GB/T 3536-2008 Petroleum products — Determination of flash point and fire point — Cleveland open cup method

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Card type: Test method

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

• Standard number: GB/T 3536—2008
• Chinese full title: Petroleum products — Determination of flash point and fire point — Cleveland open cup method
• English name: Petroleum products—Determination of flash and fire points—Cleveland open cup method
• Replacement relationship: Replaces GB/T 3536—1983 "Determination of flash point and fire point of petroleum products (Cleveland open cup method)" (the 1983 edition was formulated by equivalent adoption of ISO 2592:1973)
• Adoption relationship: Modified adoption of ISO 2592:2000 "Determination of flash point and fire point (Cleveland open cup method)" (English version), MOD
• Publication / implementation: published by 2008-08-25, implemented by 2009-02-01
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Chen Jie, Guo Tao
• Appendix attributes: Appendix A is a normative appendix; Appendix B and Appendix C are informative appendices

2. Scope of application and non-applicability

• Applicable: Method for determining the flash point and fire point of petroleum products using a Cleveland open cup apparatus; applicable to petroleum products other than fuel oils whose open cup flash point is higher than 79 °C.
• Not applicable: Fuel oils (fuel oils are usually determined in accordance with GB/T 261).
• Note (original 1 clause note): Flash point and fire point indicate the ability of a substance to form a flammable mixture with air and to sustain combustion under specified conditions; flash point and fire point are only two of many analytical means used to evaluate the flammability and combustibility of a substance.

3. Method principle

Fill the test cup with the sample to the specified mark. First raise the temperature of the sample rapidly, and when approaching the flash point, raise the temperature slowly at a constant rate. At specified temperature intervals, sweep a small test flame over the test cup; the lowest temperature at which the test flame causes the vapor above the liquid surface of the sample to flash is the flash point. If the fire point is to be determined, continue the test until the test flame causes the vapor at the liquid surface of the sample to ignite and sustain burning for at least 5 s; the lowest temperature at which this occurs is the fire point. The flash point and fire point measured at ambient atmospheric pressure are corrected by formula to the flash point and fire point at standard atmospheric pressure.

4. Reagents and materials (purity / preparation)

• 5.1 Cleaning solvent: used to remove a small amount of sample adhering to the test cup. Note: The choice of cleaning solvent is based on the viscosity of the sample and its residue (the source term is unclear; its interpretation as viscosity remains unverified). Low-volatility aromatic (benzene-free) solvents can be used to remove traces of oil; mixed solvents such as toluene-acetone-methanol can effectively remove gum-like deposits.
• 5.2 Calibration liquid: see B.2 clause in Appendix B.
• 5.3 Steel wool: steel wool capable of removing carbon deposits without damaging the test cup.
• Purity index: not provided in the available source.

5. Instruments and equipment

• 6.1 Cleveland open cup tester: see Appendix A.
  • 6.1.1 If an automated instrument is used, ensure that its measurement results can achieve the precision specified in this standard, and that the size and mechanical properties of its test cup and test flame comply with the provisions of Appendix A. The user should ensure that all operations are carried out in accordance with the instrument instructions.
  • 6.1.2 In case of dispute, the referee test for flash point shall use a manual instrument.
• 6.2 Protective screen: approximately 460 mm×460 mm, height 610 mm, with one open side.
• 6.3 Thermometer: meets the requirements of No. GB-5 in GB/T 514. Note: Other types of thermometers that can meet the provisions of clause 6.3 may also be used.
• 6.4 Barometer: accuracy 0.1 kPa; barometers used by meteorological stations or airports that have been pre-calibrated to sea level readings shall not be used.
• Appendix A (normative appendix) Composition of the Cleveland open cup tester:
  • A.1 Test cup: made of brass or other stainless metal with equivalent thermal conductivity, dimensions shall comply with the requirements of Figure A.1. Note: The test cup may be fitted with a handle.
  • A.2 Heating plate: made of brass, cast iron, wrought iron, or steel plate, with a central hole, around which there is a slightly recessed area; except for this recessed flat area where the test cup is placed, the other parts of the metal plate shall be covered with a heat-resistant plate (excluding asbestos). The dimensions of the heating plate shall comply with the requirements shown in Figure A.1. Note: The heating plate may be square instead of circular and may be appropriately enlarged to facilitate installation of the test flame generator and thermometer holder; the metal comparison ball mentioned in clause A.3 may also be mounted on the heating plate so that it passes through and slightly protrudes above a suitable small hole in the heat-resistant plate.
  • A.3 Test flame generator: The sweeping flame device may take any suitable form, but it is recommended that the top of the flame head have a diameter of about 1.6 mm and the orifice diameter be about 0.8 mm. When installing and operating the test flame device, the sweep of the test flame should be capable of automatic repetition, and the radius of the sweep should be not less than 150 mm. The center of the orifice should be able to move on a plane not more than 2 mm above the edge of the test cup. It is preferable to install a metal comparison ball with a diameter of 3.2 mm~4.8 mm at a suitable position on the instrument to compare the size of the test flame.
  • A.4 Heater: It is preferable to use an electric heater with a variable transformer; gas lamps or alcohol lamps are permitted. In no case shall the flame rise around the test cup. The heat source shall be concentrated below the hole and there shall be no local overheating. If an electric heater is used, ensure that it does not directly contact the test cup. Note: A flame-type heater may use any suitable protective screen to prevent air movement or excessive radiation, but the protective screen shall not be higher than the upper surface of the heat-resistant plate.
  • A.5 Thermometer holder: a holder that can fix the thermometer in the specified position during the test and can conveniently remove the thermometer from the test cup after the test.
  • A.6 Heating plate support: any suitable support that can hold the heating plate horizontally and stably.
  • A.7 Flame extinguishing cover (optional): an example of a flame extinguishing cover is shown in Figure A.2.
• Figure A.1 annotations (source-text extraction extracted, dimension values require confirmation (source-text extraction)): R150 minimum; φ1.6; 2 maximum; φ100; φ97; φ64; φ63; 45°; 32; 31; 3.2; 34; 32; –R4; 10; φ69; φ67.5; φ159; φ146; φ70.5; φ69.5. Figure A.1 components: 1— thermometer; 2— igniter; 3— test cup; 4— metal comparison ball φ3.2 mm–4.8 mm; 5— heating plate; 6—φ0.8 mm hole; 7— to gas source; 8— heater (flame type or resistance type); 9— sample filling mark; 10— metal; 11— heat-resistant material.
• Figure A.2 annotations (source-text extraction extracted, dimension values require confirmation (source-text extraction)): φ77.5°; 4 M4; φ62.5; φ70.5. Figure A.2 components: 1— cover made of metal or other flame-retardant material; 2— handle. a reference dimension.

6. Recommended operating conditions

• 7.1 Placement of the instrument: Place the instrument in a room free from air currents and on a stable tabletop. To facilitate observation of the flash point during the test, a suitable means should be used to provide a light shield at the top of the instrument to protect against strong light. Note 1: If air currents cannot be avoided, it is preferable to shield the instrument with a protective screen. Note 2: If the sample produces toxic vapors, the instrument should be placed in a fume hood with independently controlled air flow, adjusted so that vapors can be drawn away, but the air flow must not affect the vapor above the test cup.
• 7.2 Cleaning of the test cup: First rinse the test cup with cleaning solvent to remove all traces of gum or residue left from the previous test. Then blow dry the test cup with clean air to ensure removal of the solvent used. If carbon deposits remain on the test cup, they may be wiped off with steel wool.
• 7.3 Preparation of the test cup: Before use, cool the test cup to at least 56 °C below the expected flash point.
• 7.4 Assembly of the instrument: Place the thermometer vertically so that the bottom of its temperature-sensing bulb is 6 mm from the bottom of the test cup, and located on the diameter perpendicular to the arc (or line) swept by the test flame, at the midpoint between the center of the test cup and the edge of the test cup, and on the side opposite the igniter arm. Note: The correct position of the thermometer should place the immersion depth line on the thermometer 2 mm below the edge line of the test cup. Alternatively, first lower the thermometer slowly until it contacts the bottom of the test cup, then raise it by 6 mm.
• 7.5 Calibration of the instrument:
  • 7.5.1 Calibrate the instrument at least once a year using certified reference materials (CRM). The difference between the obtained result and the CRM calibration value shall be less than or equal to R/√2, where R is the reproducibility of this standard. It is recommended to use working reference samples (SWS) for frequent calibration of the instrument. Note: For the recommended procedure for calibrating the instrument using CRM and SWS, and the method for obtaining SWS, see Appendix B.
  • 7.5.2 The results obtained from the calibration test cannot be used as the bias of the method, nor can they be used to correct subsequent flash point measurement results.
• Heating rate (see 10.5): At the beginning of heating, the sample heating rate is 14 °C/min–17 °C/min; when the sample temperature reaches about 56 °C before the expected flash point, slow the heating rate so that during the last 23 °C±5 °C before reaching the flash point, the heating rate is 5 °C/min–6 °C/min.
• Test flame: Ignite the test flame and adjust the flame diameter to 3.2 mm~4.8 mm; if a metal comparison ball is installed on the instrument, the flame diameter should be the same as the diameter of the metal comparison ball (10.4).
• Sweep conditions (10.6): At least 23 °C±5 °C before the expected flash point, begin sweeping with the test flame, sweeping once for every temperature rise of 2 °C; use a smooth, continuous motion for sweeping, and the time required for the test flame to pass through the test cup each time is approximately 1 s; the test flame should pass across the center of the test cup at a position at right angles to the diameter of the test cup through the thermometer, and the sweep should be made in a straight line or along a circle with a radius of at least 150 mm; the center of the test flame must move on a plane within 2 mm above the upper edge of the test cup; first sweep in one direction, and the next time sweep in the opposite direction; if a film forms on the surface of the sample, the oil film should be pushed aside before continuing the test.
• Heating rate during the fire point stage (11.1): After determining the flash point according to the flash point test procedure in Chapter 10, continue heating at a rate of 5 °C/min~6 °C/min; sweep once for every temperature rise of 2 °C of the sample until the sample ignites and can burn continuously for no less than 5 s.

7. Sampling and Sample Preparation

• 8.1 Unless otherwise specified, sampling shall be carried out in accordance with GB/T 4756, SY/T 5317.
• 8.2 Place the collected sample into a suitable sealed container. For safety, the sample should only fill 85%~95% of the container volume.
• 8.3 Store the sample under suitable conditions to minimize sample evaporation loss and pressure increase. The sample storage temperature should avoid exceeding 30 °C.
• 9.1 Subsampling: Carry out subsampling at least 56 °C below the expected flash point. If a portion of the original sample is to be subdivided and stored before testing, ensure that each sample portion fills more than 50% of its container volume (see 10.1).
• 9.2 Samples containing undissolved water: If the sample contains undissolved water, separate the water before mixing the sample. Note: The presence of water will affect the flash point determination result.
• 9.3 Samples that are liquid at room temperature: Before sampling, gently shake to mix the sample, then carefully sample, avoiding loss of volatile components as much as possible, and then operate according to Chapter 10.
• 9.4 Samples that are solid or semi-solid at room temperature: Place the container with the sample into a heating bath or oven, and heat at least 56 °C below the expected flash point. Avoid overheating, as this will cause loss of volatile components. After gently mixing the sample, operate according to Chapter 10.

8. Analytical Procedure

Flash point test procedure (Chapter 10):

• 10.1 If the volume of the sample in the sample container is less than 50% of the container volume, the flash point determination result will be affected.
• 10.2 Observe the barometer and record the ambient atmospheric pressure near the instrument during the test. Note: Although some barometers automatically correct for pressure, this standard does not require correction to the atmospheric pressure at 0 °C.
• 10.3 Place the sample at room temperature or already heated into the test cup so that the top of the meniscus of the sample is exactly at the filling mark of the test cup. If too much sample is poured into the test cup, it can be removed with a pipette or other suitable tool; if the sample touches the outside of the instrument, pour out the sample, clean it, and then refill. Break or remove bubbles or sample foam on the surface of the sample, and ensure that the sample liquid level is at the correct position. If foam still exists on the sample surface at the final stage of the test, the result is invalid.
• 10.4 Ignite the test flame and adjust the flame diameter to 3.2 mm~4.8 mm. If the instrument is equipped with a metal comparison bead, it should be the same diameter as the metal comparison bead.
• 10.5 When starting to heat, the heating rate of the sample is 14 °C/min–17 °C/min. When the sample temperature reaches about 56 °C before the expected flash point, slow down the heating rate so that the heating rate of the sample during the last 23 °C±5 °C before reaching the flash point is 5 °C/min–6 °C/min. During the test, avoid walking around or breathing near the test cup to prevent disturbing the sample vapor.
• 10.6 At least 23 °C±5 °C before the expected flash point, begin sweeping with the test flame, sweeping once for every temperature rise of 2 °C. Use a smooth, continuous motion for sweeping, and the time required for the test flame to pass through the test cup each time is approximately 1 s. The test flame should pass across the center of the test cup at a position at right angles to the diameter of the test cup through the thermometer, and the sweep should be made in a straight line or along a circle with a radius of at least 150 mm. The center of the test flame must move on a plane within 2 mm above the upper edge of the test cup. First sweep in one direction, and the next time sweep in the opposite direction. If a film forms on the surface of the sample, the oil film should be pushed aside before continuing the test.
• 10.7 When a flash appears at any point on the sample liquid surface, immediately record the temperature reading of the thermometer as the observed flash point, but do not confuse the pale blue halo sometimes produced around the test flame with a true flash.
• 10.8 If the observed flash point differs from the initial ignition temperature by less than 18 °C, the result is invalid. Replace with a new sample and re-determine, adjusting the initial ignition temperature until a valid result is obtained, that is, the result should be at least 18 °C higher than the initial ignition temperature.

Fire point test procedure (Chapter 11):

• 11.1 After determining the flash point according to the flash point test procedure in Chapter 10, continue heating at a rate of 5 °C/min~6 °C/min. Sweep once for every temperature rise of 2 °C of the sample until the sample ignites and can burn continuously for no less than 5 s. Record this temperature as the observed fire point of the sample.
• 11.2 If the burning exceeds 5 s, extinguish the flame with a metal cover with a handle or a cover made of other flame-retardant material. For an example of the cover, see Figure A.2 in Appendix A.

9. Qualitative and Quantitative Determination and Calculation Formulas

• 12.1 Conversion of barometric pressure readings:
  • Barometric pressure reading in hPa × 0.1 = barometric pressure reading in kPa
  • Barometric pressure reading in mbar × 0.1 = barometric pressure reading in kPa
  • Barometric pressure reading in mmHg × 0.1333 = barometric pressure reading in kPa
• 12.2 Correction of observed flash point or fire point to standard atmospheric pressure: Use formula (1) to correct the observed flash point or fire point to standard atmospheric pressure (101.3 kPa), T, °C.
  • T = T₀ + 0.25(101.3 − p) …………(1)
  • Where: T₀—observed flash point or fire point, °C; p— ambient atmospheric pressure, kPa.
  • Note: This formula is precisely corrected only within the range of atmospheric pressure from 98.0 kPa~104.7 kPa.
• 13 Expression of results: Report the corrected flash point or fire point in °C, and round the result to an integer.
• Appendix B Expression of results (instrument verification):
  • B.4.1.1 Single test: For a single test of CRM or SWS, the difference between the single result and the CRM calibration value or the given value of SWS shall satisfy the requirement of formula (B.1): |x − M| ≤ R/√2. Where: x— single test result; M—CRM calibration value or given value of SWS; R— reproducibility of this standard.
  • B.4.1.2 Multiple tests: For n tests of CRM or SWS, the difference between the average of the n results and the CRM calibration value or the given value of SWS shall satisfy the requirement of formula (B.2): |x̄ − M| ≤ R′/√2 …………(B.2). Where: x̄—average of test results; M—CRM calibration value or given value of SWS; R′ is √{R² − [1 − (1/n)]r²} (original text source-text extraction is “R is VR [1 (1/n)]”, requires confirmation against the source standard (source-text extraction)); R— reproducibility of this standard; r— repeatability of this standard; n— number of replicate tests conducted using CRM or SWS.

10. Precision

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

• 14.1 Repeatability, r: In the same laboratory, by the same operator using the same instrument, according to the same method, the difference between two consecutive test results on the same sample shall not exceed 8 °C for both flash point and fire point.
• 14.2 Reproducibility, R: In different laboratories, by different operators using different instruments, according to the same method, the difference between two single, independent results on the same sample shall not exceed 17 °C for flash point and shall not exceed 14 °C for fire point.

11. Report

The test report shall at least include the following contents:

• a) Indicate the number of this standard;
• b) Type and relevant information of the tested product;
• c) Test results;
• d) Indicate any differences from the specified test procedure due to agreement or other reasons;
• e) Date of test.

12. Normative References

• GB/T 261 Determination of flash point—Pensky-Martens closed cup method (GB/T 261—2008, ISO 2719:2002, MOD)
• GB/T 514 Technical conditions for glass liquid thermometers for petroleum product testing
• GB/T 4756 Manual sampling of petroleum liquids (GB/T 4756—1998, eqv ISO 3170:1988)
• GB/T 6683 Determination of precision data for petroleum product test methods (GB/T 6683—1997, neq ISO 4259:1992)
• GB/T 15000.3 Directives for the work of reference materials (3) General principles and statistical methods for the certification of reference materials (GB/T 15000.3—1994, neq ISO Directives 35)
• GB/T 15000.7 Directives for the work of reference materials (7) General requirements for the competence of reference material producers (GB/T 15000.7—2001, ISO Directives 34, IDT)
• GB/T 15000.8 Directives for the work of reference materials (8) Uses of certified reference materials (GB/T 15000.8—2003, ISO Directives 33, IDT)
• SY/T 5317 Standard practice for automatic sampling of petroleum liquids (SY/T 5317—2006, ISO 3171:1988, IDT)

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