Selecting an appropriate mechanical conveyor for moving flour is an important task for millers and food processors alike. Millers look for quality in their final product while food processors that use flour blends as an input material seek to preserve the consistency of the blend as it moves through their production process. Finally, millers and food processors both seek hygiene and product purity, as well as conveying efficiency and safety. In this blog, we take a closer look at mechanical conveyors for flour applications, focusing on three equipment types.
Flour is a powder usually made by grinding raw grains or roots. Wheat is the most commonly used base grain for making flour, although other grains, such as rye and corn, are often used. Cereal flour (whole grain or refined flour), is a key ingredient used in making bread and other foodstuffs. Refined flour has the germ or bran removed and is typically referred to as “white flour”. Milling of flour is usually carried out by grinding grain between wheels or rollers made of stone or steel.
As a powdered material, flour and flour blends can have challenging handling characteristics. These are discussed below under the various equipment types.
A variety of mechanical, and non-mechanical, conveying methods have been used to move flour in milling and production operations. The main mechanical methods employed include the following:
Let’s examine in greater detail three of these equipment types for conveying flour: flexible screw conveyors, aeromechanical conveyors, and continuous bucket elevators.
Flexible screw conveyors can convey flour within an enclosed tube at inclined angles. Flexible screw conveyors, such as the UniFlex line from UniTrak, can be fitted with shaftless augers which are purpose-designed to handle materials such as flour. For example, when moving flour through an inclined flexible screw conveyor, a flat wire auger will be preferred. Flexible screw conveyors are suitable for moving materials, such as flour, that will not be damaged by particles being “ground” between the auger and the conveyor tube walls. These types of conveyors are less suitable for moving materials such wheat, millfeed pellets, semolina, and the like which can be harmed by particle attrition resulting from such grinding.
Aeromechanical conveyors, like the Powderflight line from UniTrak, work well for moving most flours. Working on the principle of a fluidized airstream, these types of conveyors can move significant quantities of flour without dusting. The aeromechanical conveyor avoids many of the problems associated with conveying difficult-to-handle materials such as flour because the high-speed airstream fluidizes and carries the material through the conveying tube. The material “rides” through the conveying tube quickly, making little contact with the tube wall and discharging completely during operation. This greatly reduces the likelihood of caking, packing, or smearing and prevents material deposits or buildup inside the conveying tube and housings.
Bucket elevators are a proven way to move significant quantities of flour within a processing operation. An advantage of bucket elevators is that they can move flour blends without any separation or degradation of the blend.
Because flour dust is potentially explosive, continuous bucket elevators designed for the purpose of handling explosive dusts should be employed. Fully sealed, explosion-resistant designs, such as the Tiptrak™ Monocoque line of continuous bucket elevators from UniTrak, are a preferred choice in flour applications. These elevators feature, among other things, fully conductive bucket assemblies that reduce the risk of sparks, explosion relief panels, and fully sealed constructions that prevent fugitive dust emissions. Hygiene considerations are addressed through the use of optional Clean-In-Place (CIP) systems, food-grade components, and cleanout drawers.
Since the characteristics of flour vary, depending upon the base material which was milled to make the flour, most flours tend to be very free-flowing but some will tend to agglomerate or bridge within infeed hoppers. For this reason, the infeed of the bucket elevator may need to be designed to alleviate this problem or the elevator may need to be fitted with an infeed flow aid.
Reduced material buildup and complete material discharge minimizes material waste and means that the aeromechanical conveyor is typically easier and faster to clean than mechanical conveyors. The gentle conveying action also reduces abrasion and particle degradation.
If you are milling flour, or using it within your processing operations, UniTrak has conveying equipment that can help. To find out more about how our lineup of fine conveyors can support your flour handling needs, please contact our sales team for an application review.
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