Definition
A screener is a laboratory instrument that separates and measures particle size distribution, which is widely used in the particle size analysis of solid particle materials. It grades samples by particle size through a series of standard screens, resulting in distribution data for particle populations. The instrument adheres to international and national standards, such as ISO 3310 and GB/T 6005, ensuring the standardization of the measurement process and the comparability of the results.
Principle
The working principle of the screener is based on mechanical screening and vibration separation. The instrument places the sample on the top screen and uses a vibrating device to make the screen move horizontally or vertically, and the particles pass through the screen hole under the action of gravity and vibration. Particles smaller than the size of the screen hole fall into the lower screen, while particles larger than the size of the screen hole remain on the current screen surface. After a set time, the mass of residual particles on each screen is weighed to calculate the mass percentage for each particle size interval. The screening process can be expressed by the screening efficiency formula: E = (m_s / m_t) × 100%, where E is the screening efficiency, m_s is the mass of particles passing through the screen, and m_t is the total mass of the sample.
Screening measurement method
Screening measurement is usually divided into two types: dry and wet. Dry screening is suitable for dry, non-viscous particles, and samples are separated by vibration in a dry state. Wet screening is suitable for fine particles or easily agglomerated materials with the help of water flow to reduce static electricity and adhesion effects. Standard operations include sample preparation, screen stacking, vibration parameter setting, screening time control and result weighing. The measurement results are presented in the form of cumulative distribution or interval distribution to provide a data basis for subsequent analysis.
Factors affecting screening results
The screening results are influenced by a variety of factors. Sample characteristics such as particle shape, density and surface properties may change the behavior of the sieve hole. Environmental conditions such as humidity and static electricity can cause particles to stick and affect the accuracy of separation. The instrument parameters include vibration amplitude, frequency and screening time to be adjusted according to the sample to avoid screen blockage or particle damage; Operational normativeness such as sample volume and screen cleanliness are also directly related to data reliability. Therefore, standardized operating procedures and conditional control are significant to ensure the consistency of results.
Applications
Screening meters play an important role in several industries. in the field of building materials, it is used for particle size control of sand and gravel and cement; In the chemical industry, the distribution characteristics of powder raw materials are analyzed; In food processing, the particle uniformity of flour and powdered sugar is monitored; In terms of environmental monitoring, assist in the classification of soil and sediment particle size. These applications rely on quantitative data from screeners to support product quality assessment and process optimization.
Selection considerations
When selecting, it is necessary to comprehensively evaluate the technical parameters and usage requirements. The screen specifications should conform to the standard system, and the material should be corrosion and wear resistant; The vibration method such as electromagnetic vibration or mechanical vibration should match the characteristics of the sample; The degree of automation involves sample processing and data logging functions, which can improve operational efficiency; In addition, the compatibility and ease of maintenance of the instrument are also considerations for long-term use. Users should choose based on the actual sample type, throughput requirements, and standard compliance to ensure instrument suitability.