GENCOAT Peabody and Electrostatics

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2 GENCOAT Peabody and Electrostatics The present Peabody Division of GENCOAT began in 1947, handling electrostatic spray painting processes where paint particles are subjected to a high charge and attracted to the object to be painted. In the late 1960's, Peabody Industrial developed an electrostatic blade applicator which was simpler than spray atomizer. The blade applicator has subsequently been used for an increasing variety of applications where the substrate forms a continuous strip or separate items such as panel blanks. Since 1979 Peabody Industrial has concentrated on industrial electrostatic oiling applications. Peabody Industrial subsequently became a Division of Sale Tilney Technology Ltd (STT), the industrial technology company within the Sale Tilney Group established in In 1992 GFG, now known as GENCOAT, purchased the Peabody division and all rights to manufacture, with all existing patents. GENCOAT is a leading technology engineering company with sales of $20 million, exporting 60% of its production. It specializes not only in electrostatics but also in Roll coaters, and Process lines. GENCOAT Peabody electrostatic spray systems have been particularly well accepted in the steel, aluminum and automobile industries. Over 600 installations have been provided in 40 countries world-wide, backed up by a comprehensive after-sales service. Typical Blade Coater installation retrofitted to an inspection line at Voest Alpine in Linz, machine features open end C Frame to allow machine to be driven on or off line with the strip in position. 2

3 Contents 4 Electrostatics 5 Features 6 Typical System 8 Applicators 10 Coatings Electrostatic Blade Coater on a rewind line in Hoesch Stahl's, Westfallenhuette, Germany, applying a uniform controlled coating of oil prior to delivery. The Blade Coater makes no mechanical contact with the strip, uses no compressed air to atomize the oil and has few moving parts. The uniform distribution of oil is clearly evident. The area around the oiler remains oil free, and air pollution is also minimized to provide an improved working environment. 3

4 Electrostatics Explained The electrostatic principle is based on the law of physics which simply states: 'like charges repel, unlike charges attract'. Thus, when a suitable liquid (oil) is formed into a thin film exposed to an intense electrostatic energy field, it will separate almost immediately into a collection of very uniform and equally charged particles. The reason for this is that the electrostatic charge in a sprayed particle tends to be forced to the outer surface, as all of the like-charged ions repel each other. Because of factors like surface tension, resistively, etc., only so much charge (energy) can exist in a droplet before it spontaneously breaks up into smaller 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 value and polarity and will therefore repel its neighbor. In consequence, this controlled dispersion within the electrostatic field ensures excellent uniformity over the surface being coated: more drops for less coating material. Electrostatics ensure that each charged particle of liquid is attracted strongly to the target, which is grounded and hence seen by the particle as being of opposite 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 the system to work equally well "upside down" to ensure uniform application on both sides of the target when presented horizontally. (For vertical presentation of strip, the sprayers are positioned to discharge horizontally). Left: Steel Linear Accelerator blade showing non conductive edge (which multiplies the charge density available), oil distribution manifold and blade heating. Right: Visual evidence of electrostatic energy at work. Operating upwards in this instance, opposing gravity, oil is pulled from the blade edge where there is maximum electrostatic activity. The oil particles then separate due to mutual repulsion into a uniform pattern which is itself strongly attracted to the underside of the target surface. The electrostatic effect is seen in its purest form in the GENCOAT Peabody Linear Accelerator (L.A.) Blade, described later. However, for special applications, electrostatic systems from GENCOAT can also use air-assisted nozzles or high speed Rotary Atomizer rotating cup (bowl), thus extending the range of liquids which can be sprayed electrostatically. Oil transfer efficiency is extremely high. Oil particles, having attached themselves to the strip, remain there with no loss to atmosphere. 4

5 Features and Benefits of Electrostatics Top Left: Totally uniform oil distribution with needle sharp cusps emanating from the high profile edge of the LA Blade. Top Right: Graphical analysis of savings achieved by Republic Steel with their first GENCOAT Peabody electrostatic blade coater. The graph shows a saving of 70% in oil consumption after the blade coater was installed. Bottom: The before and after effects of using electrostatic coating methods showing the virtual elimination of oil seepage from the coil. Uniform Coating: Electrostatics ensure that a uniform coating of oil is applied to the item at a preciselycontrolled coating weight - thus reducing reject rates and hence costs as well as being better able to satisfy customer demands. Significant Oil (Coating) Savings: Due to the high transfer efficiencies occurring, electrostatics reduce significantly the amount of oil/coating fluid needed for complete protection in comparison with nonelectrostatic methods - therefore reducing coating costs. This saving is considerable and can result in the machine paying for itself in under a year. Coating Weight Flexibility: GENCOAT Peabody electrostatic applicator systems are capable of applying coating weights from as low as 10 mg/m2 to more than 5 Grams/m 2, if required. Hence, a wide variety of different coating programs and oil (coating) types can be handled by a single machine. If coating requirements change, the machine can normally accommodate them. No Mechanical Contact: There is no mechanical contact with the target surface. Thus, the risk of surface damage is negligible and wear in the machine is minimal. Also, intermittent or patchy covering of, say, the strip, as can occur with other systems using contact rollers, is eliminated. Further, roller bounce from uneven strip surfaces is avoided, as is costly maintenance of rollers and their bearings. Coating Material Transfer Efficiency Near 100 Per Cent: Any unused coating oil is confined within the machine and is recycled, giving an overall transfer 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 lose shape and hence the tension in the coils remains stable. Further, capillary evacuation from high pressure points (which can cause circular dry patches) can not occur. Oil spillage to floors and nearby machinery and oil mist emissions are effectively eliminated, thereby improving the working environment and often allowing for reduced insurance costs. Few Moving Parts/Low Maintenance Costs: The GENCOAT Peabody electrostatic coating system achieves its objectives using very few moving parts. Hence, maintenance is minimized so downtime of the line is reduced to the lowest possible level, giving further cost savings. 5

6 Typical Peabody Bla 1. Solid State High voltage power supplies mounted on the cabin to minimize the length of the connecting cable. 2. Linear Accelerator (L.A.) blades giving optimum atomization of oil under all operating conditions. 3. Non conductive blade Supports. 4. Telescopic blade mounts top and bottom to allow blades to be completely withdrawn from the cabin for cleaning or maintenance. 5. Movable drip trough for overhead blade to prevent oil falling onto the strip during line stop conditions. 6. "Table" type protection to protect blades from movement in the strip, particularly during threading operations. 7. Dedicated blade heating to ensure oil in the blade is always at the optimum temperature for atomization, even when line is stopped and no oil is flowing. 8. Strong steel cabin ruggedly constructed in 12 mm (1 inch) thick plate. 9. Full length maintenance doors at both ends of the cabin with safety security locks and gutters to ensure oil is kept inside the cabin. Special design fully insulated oil tank for storage of water base oils. Left: High quality conveyors used on cut to length applications to provide total control of each sheet as they pass through the machine. Right: Complete assembly for the automobile industry, showing washer and oiling unit coating cut sheet directly in front of a multi axis transfer press. 6

7 de Coating System 10. Oil storage tanks, heated where necessary, with automatic oil changeover control for multi oil types. 11. Precision metering pumps with servo motors to precisely meter oil to each blade. 12. Operators interface (MMI) with all necessary control and alarm functions (remote mounted where required). 13. Main electrical enclosure housing PLC (Programmable Logic Controller), Servo Motor controllers, all relays, transformers, and overload circuits. Cabin available to a variety of different standards including DIN Oiler installation on a continuous annealing line in Europe. Left: Machine built to DIN standards retrofitted neatly into existing color coating line in Germany. Right: Typical machine awaiting shipment. This unit applies oil to steel strip. 7

8 Types of Applicator Blade Coaters GENCOAT Peabody can offer several methods of spraying the various types of coating oils, waxes or other materials, to give a quality and uniformity of particle size suitable for electrostatics. These are described below: GENCOAT Peabody originally developed the concept of electrostatic blade coaters some 30 years ago. The latest form is the so-called L.A. (Linear Accelerator) blade and it offers a wide range of coating weights and product speeds. 8 Top Left: 'Typical cabin interior featuring substantial blade protectors. Top Right: Cabin detail showing combined threading table and blade protection designed for aluminum strip, The table closes automatically during strip threading operations. Bottom Left: Rotary Atomizer array in a machine supplied to South Korea applying food grade lubricants at 10 milligram/m 2 levels. Bottom Right: High quality bearing, support rotary atomizer turbine capable of operation at up to 40,000 rpm with almost no friction or exhaust noise, The atomizing cup is designed to be speedily removed for maintenance. Blade coaters utilizes a narrow slot to distribute the coating fluid. A natural interaction between the electrostatically charged particles after atomization ensures complete uniformity of coating fluid over the entire target surface. The blade converts the fluid into a dense, well-defined pattern of electrostatically charged particles, which are strongly attracted to the target surfaces with a transfer efficiency approaching 100 per cent. The latest L.A. blade embodies design features which increase the density of the atomized particles within the charged pattern almost six-fold over earlier blade types. The linear accelerator blade therefore uses less coating fluid and is able to operate over a much wider range of coating weights than earlier blade designs, generally from 50-5,000 mg/m 2. Rotary Atomizers Rotary atomizers have been used for many years in industrial applications. In electrostatics, the coating fluid applied to the bowl of an atomizer is spun out 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) using a friction- free air turbine and utilizes a combination of centrifugal and electrostatic energy to atomize and distribute uniformly coating fluids down to low mg/m 2 levels. The resultant dense, uniformly distributed pattern of charged fluid particles is strongly attracted to the grounded target, providing almost 100 per cent transfer efficiency. The particular advantage of the rotary atomizer is its ability to maintain uniform distribution down to extremely low coating weights (as low as 3 mg/m 2 ) and generally up to 200 mg/m 2, with excellent control characteristics. Further, many types of coatings can be used, including waxes and waterbased fluids. Another advantage is that the rotary atomizer has excellent response time to maintain coating weight where fast strip accelerations/ decelerations are required.

9 Types of Applicator Spray Nozzles The GENCOAT Peabody electrostatic spray nozzle uses air- assisted atomization and is designed to handle a wide range of coating weights from low mg/m2 levels. It is thus ideally suited to sheet coating processes particularly where mineral or water-soluble coating fluids are used. Each spray nozzle is supplied with its own fluid control valve, offering unique air flow adjustments for both atomizing and pattern shape control. A needle electrode at the nose of the gun creates a high energy electrostatic field which induces an electrostatic charge on each atomized fluid particle. The resulting electrostatic attraction ensures efficient transfer of the coating material to the target. Air-assisted spray nozzles are normally incorporated in completely integrated systems designed to coat and handle varying widths or lengths of cut sheet. Of special note is the facility to spray on to selected areas of, say, blanks for press feeding in the automotive industry using PLC (programmable logic controller) control. Coating weights handled are typically in the range 100 to 1,500 mg/m 2. Left: Cut Sheet Oiler employing air assisted electrostatic atomizers especially designed for applying either mineral or water base oils and dry film lubricants. Below: Air atomizing guns in operation applying water based lubricants. Metering Pumps A closely controlled flow of coating fluid to the electrostatic blades atomizers is an essential feature of the GENCOAT Peabody system. Positive displacement gear pumps of high accuracy are used, coupled to a direct current Servo Motor drive system, the speed of which can be directly related to any change in the speed of the target. The Servo drive system can be under operator or computer control, to ensure that fluid application weights are precisely maintained at selected values during strip speed variations. For blade coaters, separate systems of one or two pumps are provided for each blade. For rotary atomizers or spray nozzles, a dedicated metering pump is employed for each atomizer or nozzle. Depending on oil type and flow rates, a combination of the L.A. Blades, rotary atomizers or spray nozzles can handle coating weights from 3-3,000 mg/m 2. 9

10 Types of Coatings Edge Control Top Left: Testing DC voltage at the blade Top Right: Peabody tests a wide variety of different oils each year. Over eight hundred different types of oil have now been tested. Bottom Left: Testing oil for electrical resistance using the Peabody oil test meter and probe. Bottom Right: Measurement of oil viscosity. Different coating applications require widely different liquid/oil types. Almost all oils currently available can be applied by GENCOAT electrostatically - whether water-based, mineral or natural (vegetable) oils - as can a wide range of waxes, paints, dyes and chemical additives. Optimum performance, however, is obtained with coating materials having a balanced combination of electrical resistance, viscosity and surface tension characteristics, in all of which temperature can be crucial. GENCOAT Peabody test and evaluation facilities are available at our main manufacturing facilities in Sussex, Wisconsin, USA. Above: 'C' Frame unit with motorized wheeled base. 10 ROBBER PLATES Recommended for use where total coating uniformity is required across the target (strip). They: (a) attract unwanted coating material, (b) inhibit excess edge coating, (c) eliminate dry edges and (d) control coating uniformity at edges. The robber plate assembly can be supplied complete with independent positioning equipment and PLC control to follow increasing or decreasing (strip) widths automatically. New technology of a negative and positive power supply has eliminated the need for robber plates except for threading or a Rotary Atomizer machine. ACTIVE GROUND SYSTEM This is particularly useful for cut-to-length line applications where total uniformity of coating over the whole sheet is required. The "active ground" acts to deflect excess oil away from the area of the sheet, ensuring only the desired coating weight is applied. Further, it eliminates overoiling, not only of the sides but also the ends of the cut sheet, giving a premium quality product.

11 GENCOAT Peabody Capabilities and Options A wide range of specialized electrostatic coating systems is available from GENCOAT Peabody to meet specific applications. These are indicated in separate leaflets. GENCOAT Peabody offers a complete design, engineering and installation service 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 designed to work above the tension reel applying up to 5g/m 2 at a maximum speed of 2000 MPM. Top Right: Typical Control Panel incorporating key pad access and operation of PLC control system for quick and easy modification of operating set points and monitoring of alarm conditions. Bottom Left: Standard control panel with full G.E. Programmable Control. Bottom Right: Underside view of a temper mill oiler in raised position. 11

12 GENCOAT Corporate Headquarters N53 W24900 South Corporate Circle Sussex, Wisconsin Phone: (262) Fax: (262) Web Site: