GB/T 12577-1990 Determination of Flocculation Point of Refrigeration Oils

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

1. Method number / full title / English title / supersession relationship

• Standard number: GB/T 12577-90
• Chinese title: Determination of Flocculation Point of Refrigeration Oils
• English title: Refrigerator oils - Determination of floc point (original text reads "Refrlgerator olls -Determinatlon of floc polat", requires confirmation against the source standard (source-text extraction))
• Supersession relationship: not provided in the available source
• Issuance/implementation: approved by the State Bureau of Technical Supervision 1990-12-14, implemented on 1991-10-01
• Reference adoption: Federal Republic of Germany national standard DIN 51351-82 "Determination of Flocculation Point of Refrigeration Oils"

2. Scope of application and non-applicability

• Applicable to mineral oil refrigeration oils, and also applicable to synthetic oil refrigeration oils.
• Not applicable: not provided in the available source.

3. Method principle

Mix 1 mL of test sample and 6 mL of refrigerant in a test tube; after mutual dissolution, place it in the cold bath of the flocculation point tester, gradually cool it at a certain rate, and observe under illumination. When turbidity or flocculation first appears, record the temperature at that time. The highest temperature at which this phenomenon occurs is taken as the flocculation point of the sample, expressed as "℃".

4. Reagents and materials (purity / preparation)

• 5.1 Refrigerant: F12 or other refrigerants.
• 5.2 Anhydrous ethanol: chemically pure.
• 4.2.1 Dry ice.
• 4.2.2 Silica gel with moisture indicator.
• 4.2.3 Solvent naphtha: No. 120 in GB 1922.

5. Apparatus and equipment

• 4.1.1 Test tube: see Figure 1a or Figure 1b, both made of borosilicate glass.
• 4.1.2 Flocculation point tester: see Figure 2.
• 4.1.3 Refrigerant injection bath: see Figure 3, volume about 1.5 L.
• 4.1.4 Spherical closed cap: see Figure 4, made of borosilicate glass.
• 4.1.5 Fastening spring clip: see Figure 5.
• 4.1.6 No. 12 standard spherical ground joint connector: see Figure 6, made of borosilicate glass.
• 4.1.7 Syringe: 1 mL, 10 mL.
• 4.1.8 Stainless steel injection needle: long type No. 9.
• 4.1.9 Thermometer: -70–50 ℃, -80–60 ℃ and 0–100 ℃, all with scale division value 1 ℃ (original text reads "70–50°C", requires confirmation against the source standard (source-text extraction)).
• 4.1.10 Vacuum pump: vacuum degree can reach 10 Pa.
• 4.1.11 Water bath.
• 4.1.12 Pressure reducer: 0–25 MPa, partial pressure 0–2.5 MPa.
• 4.1.13 Changeover switch.
• 4.1.14 Flow-splitting control valve.
• 4.1.15 Drying tower: 500 mL.

6. Recommended operating conditions

• Evacuation drying pressure: 10~20 Pa, time 0.5 h.
• Refrigerant injection bath pre-cooling: -70~-78 ℃.
• Refrigerant filling pressure: about 10 Pa (original text reads thus, requires confirmation against the source standard (source-text extraction)).
• Cold bath cooling rate: 1 ℃/min.
• Pre-test sample cooling rate (rough prediction): 5 ℃/min.
• For samples with evaporation temperature lower than 0 ℃, the test tube may be placed directly into a cold bath already cooled to 0 ℃.

7. Sampling and sample preparation

• Take two test tubes and inject 1 mL of sample into each with a syringe.
• Place the test tubes in a boiling water bath and connect them to an evacuation drying device equipped with a changeover switch (for cap-type test tubes, connect using the connector in Figure 6 and clamp with a spring clip). Turn on the vacuum pump and evacuate-dry at 10~20 Pa pressure for 0.5 h, so as to avoid ice crystal formation during test cooling, which would cause precipitation above the flocculation point and lead to measurement error.
• After removing the two evacuated-dried test tubes from the water bath and allowing them to cool slightly, place them in a refrigerant injection bath already cooled to -70~-78 ℃. Turn the changeover switch so that it connects with the refrigerant filling system, open the refrigerant cylinder valve, fill refrigerant at about 10 Pa pressure up to the 7 mL mark of the test tube, close the refrigerant cylinder valve, and seal the test tube. For cap-type test tubes, quickly replace with the spherical closed cap and fasten with the fastening spring clip, then take out and shake to mix the sample and refrigerant into mutual solution. For sealed-by-fusion test tubes, sealing by fusion should be carried out rapidly at low temperature, and safety must be observed by wearing protective goggles and gloves.

8. Analytical procedure

• 7.1 Place the test tube containing the sample and refrigerant into the cold bath of the flocculation point tester, so that the liquid level of the sample and refrigerant mixture is at least 50 mm below the cold bath liquid level.
• 7.2 Turn on the stirring system and cool the cold bath with clean dry ice or another cooling method at a cooling rate of 1 ℃/min until precipitation is observed under illumination. At this time the mixture becomes milky and turbid but can still transmit light. Read and record the temperature at this time (read to 0.5 ℃); this temperature is the flocculation point of the sample.
• 7.3 For samples with evaporation temperature lower than 0 ℃, the test tube may be placed directly into a cold bath already cooled to 0 ℃. To roughly predict the flocculation point of the sample, the test tube may also be cooled at a cooling rate of 5 ℃/min.

9. Qualitative and quantitative determination and calculation formula

• Qualitative: observed under illumination, when the mixture becomes milky and turbid but can still transmit light, precipitation is considered to have occurred.
• Quantitative: read and record the temperature at this time (read to 0.5 ℃); this temperature is the flocculation point of the sample, expressed as "℃".
• Calculation formula: not provided in the available source.

10. Precision

Judge the reliability of test results according to the following provisions (95% confidence level).

• Repeatability: the difference between two results obtained by repeated determination by the same operator shall not be greater than 2.5 ℃.

11. Report

Take the arithmetic mean of the two flocculation point results from repeated determination as the determination result.

12. Referenced documents

• GB 1922 Solvent naphtha

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick-reference Q&A