Rotary Feeders for Handling Bulk Solids Material to ensure Continuous Control

Rotary Feeders for Handling Bulk Solids Material to ensure Continuous Control
Rotary feeders, also known as rotary valves or rotary airlocks are mechanical devices used to feed or discharge bulk solid materials that are in granular or powder form to ensure continuous control or regulatory function.

Feeders are mostly used for metering the flow of material between equipment. Some amount of material between blades are transported with rotation of the rotor and the required amount can be adjusted by custom design rotary feeders with accurate feeding. Feeding can be required in terms of volume or mass. When our case is this type of metering application, we need to ask some questions to select and design the right feeder for intended functionality. We can classify and list these questions below and answer them to give you more insight into this decision and design process:

Which material are we working with?

According to material classification and process type, there should be some changes in the rotary feeder’s design and properties.

Is this material abrasive?

If yes, the material that the rotary feeder is made of plays a critical role in the long and effective operational lifespan of the equipment.

What is the moisture level of the material?

Material’s moisture level affects the flow while passing through the rotary feeder, humidity or dampness in handled material slows downflow of material and may cause clogging in the feeder.

What is the particle size of our material right before feeding it to the process?
Particle size is a point that needs attention while designing rotary feeder. Particle size of material affects overall dimensions of feeder, blade geometry and additional features.

Is the material classified as explosive or combustible? Does an explosive atmosphere exist?

Combustible dust may present an explosion hazard when suspended in the air. Processing combustible powders need extreme care and require important counter-measures to avoid possible unfortunate incidents. These incidents can cause tragic loss of life, injuries, and destruction of industrial buildings, and occur within milliseconds. Rotary feeders that will be used in this kind of environment or with this kind of material must be designed and manufactured according to ATEX regulations for the safety of operation and operators.

Are we doing continuous or batch-wise feeding?

Selection of feeding type is essential for an efficient and reliable production process. Thus, the selection of rotary valve and feeder design plays an important role at the same time. Continuous feeding cases generally need non-stop feeding of small amounts of material compared to the total amount of mixture. On the contrary, batch-wise feeding processes take a definite amount of material
and proceed to the operation. In batch-wise processes, rotary feeders operate for determining time intervals and shift to the standby mode until the next batch of operation.

Which way is the dosage of material will be measured? Volumetric or gravimetric?

Rotary feeders give average but not precise dosage to process. With aim of ensuring precise dose, additional measuring equipment may be required. To decide if there is a need for this type of equipment, we need to understand the process and material properties completely. One of the suitable pieces of equipment is a weighing hopper. Weighing hoppers have built-in load cells, like most weight measuring equipment. The load cell will measure the force applied and translate it to a weight that is readable by the user or control mechanism of the process. The placement of the load cell gives two different configurations and applications to bulk solid handling feeder applications. The first type is Gain-in-Weight is done by measuring the weight of a hopper located after the dosing rotary feeders. On the other hand, when the dosing rotary feeder runs and transports the product, the weight of the hopper from which the material is taken is measured and it is decreased, it is Loss-inWeight dosing. Volumetrically measured feeder processes mostly based on material’s flow density and required flow rate, according to these values, the required flow rate of material is computed and the rotary feeder is chosen or designed to meet with it.

What is the requested capacity?

According to the value of the rate of material feed, we will calculate the required volumetric capacity of our feeder, the revolution of rotor per minute or hour, motor & gearbox, and power supply to meet essential values for functionality.

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Polimak is a solution provider in bulk solids handling industry with 40 years of experience. Though, our main product lines are bulk solid handling, conveying, dosing, batching, dust collection, filter systems and pumps. Food, cement, iron, steel, agriculture, chemicals, plastics are some of the industries we serve. Being one of the solutions of ...