Operating Guidelines

1. Equipment.

• Laboratory balance of BBK-500 type as per GOST 19491 or of other type with a weighing error of 0.01 g;
• Refractometer of PP1 or other type with refractive index measurement range of 0 to 10 or 1.2 to 1.7.

2. Test preparation.

Prepare 1%, 2%, 3%, 4%, 5% cutting fluids and reference working solutions from the concentrate.
Measure off 1, 2, 3, 4, 5 g of the concentrate with an accuracy of +/- 0.01 g using a laboratory balance, and pour distilled water into each sample up to a total weight of 100 g (99, 98, 97, 96, 95 g, respectively).
Stir these reference working solutions with glass sticks and leave for at least 60 minutes at room temperature.
Determine the refractive index for each concentration using a refractometer.
Plot the refractive indices of standard working solutions along the X-axis.
Plot the concentrations of the working solutions of the cutting fluid along the Y-axis.
Plot a calibration curve of the cutting fluid concentration dependence on the refractive index according to the data obtained.

3. Determination of the concentration (%) of working cutting fluid solutions.

Sample preparation:

Collect a sample of the working solution in a beaker. Next it is recommended to centrifuge the sample to separate the “foreign” oil, impurities and solids. If a centrifuge is not available, pour the sample into the cylinder and allow it to settle for 24 hours. Collect 1.2 ml of the working solution from the middle part of the centrifuge tube (cylinder) with a measuring pipette without disturbing the residue or surfaced oil.
Filter the sample from the middle part of the cylinder if it was not centrifuged.
Determine the refractive index of the tested sample using a refractometer.
Using the calibration curve, determine concentration of the working cutting fluid solution in %.

If the border between light and dark areas is not clearly defined, the emulsion contains a lot of “foreign” oil and likely needs to be replaced by fresh one.

Temperature control is crucial for determining the refractive index. The test is usually conducted at 20±0.3°C. Temperature increase causes refractive index to reduce, and vice versa.
The correction is calculated as follows:

c = n20 + (20-t) * 0.0002

Determine the concentration of the working cutting fluid solution in % using corrective parameters given in Table 1.

Example of calculating the concentration of the working cutting fluid solution:
Refractometer readings: Y
Actual concentration of the working emulsion C,% = (Y + X) / K, where X, K are values calculated theoretically separately for each cutting fluid.

Refractometric method is the simplest in terms of its application.

However, its results cannot be considered completely accurate. A refractometer measures the concentration of the emulsion including all “foreign” oils and contaminants in the system. Due to the fact that foreign oils are accumulated in the system over time, additional methods are required to determine the concentration of the working emulsion in order to obtain more accurate results. Operational procedures for the cutting fluids include additional methods for determining the concentration of the working emulsion.

Table 1

* Considering the ongoing work on the improvement of product quality, indices X and K are not permanent and may change over time. Therefore, refer to the table and check the index values ​​from time to time.