weights (as low as 3 mg/m2) andgenerally up to 200 mg/m2, with excellent control characteristics.

Further, many types of coatings can be used, including waxes and water-based fluids. Another advantage is that the rotary atomizer has excellentresponse time to maintain coating weight where fast strip accelerations/decelerations are required.

Top Left: 'Typical cabin interiorfeaturing substantial blade protectors.

Top Right: Cabin detail showingcombined threading table and blade

protection designed for aluminumstrip, The table closes automatically

during strip threading operations.

Bottom Left: Rotary Atomizer array ina machine supplied to South Korea

applying food grade lubricants at 10 milligram/m2 levels.

Bottom Right: High quality bearing,support rotary atomizer turbine

capable of operation at up to 40,000rpm with almost no friction or exhaust

noise, The atomizing cup is designed tobe speedily removed for maintenance.

Types of Applicator

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Spray NozzlesThe GENCOAT Peabody electrostatic spray nozzle uses air- assistedatomization and is designed to handle a wide range of coating weights fromlow mg/m2 levels. It is thus ideally suited to sheet coating processesparticularly where mineral or water-soluble coating fluids are used. Eachspray nozzle is supplied with its own fluid control valve, offering unique airflow adjustments for both atomizing and pattern shape control.

A needle electrode at the nose of the gun creates a high energy electrostaticfield which induces an electrostatic charge on each atomized fluid particle.The resulting electrostatic attraction ensures efficient transfer of the coatingmaterial to the target.

Air-assisted spray nozzles are normallyincorporated in completely integratedsystems designed to coat and handlevarying widths or lengths of cut sheet.Of special note is the facility to sprayon to selected areas of, say, blanks forpress feeding in the automotiveindustry using PLC (programmablelogic controller) control. Coatingweights handled are typically in therange 100 to 1,500 mg/m2.

Metering PumpsA closely controlled flow of coating fluid to the electrostatic bladesatomizers is an essential feature of the GENCOAT Peabody system.

Positive displacement gear pumps of high accuracy are used, coupled to adirect current Servo Motor drive system, the speed of which can be directlyrelated to any change in the speed of the target.

The Servo drive system can be under operator or computer control, toensure that fluid application weights are precisely maintained at selectedvalues during strip speed variations.

For blade coaters, separate systems ofone or two pumps are provided for eachblade. For rotary atomizers or spraynozzles, a dedicated metering pump isemployed for each atomizer or nozzle.Depending on oil type and flow rates, acombination of the L.A. Blades, rotaryatomizers or spray nozzles can handlecoating weights from 3-3,000 mg/m2.

Left: Cut Sheet Oiler employing airassisted electrostatic atomizersespecially designed for applyingeither mineral or water base oils anddry film lubricants.

Below: Air atomizing guns inoperation applying water basedlubricants.

Types of Coatings –Edge Control

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Different coating applications require widely different liquid/oil types. Almostall oils currently available can be applied by GENCOAT electrostatically -whether water-based, mineral or natural (vegetable) oils - as can a wide rangeof waxes, paints, dyes and chemical additives. Optimum performance,however, is obtained with coating materials having a balanced combination ofelectrical resistance, viscosity and surface tension characteristics, in all ofwhich temperature can be crucial. GENCOAT Peabody test and evaluationfacilities are available at our main manufacturing facilities in Sussex,Wisconsin, USA.

ROBBER PLATES Recommended for use where total coating uniformity is required across thetarget (strip). They: (a) attract unwanted coating material, (b) inhibit excess edgecoating, (c) eliminate dry edges and (d) control coating uniformity at edges.

The robber plate assembly can be supplied complete with independentpositioning equipment and PLC control to follow increasing or decreasing(strip) widths automatically. New technology of a negative and positivepower supply has eliminated the need for robber plates except for threadingor a Rotary Atomizer machine.

ACTIVE GROUND SYSTEM This is particularly useful for cut-to-length line applications where totaluniformity of coating over the whole sheet is required. The "activeground" acts to deflect excess oil away from the area of the sheet, ensuringonly the desired coating weight is applied. Further, it eliminates over-oiling, not only of the sides but also the ends of the cut sheet, giving apremium quality product.

Above: 'C' Frame unit with motorizedwheeled base.

Top Left: Testing DC voltage at the blade

Top Right: Peabody tests a widevariety of different oils each year.

Over eight hundred different types ofoil have now been tested.

Bottom Left: Testing oil for electricalresistance using the Peabody oil test

meter and probe.

Bottom Right: Measurement of oil viscosity.

GENCOAT PeabodyCapabilities and Options

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A wide range of specialized electrostatic coating systems is available fromGENCOAT Peabody to meet specific applications. These are indicated in separate leaflets.

GENCOAT Peabody offers a complete design, engineering and installationservice to suit a customer's specific needs.

Options available cover a wide variety of customer requirements, including:- • PLC (Programmable Logic Controller) Control - with G.E. and

Siemens controllers as standard • Specific Coating Patterns - can be produced, using special atomizer

designs and PLC control • Robber Plate Edge Control Device - to eliminate excess oil attraction

and coating at strip edges (see below) • Active Ground Targeting System - to avoid excess coating of edges

and ends in cut-sheet applications (see below) • 'C'-Frame Cabin Design - to permit machine removal off-line with

strip present in the machine • Driven Wheel Assembly - to remove machine off-line as required • Automatic Oil (Coating) Change-Over -employing multi-tank systems • Strip Threading - using specialized equipment • Various Design Standards - alternative basic standards such as DIN are

available. Specific client specifications can also be accommodated.• Turnkey Contracts - can include installation and/or cross-site

electrical wiring

Top Left: Temper Mill oiler designedto work above the tension reelapplying up to 5g/m2 at a maximumspeed of 2000 MPM.

Top Right: Typical Control Panelincorporating key pad access andoperation of PLC control system forquick and easy modification ofoperating set points and monitoring ofalarm conditions.

Bottom Left: Standard control panelwith full G.E. Programmable Control.

Bottom Right: Underside view of atemper mill oiler in raised position.

GENCOAT Corporate Headquarters

N53 W24900 South Corporate CircleSussex, Wisconsin 53089Phone: (262) 691-0400Fax: (262) 820-1688E-mail: Gencoat.Sales@gen-world.comWeb Site: www.gen-coat.com