GB/T 8019-2025 Determination of gum content in fuels — Jet evaporation method

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GB/T 8019-2025 specifies the jet evaporation method for determining the existent gum of military diesel fuel and aviation fuel and the gum content of motor vehicle gasoline and other volatile distillates, including products containing alcohol and ether oxygenates and deposit-control additives.

Evidence note: the content of this page was compiled from the original text of this standard held in the Origin Standard library (points marked "[to be verified]" are "[source unclear]" in the original); for individual values and current status, refer to the original pages of the standard and the product certificate.

Scope: This document describes the method for determining the existent gum of military diesel fuel and aviation fuel, and the gum content of motor vehicle gasoline and other volatile distillates (including products containing alcohol and ether oxygenates and deposit-control additives). It applies to the determination of existent gum in military diesel fuel and aviation fuel, and also to the determination of unwashed gum content and solvent-washed gum content in motor vehicle gasoline and other volatile distillates. Note 1: For the determination of existent gum in diesel fuel, military diesel fuel is taken as the reference, but the samples included in the precision test all have a 95% recovery temperature below 345 °C. Note 2: For other volatile distillates, the determination method and precision of gum content follow those for motor vehicle gasoline. Note 3: In this document, aviation fuel includes aviation gasoline and jet fuel. Not applicable: not provided in the available material.

Principle: A known quantity of motor vehicle gasoline or other volatile distillate, military diesel fuel or aviation gasoline sample is evaporated under specified temperature and air flow conditions; a known quantity of jet fuel sample is evaporated under specified temperature and steam flow conditions. If the sample is military diesel fuel or aviation fuel, the evaporation residue obtained is weighed and reported in "mg/100 mL"; if the sample is motor vehicle gasoline, the evaporation residues before and after n-heptane extraction are weighed separately and the results are reported in "mg/100 mL".

Apparatus: 5.1 Balance: scale interval 0.1 mg. 5.2 Beakers: 100 mL; quartz, borosilicate glass or another material meeting the test requirements should be selected. Dimensions as shown in Figure 1. The beakers are arranged in groups, the number per group depending on the number of beaker holes in the evaporation bath; each beaker in each group is marked with a number or letter, including the tare beaker. If the mass difference of a tare beaker before and after evaporation is too large over several tests, the environmental, equipment and operating factors should first be excluded, then the beaker should be soaked in chromic acid cleaning solution, thoroughly washed with tap water and water (6.1) and dried in accordance with 10.1, until the weighed mass of the beaker becomes stable. If the mass difference between two consecutive weighings still exceeds 0.0004 g, replacement of the beaker is recommended. Other methods such as high-temperature calcination may also be used to treat the beaker, with an effect equivalent to chromic acid cleaning solution; when high-temperature calcination is used, care should be taken to select a calcination temperature and time appropriate to the beaker material. 5.3 Cooling container: a desiccator or other tightly closable container used to cool the beakers before weighing. No desiccant should be used in the cooling container. Note: the use of a desiccant will cause erroneous results. 5.4 Evaporation bath: a solid metal bath or a liquid bath may be used for heating, with the principle and construction as shown in Figure 1. The evaporation bath should have at least 2 beaker holes and exhaust ports; for the determination of military diesel fuel the evaporation bath is recommended to have at least 3 beaker holes and exhaust ports. When fitted with conical adapters made of 500 μm–600 μm copper or stainless steel screen, the flow at each exhaust port should be 1 000 mL/s±150 mL/s. If a liquid bath is used, a suitable liquid should be used so that its upper surface is within 25 mm of the top at the test temperature. The temperature may be kept constant by a temperature controller or by suitable liquid reflux. 5.5 Flowmeter: as shown in Figure 1, a flowmeter capable of measuring the air or steam flow of a single exhaust port or of all exhaust ports. Depending on the measurement method selected, the range of the flowmeter should be greater than the specified flow of a single outlet or the total flow (specified flow of a single outlet × number of outlets). Optional air flowmeter: a separate flowmeter independent of the apparatus shown in Figure 1. The flowmeter should be calibrated and its back pressure less than 1 kPa. A rotameter or other flowmeter meeting the requirements may be selected when the range of the flowmeter is greater than the specified flow of a single outlet. 5.6 Sintered glass funnel: coarse porosity, 150 mL. 5.7 Steam generating device: a device capable of generating steam at 232 °C–246 °C at the inlet of the evaporation bath. The maximum steam output of the device must be greater than the total steam required by all bath holes during evaporation, and the output steam must be continuous and steady throughout. 5.8 Thermometer: meeting the technical requirements for thermometer No. GB-29 in GB/T 514—2005. 5.9 Graduated cylinder: 50 mL±0.5 mL or 25 mL±0.5 mL (for the determination of military diesel fuel). 5.10 Transfer tools: flat-tipped stainless steel tweezers or stainless steel tongs, used to insert and remove the beakers and conical adapters. Warning: if a liquid bath is used for heating, the flash point of the liquid should be at least 30 °C above the highest expected bath temperature. Do not operate the instrument before fully understanding the components and functions of the high-temperature apparatus. Protective measures should be worn when operating the instrument. Safety inspections should be carried out regularly.

Reagents and reference materials: General: unless otherwise stated, only reagents of analytical grade and above are used in the analysis. 6.1 Water: meeting the requirements for grade 3 water in GB/T 6682—2008. 6.2 n-Heptane. 6.3 Gum solvent: a mixture of toluene and acetone, volume ratio 1:1. 6.4 Chromic acid cleaning solution: first weigh 20 g of potassium dichromate and dissolve it in 40 mL of water (6.1). Then measure 360 mL of concentrated sulfuric acid and, while stirring, slowly add the concentrated sulfuric acid along the vessel wall to the potassium dichromate solution. 6.5 Detergent: alkaline, neutral cleaning agent or other suitable organic reagent. 6.6 Quality control check sample: a stable sample with properties similar to those of the test sample, which should be representative of the sample. 6.7 Air: to be purified, free of water, oil and other solid particles, pressure not greater than 35 kPa. 6.8 Steam: free of oily residue, pressure not lower than 35 kPa. Warning: chromic acid cleaning solution is strongly oxidizing and corrosive; protective measures should be worn for its preparation and use, which should be carried out in a well-ventilated environment, and it should be kept sealed when stored. When a steam generator is used, protective equipment or measures should be used to avoid direct contact with the skin.

Key conditions: Table 1 Test operating conditions: | Sample type | Evaporation medium | Bath temperature/°C | Test hole temperature/°C | |---|---|---|---| | Aviation gasoline and motor vehicle gasoline | Air | 160–165 | 150–160 | | Jet fuel | Steam | 232–246 | 229–235 | | Military diesel fuel | Air | 248–252 | 244–250 | Air flow (7.1.1): when testing aviation gasoline and motor vehicle gasoline samples, adjust the air flow at the outlet of the test apparatus to 600 mL/s±90 mL/s at room temperature; when testing military diesel fuel, adjust the air flow at the outlet of the test apparatus to 166 mL/s±16 mL/s, 292 mL/s±25 mL/s and 459 mL/s±41 mL/s respectively. Check whether the air flow at the remaining outlets is consistent. Note: a reading of 600 mL/s±90 mL/s at each outlet at normal temperature and pressure will ensure an output of 1 000 mL/s±150 mL/s at 155 °C±5 °C (the numerical statement at this point in the original is [to be verified] ([source unclear])). Steam flow (7.2.2): when the bath temperature reaches 232 °C, slowly introduce steam into the apparatus until the flow at each outlet reaches 1 000 mL/s±150 mL/s. Adjust the bath temperature within the range 232 °C–246 °C.

Calculation and results: The existent gum content of aviation fuel is calculated according to formula (2): A = 2 000 (B − D + X − Y) where: A—existent gum content, mg/100 mL; B—mass of the sample beaker plus evaporation residue recorded in 10.5, g; D—mass of the empty beaker recorded in 10.1, g; X—mass of the tare beaker recorded in 10.1, g; Y—mass of the tare beaker recorded in 10.5, g. 11.2 The solvent-washed gum content of motor vehicle gasoline is calculated according to formula (3): S = 2 000 (C − D + X − Z) where: S—solvent-washed gum content, mg/100 mL; C—mass of the sample beaker plus evaporation residue recorded in 10.11, g; Z—mass of the tare beaker recorded in 10.11, g. (The symbol printed in the original formula is a single East Asian character and is [to be verified] ([source unclear]); according to the context it should be Z.) 11.3 The unwashed gum content of motor vehicle gasoline is calculated according to formula (4): U = 2 000 (B − D + X − Y) where: U—unwashed gum content, mg/100 mL. 11.4 The existent gum content of military diesel fuel is calculated according to formula (5): M = 4 000 (B − D + X − Y) where: M—existent gum content, mg/100 mL. 9.2.2 The steam flow is calculated according to formula (1): R = 1000 (m1 − m2)/(m_k × t) where: R—steam flow, mL/s; m1—mass of the graduated cylinder containing condensed steam, g; m2—mass of the ice and graduated cylinder, g; m_k—mass of 1000 mL of steam at 232 °C under normal pressure, value 0.434, g; t—condensation time, s. (The subscript of the formula symbol in the original is [to be verified] ([source unclear]).) 13 Expression of results: 13.1 When the existent gum content of an aviation fuel sample is greater than or equal to 1 mg/100 mL, report the existent gum content result, rounded according to GB/T 8170 to 1 mg/100 mL; for results less than 1 mg/100 mL, report the existent gum content as "<1 mg/100 mL". 13.2 When the solvent-washed gum or unwashed gum content of a motor vehicle gasoline sample is greater than or equal to 0.5 mg/100 mL, report the solvent-washed gum or unwashed gum content result, rounded according to GB/T 8170 to 0.5 mg/100 mL; for results less than 0.5 mg/100 mL, report as "<0.5 mg/100 mL". If the unwashed gum content is less than 0.5 mg/100 mL, the solvent-washed gum content is also reported as "<0.5 mg/100 mL". 13.3 For military diesel fuel samples, the average of two repeat determination results is taken as the existent gum content. When the existent gum content of military diesel fuel is greater than or equal to 2 mg/100 mL, report the existent gum content result, rounded according to GB/T 8170 to 1 mg/100 mL; for results less than 2 mg/100 mL, report the existent gum content as "<2 mg/100 mL". 13.4 For all samples, if a filtration step was carried out before evaporation (see 10.3), note the words "after filtration" after the numerical value of the gum content result.

Quality control: General: the precision obtained from interlaboratory statistical test results is given in 14.2 and 14.3 (95% confidence level). Figures 2 and 3 are the repeatability and reproducibility curves for aviation gasoline and jet fuel respectively. Note 1: The precision for solvent-washed gum and unwashed gum given in this method was determined in 1997 by an interlaboratory statistical study. The precision samples selected were 14 refined gasolines (2 of which contained 10% (by volume) ethanol, and 5 of which contained 15% (by volume) MTBE and deposit-control additives). The precision ranges for solvent-washed gum content and unwashed gum content were 0 mg/100 mL–15 mg/100 mL and 0 mg/100 mL–50 mg/100 mL respectively. Note 2: The precision for military diesel fuel was determined by an interlaboratory statistical study among 6 laboratories. To cover the precision range of existent gum, the precision samples for military diesel fuel were prepared by blending military diesel fuel with No. 3 jet fuel, or military diesel fuel with motor vehicle diesel fuel, 8 samples in total. The military diesel fuel and No. 3 jet fuel were both hydrotreated fuels, and the motor vehicle diesel fuel was a commercial product. The precision range was 3 mg/100 mL–51 mg/100 mL. 14.2 Repeatability (r): the difference between two test results obtained by the same operator, in the same laboratory, using the same apparatus, following the same test method, on the same sample in successive determinations shall not exceed the repeatability limit in Table 2. 14.3 Reproducibility (R): the difference between two single, independent test results obtained by different operators, in different laboratories, using different apparatus, following the same test method, on the same sample shall not exceed the reproducibility limit in Table 2. Table 2 Precision for different types of sample: | Sample type | Repeatability (r) | Reproducibility (R) | |---|---|---| | Aviation gasoline | 1.11+0.095X | 2.09+0.126X_R | | Jet fuel | 0.588 2+0.249 0X | 2.941+0.279 4X_R | | Motor vehicle gasoline (unwashed) | 0.997X^0.4 | 1.928X_R^0.4 | | Motor vehicle gasoline (solvent-washed) | 1.298X^0.3 | 2.494X_R^0.3 | | Military diesel fuel | 0.121 4X+0.036 1 | 0.320 6X_R+0.786 1 | Note: X—the average of two repeat determination results; X_R—the average of two single, independent results. (The symbol in the note in the original is [to be verified] ([source unclear]).)

Normative references: GB/T 514—2005 Liquid-in-glass thermometers for testing of petroleum products — Specification GB/T 4756 Petroleum liquids — Manual sampling GB/T 6682—2008 Water for analytical laboratory use — Specification and test methods GB/T 8170 Rules for rounding off numerical values and expression and determination of limiting values GB/T 27867 Petroleum liquids — Automatic pipeline sampling SH/T 0635 Liquid petroleum products — Sampling method (semi-automatic method)

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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