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Electrostatic Powder Coating

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									TIM 018 07.97




Electrostatic Powder Coating
Monitoring Moisture in a Coating System’s Compressed Air Supply
For decades, the electrostatic powder application process         The coating applied during the electrostatic process is
has been used to finish metal parts. Major appliances such as     typically an organic powder. As the powder is sprayed out of
washers, dryers, and refrigerators have been powder coated        the applicator, it travels through an electrostatic field. Parts
for more than 25 years. The cost savings from reduced waste       targeted for coating are typically grounded by hanging them
(high transfer efficiency) and the durability of the finish       from an overhead conveyor. The static charge in the
make powder coating the finish of choice. This finishing          airborne powder is attracted to the part. Enough residual
system is also popular for automotive components and              charge remains on the powder to prevent the powder from
furniture.                                                        falling off. The part continues along the conveyor line into
                                                                  an oven. The powder coating melts, flowing into a resilient,
One of the benefits of powder coating systems is the ability
                                                                  color-fast coating. A large volume of parts can be coated if
to reclaim nearly all of the oversprayed powder. The ratio of
                                                                  the conditions within the system are properly monitored and
coating material applied to an object divided by the amount
                                                                  controlled. In any continuous coating application, large
of coating used is called transfer efficiency. Through a
                                                                  quantities of powder must course through the entire system
reclamation system, the electrostatic powder application
                                                                  smoothly and without interruption. Large hoppers store bulk




process achieves transfer efficiencies near 99 percent. A         quantities of the powder for transfer into the system. They
conventional “spray gun” using liquid paint can have              typically use compressed air to fluidize the powder,
transfer efficiencies as low as 30 percent.             Another   simplifying its transfer. A venturi pump, also powered by
advantage of the electrostatic powder coating process is the      compressed air, usually transfers the fluidized powder into
durability of the finish. Although the texture is not as smooth   the system.
as many liquid paints, powder coatings provide an extremely
                                                                  Fluidized bed hoppers, venturi pumps, and other pneumatic
durable, scratch-resistant finish.
                                                                  components of a powder coating system must have a dry
                                                                  compressed air supply to function properly. If the


                                                                                                                                1
compressed air were to become saturated with water, wet          Systems using a desiccant air dryer would benefit from a
powder would clog the entire system in minutes, forcing the      HygroGuard, or MMY 30 DewPro transmitter to monitor
entire coating system to grind to a halt.                        the trace moisture content of the compressed air lines.
                                                                 Installing either of these General Eastern systems to monitor
It's very expensive to shut down an entire system to find one
                                                                 air quality in an electrostatic powder coating system
faulty compressed air dryer. Many powder coating systems
                                                                 provides an early early warning system at a small price.
use refrigerated air dryers, making them perfect candidates
for an rh-plus analyzer, or MMR 30 DewPro transmitter. It
would monitor the moisture content of the air at the outlet.




                                                 General Eastern Instruments, Inc
                                             20 Commerce Way Woburn, MA 01801                                               2
                                              Tel 781-938-7070 Fax 781-938-1071
                                                        www.geinet.com

								
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