SH/T 0642-1997 Determination of Spontaneous Ignition Temperature of Liquid Petroleum and Petrochemical Products

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Card type: Test method

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

• Standard number: SH/T 0642-1997
• Chinese name: Determination of Spontaneous Ignition Temperature of Liquid Petroleum and Petrochemical Products
• English name: Petroleum and petrochemical products — Determination of autoignition temperature
• Replacement relationship: not provided in the available source (only “2004 confirmed in the year” is seen)
• Adoption relationship: non-equivalent adoption of ASTM E659-78(1989) Standard Test Method for Spontaneous Ignition Temperature of Liquid Chemicals
• Main differences from ASTM E659-78(1989) (listed in the original text):
  • The ASTM method applies not only to liquid chemicals but also to solid chemicals that readily melt and evaporate at the test temperature; this standard applies only to liquid petroleum and petrochemical products for which spontaneous ignition temperature requirements exist.
  • This standard does not adopt the terminology relating to cool flames, the definition of cool-flame spontaneous ignition temperature, or the determination method in the ASTM method.
  • This standard does not adopt the definition of the critical temperature of pre-combustion reactions in the ASTM method.
  • This standard does not adopt the significance and use in the ASTM method.
  • This standard reports only the hot-flame spontaneous ignition temperature (i.e., spontaneous ignition temperature), together with its corresponding ignition delay time and atmospheric pressure.
• Responsible body: Research Institute of Petroleum Processing, China Petrochemical Corporation
• Drafting unit: Research Institute of Petroleum Processing, China Petrochemical Corporation
• Main drafter: Chen Liqing
• Approval/implementation: approved in 1997-07-12, implemented in 1997-12-01
• Appendix A is an appendix of the standard

2. Scope of application and non-applicability

• This standard specifies a method for determining the spontaneous ignition temperature of test samples.
• It applies to liquid petroleum and petrochemical products such as heat transfer fluids, fire-resistant hydraulic fluids, fire-resistant turbine oils, and fire-resistant transformer oils.
• Not applicable: the original text does not list a separate “not applicable” clause; according to the differences statement, it is not applicable to the solid chemicals covered by the ASTM method (solid chemicals that readily melt and evaporate at the test temperature).

3. Method principle

Measure a small amount of test sample and add it to a 500 mL glass flask that is maintained at a predetermined constant temperature and contains air, and observe the contents of the flask 10 min, or until spontaneous ignition occurs. Spontaneous ignition is judged by the sudden appearance of a flame in the flask and a sudden rise in the temperature of the gas mixture. When the specified volume of test sample ignites, the lowest temperature of the gas mixture inside the flask (T) is taken as the spontaneous ignition temperature of the test sample (AIT), and the ignition delay time is recorded at the same time.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 4.1.1 Petroleum ether: 30～60 ℃, analytical reagent
• 4.1.2 Benzene: analytical reagent
• 4.1.3 Acetone: analytical reagent
• 4.1.4 Anhydrous ethanol: analytical reagent
• 4.1.5 Diethyl ether: analytical reagent
• Note: the vapors of the above reagents are all toxic (or harmful); operations must be carried out in a fume hood to prevent prolonged inhalation of their vapors; reagent containers should be kept sealed; keep away from heat sources, sparks, or open flames during use and storage, prevent contact with eyes and skin, and prevent inhalation into the body.

4.2 Materials

• Aluminum foil: used to wrap the flask and to line the bottom face of the cover.

5. Apparatus and equipment

• 5.1 Heating furnace: electrically heated crucible furnace, cylindrical inner chamber, diameter 12.7 cm, depth at least 17.8 cm; capable of accommodating the test flask and maintaining uniform flask temperature, with temperature reaching 600 ℃ or higher. Note: it should be installed in a fume hood.
• 5.2 Temperature control system: capable of controlling within the range of ±1 ℃ when the temperature is below 350 ℃, and capable of controlling within the range of ±2 ℃ when above 350 ℃; temperature is detected by external thermocouples at three points: the bottom, middle, and neck of the flask.
• 5.3 Test flask: borosilicate glass 500 mL round-bottom, short-neck flask; suspended in the heating furnace by a thick insulating clamping device, with the top of the neck fitted under an insulating cover sleeve so that the flask is completely enclosed in the furnace; the flask is tightly wrapped with aluminum foil; the insulating clamping device is lined with aluminum foil (see Figure 1).
• 5.4 Syringe: 500 μL or 1000 μL, equipped with a 15.2 cm long stainless steel needle; graduations of 10 μL or 20 μL; the steel needle is bent at a suitable angle (see Figure 2). Note: immediately remove the hand from the test flask after injecting the sample.
• 5.5 Thermocouple: precision nickel-chromium–nickel-aluminum alloy thermocouple, measuring the gas temperature inside the flask (t), frequently rechecked, and iron–constantan (copper-nickel alloy) thermocouples must not be used by mistake; for measuring the external flask temperature, use a nickel-chromium–nickel-aluminum thermocouple or a more precise thermocouple, placed at the top (t₁), middle (t₂), and bottom (t₃) of the flask.
• 5.6 Stopwatch: graduations of 0.1 s or 0.2 s (original text “OAS or 0.2s” requires confirmation against the source standard (source-text extraction)).
• 5.7 Mirror: a square mirror with side length 7.6 cm or another suitable size, placed directly above the flask so that the interior of the flask can be observed. Note: the operator should observe the flame through the mirror.
• 5.8 Hair dryer.
• 5.9 Appendix A provides explanations concerning the apparatus and factors affecting test results.

Figure 1 Spontaneous ignition temperature determination apparatus (unit: mm): 1— mirror; 2— aluminum foil; 3— furnace wall; 4— control thermocouple; 5—500 mL flask; 6— internal thermocouple; 7— glass tube. Figure 2 Modified needle (unit: mm): cleaning wire inside the needle.

6. Recommended operating conditions

• The heating furnace temperature can reach 600 ℃ or higher.
• Temperature control: at ≤350 ℃, ±1 ℃; when >350 ℃, ±2 ℃.
• Sample amount: initial 100 μL; increase or decrease according to 6.5.3, 6.5.4 (150, 200, 250 μL or 70, 50 μL).
• Observation time: 10 min (for the final test, use 10 min).
• Heating/cooling interval: repeat after increasing by about 30 ℃; lower the temperature at intervals that are multiples of 3 ℃ to determine the ignition/non-ignition boundary point.
• Examples of temperature uniformity are shown in Table A1 (test temperature t / external flask temperature t₁, t₂, t₃, ℃):
  • 81 / 81, 82, 82
  • 232 / 232, 236, 235
  • 343 / 342.3, 349, 347
  • 505 / 504.5, 512, 509

7. Sampling and test sample preparation

• The original text does not provide a separate clause for sampling and test sample preparation.
• Before the test, rinse the syringe and needle with the test sample to be tested (6.2).
• A clean flask should be used for each test sample; if residue has already formed in the flask before the test is completed, the flask should be replaced for subsequent tests (6.5.5).

8. Analytical procedure

• 6.1 Install the flask according to Figure 1, preset the heating temperature, turn on the heating furnace and heat the flask; when the internal temperature of the flask (t) reaches the required temperature, adjust the temperature controller to keep the temperature stable so that the entire system reaches equilibrium.
• 6.2 Rinse the syringe and needle with the test sample to be tested.
• 6.3 Inject 100 μL of test sample into the flask with the syringe for the test, and quickly withdraw the syringe.
• 6.4 When the test sample is injected into the flask, start the stopwatch to begin timing.
• 6.5 Use a mirror placed at the upper end of the flask at a suitable angle to observe the interior of the test flask.
  • 6.5.1 If no ignition is observed within 10 min, it is considered that the test sample tested at the internal flask temperature does not undergo spontaneous ignition; blow away the residual gas in the flask with a hair dryer and stop the stopwatch. Note: most substances ignite in less than 10 min; some chemical substances (such as saturated cyclic organic substances) will show long delay times; a shorter time may be used for the initial test, but the final test must use 10 min.
  • 6.5.2 Raise the temperature by about 30 ℃ and repeat the above test procedure; if ignition is observed, stop the stopwatch immediately and record the delay time from sample introduction to ignition; then lower the temperature at intervals that are multiples of 3 ℃ and repeat the test procedure until spontaneous ignition no longer occurs; determine the boundary point between ignition and non-ignition at intervals of 3 ℃ to obtain the lowest ignition temperature.
  • 6.5.3 Repeat the above test procedure with a larger amount of test sample (150 μL); if the lowest ignition temperature determined after increasing the sample amount is lower than the lowest ignition temperature determined with the 100 μL test sample, then repeat the test procedure with even more sample (200 μL, finally 250 μL) until the lowest spontaneous ignition temperature is obtained.
  • 6.5.4 If the lowest ignition temperature determined with the 150 μL test sample is higher than the lowest ignition temperature determined with the 100 μL test sample, then repeat the test procedure with a smaller amount of sample (70 μL, finally 50 μL) until the lowest spontaneous ignition temperature is obtained.
  • 6.5.5 A clean flask should be used for each test sample; if a layer of residue has already formed in the flask before the test is completed, the flask should be replaced for subsequent tests.
  • 6.5.6 After the test, completely expel the test sample remaining in the syringe and needle from the previous test, and repeatedly clean with solvent until clean; then blow away the solvent in the needle with a rubber bulb, blowing several times, and allow to dry naturally or dry in an oven; dry the syringe with a hair dryer or in an oven, and place it aside for later use.
  • 6.5.7 Remove the residue from the flask used in the previous test, wash the flask clean, dry it, and keep it for later use.
  • 6.5.8 Spontaneous ignition is usually evidenced by flames of various colors produced during the test, such as yellow, red, or blue; in general, when spontaneous ignition occurs, the temperature suddenly rises by at least 200 ℃～300 ℃ or more.
• 6.6 Record the test temperature, atmospheric pressure, volume of test sample used, ignition delay time, and spontaneous ignition temperature.

9. Qualitative and Quantitative Determination and Calculation Formula

• Qualitative determination: Autoignition is determined by the sudden appearance of flame in the flask and a sudden increase in the temperature of the gas mixture; it is usually evidenced by flames of various colors (yellow, red, or blue), with a sudden temperature rise of at least 200 ℃～300 ℃ or more.
• Quantitative results: Autoignition point AIT (℃); corresponding ignition delay time (s) and barometric pressure (kPa).
• Calculation formula: not provided in the available source.

10. Precision

Use the following provisions to judge the reliability of test results (95% confidence level):

• Repeatability: The difference between two autoignition point results obtained by the same operator from repeated determinations shall not exceed 2% of their arithmetic mean.
• Reproducibility: The difference between the autoignition point results obtained by two laboratories shall not exceed 5% of their arithmetic mean.

11. Report

• 8.1 autoignition point, AIT (℃).
• 8.2 corresponding ignition delay time (s) and barometric pressure (kPa).

12. Referenced Documents

• ASTM E659-78(1989) "Standard Test Method for Autoignition Point of Liquid Chemicals" (not equivalently adopted).
• Other referenced documents: not provided in the available source.

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