What are preconditioner mixing components?

In addition to understanding preconditioner design, it’s important to understand the varying types of mixing components and their configuration.

How paddles are attached

Figure 8 shows the three main methods of paddle attachment. At left is a threaded paddle design. This design offers the best adjustment capabilities because each paddle can be independently adjusted for interior wall clearance and conveying angle.

The middle example shows the welded method. This is the least desired and least versatile design because it offers no adjustment.

The example on the right depicts the bolted method. This method offers conveying angle adjustment only.

Paddle design is key

Figure 9 The three most common types of paddles.

Figure 8 The three main methods of preconditioner paddle attachment.

Figure 9 represents the three most

common types of paddles. Starting from the left is the “true paddle” featuring a thin, narrow blade designed to provide excellent mixing without promoting product build-up on its surface. With proper speed management, this design offers the best conveying and level management within the preconditioner.

The middle example is a “beater” or “wide paddle.” A fairly good product, it can facilitate mixing but is limited because of the extra force applied to the mounting points due to the extra surface area of the beater. Because of this, product build-up also becomes a limitation in maintaining higher speeds.

The final example is a “T-beater” design that is simply a beater with a perpendicular appendage that silhouettes a T-shape. Due to its design, regardless of the T-beater position angle, either the paddle or the T will convey the product, providing no level management and erratic mixing actions. ■

September 2007 Extru-Technician 7