GB/T 267-1988 Determination of Flash Point and Fire Point of Petroleum Products (Open Cup Method)

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

• Standard number: GB/T 267-88
• Chinese name: Determination of Flash Point and Fire Point of Petroleum Products (Open Cup Method)
• English name: Petroleum products—Determination of flash and fire points—Open cup
• Replacement relationship: replaces GB 267-77
• UDC number: UDC 685.52 (the source text also shows “/54.[unreadable character]1.4”, suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Approval/implementation: approved by China Petrochemical Corporation 1988-07-2T (the last character of the date is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)); implemented on 1989-06-01

2. Scope of application and non-applicability

• This standard specifies the method for determining flash point and fire point using an open cup.
• This standard applies to the determination of lubricating oils and dark petroleum products.
• Not applicable: not provided in the available source.

3. Method principle

Place the test sample into the inner crucible up to the specified mark. First rapidly raise the temperature of the test sample, then slowly raise the temperature; when approaching the flash point, raise the temperature at a constant rate. At specified temperature intervals, pass a small igniter flame over the surface of the test sample as specified; the lowest temperature at which the vapor above the test sample surface is ignited by the igniter flame is taken as the flash point by the open cup method. Continue the test until the lowest temperature at which the test sample is ignited by the igniter flame and burns for at least 5 s is taken as the fire point by the open cup method.

4. Reagents and materials (purity / preparation)

• Solvent naphtha: meets the requirements of SH/T 0004 (one place in the source text writes “SH 0004”, which is inconsistent with “SH/T 0004” in the referenced standard, requires confirmation against the source standard (source-text extraction)).
• Dehydrating agent: freshly calcined and cooled sodium chloride, sodium sulfate, or anhydrous calcium chloride (the source text “anhydrous calcium chloride” is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
• Fine sand: calcined, used for filling the outer crucible.
• Purity and specific preparation method: not provided in the available source.

5. Apparatus and equipment

• Open flash point tester: meets the requirements of SH/T 0318.
• Thermometer: meets the requirements of GB/T 514 (in the source text “GB/T 514 W[unreadable character]”, the text after the standard number is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
• Gas burner, alcohol blowtorch, or electric furnace (when determining test samples with a flash point higher than 200℃, an electric furnace must be used).
• Inner crucible, outer crucible, support, iron ring, thermometer clamp, protective screen: mentioned in the source text but specifications and dimensions are not provided.

6. Recommended operating conditions

• Heating rate: when the test sample temperature reaches 40℃ before the expected flash point, control the heating rate to increase by 4±1℃ per minute.
• Igniter flame length: pre-adjust to 3～4 mm.
• Ignition position: when the test sample temperature reaches 10℃ before the expected flash point, place the igniter flame at a distance of 10～14 mm from the test sample liquid surface.
• Ignition movement: move in a straight line along the inner diameter of the crucible on the horizontal plane at that position; the time taken to move from one side of the crucible to the other is 2～3 s.
• Ignition interval: repeat the ignition test once for every 2℃ increase in test sample temperature.
• Heating rate for fire point determination: after measuring the flash point, continue heating so that the test sample temperature increases at a rate of 4±1℃ per minute.
• Environmental requirements: the determination apparatus should be placed in a wind-free and dimly lit place and surrounded by a protective screen so that the flash point phenomenon can be seen clearly.

7. Sampling and test sample preparation

• When the water content of the test sample is greater than 0.1%, dehydration is required. Dehydration treatment is carried out by adding freshly calcined and cooled sodium chloride, sodium sulfate, or anhydrous calcium chloride to the test sample.
• For test samples with a flash point below 100℃, heating is not necessary during dehydration; other test samples may be heated to 50～80℃ and dehydrated with a dehydrating agent.
• After dehydration, take the upper clear portion of the test sample for testing.
• After washing the inner crucible with solvent naphtha, heat it on a lit gas burner to remove residual solvent naphtha. When the inner crucible has cooled to room temperature, place it into the outer crucible containing fine sand (calcined), so that the fine sand surface is about 12 mm from the rim of the inner crucible, and maintain a sand layer with a thickness of 5～8 mm between the bottom of the inner crucible and the bottom of the outer crucible. When determining test samples with a flash point above 300℃, the thickness of the sand layer between the bottoms of the two crucibles may be appropriately reduced, but the heating rate specified in 6.1.1 must be maintained during the test.
• Injecting the test sample into the inner crucible: for test samples with a flash point at 210℃ and below 210℃, the liquid surface is 12 mm from the rim of the crucible (i.e., at the upper mark in the inner crucible); for test samples with a flash point above 210℃, the liquid surface is 18 mm from the rim (i.e., at the lower mark in the inner crucible).
• When injecting the test sample into the inner crucible, it should not splash, and the crucible wall above the liquid surface should not be contaminated with the test sample.
• Place the crucible containing the test sample steadily in the iron ring (or electric furnace) on the support, then fix the thermometer vertically on the thermometer clamp, and position the mercury bulb of the thermometer in the center of the inner crucible, approximately equidistant from the bottom of the crucible and the test sample liquid surface.

8. Analytical procedure

8.1 Flash point

• Heat the crucible to gradually raise the temperature of the test sample; when the test sample temperature reaches 60℃ before the expected flash point, adjust the heating rate so that when the test sample temperature reaches 40℃ before the flash point, the heating rate can be controlled to increase by 4±1℃ per minute.
• When the test sample temperature reaches 10℃ before the expected flash point, place the igniter flame at a distance of 10～14 mm from the test sample liquid surface, and move it in a straight line along the inner diameter of the crucible on the horizontal plane at that position; the time taken to move from one side of the crucible to the other is 2～3 s. Repeat the ignition test once for every 2℃ increase in test sample temperature.
• The flame length of the igniter should be pre-adjusted to 3～4 mm.
• When a blue flame first appears above the test sample liquid surface, immediately read the temperature from the thermometer as the flash point determination result, and record the atmospheric pressure at the same time.
• Note: The flash of the test sample vapor should not be confused with the flash of the igniter flame. If the flash phenomenon is not obvious, ignition must be continued to confirm when the test sample has increased by 2℃.

8.2 Fire point

• After measuring the flash point of the test sample, if the fire point also needs to be determined, continue heating the outer crucible so that the temperature increase rate of the test sample is 4±1℃ per minute. Then, perform the ignition test with the igniter flame as described in 6.1.2.
• When the test sample ignites immediately upon contact with the flame and can continue burning for not less than 5 s, immediately read the temperature from the thermometer as the fire point determination result.

8.3 Correction of the influence of atmospheric pressure on flash point and fire point

• When the atmospheric pressure is lower than 99.3 kPa (745 mmHg), the flash point or fire point t₀ (℃) obtained in the test is corrected according to formula (1) (accurate to 1℃):
  • t₀ = t + Δt ………………(1)
  • Where: t₀—the flash point or fire point corresponding to an atmospheric pressure of 101.3 kPa (760 mmHg), ℃; t— the flash point or fire point measured under the test conditions, ℃; Δt— correction number, ℃.
• When the atmospheric pressure is in the range of 72.0～101.3 kPa (540～760 mmHg), the correction number Δt (℃) can be calculated according to formula (2), (3):
  • Δt = (0.00015t + 0.028)(101.3 − P)×7.5 ………………(2)
  • Δt = (0.00015t + 0.028)(760 − P₁) ………………(3)
  • Where: P— atmospheric pressure under the test conditions, kPa; 0.00015, 0.028— test constants; 7.5— atmospheric pressure unit conversion coefficient; P₁—atmospheric pressure under the test conditions, mmHg; t— the flash point or fire point measured under the test conditions (above 300℃ is still calculated as 300℃), ℃.
• Note: For the atmospheric pressure range of 64.0～71.9 kPa (490～539 mmHg), the correction number Δt (℃) for the measured flash point or fire point may also be calculated by referring to formula (2) or formula (3).
• In addition, the correction number Δt (℃) can also be found from the following table (the source table header and data source-text extraction are severely misaligned, values require confirmation against the source standard (source-text extraction)):
  • Table header: Flash point or fire point ℃ | Correction number Δt at the following atmospheric pressures [kPa (mmHg)], ℃
  • Pressure column: 72.0(540), 74.6(560), 77.3(580), 80.0(600), 82.6(620), 85.3(640), 88.0(660), 90.6(680), 93.3(700), 96.0(720), 98.6(740)
  • Flash point or fire point row: 100, 125, 150, 175, 200, 225, 250, 275, 300
  • Specific corresponding values: the source text source-text extraction is severely misaligned, requires confirmation against the source standard (source-text extraction)

9. Qualitative and quantitative determination and calculation formulas

• Flash point: when a blue flame first appears above the test sample liquid surface, immediately read the temperature from the thermometer as the flash point determination result, and record the atmospheric pressure at the same time.
• Fire point: when the test sample ignites immediately upon contact with the flame and can continue burning for not less than 5 s, immediately read the temperature from the thermometer as the fire point determination result.
• The atmospheric pressure correction formulas are given in Section 8.3, formula (1), formula (2), formula (3).
• Result value: take the arithmetic mean of two flash point results from duplicate determinations as the flash point of the test sample; take the arithmetic mean of two fire point results from duplicate determinations as the fire point of the test sample.

10. Precision

10.1 Repeatability

• The difference between two flash point results obtained by the same operator in duplicate determinations shall not exceed the following values:
  • Flash point ≤150℃: repeatability 4℃
  • Flash point >150℃: repeatability 6℃
• The difference between two fire point results obtained by the same operator in duplicate determinations shall not exceed 6℃.
• Reproducibility: not provided in the available source.

11. Report

• Take the arithmetic mean of two repeated flash point results as the flash point of the sample.
• Take the arithmetic mean of two repeated fire point results as the fire point of the sample.

12. Reference Documents

• GB/T 514 Technical conditions for liquid thermometers used in petroleum product testing
• SH/T 0004 Rubber industry solvent naphtha
• SH/T 0318 Technical conditions for open flash point testers

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