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Aluminum Wire Production & Filtration System Concepts

Proper clarification and maintenance is critical to long oil life, improved product quality and to maximize return on investment.

There has been a sharp increase in aluminum wire and cable production and the associated products. Aluminum rod breakdown requires the use of viscous mineral oil which is the first step towards meeting these product demands. As a result, filter systems that require centrifuges as the clarifier have also been in high demand.

The Oil

Today's oil products vary in physical properties, but are common in one way—they are all expensive to replace. Viscosities can range from 750 SSU to 3000 SSU making the oil supply pumps and heat exchanger, quite different in equipment selection and initial costs.

The continuous removal of the aluminum particulate and other suspended solids that are produced during the drawing operation stabilize the oil chemically, extend die life, preserve the oil additive package for optimum performance and promote a better wire finish.

System Design Concepts

Recommended as the best alternative for higher viscosity oil maintenance applications, Figures 1 and 2 show two different system concepts, one with a conveyor tank and centrifuge, the second with a baffled static tank and centrifuge.

Aluminum Wire Production System Concept with Conveyor Tank and Centrifuge

Figure 1

Aluminum Wire Production System Concept with Baffled Static Tank and Centrifuge

Figure 2

For either of the centrifuge system concepts, special attention must be given to the sizing of the tank, the heat exchanger and pump sizing making sure the viscosity of the oil is taken into serious consideration to assure the best performance.

Additionally, the system's heaters are an important component designed to maintain the oil at 85°F (30°C) during a downtime to eliminate cold start ups and also drive off any accumulation of “free” water that may find its way into the oil.

How the Centrifuge Separates Solids & Oil

A centrifuge is a device that magnifies the forces of gravity in a gravity separation (settling) process. Figure 3 illustrates that in the static tank, one G exists and is the reason solids settle and collect on the bottom. The rotating vertical bowl depicted creates the same results, but in a much shorter time and in a much smaller package due to the increase in G-force, which could be over 2000 Gs. Increased G-force is the primary factor in improved liquid/solid separation, and the factors that determine G-force are rotational speed and bowl diameter.

The other factors that improve gravity separation in the tank or centrifuge are residence time (the amount of time the combination of solids and liquid are in the tank or centrifuge) and turbulence control. In a centrifuge, the residence time is limited by the diameter and length of the bowl. However, the residence time in the centrifuge can be controlled by increasing or decreasing the flow rate.

In a typical settling tank, any turbulence could stir the contents and lengthen the time it will take to separate the solids from the oil under one G force, and the same is true with a centrifuge under 2000 G force. In modern centrifuging, the control of turbulence within the centrifuge is possible by the addition of design features as seen in Figure 4 and Figure 5 showing the rotating feed impeller supplying the four quiet zones created by the plow blades that are also used to discharge solids. The plow blades are locked, via a special clutch mechanism and establish the same rotational speed as the centrifuge bowl. This furthers the ability to maintain the four quiet zones, thus allowing the most efficient solids separation and even distribution of solids within the centrifuge bowl.

All of the design features combine to shorten the distance of particle travel within the bowl and assure the best opportunity for removal with the least amount of turbulence.