SH/T 0733-2004 Determination of flash point (Tag closed cup method)

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

SH/T 0733-2004 specifies the determination of flash point by the Tag manual or automatic closed cup flash point tester for liquids with a viscosity less than 5.5 mm²/s at 40 °C, or less than 9.5 mm²/s at 25 °C, and a flash point below 93 °C.

Evidence note: this page is a partial study compilation made from the original SH/T 0733-2004 document; the thermometer specification numbers, the upper dimension limits and the number of cooperating samples have been revised, and the boundaries of sample/verification and reporting have been added. All apparatus drawings, dense specification tables, software and controlled safety items still await technical review; this page is not an operating procedure for an actual instrument, and the method precision is not the uncertainty of a commercial batch certificate.

Scope: Applies to the determination of the flash point, using a Tag manual or automatic closed cup flash point tester, of liquids with a viscosity less than 5.5 mm²/s at 40 °C, or less than 9.5 mm²/s at 25 °C, and a flash point below 93 °C. 1.1.1 For liquids with a viscosity not less than 5.5 mm²/s at 40 °C, not less than 9.5 mm²/s at 25 °C, or a flash point not lower than 93 °C, or which tend to form a surface film under the test conditions or contain suspended solids, the closed cup flash point shall be determined by the method of GB/T 261. 1.1.2 For the determination of the flash point of cutback asphalt, see ASTM D1310 and ASTM D3143. 1.2 This test method may be used to determine and describe the response of materials, products or compositions to heat and flame under controlled laboratory conditions, and shall not be used to describe or assess the fire hazard of materials, products or compositions under actual fire conditions. However, the test results of this method may serve as one element in assessing fire hazard. 1.3 This standard uses SI units; values in parentheses are for reference only. 1.4 This standard involves certain hazardous materials, operations and equipment, but does not purport to address all safety issues associated with them. For specific hazard warnings see 8.2 and 8.3, and refer to the material safety data sheet.

Principle: The sample is poured into the test cup, the lid is fitted, and the sample is heated at a slow, uniform rate of temperature rise. The test flame is introduced into the test cup at specified time intervals. The lowest temperature at which the flame causes the vapour of the sample to flash is taken as the flash point of the sample. (Clause 4, method summary)

Apparatus: Tag closed cup flash point tester: as shown in Figure 1, details in Annex A. 6.2 Guard screen: a guard screen 460 mm × 460 mm, 610 mm high, open at the front, is recommended. 6.3 Thermometer: the thermometer used in the test cup is as shown in Table 1. For the liquid bath, a simple thermometer with an open scale cover covering the required range may be used; usually the same type of thermometer as for the test cup is used. Note: if an ASTM-conforming thermometer cannot be obtained, an IP 15C PM-LOW thermometer conforming to the Institute of Petroleum specification may be used. Table 1 Thermometer: for sample flash points below 4 °C use ASTM 57C; for 4–49 °C use 9C or 57C; for above 49 °C use 9C. 9C and 57C are thermometer specification numbers, not temperature values of 9 °C or 57 °C; for specific specifications see Annex D. Annex A Apparatus (normative): A.1 The Tag closed cup flash point tester consists of a test cup, a lid with a test flame source, and a liquid bath. A.1.1 Test cup: made of brass or another stainless metal of comparable thermal conductivity, details in Figure A.1, mass 68 g ± 1 g. A.1.2 Lid: consists of a stainless metal disc with a rim projecting downward about 15.9 mm, a sliding shutter, a device that opens the shutter and simultaneously lowers the test flame nozzle, and an inclined sleeve for inserting the thermometer sleeve. A.1.2.2 The rim of the lid fits tightly against the collar of the liquid bath, with a gap not greater than 0.4 mm. A.1.2.3 Shutter size and shape: when closed it covers all three holes in the lid; when open it fully exposes the three holes. Flame nozzle dimensions conform to Table A.1. A.1.2.4 The thermometer sleeve is inclined at an angle such that the thermometer bulb approaches the horizontal centre of the cup; bulb depth see Table A.1. A.1.3 Liquid bath: conforming to the minimum dimensions shown in Figure A.3, made of brass, copper or another stainless metal, and coated with thermal insulation where necessary. A.1.4 Heater: a temperature-controllable heater meeting the requirements of clause 9 (electric, gas, alcohol, etc.); an external electric heater controlled by a variable transformer is recommended. A.1.5 Bath support: for electric heating, any stand may be used. For heating with an alcohol lamp or gas burner, the stand shown in Figure 1 shall be used. Table A.1 Dimensional requirements: | Item | Value | |---|---| | Height of bath liquid surface from top of test cup/mm | 27.8 ± 0.4 | | Height of sample surface from top of test cup/mm | 29.4 ± 0.8 | | Height of thermometer bulb bottom from top of test cup when thermometer inserted/mm | 45.0 ± 0.8 | | Internal diameter of test cup/mm | 54.0 ± 0.3 | | Diameter of flame bead on lid top/mm | 4.0 ± 0.8 | | Diameter of test flame nozzle top opening (internal diameter)/mm | 1.2 ± 0.3 | | Outer diameter of test flame nozzle top (internal diameter)/mm | ≤2.0 (the wording "outer diameter (internal diameter)" in the original row awaits technical review; the column name has not been changed unilaterally) | Annex C Standardization of apparatus manufacture (normative): thermometer sleeve dimensions (Figure C.1, non-mandatory), thermometer gasket dimensions (Figure C.2, non-mandatory). Annex D Thermometer specifications (normative): the specifications in Table D.1 are on physical page 14 of the original PDF, and the original table does exist; some of the listed specifications are compared below for study, and the unlisted values and the complete assembly are still to be verified.

Reagents and reference materials: Bath liquid: for samples with a flash point below 13 °C or above 60 °C, use a mixture of water and ethylene glycol (volume ratio 1:1) as bath liquid; for samples with a flash point between 13 and 60 °C, use water or a water–ethylene glycol mixture as bath liquid. (8.3) Ethylene glycol: toxic; harmful or even fatal if swallowed; vapour is harmful; avoid contact with the skin. (8.3 warning) High-vacuum silicone grease: used to reduce ice formation on the slide; lubricate the slide of the ignition shutter with care. (8.3 note) Certified reference material (CRM): a stable pure hydrocarbon [purity greater than 99% (mole fraction)], or another stable petroleum product whose flash point by this method has been established by interlaboratory study in accordance with ISO Guide 34 and ISO Guide 35. (Annex B.1) Working standard sample (SWS): a stable pure hydrocarbon [purity greater than 99% (mole fraction)], or another stable petroleum product of known composition. (Annex B.2) p-Xylene: obtainable from any reputable chemical supplier, provided it complies with B.1.1. (Footnote to original Annex B.2.1; this footnote does not establish that a specific product is a CRM or is already available) Test flame gas source: natural gas, bottled gas and electronic flame may be used as the test flame. (8.2)

Key conditions: Place the apparatus on a level, stable bench. Unless the test is carried out in a draught-free room or chamber, screens shall be fitted on three sides of the test apparatus. The test shall not be carried out in a laboratory fume hood or near a ventilator. 8.2 Natural gas, bottled gas and electronic flame may be used as the test flame. Warning: the gas supply pressure to the apparatus shall not exceed 3 kPa. 8.3 The bath liquid temperature shall be at least 10 °C below the expected flash point. Dry ice (solid CO₂) shall not be used to cool the bath liquid directly. 9.3 Samples with a flash point below 60 °C: adjust the sample heating rate to 1 °C/(min ± 6 s). When the sample temperature in the test cup is 5 °C below the expected flash point, introduce the test flame, and repeat the introduction of the test flame at each 0.5 °C rise in temperature. 9.4 Samples with a flash point of 60 °C or above: adjust the sample heating rate to 3 °C/(min ± 6 s). When the sample temperature in the test cup is 5 °C below the expected flash point, introduce the test flame, and repeat the introduction of the test flame at each 1 °C rise in temperature. 9.2 Adjust the flame diameter to match the size of the flame bead on the lid. The time for introducing and lifting the flame shall be 1 s. 12.4 When a gas test flame is used, ignite the flame and adjust the diameter of the test flame to 4 mm. 12.6 When the apparatus has cooled below the safe operating temperature (below 55 °C), remove the test cup lid and the test cup.

Calculation and results: Definition of flash point: under the specified test conditions, the lowest temperature, corrected to a pressure of 101.3 kPa (760 mmHg), at which a source of ignition causes the vapour of the sample to flash. Note 1: the sample is considered to have reached its flash point when a flame appears and spreads momentarily over the entire surface of the liquid. Note 2: when a burning source of ignition is used as the test flame, a blue halo or an enlargement of the flame may occur before the true flash point appears; this is not a flash and shall be ignored. 13.1 Correction for atmospheric pressure: observe and record the ambient atmospheric pressure during the test; when the ambient pressure is not 101.3 kPa (760 mmHg), correct the flash point data according to formula (1) or formula (2): Corrected flash point = C + 0.25(101.3 − p) (1) Corrected flash point = C + 0.033(760 − P) (2) where: C — observed flash point, °C; p — ambient atmospheric pressure, kPa; P — ambient atmospheric pressure, mmHg. 13.2 The atmospheric pressure used in the calculation must be the ambient pressure of the laboratory at the time of the test. Many aneroid barometers, such as the capsule-type barometers used at weather stations and airports, require prior correction to give sea-level readings and are generally not used. 13.3 Report the corrected flash point to the nearest 0.5 °C.

Quality control: Precision: the following criteria may be used to judge the level of reliability of results (95% confidence level). 14.1.1 Repeatability: the difference between results obtained by the same operator, in the same laboratory, using the same apparatus, following the procedure specified in the method, in repeated determinations on the same sample shall not exceed the following values: Flash point below 60 °C: repeatability 1.2 °C Flash point above 60 °C (including 60 °C): repeatability 1.6 °C 14.1.2 Reproducibility: the difference between two independent test results obtained by different operators, in different laboratories, following the procedure specified in the method, on the same sample shall not exceed the following values: Flash point below 60 °C: reproducibility 4.3 °C Flash point above 60 °C (including 60 °C): reproducibility 5.8 °C 14.2 Bias: there is no bias in the flash point determined by the procedure of this test method, because the Tag flash point tester defines this test method. Interlaboratory tests to date show no relative bias between the manual and automatic procedures. When measured flash points are in dispute, the manual method shall be used as the referee test. Note 1: for mixtures such as chlorinated or water-containing samples, results obtained with manual and automatic apparatus will differ significantly; for these mixtures the stated precision does not apply. Note 2: the precision data were obtained using 8 samples under the 1991 cooperative test programme. Twelve laboratories using manual apparatus and 17 laboratories using automatic apparatus took part. Information on the types of sample and their mean flash points is available in the research report RR: S15-1007 from ASTM headquarters.

Specification numbers, verification and reporting boundaries: Selected items of Table D.1: | Item | 9C | 57C | |---|---|---| | ASTM specification No. | 9C | 57C | | IP No. | 15C | — | | Temperature range/°C | −5–110 | −20–50 | | Immersion depth/mm | 57 | 57 | | Scale division/°C | 0.5 | 0.5 | | Indication tolerance/°C | 0.5 | 0.5 | | Permitted heating to/°C | 160 | 100 | | Total length/mm | 285–295 | 282–292 | | Stem outer diameter/mm | 6.0–7.0 | 6.0–7.0 | The temperature range, indication tolerance and permitted heating in the table are thermometer specifications and shall not be taken as the flash point range of the sample, the bath temperature or product storage conditions. The remaining dense scale values of Table D.1, such as graduations, bulb and expansion chamber, as well as the complete assembly drawing, are still awaiting technical review, and no conclusion of manufacturing conformity is drawn from partial scale values. The anti-volatilization sampling conditions of clause 7 are separate from the 50 mL±0.5 mL sample charge of clauses 9 and 12; the original sample temperature is 27 °C±5 °C or at least 10 °C below the expected flash point, whichever is lower. If a flash occurs on the first introduction, or within the time of introducing the flame, the test shall be terminated under the corresponding manual/automatic clause, the result discarded and not recorded, and a new sample used and the test repeated with the temperature at least 10 °C below the original expected flash point. Clause 9.8 does not permit repeated testing of the same already-tested sample; below 55 °C is the safe temperature for dismantling automatic apparatus and shall not be taken as a flash point limit. The CRM instrument calibration of manual 8.4 and automatic 11.2.3 shall be carried out at least once a year; after performance verification, SWS may be used for frequent checks; the original does not give a uniform number of daily QC checks, and no fixed number is invented here. In Table B.1, n-decane 50.9 °C and n-undecane 67.1 °C, each ±2.3 °C, are typical values/limits listed by the method and do not replace the assigned value or uncertainty of a specific batch. The 95% precision of clause 14 does not apply to the mixtures listed in its note 1 for which manual and automatic results differ significantly; "the method defines no bias" does not mean the instrument is free of error. Clause 13 uses the ambient pressure actually measured in the laboratory; the p/kPa and P/mmHg equations shall not be mixed, and the final corrected flash point is reported to 0.5 °C. These are conditions for studying the method and do not constitute a commitment regarding product storage, batch quantity values or applicability.

Normative references: GB/T 261 Petroleum products — Determination of flash point (closed cup method) (GB/T 261-83(91), ISO 2719:1973, neq) GB/T 4756 Petroleum liquids — Manual sampling (GB/T 4756-1998, ISO 3170:1988, eqv) ISO Guide 34 Quality system for the production of reference materials ISO Guide 35 Certification of reference materials — General and statistical principles ASTM D1310 Standard test method for flash point and fire point of liquids (Tag open cup method) ASTM D3941 Standard test method for flash point (closed cup equilibrium method) ASTM E502 Standard test methods for flash point of chemicals by closed cup methods

Evidence note: [to be verified] and [source unclear] mark specific points that still require checking against the original text of the standard and do not indicate that they have been verified. Do not use these values or steps directly as a basis for work.

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