Gravimetric analysis of solid particle contamination in oil purifiers

The gravimetric analysis of solid particle contaminants in oil purifiers is a method to evaluate the cleanliness of oil by measuring the weight of solid particles in the oil. This method is simple and intuitive and is suitable for laboratory or on-site testing. The following are the detailed steps and precautions of the gravimetric analysis method:

1. Principle

By filtering a certain volume of oil, the solid particles are trapped on the filter membrane, and then the weight difference before and after the filter membrane is measured to calculate the weight concentration of solid particles in the oil.

2. Required equipment and materials

- Filter membrane: The pore size is usually 0.45 microns or 0.8 microns, and the material is cellulose or polytetrafluoroethylene (PTFE).

- Filter device: Includes filter, vacuum pump, or pressure pump.

- Balance: Analytical balance with an accuracy of at least 0.1 mg.

- Oven: used to dry the filter membrane.

- Desiccator: used to cool and store the filter membrane.

- Solvent: used to clean equipment and filter membranes (such as petroleum ether or n-hexane).

- Cylinder: used to measure the volume of oil.

3. Operation steps

Preparation

1. Filter membrane treatment:

- Place the filter membrane in an oven and dry it at 105℃ for 1 hour.

- Take out the filter membrane and place it in a desiccator to cool to room temperature.

- Use a balance to weigh the initial weight of the filter membrane (\( W_1 \)) and record it.

2. Cleaning equipment:

- Use solvent to clean the filter device and measuring cylinder to ensure that there are no residual contaminants.

4. Filtering oil

1. Measuring oil:

- Use a measuring cylinder to measure a certain volume of oil (usually 100-500 ml, the specific volume is adjusted according to the degree of oil contamination).

2. Filtration:

- Install the filter membrane in the filtration device.

- Pour the oil into the filtration device and start the vacuum pump or pressure pump for filtration.

- After filtration, rinse the filter membrane with a small amount of solvent to ensure that all solid particles are retained.

5.Drying and weighing

1. Drying the filter membrane:

- Place the filter membrane with solid particles in an oven and dry it at 105℃ for 1 hour.

2. Cooling and weighing:

- Take out the filter membrane and place it in a desiccator to cool to room temperature.

- Use a balance to weigh the final weight of the filter membrane (\( W_2 \)) and record it.

6. Calculation results

The weight concentration of solid particles (\( C \)) can be calculated by the following formula:

\[

C \, (\text{mg/L}) = \frac{(W_2 - W_1)}{V} \times 1000

\]

Where:

- \( W_1 \): initial weight of the filter membrane (mg);

- \( W_2 \): final weight of the filter membrane (mg);

- \( V \): volume of filtered oil (L).

7. Precautions

- Filter membrane selection: ｓｅｌｅｃｔ the appropriate filter membrane pore size according to the size of the particles in the oil.

- Operating environment: Operate in a dust-free environment to avoid interference from external pollutants.

- Solvent selection: Use solvents compatible with the oil to avoid dissolving the filter membrane or oil components.

- Repeatability: Perform at least two parallel tests for each sample and take the average value to improve accuracy.

- Equipment cleaning: Clean the equipment thoroughly before and after each test to avoid cross-contamination.

8. Advantages and disadvantages

Advantages:

- Simple and intuitive, no complex equipment required.

- Applicable to a variety of oil types.

- Can directly measure the weight concentration of solid particles.

Disadvantages:

- Cannot distinguish the size and type of particles.

- The operation process is time-consuming.

- Low sensitivity to low-concentration pollutants.

9. Application Scenarios

- Laboratory testing: used to evaluate the cleanliness of the oil.

- On-site testing: used to monitor the filtering effect of the oil purifier.

- Quality control: used for quality control during oil production and use.

Summary

Gravimetric analysis is a simple and effective method for detecting solid particle contaminants, suitable for evaluating the cleanliness of oil and the filtering effect of oil purifiers. Through strict operating procedures and precautions, accurate test results can be obtained, providing a basis for oil management and equipment maintenance.