Roller screen is commonly used in the pre classification stage after quartz
sand crushing, but after running for a period of time, the screening efficiency
drops sharply from the design value of over 85% to below 60%, and a large amount
of fine or coarse particles that should have been screened out are mixed in the
finished product. The root cause of the problem is mostly due to clogged sieve
holes.
The high moisture content of the material is the primary cause of blockage.
When the moisture content of quartz sand exceeds 5%, fine powder will adhere to
the inner wall of the sieve and accumulate thicker, forming blockages. The
higher the moisture content, the faster the blockage speed. The solution is
simple - add a hot air duct or a simple dryer at the front end of the drum
screen to reduce the moisture content of the material to below 3% before
entering the screen. If there is already a dehydration screen in the front-end,
the dehydration time can be appropriately extended to reduce the moisture
content of the screened material.
The screen cleaning device becomes virtually useless after wear and tear.
Roller screens are usually equipped with roller brushes or scrapers for cleaning
the screen surface. When the roller brush wears down to less than half of its
original size, the cleaning effect basically disappears, and the clogging of the
sieve holes intensifies. The roller brush is a vulnerable part, and it is
recommended to check the wear condition every three months and replace it in a
timely manner. During the shutdown period, high-pressure water guns can be used
to rinse the sieve holes, paying attention to controlling the water pressure
within 0.5MPa to avoid damaging the sieve mesh.
The mismatch between the sieve size and the material can also cause blockage.
When the sieve aperture is too small, particles are prone to getting stuck in
the aperture, while when the sieve aperture is too large, the screening accuracy
is insufficient. The appropriate aperture should be selected based on the
particle size distribution of the incoming material - the common configuration
is a three-layer sieve with an upper layer of 20mm, a middle layer of 5mm, and a
lower layer of 1mm. If there are many sheet-like particles in the raw material,
the sieve size should be appropriately enlarged by one level to reduce the
probability of clogging.
During daily inspections, observe the particle size of the screened material
once per shift. If a large amount of coarse particles that should have been
intercepted are found mixed in the screened material, it indicates that the
blockage is severe and cleaning should be arranged immediately. For equipment
operation related issues, please feel free to contact the technical team of
Shandong Heavy Industry: Manager Zhang at 13583776655 (same as WeChat).