SH/T 0644-1997 Low-temperature stability test method for aviation hydraulic oil

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 name / English name / replacement relationship

• Method number: SH/T 0644-1997
• Chinese full name: Low-temperature stability test method for aviation hydraulic oil
• English name: Aviation hydraulic oils — Test method of low temperature stability
• Replacement relationship: not provided in the available source (the foreword only states non-equivalent adoption of FED-STD-791C-3459.1 "Low-temperature stability test method" 1986 edition, and does not mention replacement of any standard)
• Other: confirmed in 2004; approved by China Petrochemical Corporation 1997-07-12, implemented on 1997-12-01

2. Scope of application and non-applicability

• This standard specifies the test method for low-temperature stability of aviation hydraulic oil.
• Applicable to aviation hydraulic oil and other hydraulic oils.
• Not applicable: not provided in the available source.

3. Method principle

A certain amount of sample is placed under specified temperature conditions for a certain period of time, then oscillated, and its turbidity is compared with the turbidity of a reference solution, so as to judge the stability of the sample by observing whether gel, crystallization, and solidification phenomena occur.

4. Reagents and materials (purity / preparation)

• 4.2 Materials
  • 4.2.1 Industrial methanol.
  • 4.2.2 Industrial ethanol.
  • 4.2.3 Glycerol.
  • Industrial methanol and glycerol are mixed in a ratio of 1:1 to prepare a methanol-glycerol solution.
• 5 Reagents
  • 5.1 Barium chloride: analytical reagent, prepared as a 0.00322 mmol/L barium chloride solution. Requires confirmation (source-text extraction): the source writes "0.00322nmol/L"; the unit is suspected to be mmol/L.
  • 5.2 Sulfuric acid: analytical reagent, prepared as a 0.025 mol/L sulfuric acid solution.
  • 5.3 Sodium hydroxide: analytical reagent, prepared as a 1 mol/L sodium hydroxide solution.
  • 5.4 Red dye: azo-type red dye 5GN, produced by Shanghai No. 3 Dye Chemical Plant. Distilled water is used to prepare a 0.2 g/L red dye staining solution. Requires confirmation (source-text extraction): the source writes "0.2 years L"; the concentration unit is suspected to be g/L.

5. Instruments and equipment

• 4.1.1 Sample bottle: see Figure 1, made of colorless glass, capacity 250 mL, with a ground-glass stopper.
• 4.1.2 Cooling equipment: a thermostat or cooling bath that can maintain a constant temperature at -60℃±1℃; the coolant is industrial ethanol. Requires confirmation (source-text extraction): the source here writes "one 0℃ shi 1℃"; based on 7.3 and the foreword "-60℃", it should be -60℃±1℃.
• 4.1.3 Thermometer: meets the technical requirements for thermometers used for crystallization point and freezing point (alcohol) in GB/T 514.

6. Recommended operating conditions

• Test temperature: -60℃±1℃ (7.3). Requires confirmation (source-text extraction): the source writes "one yin ℃ tu 1℃".
• Standing time: 72 h (7.3).
• The test temperature and standing time for other hydraulic oils are determined according to the product standard (7.3 note).
• If a thermostat is used as the cooling equipment, the methanol-glycerol solution must be cooled to -60℃±1℃ before the specified test time ends (7.4). Requires confirmation (source-text extraction): the source writes "one yin ℃ shi 1℃".

7. Sampling and sample preparation

• 7.1 Clean the sample bottle and dry it under 105℃±5℃ conditions for at least 24 h, then cool and dry it for later use.
• 7.2 Measure 240 mL of sample, pour it into the sample bottle, and tightly close the bottle stopper.
• Other sampling requirements: not provided in the available source.

8. Analysis procedure

• 6.1 Preparation of turbidity reference solution: prepare within 30 min before use.
  • 6.1.1 Inject 0.00322 mmol/L of barium chloride solution 25 mL into a 250 mL volumetric flask.
  • 6.1.2 Add 0.025 mol/L of sulfuric acid 125 mL, and oscillate thoroughly to ensure complete precipitation.
  • 6.1.3 Add about 1 mol/L of sodium hydroxide solution 25 mL to make the solution alkaline.
  • 6.1.4 Add distilled water until the volume reaches the 250 mL mark, pour the prepared solution into a cleaned sample bottle, and tightly stopper it.
  • 6.1.5 For red hydraulic oil, use 0.2 g/L red dye staining solution instead of distilled water in 6.1.4.
• 7 Test procedure
  • 7.1 Clean the sample bottle and dry it under 105℃±5℃ conditions for at least 24 h, then cool and dry it for later use.
  • 7.2 Measure 240 mL of sample, pour it into the sample bottle, and tightly close the bottle stopper.
  • 7.3 Adjust the thermostat or cooling bath, control the temperature at -60℃±1℃, and let the above sample stand in the thermostat or cooling bath for 72 h.
  • 7.4 If a thermostat is used as the cooling equipment, the methanol-glycerol solution must be cooled to -60℃±1℃ before the specified test time ends.
  • 7.5 Within 5 min before comparing the sample with the turbidity reference solution, oscillate the reference solution vigorously for 10 s.
  • 7.6 When the sample standing time ends, take out the sample and oscillate vigorously for about 10 s.
  • 7.7 If the sample was left standing in a thermostat, after taking it out and oscillating it, it must be dipped briefly in the methanol-glycerol cold bath to prevent frost formation. Take the sample out from the cooling location and visually compare it with the turbidity reference solution within 1 min.

9. Qualitative and quantitative determination and calculation formulas

• 8 Result judgment
  • 8.1 The sample is compared with the reference solution, expressed as the sample turbidity being lower than, equal to, or higher than the turbidity of the reference solution, and the presence of gel, crystallization, and solidification phenomena is also indicated.
  • 8.2 It is required that the judgment results of two parallel determinations must be consistent; otherwise, the test must be redone.
• Calculation formula: not provided in the available source.

10. Precision

• Not provided in the available source (only 8.2 specifies that the judgment results of two parallel determinations must be consistent; otherwise, redo).

11. Report

• When the judgment result is "lower than the turbidity of the reference solution" and there is no gel, crystallization, or solidification phenomenon, report the sample low-temperature stability test as "qualified".
• For all other judgment results, report the sample low-temperature stability as "unqualified".

12. Referenced documents

• GB/T 514 Technical conditions for liquid thermometers used in petroleum product testing

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