Condensation point determination is a test that combines manual observation with automatic temperature control - the instrument is responsible for precise temperature reduction, while the operator is responsible for periodically checking whether the oil surface is flowing and making judgments. Each step has standardized operational details, and omitting any step may affect the results.

Step 1: Sample preparation and loading

Take the oil sample to be tested and fill it into a dedicated test tube up to the scale mark. Note:

If dealing with high-viscosity oils (such as heavy lubricating oils), it is necessary to pre-treat the oil sample at a lower temperature before sample loading (refer to specific standard requirements) to ensure that the sample is in a uniform liquid state

The test tube must be clean and free of any residue from previous samples - it must be thoroughly cleaned, rinsed with solvent, and dried before changing samples

The sample volume should not exceed the scale mark; if it is insufficient, the measurement result does not represent standard conditions

Step 2: Insert the thermometer

Insert the temperature measuring thermometer into the sample to be tested, ensuring that the bulb of the thermometer is immersed to the specified depth in the oil sample (it should not touch the bottom of the tube, nor should it be exposed above the oil surface). The thermometer must be kept clean and free from oil stains - oil stains can affect the thermal conductivity and measurement sensitivity of the thermometer, leading to delayed readings.

Step 3: Start the instrument

Turn on in order: power switch → stirring switch → cooling switch. The sequence cannot be reversed - turning on the stirring first is to ensure that the ethanol circulates evenly before the cooling begins, preventing local overcooling. Set the preset temperature on the thermostat (5-10°C lower than the expected freezing point), and observe the gradual decrease in cooling temperature on the thermostat.

Step 4: Periodic inspection and judgment

During the temperature drop process at a predetermined rate, at regular temperature intervals (the condensation point is checked every 2℃ drop according to GB/T 510 standard), the test tube is taken out of the freezer, quickly tilted at 45°, and held for 1 minute to observe whether the oil level moves:

Oil surface movement: This indicates that the oil product still has fluidity at this temperature. Continue to cool it down and check again

The oil surface does not move: This indicates that the oil has solidified, and this temperature is the freezing point. Record the value

Step 5: Record and Reset

After recording the condensation point value, stop the refrigeration, remove the test tube, and allow the oil sample to return to room temperature for retesting. The shutdown sequence is: first turn off the refrigeration, then turn off the stirrer, and finally turn off the power. Keep the ethanol in the freezer chamber without draining it, and check the liquid level for replenishment before the next use.