1、 Visually inspect the physical integrity of the screen mesh (the most direct basis for judgment)

After shutting down the machine and cutting off the power, disassemble the screen mesh and conduct a comprehensive inspection, focusing on the following signs of damage or aging. If any of them appear, it is recommended to replace them:

Mesh blockage and deformation

If the mesh is blocked by sample particles (especially viscous and prone to clumping samples) and cannot be unblocked after conventional cleaning (such as ultrasonic cleaning, high-pressure water flushing, brush cleaning), it will lead to a decrease in effective screening area and a significant reduction in screening efficiency. At this time, the screen mesh needs to be replaced.

Observing the shape of the mesh, if the mesh is stretched and deformed due to long-term vibration or material impact, and the aperture becomes larger, it will cause the screening particle size to deviate from the set value (such as the nominal 200 mesh sieve with an actual aperture exceeding the standard), directly affecting the screening accuracy and must be replaced.

Surface damage and cracking of the screen mesh

Check whether there are holes, tears, and edge shedding in the sieve: Small holes can allow fine particle samples to leak through, resulting in a lower content of coarse particle components; Large scale tearing or edge shedding will completely lose the screening function.

Pay attention to the welding points/bonding areas of the screen mesh: The screen mesh of the 3D vibration screening instrument is often fixed to the grid by welding or bonding. If the welding points fall off or the bonding area opens, it will cause the screen mesh to loosen, the material to deviate during the screening process, and at the same time exacerbate the damage to the screen mesh. It needs to be replaced in a timely manner.

Aging of screen material

For non-metallic mesh screens such as nylon and polyester, if they become brittle, yellowed, or have decreased toughness (cracking upon gentle bending), or if the metal mesh screen shows extensive rusting and thinning of the mesh, it indicates that the material has aged and lacks strength. Even if there is no damage temporarily, it is highly likely to be damaged in subsequent use. It is recommended to replace them preventively.

2、 Judging based on abnormal screening effect (indirectly verifying screen failure)

If there is no obvious physical damage to the sieve, but the screening results show the following abnormalities, it indicates that there may be hidden problems with the sieve (such as pore size deformation, local blockage), and further inspection or replacement is needed:

Screening accuracy deviation exceeds the standard

Using standard screening reference materials (such as standard powders with known particle size distribution) for verification tests, if the deviation between the mass proportion of each particle size after screening and the standard value exceeds the allowable range of the instrument (usually ± 3%~± 5%), and after excluding factors such as sample preparation and vibration parameter settings, it can be determined that the sieve aperture no longer meets the requirements and needs to be replaced.

The repeatability of repeated screening results for the same batch of samples under the same vibration parameters is extremely poor (such as a deviation of fine powder yield>5% between two screenings), most likely due to local blockage or uneven pore size of the sieve mesh.

Significant decrease in screening efficiency

Compared with historical data, if the screening time of the same sample is significantly extended (such as originally 10 minutes for screening, now it takes more than 20 minutes), and there is no improvement after cleaning the sieve, it indicates that the effective mesh area is insufficient and the sieve needs to be replaced.

After screening, there are still a large number of fine particles that should be sieved out in the sieved material (coarse particles), or coarse particles mixed in the sieved material (fine particles), indicating that the sieve mesh is clogged or damaged.

3、 Auxiliary judgment based on equipment operating status

The abnormal performance of the three-dimensional vibration screening instrument during operation can also reflect the state of the screen mesh:

During the screening process, if there is uneven distribution and local accumulation of materials on the screen surface, and the vibration frequency and amplitude are adjusted without improvement, it may be due to local blockage or decreased flatness of the screen mesh. The screen mesh needs to be checked and replaced.

The equipment emits abnormal noises (such as friction and shaking sounds) during operation. After shutdown, it is found that there are loose and friction marks between the screen and the grid, indicating that the fixing of the screen has failed. The screen needs to be replaced and the grid needs to be checked for deformation.

4、 Time nodes for preventive replacement (to avoid sudden failures)

Even if there are no obvious abnormalities in the sieve, it should be replaced regularly according to the frequency of use and sample characteristics. It is recommended to follow the following principles:

Replace according to frequency of use: For regular laboratory use (1-2 times a day), it is recommended to replace metal screens every 3-6 months, and non-metallic screens every 1-3 months; In industrial high-frequency usage scenarios (using ≥ 4 times a day), it is necessary to shorten the replacement period to 1-2 months.

Adjust according to sample characteristics: When processing high hardness and sharp particle samples (such as quartz sand and metal powder), the screen mesh wears out quickly and needs to be replaced more frequently; When handling viscous and corrosive samples (such as mud, acid alkali powder), if the sieve mesh becomes clogged or corroded, it is recommended to clean it after each use and replace it preventively every 1-2 months.

Summary and judgment process

Stop the machine and visually inspect the physical condition of the screen mesh → if there is any damage/aging/blockage → replace it directly;

No abnormality in physical state → Verify screening accuracy with standard substances → Deviation exceeds standard → Replace;

Regularly replace based on frequency of use and sample characteristics → preventive replacement.