SH/T 0770-2005 Determination of Freezing Point of Aviation Fuels (Automatic Phase Transition 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 title / English name / replacement relationship

• Standard number: SH/T 0770—2005
• Chinese title: Determination of Freezing Point of Aviation Fuels (Automatic Phase Transition Method)
• English title: Standard test method for freezing point of aviation fuels (Automatic phase transition method)
• Replacement relationship: not provided in the available source (the foreword only states modified adoption of ASTM D 5972-02, and does not mention replacement of an old standard)
• Adoption relationship: modified adoption of ASTM D 5972-02 "Standard Test Method for Freezing Point of Aviation Fuels (Automatic Phase Transition Method)", redrafted according to ASTM D 5972-02
• Main differences from ASTM D 5972-02: the referenced standards of this standard add the corresponding national standards of our country
• Editorial modifications: the wording of repeatability and reproducibility is modified according to our country's conventions; the keywords of Chapter 13 are deleted
• Publication/implementation: published on 2005-10-10, implemented on 2006-02-01
• Issuing authority: National Development and Reform Commission of the People's Republic of China
• Custodian: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Zhang Ji, Gong Dongmei

2. Scope of application and non-applicability

• 1.1 specifies the method for determining the freezing point of jet fuels, below which solid hydrocarbon crystals will form in the jet fuel.
• 1.2 is applicable to the determination of freezing points in the range of −80 ℃ to +20 ℃; however, the interlaboratory study mentioned in clause 12.4 was verified only for jet fuel freezing points in the range of −45 ℃ to −65 ℃.
• When 1.3 is used to determine JetB and JP4 samples with this standard, users should pay attention (see clause 12.3). Note: JetB and JP4 correspond to the wide-cut jet fuels specified in our country's GJB 2376.
• 1.4 uses SI (International System of Units) as the standard unit of measurement.
• The use of 1.5 may involve hazardous materials, operations, and equipment; this standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user to establish appropriate safety and protection measures before use and to determine the applicability of its restricted scope.
• When the specification requires the use of method GB/T 2430, 5.4 cannot be replaced by this standard or other test methods.

3. Method principle

• Chapter 4 Method summary: The sample is cooled with a Peltier cooler at a rate of 15 ℃/min±5 ℃/min while being continuously illuminated by a light source. The sample is continuously monitored with an optical array detector to observe the initial formation of solid hydrocarbon crystals. Once hydrocarbon crystals form, the sample begins to warm at a rate of 10 ℃/min±0.5 ℃/min until the last hydrocarbon crystals transform into the liquid phase. The temperature at which the last solid hydrocarbon crystals transform into the liquid phase is recorded as the freezing point.
• 3.1 Definition of freezing point: For aviation fuels, after the fuel is cooled to form solid hydrocarbon crystals, the sample then begins to warm under specified conditions, and the temperature at which the hydrocarbon crystals disappear is the freezing point of the aviation fuel.
• 3.2 Definition of automatic phase transition method: The process of automatically cooling an aviation fuel sample until solid crystals appear, then controlling the temperature rise and recording the temperature at which these solid crystals completely remelt into the liquid phase.
• 3.3 Definition of Peltier cooler: A solid-state thermoelectric device composed of different semiconductor materials that, depending on the direction of current applied to the device, transfers heat into or away from the test sample.

4. Reagents and materials (purity / preparation)

• 7.1 n-Octane: analytical reagent. Warning: flammable, harmful if inhaled, keep away from heat, sparks, and open flames.
• 7.2 Cooling medium: a liquid heat exchange medium used to carry away heat generated by the Peltier cooler and other electronic components of the instrument.
  • Note: Some instruments are designed to use tap water as the cooling medium, which can lower the sample temperature to −60 ℃; if the sample temperature is to be lowered to −80 ℃, an instrument capable of producing a circulating cooling medium at −30 ℃ or lower is required. Since water freezes at 0 ℃, industrial-grade isopropanol can be used as the cooling medium. The relationship between the temperature of the cooling medium and the minimum sample temperature can be found in the manufacturer's operating instructions.
• 9.2 mentions that analytical reagent grade n-octane or n-nonane with known freezing point values may be used (the source text source-text extraction writes "n-jadeane", requires confirmation against the source standard (source-text extraction)) to calibrate the temperature measuring device in the instrument.

5. Apparatus and equipment

• 6.1 Automatic instrument: includes a microprocessor-controlled test chamber capable of cooling and heating the sample, optically observing the formation and disappearance of solid hydrocarbon crystals in the sample, and recording the sample temperature. Detailed description see Annex A.
• 6.2 requires a sample cup, an optical array detector, a light source, a digital display, a Peltier cooler, and a sample temperature measuring device.
• 6.3 The sample temperature measuring device is capable of measuring samples from −80 ℃ to +20 ℃ with a resolution of 0.1 ℃ (the source text "granularity is 0.10" is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
• 6.4 requires a liquid medium circulation system to carry away heat generated by the instrument's Peltier cooler and other electronic components.
• 6.5 requires a purge gas circulation component to purge with clean gas to remove moisture from the test chamber containing the sample cup.
• Annex A (normative annex) Detailed description of the instrument:
  • A.1 Test chamber: composed of an optical detector, lens, light source, sample cup, temperature sensor, Peltier cooler, and heat dissipation device (see Figure A.1). The test chamber lid can be opened when cleaning the sample cup and injecting a new sample; once the lid is closed and locked, the test chamber is sealed. The lid and the rest of the test chamber are sealed with O type rings. The air remaining in the test chamber is purged with dry gas. The test chamber walls are made of black metal or plastic components to minimize light reflection.
  • A.1.1 Sample cup: composed of a black plastic inner wall and a highly polished metal bottom. The polished surface of the bottom serves as a reflective light surface. Sample heat exchange occurs through the metal bottom, controlled by the Peltier cooler.
  • A.1.2 Temperature sensor: reads to 0.1 ℃ and has a minimum accuracy of 0.1 ℃, fixedly embedded in the bottom of the sample cup, positioned within 0.1 mm of the bottom of the sample cup. Made of a single strand of platinum.
  • A.1.3 Peltier cooler: can control the sample temperature over a wide range, the range depending on the model type. During cooling, heat is transferred from the top of the Peltier cooler to the bottom, cooling the sample through heat exchange between the top and the bottom of the sample cup; the bottom is connected to a heat dissipation device, and heat is dissipated into the cooling medium. During warming, the process is reversed.
  • A.1.4 Light source: capable of providing a beam of light with a wavelength of 660 nm±10 nm. Positioned so that the beam forms an acute angle with the sample (see Figure A.1). The beam is reflected from the polished bottom of the sample cup. When the sample is a uniform liquid, the reflected light strikes the test chamber lid, which is black, and the black surface absorbs the reflected light. When wax crystals appear in the sample, the solid-liquid interface disperses and reflects the light beam, and a large amount of scattered light is projected onto the lens (see Figure A.2).
  • A.1.5 Optical detector: placed on the lens to monitor the transparency of the sample. The distance between the optical detector and the lens is automatically adjusted so that the sample image is projected onto the photosensitive surface of the optical detector, and the optical detector provided by the instrument is sufficient to cover the entire image area.
  • A.2 Instrument appearance: designs may vary, but the display and buttons are the same. A typical appearance is shown in Figure A.3.
  • A.2.1 Information display: provides instrument status information. Appropriate information is displayed when the instrument is not working or no error occurs; results are displayed at the end of the test; diagnostic information is displayed when an error is detected in a major component. Detailed diagnostic information is described in the manufacturer's service manual.
  • A.2.2 Sample temperature display: gives the corrected temperature of the sample during the measurement process.
  • A.2.3 Optical signal display: gives the corrected signal of scattered light absorbed by the optical detector along the horizontal plane, for maintenance personnel to troubleshoot.
  • A.2.4 Menu button: allows the operator to change the temperature unit from Celsius to Fahrenheit and vice versa; the Celsius unit is the standard unit of measurement.
  • A.2.5 Run button: after the sample is injected into the test chamber, the operator can start the measurement program.
  • A.2.6 Reset button: allows the operator to stop the measurement program. When pressed, the instrument immediately stops the measurement program and heats the sample to ambient temperature.
  • Note: Each instrument is provided with a manufacturer's operating manual detailing installation, use, and maintenance instructions.

6. Recommended operating conditions

• Cooling rate: 15 ℃/min±5 ℃/min (Chapter 4, 10.6).
• Heating rate: 10 ℃/min±0.5 ℃/min (Chapter 4, 10.6).
• Light source wavelength: 660 nm±10 nm (A.1.4).
• Sample amount: 0.15 mL±0.01 mL (10.2, 10.4).
• Purge gas: clean gas, pressure adjusted according to the manufacturer's operating instructions (6.5, 8.3).
• Cooling medium temperature: the relationship with the minimum sample temperature is according to the manufacturer's operating instructions (7.2 Note).

7. Sampling and sample preparation

• No independent sampling and sample preparation chapter is provided in the available source. Sample amount see 10.2, 10.4: measure 0.15 mL±0.01 mL of sample with a syringe and inject into the sample cup.

8. Analysis procedure

• 8 Instrument preparation:
  • 8.1 Install the instrument according to the manufacturer's operating instructions.
  • 8.2 Turn on the liquid cooling medium circulation system according to the manufacturer's operating instructions, and ensure that the temperature of the cooling medium is suitable for the test requirements of the sample (see clause 7.2 Note).
  • 8.3 Turn on the gas purge system according to the manufacturer's operating instructions, and ensure it is adjusted to a suitable pressure. Note: Some instruments can be equipped with a gas source capable of producing dry purge gas, so that separate compressed gas equipment is not required.
  • 8.4 Turn on the main power switch of the analyzer.
• 9 Calibration and standardization:
  • 9.1 Ensure that the instrument is calibrated, checked, and operated according to the manufacturer's operating instructions.
  • 9.2 A jet fuel sample that has been determined by the GB/T 2430 method and has a large amount of freezing point data can be used to verify the performance of this instrument. Samples that have been cross-checked among multiple laboratories can be used as calibration standards; these calibration standard samples can be obtained from samples that have been cross-checked within the laboratory. Analytically pure n-octane or n-nonane with a known freezing point value (the source text source-text extraction writes "n-hentriacontane", requires confirmation against the source standard (source-text extraction)) can be used to verify the temperature measurement device in the instrument.
• 10 Test procedure:
  • 10.1 Open the lid of the detection chamber, and wipe the sample cup inside the detection chamber with a cotton swab (the source text "guess" is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
  • 10.2 Use a sampler to measure 0.15 mL±0.01 mL of sample and inject it into the sample cup for cleaning. Wipe the sample cup clean with a cotton swab; the sample cup must be wiped until no obvious sample droplets remain.
  • 10.3 Clean the sample cup according to the procedure in clause 10.2.
  • 10.4 Accurately measure 0.15 mL±0.01 mL of sample and inject it into the sample cup.
  • 10.5 Cover and lock the lid of the detection chamber.
  • 10.6 Operate the instrument according to the manufacturer's operating instructions; all operations from start to end of testing are automatically controlled by the instrument. When the purge gas and liquid cooling medium begin to flow through the instrument, the Peltier cooler cools the sample at a rate of 15 ℃/min±5 ℃/min, the optical detector continuously monitors the formation of hydrocarbon crystals in the sample, and the instrument continuously monitors the sample temperature and displays it on the display screen. Once the formation of hydrocarbon crystals is detected, the sample is heated at a rate of 10 ℃/min±0.5 ℃/min until the hydrocarbon crystals are converted back into the liquid phase. When the last crystals in the sample disappear, the sample temperature is recorded and the measurement is terminated.
  • 10.7 This instrument will display the measured freezing point value.
  • 10.8 Open the lid of the detection chamber, and wipe the sample cup clean with a cotton swab.

9. Qualitative and quantitative determination and calculation formulas

• 11 Report: Report the temperature recorded in clause 10.7 as the freezing point of the sample tested by this standard, to the nearest 0.1 ℃.
• Calculation formula: not provided in the available source.

10. Precision

• 12.1 Repeatability (r): For the same operator, using the same instrument, on the same sample, the difference between two test results shall not be greater than 0.6 ℃ (the source text source-text extraction writes "0.69Co", requires confirmation against the source standard (source-text extraction)).
• 12.1.1 Reproducibility (R): For different operators in different laboratories, using different instruments, on the same sample, the difference between two test results shall not be greater than 1.3 ℃ (the source text source-text extraction writes "1.30°", requires confirmation against the source standard (source-text extraction)).
• 12.2 Bias: Because there is no hydrocarbon mixture with a known freezing point that can be used to simulate aviation fuel, the bias has not been determined (the source text source-text extraction writes "because there is no hydrocarbon mixture with a known freezing point that can be used to simulate aviation fuel, the bias is unclear in the source text", requires confirmation against the source standard (source-text extraction)).
• 12.3 Relative bias: The results of all samples among laboratories from the 1994 annual laboratory cooperative test program were used to verify the relative bias of this standard with ASTM D2386 (i.e., GB/T 2430). Differences in the results of some fuels were observed. However, there was no identical bias among all samples, and all differences were within the reproducibility range of ASTM D2386 (i.e., GB/T 2430) (2.5 ℃), except for samples of two fuels. These two samples were samples of JP4 and JetB, which were higher than the average results of test method ASTM D2386 (GB/T 2430) by 2.5 ℃ and 2.8 ℃. Therefore, when using this standard to determine JetB and JP4 samples, users need to pay attention.
• 12.4 Precision was also obtained from the 1994 annual laboratory cooperative test program. The 14 sample groups participating in the analysis included various aviation fuels with freezing point ranges from −45 ℃ to −65 ℃; 9 participating laboratories used automatic phase transition instruments, and 15 participating laboratories used the manual ASTM D2386 (i.e., GB/T 2430) method. The precision statistics were compiled and calculated based on the 0.1 ℃ resolution provided by the automatic phase transition method.

11. Report

• See Chapter 11: Report the temperature recorded in clause 10.7 as the freezing point of the sample tested by this standard, to the nearest 0.1 ℃.

12. Normative references

• GB/T 2430 Jet fuel freezing point determination method
• GJB 2376 Wide-cut jet fuel specification
• ASTM D2386 Aviation fuel freezing point test method
• ASTM D 5972-02 Standard test method for freezing point of aviation fuels (automatic phase transition method) (foreword, modified adoption)

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