Powder vacuum feeders typically use the average particle size of the material as the granularity reference. Some materials are fine powders that can easily adhere and cause clogging in the feeding pipelines when moistened. Conversely, materials containing large lumps may lead to mechanical failures. Therefore, designing a feeder requires not only understanding the average particle size of the material but also its particle size distribution and the percentage of each size fraction.

The shape of particles also affects material flowability. For simplicity in calculations, particles are often assumed to be circular or spherical, represented by an equivalent diameter. However, most materials have irregular shapes. Good material flowability facilitates efficient feeding in the conveying system. Flowability is typically assessed using the angle of repose and the internal friction angle. A smaller angle of repose and a smaller internal friction angle indicate better material flowability.

The machine operates by generating an airflow under vacuum. Under the influence of this airflow, the material is transported through a hose into the vacuum hopper. After a set period (the feeding time, which is adjustable), the compressed air supply is shut off, halting the vacuum generation by the pump. Simultaneously, the hopper’s discharge door opens under the action of a pneumatic cylinder. As the vacuum dissipates, the material automatically discharges into the receiving equipment (such as tablet presses or packaging machines). Meanwhile, compressed air stored in the air reservoir blows back through the filter, automatically cleaning it. After a predetermined interval, the compressed air restarts, the pneumatic vacuum pump regenerates the vacuum, the discharge door closes, and the powder vacuum feeder resumes feeding. This cycle repeats continuously, ensuring materials are *consistently delivered to the receiving equipment.

For vacuum feeders equipped with level control, feeding is automated based on the material level in the receiving equipment’s hopper. When the material level in the receiving hopper exceeds a certain point, the vacuum feeder stops feeding. When the level drops below a set point, the feeder automatically activates to replenish the material.

In pharmaceutical plants, frequent cleaning of the vacuum feeder is often required due to product changes or different batch numbers. The design of this machine fully accommodates this need. Cleaning involves only the following steps:

Release the buckles and remove the pneumatic vacuum pump assembly (which includes the pneumatic vacuum pump, air reservoir, and cover as a single unit). This component does not require water cleaning.

For the filter assembly, use compressed air to blow off the powder adhering to the filter tubes. Then, rinse repeatedly with hot water. After thorough rinsing, use compressed air again to remove residual water from the filter tube walls. At this point, blowing through the filter tube by mouth should feel smooth. If resistance is felt, it indicates remaining moisture in the tube walls, requiring further drying with compressed air before air-drying or oven-drying.