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The vacuum feeder relies on air pressure difference to move material. Its core principle can be summed up as "using pressure difference to create directional airflow".
When the vacuum pump starts, it continuously removes air from inside the vacuum hopper and the entire conveying pipeline, creating a negative pressure zone inside the system that is lower than the outside atmospheric pressure. Once the pressure inside the hopper drops to a preset level, a stable pressure difference is established between the inside and outside. During this process, outside air – driven by atmospheric pressure – carries protein powder from the suction nozzle into the conveying pipe, forming a gas‑solid two‑phase flow that moves along the pipe toward the vacuum hopper.
For ultra‑fine powders like protein powder, different material characteristics require different vacuum levels. Typically, the vacuum is set between -0.06 MPa and -0.08 MPa, which is sufficient to overcome the adhesion force and agglomeration resistance between protein powder particles, ensuring smooth suction and maintaining a suspended state.
Why use an oil‑free, water‑free vacuum pump? Protein powder is a food ingredient that comes into direct contact with the human body, so cleanliness is critical. Ordinary vacuum pumps use lubricating oil and can generate oil mist; compressed air containing moisture can cause protein powder to absorb moisture and cake. Therefore, protein powder vacuum conveying must use an oil‑free, water‑free vacuum pump or vacuum generator, eliminating the risk of oil mist or moisture contaminating the material at the power source.
Once negative pressure is established, material is immediately drawn into the system.
The stainless steel suction nozzle is inserted into the protein powder bag or hopper. Under negative pressure, outside air and protein powder are sucked together into the nozzle, forming a two‑phase mixture of "material + air", which then passes through a food‑grade conveying hose into the vacuum hopper.
Three motion states of material in the pipeline. In pneumatic conveying systems, the motion of solid particles in the airflow depends on the material‘s characteristics. Common motion states include:
Uniform suspension state: Particles are evenly distributed in the airflow, moving forward continuously and stably. Suitable for free‑flowing materials with uniform particle size;
Non‑uniform state: Material moves forward intermittently in "clumps" or "waves", with particles gathering and dispersing alternately. This is the most common motion state in pneumatic conveying and is stable and acceptable for most powders;
Stagnation and accumulation state: Material stops moving forward, piling up like "sand dunes" or "plugs". This usually occurs when conveying speed is too low or pipeline resistance is too high, and is an abnormal working condition to be avoided.
For protein powder, which is fine and relatively free‑flowing, the material typically moves in a "non‑uniform" state in the pipeline, meaning the conveying process is stable and reliable without clogging or plugging.
Regarding the particle size distribution of protein powder, research data show that the D90 (the particle size below which 90% of particles fall) of plant protein powder is typically between 75 and 375 microns, and some processed products can have a D90 below 10 microns. Such fine powder places high demands on the sealing and filtration accuracy of the conveying system – any tiny gap can cause protein powder leakage, and insufficient filter precision will allow ultra‑fine powder to penetrate directly.
After the air‑powder mixture enters the vacuum hopper, the most critical step – air‑material separation – takes place.
The airflow carrying protein powder reaches the hopper and first passes through a filter. The filter element has a surface full of micro‑pores through which air molecules can pass, but protein powder particles are trapped on the outside of the filter. The cleaned air passes through the filter into the vacuum pump and is finally discharged to the atmosphere; the intercepted protein powder settles to the bottom of the hopper under gravity.
The special challenge protein powder poses to filters. Protein powder tends to generate static electricity when moving in high‑speed airflow. Fine particles firmly adhere to the filter surface, forming a dense "powder film" that is difficult to remove with ordinary reverse pulses. If the filter precision is insufficient, ultra‑fine protein powder will penetrate directly into the vacuum pump, causing not only material loss but also contamination of the workshop environment – a particularly critical issue in protein powder vacuum conveying.
To address this challenge, the Gaofu vacuum feeder offers multiple filter precision and material options:
| Protein Powder Type | Recommended Filter Type | Filter Precision | Application Scenario |
| Conventional soy protein (100-200 mesh) | Polyester membrane filter | 5-8μm | Clean room, GMP line |
| Whey protein (high fines content) | PTFE membrane filter | 3-5μm | Premium sports nutrition, infant food grade |
| Ultra‑fine protein powder (500 mesh+) | 316L sintered mesh filter | 0.5-3μm | Pharmaceutical grade, high‑active ingredient retention |
The polyester membrane filter is the standard configuration for protein powder conveying. Its smooth surface resists powder adhesion, and powder detaches easily during reverse‑pulse cleaning. The PTFE membrane filter has an extremely low surface energy and friction coefficient; protein powder hardly adheres at all, making it suitable for whey protein and other applications requiring higher cleanliness. The 316L stainless steel sintered mesh filter offers high mechanical strength, corrosion resistance, and heat resistance, and can be repeatedly cleaned and regenerated – suitable for pharmaceutical‑grade protein powder lines or those requiring frequent sterilisation cleaning. All filters can be selected for the Gaofu vacuum feeder based on actual material characteristics.
When the protein powder in the hopper reaches a preset level, the system enters the discharge phase.
The level sensor detects that the hopper is full and automatically sends a signal to the control system. The pneumatic discharge valve opens, and the protein powder falls by gravity into the packing machine hopper, mixer or other receiving equipment below.
At the same time, a very important action is triggered simultaneously – compressed air pulse reverse cleaning. During discharge, the compressed air reverse‑pulse device injects a momentary high‑pressure pulse of air into the filter element, shaking off the protein powder adhering to the filter surface and restoring its permeability, ready for the next suction cycle.
Why must protein powder conveying have efficient reverse cleaning? The electrostatic adhesion of protein powder makes it more likely to stick to the filter surface. The higher the protein content and the finer the particle size, the more severe the adhesion. Ordinary timed reverse cleaning cannot thoroughly remove the adhered layer; the protein powder will gradually "smother" the filter, causing a loss of permeability and a sharp drop in conveying efficiency. Therefore, protein powder vacuum conveying systems need pressure‑differential controlled reverse cleaning or high‑frequency pulse cleaning – automatically triggering reverse cleaning when the pressure difference across the filter exceeds a set value (e.g., 3-5 kPa), ensuring the filter does not fail due to adhesion.
After discharge is complete, the system automatically closes the discharge valve, the vacuum pump restarts, and the next cycle of suction‑separation‑discharge begins. The entire process is automatically controlled by a PLC or HMI. Suction time and discharge time can be continuously adjusted within a range of 0 to 99 seconds. By setting parameters, fully automatic continuous operation can be achieved without manual intervention.
The negative pressure conveying mechanism of the vacuum feeder essentially solves a very practical problem: can the movement of protein powder from point A to point B be accomplished without dust, without moisture absorption, without excessive human contact, and without contamination? From a technical perspective, the answer consists of four interconnected elements – negative pressure drives the material into an enclosed pipeline, the filtration system separates protein powder from air, level control automatically coordinates suction and discharge, and pulse reverse cleaning keeps the filter working efficiently.
When these four elements are properly coupled, protein powder can complete the entire conveying process from the screening workshop to the packing line inside a pipeline – no manual dumping, no exposure to air, no worry about caking or denaturation. To summarise the working mechanism of the vacuum feeder in one sentence: Using air pressure difference as power, an enclosed pipeline as the carrier, and automatic control as the means, protein powder goes where it needs to go by itself – throughout, no contact, no contamination, no waste.
About Gaofu Machinery
Xinxiang Gaofu Machinery Co., Ltd. was originally founded in the 1980s. After more than 40 years of development, the company has become a "National Specialized and Sophisticated 'Little Giant' Enterprise", a "National Green Factory", a "National High-tech Enterprise", a "National Intellectual Property Advantage Enterprise", and the "President Unit of the Vibration Association". It also hosts the "Henan Provincial Industrial Design Center", the "Henan Provincial Engineering Technology Research Center for Intelligent Online Screening Systems", and the "Xinxiang Municipal Engineering Technology Research Center for Fine Screening". The company has been granted more than 500 invention, utility model and design patents, has received the "Science and Technology Achievement Award" issued by the Ministry of Industry and Information Technology, and has participated in drafting four "National Standards".
Gaofu's product portfolio covers several series and hundreds of varieties, including vibrating screening equipment, conveying equipment, and automated material handling systems. Its main products include one-stop solutions such as automatic feeding systems, powder feeding systems, pneumatic conveying systems, weighing and batching systems, minor ingredient batching systems, water supply systems, oil supply systems, fluid conveying systems, central kitchen powder feeding systems, powder conveying systems, and top-loading feeding systems. The food system production lines mainly include:
Bakery production lines: bread production line, cake production line, shortbread production line, croissant production line, toast production line, pizza production line, biscuit production line, hamburger production line;
Dough product production lines: steamed bun production line, stuffed bun production line, twisted roll production line, sesame paste baked bun production line, steamed dumpling production line, dumpling production line, youtiao (fried dough stick) production line, stuffed pancake production line.
Gaofu products are not only popular in Greater China but are also exported to more than 100 countries and regions, including Russia, Canada, the United States, New Zealand, Japan, Brazil, South Africa, etc. They are widely used in many industries such as food, pharmaceuticals, chemicals, metallurgy, building materials, mining, thermal power, and environmental protection, earning the trust and praise of over 10,000 customers worldwide. The company adheres to its mission: "Enhance material quality and efficiency, meet customer needs", walking side by side with customers for harmonious and win-win cooperation. Today, Gaofu has become an approved supplier to many Fortune 500 companies, including CNPC, Sinopec, Sinochem Group, China Resources Group, Sinopharm Group, COFCO Group, China National Building Material Group, China Aerospace, and Jinchuan Group.
