On the cover: The Extru-Tech, Inc. Dual Conditioning Cylinder is an example of a dual shaft cylinder preconditioner.

What is preconditioning?

continued from cover

Which preconditioner

will meet my needs?

The short of it is this—mix, hydrate and cook:

■ Mix your raw material—the dry feed—with fat, meat, preservatives, humectants and other ingredients;

■ Hydrate the composition to a specific moisture to promote cooking in the extruder or ease the conveying of product to the extruder;

■ Cook, or more appropriately precook, to lessen costs associated with extrusion wear and operation.

Preconditioning knowledge is power

Figure 1

Single shaft and dual shaft preconditioners are the two most basic types.

Sir Francis Bacon wasn’t kidding when he said knowledge is power. A little bit of preconditioning knowledge will give you sufficient power when it comes to making decisions about which preconditioner is right for you. It will also help in understanding preconditioner mixing components and how preconditioners manage product levels.n

Choosing the right preconditioner will smooth out your extrusion process to limit extrusion surging and off-spec product. It will reduce utility costs for both steam usage in the preconditioner and electrical energy required to operate both the preconditioner and the extruder. And, most importantly, it will help reduce wear costs of your extrusion components.

There are two basic types of preconditioners: single shaft and dual shaft (see Figure 1). As Figure 2 shows, the single shaft is a simple design, but it has some nice strengths. The single shaft is an extremely cost effective, dynamic, inline mixer for dry materials. However, if retention time and

Figure 2

Single shaft preconditioners have a simple design but are cost effective.

September 2007 Extru-Technician 4