1. Introduction
Twin-shaft mixers are widely used in concrete, asphalt, and solid waste treatment due to their strong shearing force and high mixing uniformity. The liner, as the inner wall protective layer directly contacting materials, not only resists abrasion but also guides material circulation. In actual production, liner thickness (typically 12–30 mm) directly affects the mixer's internal space, material flow state, and power consumption. Clarifying the relationship between liner thickness and mixing performance is critical for optimizing mixer design, reducing costs, and improving mixing quality.
2. Influence of Liner Thickness on Key Mixing Performance Indicators
2.1 Mixing Uniformity
Excessively thin liner (<16 mm): Prone to warping, bulging, or uneven gaps under material impact and thermal stress (e.g., 150–180°C for asphalt mixing). Material accumulates in depressions, forming mixing dead zones, which leads to aggregate segregation, uneven temperature, and reduced mixing uniformity. The scraping between mixing arms and the deformed liner causes fluctuating resistance, further deteriorating mixing quality.
Moderate thickness (18–25 mm): Maintains a smooth cylinder wall and uniform gaps, ensuring smooth material circulation without dead zones. The bidirectional convection and shearing action of the twin shafts are fully utilized, with a mixing uniformity CV value ≤10%.
Excessively thick liner (>30 mm): Increases the roughness of the inner wall, hinders material flow, and causes local accumulation. The reduced effective mixing space weakens the mutual shearing and folding of materials, prolongs the mixing cycle, and may lead to insufficient mixing of local materials.
2.2 Mixing Efficiency and Effective Volume
Capacity reduction: For every 5 mm increase in liner thickness, the effective volume of the mixing cylinder decreases by 3%–5%, reducing the single-batch mixing output. For example, a 3 m³ mixer with a 30 mm liner has an actual effective volume of only about 2.6 m³.
Mixing cycle: An overly thick liner increases material flow resistance, prolonging the mixing cycle by 5%–10%. A thin liner (16–18 mm) has a smooth surface and low resistance, enabling materials to reach uniformity in a short time (60–90 seconds).
Optimal thickness: A thickness of 18–25 mm balances effective volume and flow resistance, maximizing output per unit time.
2.3 Energy Consumption and Operating Load
Thick liner: Increases the mixer's weight (by 10%–20% for every 10 mm increase) and material flow resistance, raising the motor load by 15%–25%. Long-term high-load operation increases energy consumption and accelerates the wear of bearings and reducers.
Thin liner: Light weight and low resistance result in low energy consumption, but frequent replacement due to wear increases downtime and maintenance costs.
Energy-saving range: A liner thickness of 18–25 mm keeps the motor load within 70%–80% of the rated power, achieving low energy consumption and stable operation.
2.4 Wear Resistance and Service Life
Thin liner (<16 mm): Has a small wear margin and a service life of only 3–6 months under high-impact working conditions (e.g., hard aggregates like granite). Frequent replacement increases costs and affects production continuity.
Thick liner (>30 mm): Has sufficient wear resistance, with a service life of 12–24 months. However, when the thickness exceeds twice the maximum aggregate particle size (commonly 13–19 mm), the marginal benefit of wear resistance decreases significantly.
Optimal life range: A thickness of 18–25 mm (high-chromium alloy cast iron or Ni-Hard material) provides a service life of 8–18 months, balancing wear resistance and cost.
3. Optimal Liner Thickness for Different Working Conditions
3.1 Small-sized mixers (diameter <1.5 m)
Recommended thickness: 12–15 mm (ceramic composite liner, 6–8 mm ceramic layer).
Reason: The small mixing volume requires avoiding excessive space occupation by the liner, prioritizing light weight and high efficiency.
3.2 Medium-sized mixers (diameter 1.5–3 m)
Recommended thickness: 15–20 mm (8–10 mm ceramic layer).
Reason: Balances wear resistance and structural strength, avoiding excessive motor load due to excessive weight.
3.3 Large-sized mixers (diameter >3 m) or high-impact working conditions
Recommended thickness: 18–25 mm (10–12 mm ceramic layer, steel plate substrate ≥10 mm).
Reason: Resists strong material impact, prolongs service life, and ensures mixing stability.
3.4 Special working conditions (asphalt, high-temperature materials)
Recommended thickness: 20–25 mm (high-temperature resistant alloy liner).
Reason: Prevents deformation and wear under high temperature (150–180°C), avoiding mixing dead zones caused by thermal deformation.
