Air Wiping Cost Saving Tips

An air wipe converts the potential energy of compressed air into kinetic energy by forcing the air through constricting orifices. Its performance is governed by 2 physical principles, namely:

1. K. E. = ½ Mv2 Equation of Kinetic Energy
2. A1v1 = A2 v2 Equation of Continuity

where: M = mass, which in an air wipe is the air flow
v = velocity of the air
A = cross sectional area

The equation of Kinetic Energy (K. E.) reveals that K. E. is proportional to 1: 1 of the air flow but to square of the air velocity. For a twofold increase in air supply, the K. E. will increase by a factor of 2, while your cost of compressed air doubles. However, if you manage to raise only the air velocity by twofold, the K. E. will upgrade by a factor of 4. No additional cost is involved.

You can do this by manipulating the equations. The Equation of Continuity can be re-written as follows:

3. v2 = v1 ( A1/A2)

where, in the case of an air wipe:

v2 = air velocity in the constricting orifice
v1 = air velocity in the air supply hose
A2 = area of the constricting orifice
A1 = area of the air supply hose

By substituting equation 3 into equation 1, you have:

4. Kinetic Energy = ½ M (v1)2 (A1/A2)2

which reveals that if M, v1 and A1 remain constant, the K. E. is inversely proportional to the square of the constricting orifice. In other words, you can upgrade the performance of your air wipe by reducing the cross sectional area of the individual orifice. Hypothetically, if you are happy with the K. E., you can even lower the air pressure to reduce the cost by further shrinking the cross sectional area of the individual orifices.

However, in practice, there are limitations. For example, there is a lower limit to the cross sectional area of the individual orifices, particularly when working with ultra hard materials. Furthermore, there is a need for more small orifices to pass the same amount of air that goes through a large orifice. In the end, it's a matter of compromise in air wipe design on which you as the end-user is not involved with.

Your can opt to compare among air wipe designs to select an air wipe which delivers the maximum air velocity with the least amount of air consumption.

The 2nd principle is totally under your own control.

Even after the air leaves the constricting orifice and enters the wiping cylinder, it still behaves according to the Equation of Continuity. It now reads:

5. v3 = v2 (A2/A3)

where v3 and A3 stand for air velocity in the wiping cylinder and its cross sectional area respectively. This cross sectional area is equal to:

A3 = Area of the wiping cylinder - Ø of the wire = The Gap

That is to say:

V3 is inversely proportional to the cross sectional area of the gap or, the smaller the gap, the higher the air velocity, which translates into a higher efficiency or less air consumption.

Therefore it's your move on how to maintain the smallest possible gap between the wire and the air wipe (that is, the wiping cylinder).

Last but not least, it is desirable to install the air pressure regulator upstream but close to the air wipe. Indeed, you may want many throughout the system, as by adjusting the pressure down to the lowest possible functioning level at each air wiping station, you can save a substantial amount on your monthly compressed air bill.

You can learn how these principles are implemented in actual air wipe design by visiting: http://www.wireguides.com

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