GB/T 23800-2009 Determination of thermal stability of organic heat transfer fluids

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Card type: Test method

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

• Standard number: GB/T 23800—2009
• Chinese title: Determination of thermal stability of organic heat transfer fluids
• English title: Heat transfer fluids—Determination of thermal stability
• Replacement relationship: not provided in the available source (the foreword only states modified adoption of DIN 51528:1998, and does not mention replacement of any standard)
• Adoption relationship: modified adoption of German national standard DIN 51528:1998 Determination of thermal stability of unused heat transfer fluids (English version), and redrafted in accordance with DIN 51528:1998
• Main technical differences from DIN 51528:1998 (foreword):
  • The standard title was changed to "Determination of thermal stability of organic heat transfer fluids"
  • The temperature unit was changed from K to °C
  • Requirements for the weighing accuracy of samples and instruments were added
  • The minimum volume of the glass ampoule was increased from 5 mL to 15 mL
  • Reporting of the appearance of the sample after heating was added
  • Gas chromatographic analysis requirements were added
  • 6.1.1 added to ensure uniform temperature distribution
  • The test time for each sample was changed from not less than 480 h to not less than 720 h
• Proposed by / administered by: proposed by the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280); administered by SAC/TC 280/SC 1
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Kang Yin, Liang Hong, Jin Ke
• Publication / implementation: published on 2009-05-18, implemented on 2009-11-01

2. Scope of application and non-applicability

• 1.1 This standard specifies a test method for the thermal stability of unused organic heat transfer fluids, including organic heat transfer fluids whose maximum service temperature at atmospheric pressure is higher than their boiling point.
• 1.2 This standard does not evaluate the applicability of silicone heat transfer fluids.
• 1.3 This standard involves certain hazardous substances, operations and equipment, and does not intend to provide recommendations on all safety issues related thereto; before use, appropriate safety and protective measures should be established, and the applicability of relevant regulatory restrictions should be determined.

3. Method principle

• 4.1 The organic heat transfer fluid is heated at a specified temperature, and the thermal stability of the organic heat transfer fluid is evaluated by determining its deterioration rate. The deterioration rate is the sum of the mass fractions of high boilers, low boilers, gaseous decomposition products and non-evaporable products. The mass fraction of gaseous decomposition products is usually negligible (see 7.5.1).
• 4.1.1 The unused organic heat transfer fluid may be sealed in a glass ampoule placed in a metal protective tube, or placed in a steel test vessel and sealed. The metal protective tube containing the glass ampoule or the steel test vessel is heated at the specified test temperature for the specified time; the test temperature is preferably within the upper limit of the service temperature range of the product being tested.
• 4.1.2 After heating for the specified time, open the glass ampoule or steel test vessel, and use the SH/T 0558—1993 gas chromatographic method to determine the mass fractions of high boilers and low boilers. Use a bulb-tube distillator to determine the content of non-evaporable products.
• 4.1.3 Compare the test results of the organic heat transfer fluid before and after heating.
• 5.1 Under the laboratory conditions specified in this standard, this method records and reflects the effect of heat as a function of temperature and heating time on the organic heat transfer fluid. The test results provide information on the thermal stability of different types of organic heat transfer fluids at a certain heating temperature and heating time.
• 5.2 Information on the performance of organic heat transfer fluids in industrial heat transfer equipment cannot be obtained by extrapolation from the test results of this method, because the performance of the organic heat transfer fluid in the equipment is also affected by other materials, various contaminants, heat accumulation, temperature in the circulation system and other factors.

4. Reagents and materials (purity / preparation)

• 6.2.1 Nitrogen: purity (mass fraction) 99.99% or above.
• 6.2.2 Reference oil: reference oil No. 1 or reference oil No. 2, whose boiling range distribution is given in SH/T 0558—1993 Annex B.
• 6.1.7 Dewar flask: containing a mixture of acetone or isopropanol and dry ice (for freezing, about −70 °C, see 7.3.2, 7.3.3).
• Preparation of other reagents: not provided in the available source.

5. Apparatus and equipment

• 6.1.1 Heater: temperature controlled within the range of the test temperature ±1 °C, and ensuring uniform temperature distribution. Ensure the safe storage of the organic heat transfer fluid.
• 6.1.2 Test vessel: a glass ampoule made of borosilicate glass conforming to HG/T 3115, with a volume of at least 15 mL, with a sealable steel or other metal protective tube, or a sealable stainless steel test vessel.
• 6.1.3 Gas chromatograph: meets the requirements of SH/T 0558—1993.
• 6.1.4 Bulb-tube distillator: type HI B-580 (other models meeting the requirements of 7.4.3 may also be used). [Model "HI B-580" requires confirmation against the source standard (source-text extraction)]
• 6.1.5 Vacuum pump: pressure can be evacuated to below 10 Pa.
• 6.1.6 Balance: sensitivity [the source text here is missing source-text extraction, requires confirmation against the source standard (source-text extraction)]
• 6.1.7 Dewar flask: containing a mixture of acetone or isopropanol and dry ice.
• 6.1.8 Chromatographic column: a capillary chromatographic column that, under the test conditions, can separate typical petroleum hydrocarbons in order of increasing boiling point, and whose column resolution (see SH/T 0558—1993, 8.3) is in the range 3～8. [There is noise at source-text extraction in "typical" and "chromatographic column", requires confirmation against the source standard (source-text extraction)]

6. Recommended operating conditions

• Test temperature: determined according to the requirements of the relevant product standard or specification; the test temperature is preferably within the upper limit of the service temperature range of the product being tested (4.1.1).
• Heating program: start heating from room temperature; when the temperature rises to below the test temperature 50 °C, control the heating rate to below 2 °C/min (7.2).
• Temperature stability: keep the temperature constant during the test, so that the temperature deviation at any point of the organic heat transfer fluid (including the heated wall of the test vessel) does not exceed the range of the test temperature ±1 °C (7.2).
• Test time: the test time for each sample is not less than 720 h (7.2).
• Bulb-tube distillation temperature: slowly heat to 250 °C, and the temperature deviation shall not exceed the range of the test temperature ±1 °C (7.4.3).
• Bulb-tube distillation vacuum degree: at the end of distillation, the pressure should reach below 10 Pa±0.2 Pa (7.4.3).
• Gas chromatographic simulated distillation: report only the boiling range distribution results of fractions with a final boiling point before 538 °C (7.4.2).

7. Sampling and sample preparation

• 7.1 Test preparation: at room temperature, weigh the mass of a clean and dry glass ampoule or steel test vessel (m₁), accurate to 0.1 mg. Then fill the sample to about half the volume of the glass ampoule or steel test vessel, and weigh again (m₂), accurate to 0.1 mg. Introduce nitrogen into the glass ampoule or steel test vessel to displace the air in the remaining space. Carefully seal the glass ampoule and weigh again (m₃), cooling the organic heat transfer fluid if necessary, accurate to 0.1 mg. Then place it in the protective tube. During the preparation process, the sample should not be heated. Tighten the protective tube with a screw cap and place it in the heater. Or seal the steel test vessel and weigh again (m₄), accurate to 0.1 mg, and then place it in the heater. Place a receiving plate under the test vessel to prevent overflow of the organic heat transfer fluid. To ensure the accuracy of the test results, at least 3 samples should be prepared for each organic heat transfer fluid.
• Note: In 7.1, the mass after sealing the glass ampoule is recorded as m₃, and the mass after sealing the steel test vessel is recorded as m₄; the correspondence with the definitions of m₃ and m₄ in the formulas of 7.5.1 shall be based on the source text; there is a doubt at source-text extraction here, requires confirmation against the source standard (source-text extraction).

8. Analytical procedure

• 7.2 Sample heating: start heating from room temperature; when the temperature rises to below the test temperature 50 °C, control the heating rate to below 2 °C/min. Keep the temperature constant during the test, so that the temperature deviation at any point of the organic heat transfer fluid (including the heated wall of the test vessel) does not exceed the range of the test temperature ±1 °C. The test time is the time from reaching the set test temperature to stopping heating, and the test time for each sample is not less than 720 h. The test temperature and test time are determined according to the requirements of the relevant product standard or specification. Then determine the deterioration rate of the sample according to 7.4.
• 7.3 Opening the test vessel
  • 7.3.1 Overview: after the test vessel has cooled to room temperature, remove it from the heater, then record the appearance of the sample and complete the corresponding weighing. According to the test temperature and test time, appropriate safety measures should be taken when opening the glass ampoule or steel test vessel.
  • 7.3.2 Opening the glass ampoule: place the glass ampoule in a Dewar flask, and under freezing with a mixture of acetone or isopropanol and dry ice (about −70 °C), reduce its internal pressure. After 5 min～10 min, open the glass ampoule, allow the gas to volatilize completely at room temperature, and after returning to room temperature, immediately weigh the mass of the glass ampoule (m₄), accurate to [the source text here is missing source-text extraction, requires confirmation against the source standard (source-text extraction)]. All glass fragments should be included in the weighing, and attached condensed water should be removed. Place part of the sample in a gas chromatographic vial for chromatographic analysis, and store the remaining sample in a well-sealed glass bottle for other analyses.
  • 7.3.3 Opening the steel test vessel: place the steel test vessel in a Dewar flask, and under freezing with a mixture of acetone or isopropanol and dry ice (about −70 °C), reduce its internal pressure. After 5 min～[the source text is missing source-text extraction, requires confirmation against the source standard (source-text extraction)]min, carefully open the sealing cover of the steel test vessel, allow the gas to volatilize completely at room temperature, and after returning to room temperature, remove attached condensed water. Weigh the mass of the steel test vessel (m₄), accurate to 0.1 mg. Place part of the sample in a gas chromatographic vial for chromatographic analysis, and store the remaining sample in a well-sealed glass bottle for other analyses.
• 7.4 Analysis
  • 7.4.1 Determine the content of gaseous decomposition products based on the mass difference of the glass ampoule or steel test vessel before and after opening.
  • 7.4.2 Use SH/T 0558—1993 gas chromatography simulated distillation to determine the boiling range of the sample before and after heating. Use a capillary chromatographic column. Before determination, the boiling range of the reference oil should first be determined. The boiling point of the determined reference oil should meet the repeatability requirements of the SH/T 0558—1993 method. When determining the sample by the SH/T 0558—1993 method, only report the boiling range distribution results of fractions with a final boiling point before 538 °C; for fractions in the sample higher than 538 °C, the content of non-evaporable products should be calculated according to 7.5.2.
  • 7.4.3 Weigh the mass of the empty tail bulb in the bulb tube distiller (m₅), accurate to 0.1 mg. Then add dropwise to the tail bulb about 4 g of the heated sample, and accurately weigh the mass of the tail bulb plus sample (m₆), accurate to 0.1 mg. Rotate the bulb tube in the bulb tube distiller, use a vacuum pump to evacuate, and at the end of distillation the pressure should reach below 10 Pa±0.2 Pa. The temperature of the bulb tube distiller is slowly heated to 250 °C, so that the organic heat transfer fluid does not further thermally decompose during the distillation process and to avoid boiling hysteresis, with temperature deviation not exceeding the range of ±1 °C of the test temperature. Continue distillation until the residue mass is constant. Weigh the mass of the tail bulb (including residue) after the test (m₇), accurate to 0.1 mg. Gas chromatography may be used to evaluate whether the distillation process is complete. The portion still volatile in the residue should be less than 0.1% of the total mass of the organic heat transfer fluid.

9. Qualitative and Quantitative and Calculation Formulas

• 7.5.1 Calculation of the gas-phase decomposition product content of the sample
  • Calculate the mass fraction of gas-phase decomposition products of the sample G, % according to formula (1):
    • G = (m₃ − m₄)/(m₂ − m₁) × 100
    • Where: m₁—mass of empty glass ampoule or steel tester, g; m₂—mass of glass ampoule or steel tester containing unheated sample, g; m₃—mass of glass ampoule or steel tester after sealing, g; m₄—mass of glass ampoule or steel tester after opening, g.
  • Note: The mass fraction of gas-phase decomposition products of the sample below 0.5% may be ignored.
• 7.5.2 Calculation of the non-evaporable product content of the sample
  • Calculate the mass fraction of non-evaporable products of the sample U, % according to formula (2):
    • U = (m₇ − m₅)/(m₆ − m₅) × 100
    • Where: m₅—mass of empty tail bulb, g; m₆—mass of tail bulb plus heated sample, g; m₇—mass of tail bulb (including residue) after the test, g.
  • Note: The mass fraction of non-evaporable products of the sample below 0.5% may be ignored.
• 7.5.3 Calculation of the low-boiling content (mass fraction) N (%) and high-boiling content (mass fraction) H (%) of the sample
  • 7.5.3.1 Figure 1 gives simulated distillation curves of two samples before and after heating: Figure 1a) is the simulated distillation curve in which low-boiling and high-boiling substances are produced after heating; Figure 1b) is the simulated distillation curve in which only low-boiling substances are produced after heating. Taking Figure 1a) as an example, calculate the uncorrected low-boiling content (mass fraction) N′ (%) and the uncorrected high-boiling content (mass fraction) H′ (%) of the sample after heating.
    • In Figure 1a), point A is the initial boiling point of the sample before heating; draw a horizontal line through point A to intersect the simulated distillation curve of the sample after heating at point B; draw a vertical line through point B to intersect the yield axis at point E; then the uncorrected low-boiling content (mass fraction) N′ (%) of the sample is the percentage corresponding to point E.
    • Point C is the final boiling point of the sample before heating; draw a horizontal line through point C to intersect the simulated distillation curve of the sample after heating at point D; draw a vertical line through point D to intersect the yield axis at point F; then the uncorrected high-boiling content (mass fraction) H′ (%) of the sample is 100% minus the percentage corresponding to point F.
    • Figure 1 caption: A— initial boiling point of the sample before heating; A′—initial boiling point of the sample after heating; C— final boiling point of the sample before heating; C′—final boiling point of the sample after heating; AB— uncorrected low-boiling content; CD— uncorrected high-boiling content.
  • 7.5.3.2 Considering that gas chromatography cannot determine the content of gas-phase decomposition products and the content of non-evaporable products, the uncorrected low-boiling content (mass fraction) N′ (%) and high-boiling content (mass fraction) H′ (%) must be corrected by formula (3) and formula (4):
    • N = N′ × (100 − G − U)/100 … (3)
      • Where: N— corrected low-boiling content (mass fraction) of the sample, %; N′—low-boiling content (mass fraction) determined from the simulated distillation curve of the sample, %; G— gas-phase decomposition product content (mass fraction) of the sample, %; U— non-evaporable product content (mass fraction) of the sample, %.
    • H = H′ × (100 − G − U)/100 … (4)
      • Where: H— corrected high-boiling content (mass fraction) of the sample, %; H′—high-boiling content (mass fraction) determined from the simulated distillation curve of the sample, %; G— gas-phase decomposition product content (mass fraction) of the sample, %; U— non-evaporable product content (mass fraction) of the sample, %.
• 7.5.4 Calculation of the deterioration rate of the sample
  • The deterioration rate (mass fraction) Z (%) of the sample is calculated according to formula (5):
    • Z = G + N + H + U … (5)
    • Where: G— gas-phase decomposition product content (mass fraction) of the sample, %; N— corrected low-boiling content (mass fraction) of the sample, %; H— corrected high-boiling content (mass fraction) of the sample, %; U— non-evaporable product content (mass fraction) of the sample, %.

10. Precision

• not provided in the available source (the main text does not give repeatability or reproducibility values; 7.4.2 only requires that the boiling point of the reference oil should meet the repeatability requirements of the SH/T 0558—1993 method).

11. Report

• 8.1 Type of organic heat transfer fluid;
• 8.2 Test time, h;
• 8.3 Test temperature, °C;
• 8.4 Appearance of the sample after heating;
• 8.5 Gas-phase decomposition products and low-boiling content (mass fraction), %, and accurate to one decimal place; [original text 8.5 at the numbering location source-text extraction is missing, requires confirmation against the source standard (source-text extraction)]
• 8.6 High-boiling and non-evaporable product content (mass fraction), %, and accurate to one decimal place;
• 8.7 Deterioration rate (mass fraction), take the average of 3 test results, %, and accurate to one decimal place;
• 8.8 Initial boiling point and final boiling point of the sample before and after heating, °C;
• 8.9 Test conditions inconsistent with this standard;
• 8.10 Test date.

12. Referenced Documents

• HG/T 3115 Properties of borosilicate glass 3.3 (HG/T 3115—1998, idt ISO 3585:1991)
• SH/T 0558—1993 Determination of boiling range distribution of petroleum fractions (gas chromatography)

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