A manufacturing company contacted EXAIR about their metal tube processing. They made industrial precision tubes from start to finish. This would include turning, cutting, coating, washing and drying metal tubes to specific diameters and lengths.
For one specific problem area, they manufactured a tube with the dimensions of 1” (25.4mm) in diameter and 6” (152mm) in length. They would run a batch of 750 tubes through a wash cycle and then through a vibrating dryer with a drying material made from corn cobs. At the bottom of the vibrating dryer, the tubes would fall to an open mesh shaker table to transfer the tubes to Quality Control. The idea was to remove the excess cob material from the surface of the tubes before inspection and to recycle the drying material. But the problem was static.
When non-conductive materials slide, hit, peel, and vibrate; electrons from the surface can move from one atom to another; thus, creating static. The type of material and the amount of movement governs the positive and negative charges, and the amount of static forces.
The corn cob material is a non-conductive material, but what about the metal tubes? Since the metal tubes were coated for corrosion and abrasion protection, the surface is now a non-conductive area which will contain static. Since opposite charges attract each other, the cob material would cling to the outside surface of the metal tubes (reference photo below). Being a precision tube manufacturer, they did not want to send “dirty” tubes to their customers or allow the drying material to contaminate their measuring equipment. And, with the required quality control, the measurements had to be exact.
The shaker table was 8 feet (2.4 meters) long and 2 feet (0.6 meter) wide with rigid walls. The top of the shaker table was covered with a canvas to allow for a vacuum system to collect the excess material and dust. About half way down, there was a 2” (51mm) drop to help jolt additional cob material off of the tubes as they landed. But the static forces were too strong to release the material. Thus, the static had to be removed from the surface, so they contacted EXAIR to see if we could find a solution.
They sent photos of their setup which always helps us to diagnose and find solutions. The target place that they suggested would be near the 2” (51mm) drop as the tubes would be suspended for just a moment. My recommendation was to use a Gen4 Super Ion Air Knife to blow ionized air around the tubes as they fell. By blowing air, we can use the non-contact force to remove the static and the cob material at the same time. But we had two issues to overcome. The width was fixed at 2 feet (0.6 meter), and the operation controls were 10 feet (3 meters) away from the mid-section of the shaker table.
EXAIR stocks many Gen4 Super Ion Air Knives ranging from 3” (76mm) to 108” (2.74meters) in incremental lengths for quick shipments. But our standard 24″ product was not able to fit inside that area nor was the five foot electrical cable long enough to reach the control panel. (As a note, it was important for the operator to be able to manually turn on and off the unit from the control panel.)
EXAIR uses an electromagnetically shielded cable to carry high voltage from our Gen4 Power Supply to our shockless, non-radioactive Gen4 Ionizing Bar. Our stocked length for our armored cable is 5 feet (1.5 meter). After discussing the amount of movement with the table and the desired distance to the control panel, EXAIR could not use an item off the shelf. But not to worry… Since we are the manufacturer, we have the ability to make a special design for this customer.
I recommended a model 112220-10 special length Gen4 Super Ion Air Knife Kit. (Reference model numbering system above). Specials are non-returnable and non-cancelable, but for this customer, it was exactly what they needed. The Gen4 Super Ion Air Knives are engineered to efficiently blow ionized air to the target and remove static charge and debris.
For this special model, it was made to a specific width where the Super Air Knife was manufactured to a length of 20” (508mm), and the high voltage cable was lengthened to 10 feet (3 meters). The kit includes the Gen4 Power Supply to power the Ionizing Bar, a filter to clean the compressed air, a regulator to control the force, and a shim set to change force rates. This complete kit had everything required to begin operations to remove static and cob material from their precision tubes. The customer was able to mount the special length Gen4 Super Ion Air Knife within the shaker table and mount the power supply near the control panel.
Static can be an issue even with coated metal parts. For the customer above, EXAIR was able to make a special length Gen4 Super Ion Air Knife to work in their system. If you believe that static is causing issues, EXAIR has a great range of Gen4 Static Eliminators to remove that nuisance. You can discuss further with an Application Engineer as EXAIR for help; even if you need a custom product.
John Ball, Application Engineer