PAINT APPLICATION WATERBORNE ELECTROSTATICS CINDY M. DAIGNAULTF BUSINESS DEVELOPMENT SPECIALIST NORDSON CORPORATION (216)

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1 PAINT APPLICATION WATERBORNE ELECTROSTATICS WEDNESDAY APRIL 27, :20-9:45 A.M. 11 Day Y CINDY M. DAIGNAULTF BUSINESS DEVELOPMENT SPECIALIST -1 NORDSON CORPORATION 555 JACKSON STREET AMHERST, OHIO (216)

2 UNDERSI"ING METHODS AVAlLABLE FOR ISOLATING A WATERBORNE ELJEIRO~ATIC SYSI'F,M. 1. Isolation methods that utilize direct charging have much higher transfer efficiencies than remote or indirect charging methods. 2. Isolation of a waterborne electrostatic system can be accomplished in a number of ways: Conventional Isolation systems (Direct Charging) Remote Charging svstems (Indirect Charging) Voltage Block svstems (Direct Charging) cowentional Isolated Systems: 3. The conventional isolated system requires that all portions of the system that are wetted by paint are isolated from electrical ground. Paint tanks and pumps are placed on plastic stands, and hoses are suspended by plastic hangers. 4. The entire paint system must be a caged off area to protect operators from direct contact with charged components. 5. Because this type of system is completely isolated from electrical ground, the entire system becomes electrically charged whenever the high voltage is activated. The system will store this electrical energy until it is released to ground. The larger the system the greater the capacitance to store the electrical charge. 6. There is greater potential for shock injury danger and less accessibility to the equipment due to caging requirements. PAGE 2

3 UNDERSTANDING ME'IMODS AVAILABLE FOR ISOLATING A WATERBORNE JXFCIRO!YI'ATIC SYSlXM. Cowentiod Isolated Systems (continued): 7. Isolated systems for charging waterbased coatings electrostatically are efficient provided that all safety features are maintained, and the system is kept clean. A dusting of oversprayed coating on the spray devices or fluid supply hose can provide a conductive electrical path to ground during high-humidity conditions. 8. When isolated systems are new, electrostatic efficiency is comparable to solvent spray systems. However, there are many difficult-to-control variables that do effect electrostatic efficiency and will make performance of the system inconsistent. 9. Most direct charged systems are maintenance-intensive. Even with extraordinary maintenance, the efficiency will erode over time. The larger the system, the more difficult it is to identify and correct a problem. 10. To keep an isolated system functioning properly, you must keep the system free of oversprayed paint, dust and humidity which creates a drain on your electrostatics or can completely short the system out, e.g. plant dust that settles on the top of your paint lines which are run near the ceiling, when combined with humidity, causes a dead short in the system. 11. Each time you add components to the original system, you must isolate each new component that comes in contact with the fluid. PAGE 3

4 UNDERSIANDING METHODS AVAILABLE FOR ISOLATING A WATERBORNE ELECIROSTATIC SYSIEM. Remotely Charged Systems: An external charging device, such as a probe, needle, pin or ring is used to charge the atomized paint particles. Because there is appropriate air mix with the paint during atomization, there is enough electrostatic resistance so that the electrical charge cannot bleed back through the fluid system. The fluid supply system can remain grounded because only the atomized particles of paint are charged. Atmospheric conditions must be accurately controlled in order to obtain consistent electrostatic wrap e.g., a humid day will create a more conductive environment than a dry day. The charging efficiency of remote-charge systems is typically lower than those that charge the fluid directly. This is because the atomized particies must pick up their electrical charge from the charged air. This means that the charging efficiency will vary with relative humidity. In all cases a remotely charged system will not be as efficient as the direct charging method resulting in decreased transfer efficiency and increased coating usage. The charging device can collect coating material, which reduces the charging efficiency. For this reason it must be cleaned several times a shift during production to maintain transfer efficiency. The cleaning process requires a shutdown of the paint line to enable the operator to wipe off the charging device. In addition, atomized paint particles that have collected on the probe can build up and be blown onto parts, creating rejects. Regular maintenance is necessary to keep the charging probes free of excess paint build-up that causes decreased transfer efficiency. This can interfere with production creating lost production time. PAGE 4

5 , UNDERSTANDING METHODS AVAILABLE FOR ISOLATING A WATERBORNE ELECIROEXATIC SYSEM. Nordson bflo. Voltage-Block System 1. The operating principle of an ISO-FLO Voltage Block system is that it allows paint to flow toward the guns, but blocks the voltage from flowing back to the paint kitchen. In the voltage block unit, the voltage is blocked by an air gap in the fluid stream. 1E 2. The voltage block maintains an air gap at all times between the charged equipment and the grounded fluid supply system. The amount of equipment charged is kept to a minimum, therefore, personnel barriers or caging are not required. 3. The voltage-block system charges paint directly, yet allows the fluid supply system to be grounded. It isolates the electrically charged equipment in the spray booth from ground and blocks the charge from being conducted back through the fluid-supply system. 4. Voltage blocks permit direct charging of the paint while minimizing the problems inherent in totally isolated systems. This is accomplished by limiting the hardware that gets charged. 5. Since the paint kitchen is grounded, coating replenishment and viscosity checks can be done routinely without shutting the system down. 6. The air gap is created by mounting half of a fluid coupling in a fxed position and mounting the other half on a slide shuttle. This allows the coupling halves to either mate for transferring paint or to separate with a large air gap for electrical isolation. The coupling relieves the fluid pressure just before it separates after transferring paint, to prevent paint leaks. PAGE 5

6 UNDERSMNDING METHODS AVAILABLE FOR ISOLATING A WATERBORNE JXJXXROSATIC SY!WEM. Voltage Blocking Method (continued) 7. When the slide closes and the coupling halves engage, the unit is grounded and paint fills the reservoir pump that supplies paint to the gun or atomizer. When the slide opens, the coupling disengages and the coupling halves are separated by an air gap. Now the gun or atomizer is isolated from ground and the electrostatics can be turned on. 8. The entire voltage block system is pneumatically operated, therefore, the only electrical connection required is for the high-voltage power supply. Pumps and shuttles are located in a nonconductive housing to keep the equipment clean and minimize the chance of voltage leaks from the buildup of dirt and dust. 9. For intermittent spray, triggering of the gun is what opens up the shuttle valve to isolate the gun or atomizer. This system operates without the need for controls. 10. For continuous flow, two shuttle/reservoir pump combinations are used in tandem, so that one side can refill from the paint kitchen, while the other side supplies thz atomizer with charged paint. The side that is refilling is grounded because it is directly connected to the kitchen or paint supply. The side supplying the atomizer is charged and completely isolated from the kitchen. 11. Because the coating material is charged right at the voltage block, the cable to the gun can be eliminated, making the gun lighter and more flexible. PAGE 6

7 t INTEGRATING WATERBORNE ELECIROSTATICS INTO NEW AND EXISIWG FINISHINGLINES. 1. The conversion to waterbomes need not require extensive modification to the facility or the purchase of expensive new equipment. Most of the existing painting equipment can be used for waterbomes unless the seals are not compatible with the paint or the metal corrodes in water. 2. The ISO-FLO Voltage Block system works with any manufacturer s guns as long as they can be converted to spray waterborne coatings electrostatically, therefore, the voltage block alternative can be an economical retrofit application. 3. For the most efficient waterborne electrostatic system possible, isolate as little hardware as possible, preferably only the gun or atomizer and a short hose between the atomizer and the voltage block. 4. For maximum transfer efficiency, directly charge the coating material. 5. Take advantage of the unique properties of waterborne coatings to lower costs. For example: eliminate damage-prone high voltage cables to the guns or atomizers by charging at the voltage block. 6. Lower the voltage to maximize transfer efficiency, extend equipment life, and reduce shock hazard. 40-6OKV is optimum for waterborne coatings. 7. Use inexpensive flushing solvent such as water or water with some ammonia to flush the system. PAGE 7

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