NB/SH/T 0430-2019 Determination of equilibrium reflux boiling point of brake fluid

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Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: NB/SH/T 0430—2019
• Chinese name: Determination of equilibrium reflux boiling point of brake fluid
• English name: Standard test method for determination of equilibrium refux boiling point of motor vehicle brake fluid (unclear in the source text, refux suspected to be reflux, requires confirmation against the source standard (source-text extraction))
• Replacement relationship: replaces SH/T 0430—1992 "Determination of equilibrium reflux boiling point of brake fluid"
• Previous versions: SH/T 0430—1992
• Issued/implemented: issued by 2019-11-04, implemented by 2020-05-01
• Custodian: Synthetic Lubricants Subcommittee of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC5)
• Proposed by: China Petrochemical Corporation
• Drafting organizations: Synthetic Lubricants Branch of Sinopec Lubricant Co., Ltd., Highway Science Research Institute of the Ministry of Transport
• Main drafters: Cheng Junli, Shi Guohui, Jiao Jian

2. Scope of application and non-applicability

• This standard specifies the determination method for the equilibrium reflux boiling point and wet equilibrium reflux boiling point of motor vehicle brake fluids (Chapter 1).
• This standard applies to the determination of the equilibrium reflux boiling point of motor vehicle brake fluids (Chapter 1).
• Not applicable: not provided in the available source.

3. Method principle

• 4.1 Equilibrium reflux boiling point: 60mL The sample is equilibrated with atmospheric pressure in a 100mL flask and boiled under a certain reflux rate condition; the liquid temperature during equilibrium reflux is measured and calibrated to the liquid temperature under standard atmospheric pressure.
• 4.2 Wet equilibrium reflux boiling point: after humidifying the sample by method A or method B, the equilibrium reflux boiling point of the humidified water-containing mixture is determined.
  • Method A: A 350mL sample and a 350mL humidity control fluid (6.3) are separately placed in two identical corrosion test cups (5.6), placed in the same humidifier (5.7) for humidification; when the water content of the humidity control fluid reaches 3.70%±0.05%, the sample has completed humidification.
  • Method B: 2.1mL distilled water is directly injected into the 60mL sample; after uniform mixing, the sample has completed humidification.

4. Reagents and materials (purity / preparation)

• 6.1 Boiling stones: particle size 2mm~3mm silicon carbide.
• 6.2 Distilled water: meets the grade three water requirements in GB/T 6682—2008.
• 6.3 Bisphenol A: meets the requirements of GB/T 28113 (the reference number in the source text is written as CB/T 28113, requires confirmation against the source standard (source-text extraction)).
• 6.4 Humidity control fluid: to triethylene glycol monomethyl ether with a content greater than 94% (mass fraction) (water content controlled at 0.50%±0.05%), add 0.25% (mass fraction) of bisphenol A.

5. Instruments and equipment

• 5.1 Boiling point determination apparatus (see Figure 1).
• 5.2 Flask: 100mL round-bottom short-neck heat-resistant glass flask (see Figure 2).
• 5.3 Condenser tube: straight inner-tube condenser with a condensation jacket length of 200mm, a standard ground stopper No. 19 at the lower end, and an inclined opening at the end face.
• 5.4 Thermometer: meets the requirements of GB-28 in GB/T 514.
• 5.5 Electric heater: an electric heater meeting the heating requirements of 9.1.1 (with asbestos metal mesh) or an electric heating mantle.
• 5.6 Test cup: straight cylindrical glass beaker with rim, inner diameter 75mm–80mm, height about 100mm, volume 475mL–500mL, cup cover is a tin-plated steel cover (see Figure 3).
• 5.7 Humidifier: two glass desiccators with inner diameter 250mm and total height about 295mm; the top of the desiccator cover has an opening fitted with a rubber stopper No. 8; the desiccator is equipped with a ceramic perforated plate with a diameter of 230mm (see Figure 4).
• 5.8 Graduated cylinder: 100mL (to-deliver type).
• 5.9 Oven: controlled temperature 50°C±1°C.
• 5.10 Water content analyzer: meets the method requirements of GB/T 11133, SH/T 0086 or SH/T 0246.
• 5.11 Pipette or microburette: 5mL.
• 5.12 Stopwatch: precision 0.1s.

6. Recommended operating conditions

• Heating: heat the sample to boiling within 15min, with the reflux rate reaching 1 drops/s~5 drops/s (9.1.1).
• Reflux: thereafter, within 10min, adjust the heating rate so that the reflux rate reaches 1 drops/s~2 drops/s, and maintain this constant reflux rate for 2min (9.1.1).
• Reading: read the temperature value once every 30s, continuously reading four times (accurate to 0.2°C) (9.1.1).
• Humidification (method A): oven temperature controlled at 50°C±10 (unclear in the source text, suspected to be 50°C±1°C, requires confirmation against the source standard (source-text extraction)) (9.2.1.2).
• Cooling (method A): cool at 23°C±5°C for 60min~90min (9.2.1.3).
• Thermometer installation: the end of the thermometer mercury bulb is about 6.5mm from the center of the flask bottom (8.1).

7. Sampling and sample preparation

• 7 Sample: sample not less than 1000mL.
• 8.1 Insert the thermometer through the side tube into the flask so that the end of the thermometer mercury bulb is about 6.5mm from the center of the flask bottom; fit a short rubber tube or other suitable material over the thermometer to seal it against the tube opening.
• 8.2 Add 60mL sample to the flask, and at the same time add 3 to 4 boiling stones.
• 8.3 Connect the flask to a clean, dry condenser tube through the ground joint, place it on the center of the asbestos metal mesh on the electric heater (or in an electric heating mantle), and connect the cooling water inlet and outlet tubes.

8. Analysis procedure

• 9.1 Determination of equilibrium reflux boiling point
  • 9.1.1 After assembling the boiling point test apparatus according to Figure 1, turn on the cooling water switch, then start heating; heat the sample to boiling within 15min, with the reflux rate reaching 1 drops/s–5 drops/s. Thereafter, within 10min, adjust the heating rate so that the reflux rate reaches 1 drops/s–2 drops/s, maintain this constant reflux rate for 2min, and read the temperature value once every 30s, continuously reading four times (accurate to 0.2°C).
  • 9.1.2 Record the temperature and atmospheric pressure.
• 9.2 Determination of wet equilibrium reflux boiling point
  • 9.2.1 Method A (humidification method):
    • 9.2.1.1 Lubricate the ground joints of two humidifiers with water-resistant sealing grease, add 450mL±10mL distilled water to each humidifier, place the ceramic perforated plate, and cover with the lid.
    • 9.2.1.2 Prepare four dry, clean corrosion test cups; add 350mL±5mL brake fluid sample to two of them, and add 350mL±5mL humidity control fluid to the other two. Place one corrosion test cup containing the brake fluid sample and one corrosion test cup containing the humidity control fluid simultaneously into each humidifier, cover with the humidifier lid (the corrosion test cups should be left open), and place in an oven controlled at 50°C±10. At intervals, remove the rubber stopper at the top of the desiccator and determine the water content according to SH/T 0246 (or GB/T 11133 and SH/T 0086). During the humidification process, the total amount of humidity control fluid withdrawn shall not exceed 10mL.
    • 9.2.1.3 When the water content (mass fraction) of the humidity control fluid reaches 3.70%±0.05% (average of duplicate samples), remove the corrosion test cup containing the brake fluid sample from the humidifier, cover with the lid, transfer to a sealed container, quickly close the container tightly, and let it cool at 23°C±5°C for 60min~90min. Then determine the equilibrium reflux boiling point of the sample according to 9.1.1 and 9.1.2.
    • 9.2.1.4 Record the measured temperature and atmospheric pressure.
  • 9.2.2 Method B (water addition method):
    • 9.2.2.1 Take 60mL brake fluid sample and place it in the short-neck flask of the boiling point determination apparatus; using a 5mL pipette or 5mL microburette, add 2.1mL distilled water, mix uniformly, and determine its equilibrium reflux boiling point according to 9.1.1 and 9.1.2.
    • 9.2.2.2 Record the measured temperature and atmospheric pressure.

9. Qualitative and quantitative determination and calculation formulas

• 10.1 Calculate the equilibrium reflux boiling point TERBP according to formula (1):
  • TERBP = Tobserved + Δtcorrection + Cc
  • Where:
    • TERBP— the equilibrium reflux boiling point after correction by thermometer and atmospheric pressure, °C;
    • Tobserved—the average of four consecutive boiling point readings, °C;
    • Δtcorrection—the corresponding correction value on the thermometer calibration certificate, °C;
    • Cc— the boiling point correction value corrected to standard atmospheric pressure, °C.
• 10.2 The value of Cc can be calculated according to formula (2) or formula (3), or obtained from Table 1.
  • 10.2.1 Calculate the value of Cc expressed in the legal unit system according to formula (2):
    • Cc = 9.5×10⁻⁵ × (1.33322×10² − P) × (273 + tc) (the formula layout in the source text is incomplete, requires confirmation against the source standard (source-text extraction))
    • Where:
      • 9.5×10⁻⁵—the coefficient of boiling point change caused by unit pressure and unit temperature change;
      • P— the atmospheric pressure when measuring the boiling point, Pa;
      • tc—Tobserved + Δtcorrection.
  • 10.2.2 Calculate the value of Cc expressed in the non-legal unit system according to formula (3):
    • Cc = 9.5×10⁻⁵ × (760 − P) × (273 + tc) (the original formula layout is incomplete, requires confirmation against the source standard (source-text extraction)))
    • Where:
      • 9.5×10⁻⁵—coefficient of boiling point change caused by unit pressure and unit temperature change;
      • P— atmospheric pressure at the time of boiling point determination, mmHg;
      • tc—T observed + Δt correction.
• Table 1 Boiling point correction values per unit atmospheric pressure

10. Precision

• 12.1 Equilibrium reflux boiling point: use the following values to judge the reliability of test results (95% confidence level):
  • 12.1.1 Repeatability: the difference between two results obtained by the same analyst at different times (the average of each duplicate) shall not exceed the value listed in Table 2.
  • 12.1.2 Reproducibility: the difference between results obtained by analysts in different laboratories (the average of each duplicate) shall not exceed the value listed in Table 2.
• Table 2 Repeatability and reproducibility values

• 12.2 The precision of wet equilibrium reflux boiling point test results is as follows:
  • 12.2.1 A method (humidification method): the repeatability and reproducibility of the humidification method test results have not yet been established.
  • 12.2.2 B method (water addition method): not provided in the available source.

11. Report

• 11.1 Equilibrium reflux boiling point: the arithmetic mean of two repeated determination results is used as the determination result, accurate to 0.2°C.
• 11.2 Wet equilibrium reflux boiling point:
  • 11.2.1 A method (humidification method): if the difference between the two equilibrium reflux boiling point measured values is within 4°C, take their average as the measured wet equilibrium reflux boiling point; otherwise, repeat the entire test process and take the average of the four measured equilibrium reflux boiling points as the wet equilibrium reflux boiling point of the brake fluid. Accurate to 0.2°C.
  • 11.2.2 B method (water addition method): take the arithmetic mean of two equilibrium reflux boiling point determination results as the wet equilibrium reflux boiling point of the test sample, accurate to 0.2°C.

12. Referenced documents

• GB/T 514 Technical specifications for glass liquid thermometers for petroleum product testing
• GB/T 6682—2008 Specifications for laboratory water
• GB/T 11133 Determination of water content in petroleum products, lubricating oils and additives - Karl Fischer coulometric titration method
• GB/T 28113 Industrial bisphenol A (the original writes CB/T 28113, requires confirmation against the source standard (source-text extraction))
• SH/T 0086 Determination of water content in engine coolant concentrates (Karl Fischer method)
• SH/T 0246 Determination of water content in light petroleum products (electrometric method)
• GB/T 1.1—2009 Rules given (foreword, drafting basis)

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 for questions and answers