/ / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / By Howard S. Fancher, Huestis Industrial
It is imperative that drawn and extruded products in the industrial wire and cable manufacturing process be economically dried. During the manufacturing process, bare wire and extruded products are bathed in solutions of water soluble oil or water to lubricate and/or cool them. The efficient removal of this solution and water is the object and focus of the air wiper system. This is a given for the successful downstream processes of printing, inspection, and packaging of the material produced.
In today’s economy everyone is focused on cost and results oriented production. The modern air wipers are also subject to this scrutiny. Through the decades since manufacturing processes have developed, many forms of airwipers and drying systems have been spawned. Rags, sponges, pieces of felt, have all been applied with poor results. Pipes with holes and openings, welded bearings on tubes and applied air have also been tried. All failures have led to future inventions and paths. Thus the evolution to adjustable air wipes, centrifuges, air knifes, and controlled flow air wipers. Let’s examine each type:
An adjustable air wipe is inefficient as they must dry a full range of product sizes on one unit, and the amount of air utilized to make this type of unit work can be quite high. Centrifuge blowers also require large amounts of energy to operate. Likewise, air knives utilize huge amounts of energy to dry products and while all of these systems generate different degrees of success in drying you must also consider the cost to purchase and operate these systems. Additionally, these types of units generate significantly more noise than a controlled flow air wiper.
The preferred method is the low cost controlled flow air wiper. Not only are they more efficient and quieter, but they are less expensive to purchase and operate. These units are generally made out of UHMW polyethylene build with a manifold to direct the air to a number of metal jets that reduce the incoming air pressure and increase the velocity of the air going into the cavity of the air wiper body. The venturi effect that is created within the body aids in the rapid removal of liquids from the product.
Recent changes in applied technology has led to a new down drafting air wiper that removes liquid and exits from the bottom of the air wiper as opposed to the rear of the standard controlled air flow design. This allows the manufacturer to better address the need for increased drying as higher production speeds are achieved year over year. By using a bottom exiting air wiper they can be successfully ganged in series within an enclosure or mounted to a frame. They also have the ability through a threaded port to introduce a fitting with a tube or hose to return the exiting liquid back to the process liquid system.
This “down drafting” effect prevents most liquid from being carried back to the air wiper in the rear position thus maintaining the drying effect created by the first air wiper and all subsequent units. Side drafting, bottom exiting controlled air wipers have also recently been introduced for flat shaped products having the same features of the “down drafter” along with side blowing jets to dry the surface of flat shapes of bare, and jacketed wire as well as fiber optic products. As described in table 1 the diameter of the product is matched to the correct size of air wiper using the standard practice of 50% to 90% of the cavity opening. Following this practice will yield the best results. Solution types, materials, line speeds, and temperatures will have an effect on the drying process and in some applications may require multiple units to obtain the level of dryness desired.
The quantity of compressed air required for operating the controlled flow air wiper is much less than that of a centrifuge or other systems. Cost to operate and purchase is also much more economical. Most facilities already use compressors in their process for various applications, and usually they find that changing to a controlled air flow air wiper reduces usage which translates into yearly savings.