SH/T 0771-2005 Petroleum products — Determination of pour point (automatic pressure pulse method)

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Card type: Test method

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

• Standard number: SH/T 0771—2005
• Chinese title: Petroleum products — Determination of pour point (automatic pressure pulse method)
• English title: Test method for pour point of petroleum products (Automatic pressure pulsing method)
• Replacement relationship: not provided in the available source (the foreword does not mention replacement of any standard)
• Adoption relationship: modified adoption of ASTM D5949-01 "Test method for pour point of petroleum products (automatic pressure pulse method)", redrafted according to ASTM D5949-01
• Main differences from ASTM D5949-01: some referenced standards adopt the corresponding national standards of our country; the expression of repeatability and reproducibility is modified according to the expression habits of our country; the chapter on keywords is deleted
• Publication/implementation: published on 2005-10-10, implemented on 2006-02-01
• Issuing body: National Development and Reform Commission of the People's Republic of China
• Custodian: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Lubricant Branch of China Petroleum & Chemical Corporation
• Main drafters: Zhang Chunhui, He Gang, Meng Xuemei, Chang Bin, Xia Peng
• Appendix: Appendix A is a normative appendix

2. Scope of application and non-applicability

• 1.1 specifies a method for determining the pour point of petroleum products using an automatic instrument. The instrument applies a controlled pulsed nitrogen flow to the surface of the sample being cooled, while an optical instrument is used to check the movement of the sample surface.
• The applicable range of 1.2 is -57 ℃ to 51 ℃ (the source text source-text extraction writes "-57°C–51C"). In 1992, only interlaboratory statistical testing from -39 ℃ to 6 ℃ was completed (the source text source-text extraction writes "-39C–6[garbled unit]"), and in 1998, interlaboratory statistical testing from -51 ℃ to -11 ℃ was completed (see clause 13.4).
• 1.3 may use 1 ℃ or 3 ℃ intervals for determination.
• 1.4 is not applicable to the determination of the pour point of crude oil.
• Note: The application of this standard to residual fuel samples has not yet been proven; for detailed information see clause 13.4.
• 1.5 uses International System of Units [SI] units.
• The application of 1.6 may involve certain hazardous materials, operations and equipment, but does not purport to address all safety problems associated with them; users are responsible for establishing appropriate safety and protection measures before use and for clarifying the restricted scope of application.

3. Method principle

• Summary of the 4 method: place the sample in an automatic pour point instrument to carry out the initialization test procedure, then heat the sample, and then cool it by means of a Peltier device at a rate of 1.5 ℃/min ± 0.1 ℃/min. According to the temperature interval of 1 ℃ or 3 ℃ selected by the user, the moving force formed by a pressurized nitrogen pulse is applied to the sample surface, and a set of optical detectors connected to a light source is used to detect movement of the sample surface; the lowest temperature at which the sample surface is observed to be able to move under the pulsed nitrogen is recorded as the pour point of this method.
• 3.1 Pour point pour point: under specified conditions, the lowest temperature at which the sample is observed to be able to flow.
• 3.2 No-flow point no-flow point: under the test conditions, the temperature at which a waxy structure appears in the sample, viscosity increases, or both act simultaneously to prevent movement of the sample surface. Result determination: under cooling conditions, when the no-flow point occurs, the waxy structure formation, viscosity increase, or both acting simultaneously cause the observation instrument no longer to detect movement of the sample surface under the test conditions; the previous test temperature, that is, the last test temperature at which the sample was able to flow, is the pour point.
• 3.3 Pulse pulse: controlled pulsed nitrogen with fixed pressure and flow rate that can cause movement of the sample surface but will not destroy the waxy structure that may form in the sample.
• 3.4 Peltier device Peltier device: an electronic solid-state thermoelectric device that can transfer heat to the sample or remove heat from the sample according to the direction of the input current.

4. Reagents and materials (purity / preparation)

• 7.1 Reagents
  • Coolant: tap water or other liquid cooling medium. These coolants should be sufficient to carry away the heat generated by the Peltier device and other electronic components in the instrument. In order to cool the sample to -60 ℃, the temperature of the circulating liquid cooling medium should be lower than 25 ℃. If a lower sample temperature is required or the temperature of the tap water is higher than 25 ℃, the cooling performance data of the instrument can be obtained from the instrument manufacturer.
• 7.2 Materials
  • 7.2.1 Dry nitrogen: the dew point of the nitrogen (the source text source-text extraction writes "[garbled dew-point term]") should be lower than the lowest temperature that the sample can reach. Warning: compressed gas. Inhalation of inert gas can cause suffocation.
  • 7.2.2 Pipette: adjustable in volume, with the ability to dispense 0.150 mL ± 0.005 mL of sample.
  • 7.2.3 Cotton swab: plastic-stemmed cotton swab, used to clean the sample cup.

5. Apparatus and equipment

• 6.1 Automatic instrument: includes a microprocessor-controlled measuring chamber for heating and cooling the sample, a component capable of providing controlled pulsed nitrogen blown onto the sample surface, an optical component for detecting movement of the sample surface, and a temperature sensor for recording the sample temperature; detailed specifications of the instrument are given in Appendix A. This instrument is specially designed to detect the lowest temperature at which the sample surface is observed to be able to move under the pulsed nitrogen.
• 6.2 This instrument is equipped with a sample cup, a set of optical detectors, a light source, a pressure pulse unit, a digital display meter, a Peltier device and a sample temperature measuring device.
• 6.3 Pressure pulse unit: includes a stainless steel tube of length 250 mm ± 2 mm and inner diameter 1.1 mm ± 0.1 mm; one end of the tube is connected to a stable gas source as the inlet, and the other end serves as the outlet and points at an acute angle toward the center of the sample, with the outlet at a distance of 8 mm ± 2 mm from the center of the sample.
• 6.4 Peltier device: can heat or cool the sample at a rate of 1.5 ℃/min ± 0.1 ℃/min.
• 6.5 The temperature measuring device in the sample cup has a temperature measurement range of -80 ℃ to 70 ℃, with a resolution of 0.1 ℃ (the source text source-text extraction writes "0.1°%").
• 6.6 This instrument is equipped with circulating water or another liquid cooling medium to carry away the heat generated by the Peltier device and other electronic components in the instrument.
• 6.7 This instrument is equipped with a device for delivering nitrogen to the pressure pulse unit.
• Appendix A (normative appendix) Detailed description of the instrument:
  • A.1 Measuring chamber: composed of optical detectors, lenses, a light source, a sample cup, a temperature sensor, a Peltier device and a heat exchanger, arranged as shown in Figure A.1. The lid of the measuring chamber can be opened to facilitate cleaning the sample cup and pouring in a new sample. Once the lid is closed and locked, the measuring chamber becomes sealed, and an O-type ring is used to seal the contact surface between the lid and the measuring chamber. Dry gas is used to purge the air in the sealed measuring chamber; the inlet and outlet of the dry gas are shown in Figure A.1. The side walls of the measuring chamber are made of black metal and plastic to minimize light reflection.
  • A.1.1 Sample cup: composed of black plastic side walls and a metal bottom surface of high polishing precision; the polished surface of the bottom serves as the light reflection interface, and heat transfer and cooling of the sample are controlled by the Peltier device through the metal bottom surface.
  • A.1.2 Temperature sensor: reading is 0.1 ℃, minimum accuracy is 0.2 ℃, fixedly embedded in the bottom of the sample cup and located 0.1 mm below the bottom surface of the sample cup. The temperature sensor is made of a single strand of platinum wire and provides accurate measurement of the sample temperature.
  • A.1.3 Peltier device: has the ability to control the sample temperature over a wide range, and the range variation depends on the model series. When the sample is cooled, heat is transferred from the top of the device to the bottom; because the top is in thermal contact with the bottom of the sample cup, the sample is cooled, and the bottom of the Peltier device is in thermal contact with the heat exchanger, where the heat is carried away by the cooling medium. When the sample is heated, the reverse process occurs.
  • A.1.4 Light source: provides a light beam with a wavelength of 660 nm ± 10 nm; the light source is installed at a position such that the light beam it generates can illuminate the sample at an acute angle (see Figure A.1). The light is reflected by the polished bottom surface of the sample cup and the sample surface. When the sample is a uniform liquid, the reflected light shines on the lid of the sample chamber, whose color is black, and the reflected light is absorbed by the black surface. When movement occurs on the sample surface, the reflected light is refracted by the moving surface, and a large amount of refracted light shines onto the lens (see Figure A.2).
  • A.1.5 Optical detector: installed above the lens to detect the transparency of the sample; the distance between the optical detector and the lens is adjusted so that the image of the sample is projected onto the light-sensitive surface of the optical detector, and enough optical detectors are used to cover the image area.
  • A.2 Instrument exterior surface: the exact layout of controls and displays may vary; Figure A.3 shows a typical instrument. Note: All descriptions, installation, instrument setup and maintenance instructions are included in the manufacturer's manual supplied with each instrument.

6. Recommended operating conditions

• Cooling rate: 1.5 ℃/min ± 0.1 ℃/min (4, 6.4, 11.8)
• Test interval: 1 ℃ or 3 ℃ (1.3, 5.5, 11.7)
• Circulating liquid cooling medium temperature: in order to cool the sample to -60 ℃, it should be lower than 25 ℃ (7.1)
• Sample heating conditions: if the expected pour point of the sample is higher than 36 ℃ or it is solid at room temperature, it should be heated to 45 ℃ to 70 ℃ (11.2); unless the sample temperature is below 70 ℃, it may be heated or transferred into the sample cup (8.2)
• Nitrogen pressure: adjust to a suitable pressure according to the instrument manufacturer's instructions (9.3)
• Bath temperature: confirm the bath temperature suitable for the test sample according to the instrument manufacturer's instructions (9.2)

7. Sampling and sample preparation

• 8.1 Unless otherwise specified, sampling shall be carried out in accordance with GB/T 4756.
• 8.2 Particularly viscous samples may be heated until they can flow before transfer, but not all samples must be heated. Only when the sample temperature is below 70 ℃ may it be heated or transferred into the sample cup. Note: If the sample has been heated to above 70 ℃, the sample should be cooled to below 70 ℃ before transferring the sample.
• 11.2 Use a pipette to inject the 0.150 mL ± 0.005 mL test sample into the sample cup. If the expected pour point of the test sample is higher than 36 ℃ or it is solid at room temperature, it should be heated to 45 ℃～70 ℃ (see the note after 13.3.1). Use a cotton swab to clean the test sample inside the sample cup; the sample cup should be clean to the extent that there are no test sample droplets.
• 11.3 Repeat step 11.2.
• 11.4 Accurately measure 0.150 mL ± 0.005 mL of the test sample into the sample cup.

8. Analytical procedure

• 9 Instrument preparation
  • 9.1 Install the instrument according to the instrument manufacturer's instructions.
  • 9.2 Turn on the liquid cooling bath, and confirm the bath temperature suitable for the test sample according to the instrument manufacturer's instructions.
  • 9.3 Turn on the nitrogen gas, and adjust to the appropriate pressure according to the instrument manufacturer's instructions.
  • 9.4 Turn on the main power switch of the analyzer.
• 10 Calibration and standardization
  • 10.1 Confirm that all steps regarding instrument calibration, checking, and operation in the instrument manufacturer's instructions are followed.
  • 10.2 A pour point sample with an assigned value may be used to calibrate the instrument; in addition, a sample that has been extensively tested between laboratories may also be used to calibrate the instrument.
• 11 Test procedure
  • 11.1 Open the cover of the measuring chamber, and use a cotton swab to clean the sample cup inside the measuring chamber.
  • 11.2 Use a pipette to inject the 0.150 mL ± 0.005 mL test sample into the sample cup. If the expected pour point of the test sample is higher than 36 ℃ or it is solid at room temperature, it should be heated to 45 ℃～70 ℃ (see the note after 13.3.1). Use a cotton swab to clean the test sample inside the sample cup; the sample cup should be clean to the extent that there are no test sample droplets.
  • 11.3 Repeat step 11.2.
  • 11.4 Accurately measure 0.150 mL ± 0.005 mL of the test sample into the sample cup.
  • 11.5 Close and lock the measuring chamber cover.
  • 11.6 Preheat the test sample according to the manufacturer's instructions.
  • 11.7 Select the required pour point test interval: 1 ℃ interval or 3 ℃ interval.
  • 11.8 Start the test program according to the manufacturer's instructions. The test sample is heated as described in 11.6, then cooled with a Peltier device at a rate of 1.5 ℃ ± 0.1 ℃/min. The instrument will apply a compressed pulse of nitrogen gas to the surface of the test sample once for every decrease of 1 ℃ or 3 ℃ according to the test interval determined in 11.7. The test sample is illuminated by a light source, and an optical detector is used to monitor the movement of the test sample surface when the pulse is applied. When no movement of the test sample surface is observed when the compressed pulse of nitrogen gas is applied, that is the no-flow point of the test sample. The temperature at which movement of the test sample surface can be observed when the compressed pulse of nitrogen gas was last applied is recorded as the pour point. The pour point value is displayed as an integer multiple of 1 ℃ or 3 ℃ according to the selected test interval.
  • 11.9 Open the test chamber cover, and use a cotton swab to clean the test sample inside the sample cup.

9. Qualitative and quantitative determination and calculation formula

• 12 Report: Report the temperature in 11.8 as the pour point of this method.
• Result determination (3.2): Under cooling conditions, when the no-flow point appears, the formation of a waxy structure, an increase in viscosity, or both, causes the observation instrument to no longer detect movement of the sample surface under the test conditions. The previous test temperature, that is, the last test temperature at which the test sample was able to flow, is the pour point.
• The pour point value is displayed as an integer multiple of 1 ℃ or 3 ℃ according to the selected test interval (11.8).
• Calculation formula: not provided in the available source.

10. Precision

• 13.1 Precision: Judge the reliability of the results according to the following provisions (95% confidence level). The precision of this method, determined by statistical methods from interlaboratory test results, is as follows:
• 13.1.1 Repeatability (r): The difference between two consecutive test results obtained by the same operator, using the same instrument, with the same method, on the same test sample shall not be greater than the value in Table 1.
• Table 1 Repeatability data Unit: ℃

• 13.1.2 Reproducibility (R): The difference between two consecutive test results obtained by different operators, using different instruments, with the same method, on the same test sample shall not be greater than the value in Table 2.
• Table 2 Reproducibility data Unit: ℃

• 13.2 Bias: Since there is no acceptable standard sample to determine the bias of this method, the bias has not been determined.
• 13.3 Relative bias
  • 13.3.1 Comparing the pour point test results of this method at the 3 ℃ interval with the results of ASTM D97 (equivalent to GB/T 3535), it can be found that some test samples may have possible relative bias, but the relative bias is not systematic. During the interlaboratory testing in 1998, no test sample types with bias relative to ASTM D97 (equivalent to GB/T 3535) were included. Note: In the interlaboratory test study in 1998, it was found that when testing high-sulfur winter diesel samples by different test methods, there were relatively large differences in test results. During the cooling process, the test sample forms a very thin, very large disk-shaped crystal. In addition to covering the surface of the test sample, these crystals also exist at the contact surface between the test sample and the glass. In the entire test sample, except for this thin layer of crystals, the other liquid has obvious low-viscosity characteristics. At this time, if the test sample is handled gently, the test sample will not pour out; but if the test sample is handled forcefully, the crystal-wrapped shell will break, and the test sample will pour out easily. It is recommended that when this phenomenon occurs during testing, attention should be paid to the differences in results between test methods.
  • 13.3.2 Comparing the results of this method at the 1 ℃ interval with the results at the 3 ℃ interval, there may be an average bias of 1.1 ℃. It should be noted that when testing a test sample at the 3 ℃ interval compared with testing at the 1 ℃ interval, the statistical results have a difference of 1 ℃. This is due to the increased number of tests and the different reporting format. If the difference between the test results is greater than 1, then other causes exist. During the interlaboratory testing, the test results at the 1 ℃ interval were on average lower by 1.1 ℃ than the test results at the 3 ℃ interval.
• 13.4 The precision and relative bias were obtained from the interlaboratory statistical test in 1998. Used for analysis were: two sets of the same diesel fuel oil, five sets of the same base oil, three sets of the same multigrade lubricating oil, and one set of the same hydraulic oil and automatic transmission fluid with a temperature range from -51 ℃ to -11 ℃. Nine laboratories participated in the test using 30 model, 50 model, and 70 model instruments, six laboratories participated using 70Y model instruments, and all tests were conducted at the 1 ℃ and 3 ℃ intervals. Seven laboratories participated in the test using the manual method according to ASTM D97 (equivalent to GB/T 3535). The research report on sample types and average pour point information can be obtained from ASTM headquarters.

11. Report

• 12 Report: Report the temperature in 11.8 as the pour point of this method.
• 5.4 When reporting test results at the 3 ℃ interval, the test results of this method are the same as the reporting format of GB/T 3535. Note: Some users may wish to report results in a format similar to GB/T 3535 (at the 3 ℃ interval); the precision can be obtained between 3 ℃ temperature tests. For the explanation of the relative bias with GB/T 3535, see 13.3.

12. Reference documents

• GB/T 3535 Standard test method for pour point of petroleum products (GB/T 3535-83 (91), ISO 3016:1994, MOD)
• GB/T 4756 Standard practice for manual sampling of petroleum liquids (GB/T 4756-1998, ISO 3170:1998, EQV)
• ASTM D97 Standard test method for pour point of petroleum products
• ASTM D5949-01 Standard test method for pour point of petroleum products (automatic pressure pulsing method) (modified adoption of the source standard)

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 for questions and answers