Measurement of calcium carbonate mesh

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Equipment Required for Hydrometer Test

۱- Precise computer scale with an accuracy of one hundred grams

۲- ۱۰۰۰ cc graduated cylinder

۳- Thermometer

۴- Hydrometer

۵- Small and large beakers

۶- Timer

۷- Manual stirrer (glass or metal)

۸- Electric stirrer

۹- Distilled water

۱۰- Sodium hexametaphosphate solution

۱۱- Wash bottle

۱۲- Published standard tables for obtaining certain parameters

۱۳- Required table for recording test results

Step-by-Step Procedure for Hydrometer Test

The powdered sample to be tested is taken in the required amount from the relevant line silo.
The amount of powder needed for the hydrometer test is 50 grams. This amount is weighed using the computer scale and set aside.
Pour distilled water into the large beaker and measure its temperature using the thermometer. Add the powder to the beaker, stir well with the manual stirrer, and then mix using the electric stirrer for 2 to 3 minutes.

Note:

a- The weighed powder should be completely poured into the empty beaker.

b- After thorough mixing with the electric stirrer, rinse the stirrer blades with the wash bottle so that the water returns to the beaker, ensuring no sample loss at this stage.

c- The total volume of distilled water plus the sodium hexametaphosphate solution and the powder poured into the graduated cylinder should be 1000 cc.

d- The temperature of the distilled water should not be below 22°C or above 25°C. Therefore, the laboratory temperature must always be monitored.

The sodium hexametaphosphate solution is added when pouring the mixture of distilled water and powder into the graduated cylinder, and the amount is 125 milliliters.

Note:

The sodium hexametaphosphate solution is prepared as follows:

Place 10 grams of sodium hexametaphosphate powder into a flask, add distilled water up to the 250 ml mark, and let it sit for 24 hours to dissolve completely. Shake the flask several times to aid dissolution. Note that this solution has a shelf life of one month.

Once the mixture of powder, distilled water, and sodium hexametaphosphate solution is poured into the graduated cylinder, use the wash bottle to adjust the volume to 1000 cc. Stir the solution in the cylinder one final time with the designated manual stirrer, then immediately start the timer.
Depending on the mesh (particle size), the hydrometer is placed into the graduated cylinder after a specified time. This should be done gently.

This time varies depending on the mesh size as follows:

۸۰۰ mesh after 1 minute

۱۰۰۰ mesh after 3 minutes

۱۵۰۰ mesh after 5 to 6 minutes

۲۵۰۰ mesh after 9 to 10 minutes

After placing the hydrometer in the graduated cylinder, measure the temperature. Then, begin taking hydrometer readings, initially at shorter intervals and later at longer intervals.

Note:

a- Typically, 10 to 12 readings are sufficient for the test.

b- Hydrometer readings must be taken with extreme precision.

c- Temperature measurements should be taken without disturbing the hydrometer.

d- For lower mesh sizes, the interval between hydrometer readings should be shorter because particle settling occurs faster, causing the hydrometer to sink more quickly.

Record the test results as follows on a sheet of paper:

Hydrometer immersion depth Temperature Reading time in minutes

After recording the test results, the remaining work involves calculating the required parameters to determine the product’s mesh size.
The method for calculating each parameter and filling out the test table is as follows:
The sample collection time and date should be clear and written in their designated places.
Classifier RPM: This refers to the turbo RPM, which is recorded daily by the production supervisor on the control room board. Along with the turbo RPM, the return tonnage is also noted.
Specific gravity: The value 2.70 is recorded here, as it represents the specific gravity of calcium carbonate.
Column 1: The test time is recorded.
Column 2, Parameter T: This column records the time in minutes, corresponding to the hydrometer reading times noted during the test.
Column 3, Parameter Ra: This column records the hydrometer immersion depth at the times noted in the previous column.
Column 4, Parameter C: This is the temperature measured after placing the hydrometer in the graduated cylinder, which remains constant for all readings.
Column 5, Parameter K: This parameter is determined based on temperature and specific gravity using a dedicated K table. Since the two determining parameters are constant, K is also a constant value.
Column 6, Parameter L: This parameter is obtained from a dedicated table based on Ra (hydrometer immersion depth) recorded in Column 3.
Column 7, Parameter R: This parameter depends on temperature. If the temperature is 24°C or higher, subtract 3 from Ra to obtain R. If the temperature is below 24°C, subtract 3.5 from Ra.
Column 8, Parameter D: This parameter is obtained by dividing L by T (time), taking the square root of the result, and multiplying it by the constant K (Column 5). The result of this calculation is Parameter D.

Column 9, Parameter P: This parameter is obtained by multiplying Parameter R (Column 7) by the constant 31.76.

(P= R* (31.76)

This parameter determines the mesh percentage, which is calculated in the next column (Column 10).

Column 10, Parameter M: This parameter is obtained by dividing the constant 14800 by Parameter D (Column 8). The result of this division indicates the mesh size.

Note that the 98% mesh is the target product mesh.

Additional notes should be recorded below the hydrometer test results table as follows:

The hydrometer test was performed on the product from cyclone line …………… silo ………………. The production mesh is approximately 98% …………. and the coarse test was performed on a 400-mesh sieve, where ……………. grams of coarse particles were observed per one-hundredth of a gram of powder.

Below the hydrometer test results table, a table is prepared as follows to indicate product quality in terms of color. This table is completed by comparing the sampled product with reference samples available in the laboratory.

If the product is for the filter, mark the designated filter column based on color comparison. If the product is for the cyclone, mark the cyclone column.