Laboratory sieve shaker is widely used for particle size classification and particle distribution testing of powders and granules. Its sieving efficiency, accuracy and repeatability are mainly affected by vibration amplitude, sieving duration, sample loading, sieve mesh condition, material properties and equipment assembly. Different working conditions lead to distinct sieving results, and improper operation will cause data distortion or sieving failure.

1. Working Principle

The equipment generates 3D vibration to drive sieve meshes, making materials loosen, stratify and roll. Fine particles pass through the meshes while coarse particles are retained to realize grading. Normal sieving requires materials to keep loose and fully contact with mesh holes. Any abnormal parameters or operations will disturb material stratification and bring test errors.

2. Effects of Different Working Conditions

2.1 Vibration Amplitude

Low amplitude: Materials bounce slightly with poor fluidity, easily causing accumulation and mesh clogging. Fine particles cannot pass through smoothly, resulting in low sieving efficiency and larger tested particle size. Suitable for lightweight and electrostatic-prone fine powders.

Standard amplitude: Materials stratify evenly with sufficient permeation. No particle damage occurs. It features high accuracy and good repeatability, complying with national standard requirements. This is the optimal setting for most common powders and granules.

High amplitude: Materials splash severely and fail to keep contact with meshes, reducing fine particle penetration. Brittle materials are prone to crushing, which artificially changes particle size. It also accelerates mesh wear and deformation, leading to invalid test data. Only applicable for breaking slightly agglomerated hard materials.

2.2 Sieving Duration

Short duration (< 3 mins): Materials are not fully stratified. A large number of fine particles remain on upper sieves. Sieving is incomplete, with coarse test results and poor data repeatability.

Standard duration (3 - 10 mins): Sieving reaches a stable state with thorough classification and minor errors, ideal for quantitative tests.

Excessively long duration (> 15 mins): No improvement on sieving effect. Mutual friction produces extra fine particles, powders agglomerate due to static electricity, and sieve meshes suffer fatigue wear, introducing systematic errors.

2.3 Sample Loading Capacity

Insufficient loading: The sample cannot represent the overall material well, and residues on sieves cause minor deviation in particle proportion statistics. Only for rough screening.

Proper loading (thin layer spread): Materials have enough space to flow and stratify without extrusion. It ensures the highest sieving accuracy and reliable quantitative test data.

Overloading: Materials stack thickly. Fine particles are wrapped by coarse particles and cannot penetrate meshes. Severe clogging and sieving failure occur with large data deviation.

2.4 Sieve Mesh Condition

Clogged mesh: Caused by sticky, moist materials or particles stuck in holes. The effective mesh area decreases, leading to lower detected fine particle content and coarser particle size results.

Worn, deformed or damaged mesh: Aperture size goes out of tolerance. Coarse particles pass through abnormally. The mesh loses grading accuracy completely, and test data becomes invalid.

2.5 Material Properties & Equipment Assembly

Moist and sticky materials tend to cake and block meshes. Ultra-fine lightweight powders easily agglomerate by static electricity. Brittle particles are likely to break under vibration. Loose sieve frames, unlevel equipment and unstable voltage will cause material leakage, uneven sieving and unrepeatable test results.

3. Common Problems, Causes and Impacts

1.Incomplete sieving & excessive fine particle residues: Caused by insufficient amplitude, overloading, short duration or clogged meshes; tested particle size is coarser than actual.

2.Poor data repeatability: Caused by inconsistent loading and duration, loose assembly or unstable operation; test results are not comparable.

3.Smaller tested particle size: Caused by high amplitude and long-time sieving which crush particles; fine particle content is overestimated.

4.Rapid mesh damage: Resulted from long-term high-amplitude operation, sieving hard materials and cleaning with hard tools.

4. Basic Optimal Operation Guidelines

1.For common materials: Adopt standard amplitude, 3-10 minutes sieving time and thin-layer loading.

2.For fine and sticky materials: Dry samples in advance, use low amplitude and intermittent short-time sieving.

3.For hard materials: Control amplitude and duration strictly to avoid particle crushing.

4.Inspect mesh integrity, equipment level and assembly before and after tests, and clean residual materials timely.