6.3.2 Flow Conveyor Chain
Large conveyance: Conveyance of bulk materials in a closed case; cement, chemical, and food industries
Flow Conveyor Chain moves bulk materials in a closed case. It conveys the particles horizontally, on a slight incline, or vertically in an arrangement shaped like the letter L. This conveyor is sometimes called a Redler Conveyor (Figure 6.13).
Generally, a flow conveyor is used widely in the conveyance of bulk materials such as cement and fertilizer in chemical industries, and grain in food industries. Because it is enclosed, dust from the conveyed materials is contained, and will not pollute the surrounding area. A flow conveyor is not usually used to move sticky, dusty, or low-density products.
A flow conveyor set up to move cement has an average capacity of 300 ton/h and a speed of 35 m/min. Usually one strand of chain is used.
Figure 6.13 Flow Conveyor Chain
Construction and Features
Specially shaped attachments with large clearances (Figure 6.13) are installed on small pitch or large pitch conveyor chains. The chain operates in a casing filled with conveyed material, such as grain, flour, or ash.
This is based on a phenomenon used in a basic science experiment; when you put sand in a long cylinder, closed at one end with paper, and push the sand with all your strength, the paper cannot be broken if the cylinder is long enough. This is because the friction between the sand and the cylinder absorbs all of the pushing force. Conversely, in the flow conveyor, the attachments work as moving walls, and the sand moves along with it. To lift conveyed objects, the friction at the bottom wall of the conveyor must support the weight of the vertical portion, therefore, the conveyor must have a bottom line "L" shape.
Because there is very little relative movement among the conveyed materials in this application, breakage is rare. The case width is determined by the attachment dimensions; usually it is less than 750 mm.
Chains for flow conveyors include: RF03075 (average tensile strength, 29 kN) through RF26200 (314 kN) for grain conveyance; RF450W (108 kN) through RF36300N (868 kN) for other applications.
Standard sprockets for RF-type conveyor chain are used for flow conveyors. Detachable tooth sprockets are beginning to be used these days.
Selection and Handling
- There are several types of attachments available, depending on design and arrangement of the conveyor and whether material is pushed against the bottom of the casing or its side walls.
Figure 6.14 shows several types of attachments (L, B, U2V, and W). The set-up on the right-hand side has more pushing power than the one on the left-hand side. The specific properties of the material conveyed determine the type of attachments that should be used. Discuss your application with the manufacturer.
Figure 6.14 Examples of Attachments for Flow Conveyor Chain
- KL-type attachment is an inclined version of an L attachment. This attachment can convey low-density and sticky materials.
- In grain applications, installation of a cleaner prevents mixing of different types of grains, and the cleaner removes any particles in the casing that could go bad. Usually the cleaner is installed at intervals of 6 m (Figure 6.15).
- An M-roller, which rotates more smoothly than an S-roller, is typically used in the base chain.
- If the conveyed materials are highly abrasive materials, special block chain provides longer wear life. (Figure 6.16 shows a set-up with NFX-type block chain.)
Figure 6.15 Installation of a Cleaner on a Flow Conveyor Chain
Figure 6.16 NFX-Type Block Chain