It is a common problem for a hydraulic classifier to mix a large amount of
fine powder into the bottom flow during operation. Bottom flow fine clamping not
only increases the burden of subsequent dehydration and pressure filtration, but
also leads to the loss of fine-grained products, greatly reducing the
classification efficiency. The problem usually lies in the combination of rising
water flow and spiral speed.
The excessive upward flow velocity is the primary reason for the thinning of
the bottom flow. When the water flow rate is too fast, fine particles are washed
into the bottom flow before they can settle. A water sample can be taken from
the middle of the classifier to detect the suspended solids content. If it is
significantly higher, it indicates that the rising water flow is too strong.
Turn down the inlet valve by one gear, observe for 2 hours, and then take a
sample until the fine powder content in the bottom flow drops to a reasonable
range. During normal operation, the overflow concentration should be maintained
at 10% -15%. If it is lower than 8%, it indicates that the water volume is too
large and a large amount of fine powder is lost.
Wear or improper rotation speed of spiral blades can also lead to thinning of
the bottom flow. After the wear of the blade edge, the gap between the blade and
the groove increases, and some coarse particles leak into the bottom flow, while
fine particles are carried into the bottom flow due to the fast spiral lifting
speed. It is recommended to measure the gap between the outer edge of the blade
and the inner wall of the groove once a month. If it exceeds the design value by
1.5 times, repair or replace the blade by welding. The spiral speed should be
adjusted within 5 r/min each time, and the next step should be determined by
observing the grading effect after adjustment.
A too low height of the overflow weir can also exacerbate the thinning of the
bottom flow. When the overflow weir is too low, the slurry stays in the tank for
a short time, and fine particles do not have time to float up before sinking
into the bottom flow. Properly raising the overflow weir by 50-100mm and
extending the settling time can effectively reduce the fine powder content in
the bottom flow. After adjustment, pay attention to observing whether the
overflow has become thicker, and both should be taken into account.
During daily inspections, samples are taken and tested for the fineness of
the bottom flow once per shift. If any impurities are found, they should be
promptly checked in the order of "first check the water flow rate, then check
the spiral speed, and finally check the overflow weir". For equipment operation
related issues, please call Manager Zhang at 13583776655 (same as WeChat) at
Shandong Heavy Industry.