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Before selecting a linear screen, it is important to understand what pelleted feed classification actually does. This can be considered from two aspects.
First, remove fines and broken pieces. During the pelleting process, a certain proportion of powder and broken particles is inevitably produced. The national standard GB/T 16765 "General Technical Conditions for Pelleted Feed" specifies the allowable fines content and pellet durability index for chicken, duck, piglet and rabbit pelleted feeds, requiring fines content ≤4% and pellet durability index ≤10%. Powder that is not removed not only affects the appearance of the feed but also further degrades during storage and transport, resulting in lower final product quality.
Second, separate different sizes by particle diameter. Commercial feed is often sold in different particle size grades. For broiler feed, the pellet sizes required for starter, grower and finisher stages are different; for aquatic feed, the pellet sizes for juvenile shrimp and adult shrimp also differ significantly. By configuring multiple screen decks, the linear vibrating screen can accurately separate mixed pelleted feed into different particle size fractions, directing each size to its own packing line and increasing product value.
Once it is clear "what to screen", the next question is "how to screen".
1. Working Principle: Advantages of Linear Motion
The screening principle of the linear vibrating screen is physically well‑defined. The equipment uses two synchronously counter‑rotating vibration motors as the excitation source. The horizontal excitation forces generated by the eccentric blocks of the two motors cancel each other out, while the vertical excitation forces add together, driving the screen box in a smooth linear reciprocating motion.
When material enters the screen surface, under the combined action of excitation force and gravity, it moves forward in a jumping trajectory. Particles smaller than the mesh apertures fall through, while particles larger than the apertures travel along the screen surface to the discharge port. With 1 to 5 screen decks, one machine can separate 2 to 6 different size fractions simultaneously.
This screening method has three notable characteristics: first, the material forms a clear stratified flow on the screen surface, with large and small particles naturally separating – giving high screening accuracy; second, the material moves quickly along the screen surface, providing high throughput (2 to 5 times that of ordinary round screens); third, the gentle linear jumping motion does not squeeze or impact the formed pellets, effectively protecting pellet integrity and reducing broken material loss.
2. Core Requirements of Pelleted Feed Classification for Screening Equipment
The task of pelleted feed classification is to remove broken pieces and fines after pelleting, while separating the acceptable pellets into different size grades. This puts several clear requirements on the screening equipment:
Stable screening accuracy – accurate separation between acceptable pellets and unacceptable fines, with clear cut points to avoid cross‑contamination;
High capacity – feed lines typically run continuously; the screen must not become a bottleneck;
Pellet protection – no secondary breakage of pellets during screening;
Reliable operation – feed mills often operate 24/7; equipment failure rate must be kept low;
Food‑grade hygiene compliance – feed directly affects the safety of livestock, poultry and aquatic products; material‑contact parts must meet hygiene standards.
The linear vibrating screen is widely chosen for pelleted feed classification precisely because it meets these requirements well. High‑capacity feed lines often run continuously; if the equipment stops, the whole line stops. The linear screen has a simple structure and low failure rate, meeting the reliability requirements for long‑term continuous operation – a key reason it is favoured by feed mills.
Application Scenarios: Which Pelleted Feeds Can a Linear Screen Handle?
Different types of feed have different requirements for particle size. The configurability of the linear screen allows it to meet diverse classification needs.
Pig compound feed – Piglet feed pellets are usually small, while grower‑finisher feed pellets are coarser. With different mesh sizes, the same linear screen can meet the classification requirements for different growth stages.
Poultry compound feed – Broiler feed and duck feed have clear standards for particle size and fines content. Equipped with high‑precision screens, the linear screen can keep fines content low.
Extruded aquatic feed – Fish feed and shrimp feed have stricter requirements for particle size and uniformity. The industry standard for aquatic extruded feed requires a pellet durability index below 1%, demanding higher screening accuracy. Through fine adjustment of screen deck inclination and vibration parameters, the linear screen can meet this stringent requirement.
Pet feed – Pet feed often has higher requirements for particle appearance and uniformity than ordinary livestock and poultry feed. The Gaofu SZF series linear screen, customised for pet feed, achieves precise classification of both pelleted and powdered pet feed. Its stable screening accuracy and uniform classified particles meet the high standards of the pet feed industry.
Ruminant pelleted feed – Cattle, sheep and other ruminants also have specific particle size requirements for feed at different stages, and the linear screen is equally suitable.
Based on decades of experience in screening, Gaofu Machinery has developed the SZF series linear vibrating screen solution specifically for pelleted feed classification. Gaofu Machinery has grown into a "National Specialised and Sophisticated 'Little Giant' Enterprise" and a "National Green Factory", holding more than 500 granted patents and participating in the drafting of four national standards. The following sections analyse the practical configuration from several useful perspectives.
1. Multi‑Deck Classification: One Machine Produces Multiple Sizes at Once
The Gaofu linear screen supports 1 to 5 screen decks. Taking a three‑deck configuration as an example: the top deck retains oversize pellets (returned to the pellet mill for reprocessing), the middle deck collects the target‑size finished pellets, and the bottom deck removes fines and small broken pieces.
This means that finished pellets, re‑pellet material and fines are all separated in the same machine at the same time – feed manufacturers do not need three single‑deck screens in series, significantly reducing equipment count and floor space.
2. Screen Mesh Size and Material Selection
The number of screen decks and the mesh material for the Gaofu linear screen can be customised according to needs. Based on the physical properties of different feed materials, different screening methods apply: for pelleted feed classification by particle size, round‑hole screens are used; for powder removal applications, woven square‑mesh screens are suitable.
Key points for screen mesh material selection: The Gaofu SZF series linear screen supports both 304 stainless steel and carbon steel. Carbon steel offers good rigidity and wear resistance but is less corrosion‑resistant – suitable for dry, non‑corrosive pellet classification. 304 stainless steel offers higher corrosion resistance and is suitable for high‑humidity environments or production lines with strict hygiene standards. For high‑end pet feed lines where hygiene standards are more demanding, 304 stainless steel is recommended; its finely polished surface does not trap material, is easy to clean, and meets food‑grade production requirements.
Feed manufacturers can choose the appropriate mesh material combination based on actual material characteristics, process requirements and budget. Screen changes take only a few minutes, allowing efficient switching between different product specifications.
3. Fines Content Control
The fines content in finished pelleted feed is an important quality indicator. The practical solution for controlling fines content with a linear screen is to use a fine mesh on the bottom deck, thoroughly separating fines into the undersize collection system, reducing the powder proportion in the finished product. Adjusting the screen deck inclination and vibration frequency further optimises screening performance.
4. Vibration Parameter Adjustment
The excitation angle of the Gaofu linear screen can be adjusted according to material characteristics – the speed at which material moves on the screen surface, the thickness of the material layer, and the residence time can all be changed by adjusting the direction of the excitation force. For fragile pellets, reducing the excitation force and lowering the jump amplitude effectively protects pellet integrity. For dry, free‑flowing pellets, increasing the excitation force improves throughput. This adjustability allows the same equipment to handle different types and conditions of pelleted feed.
5. Environmental Protection and Clean Production
Pelleted feed screening generates some dust, especially during fines separation. The Gaofu linear screen can be equipped with a fully enclosed structure or a negative pressure extraction system to contain dust inside the equipment, improving the workshop environment. The fully enclosed design not only reduces dust concentration in the workshop but also prevents foreign matter from entering the screening system – adding an extra safeguard for safe feed production.
About Gaofu
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, coal crushing equipment, filtration equipment, and automated material handling systems. Its main products include vibrating screens, screening machines, vibrating sifters, rotary vibrating screens, ultrasonic vibrating screens, linear screens, air flow screens, gyratory screens, roller screens, dewatering screens, bar screens, vacuum feeders, dust-free feeding stations, ton bag feeding stations, feeding systems, automatic powder feeding systems, automatic slag discharge filters, leaf filters, clay filters, toothed roll crushers, coal crushers, and other equipment. These 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.
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. 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.
Gaofu Machinery – Global No.1 in Vibrating Screen Sales. In May 2024, Frost & Sullivan, an international authoritative advisory firm, based on its research on the global vibrating screen market and calculated according to global vibrating screen sales volume in 2023, issued a market position confirmation certificate to Gaofu Machinery.
