NB/SH/T 0886-2014 Determination of pour point of petroleum products — Automatic tilt method

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Card type: Test method

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

• Standard number: NB/SH/T 0886—2014
• Chinese title: Determination of pour point of petroleum products — Automatic tilt method
• English title: Standard test method for pour point of petroleum products (Automatic tilt method)
• Replacement relationship: not provided in the available source (no replacement of any standard is mentioned)
• Adoption relationship: modified adoption using the redrafting method of ASTM D5950-12
• Main differences from ASTM D5950-12: some referenced standards adopt the corresponding national standards of our country; the treatment method for residual fuel in clause 8.3 has been added; the content of clause 13.5 has been deleted
• Publication/implementation: published on 2014-06-29, implemented on 2014-11-01
• Issuing body: National Energy Administration
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC1)
• Drafting organization: Lanzhou Lubricating Oil Research and Development Center of PetroChina Company Limited
• Main drafters: Wang Yi, Ma Shujie, Hu Yuhua, Lu Xinling

2. Scope of application and non-applicability

• Scope of application: specifies the method for determining the pour point of petroleum products using an automatic instrument; applicable to the determination of the pour point of petroleum products, applicable range -66 ℃ to 51 ℃; the determination result is determined by the selected measurement temperature interval (1 ℃ or 3 ℃).
• Not applicable: 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 chapter 13.

3. Method principle

After the preheating preparation work, place the test sample into the automatic pour point tester. After the program starts, the test sample is cooled according to the cooling steps listed in Table 1 and Figure 1, and the pour point is detected once every 1 ℃ or 3 ℃ by the automatic pour point tester; the lowest flowing temperature measured for the test sample is taken as the pour point. During the cooling process, the instrument tilts the pour point tube, while an optical instrument is used to check the movement of the test sample surface. Note: if the preheating step of the automatic pour point tester is used, after the test sample is placed and the program is started, the instrument will automatically run the preheating preparation work.

4. Reagents and materials (purity / preparation)

• 7.1 Anhydrous methanol: analytical grade; when an external cooling system is used, it serves as the cooling medium for the circulating cooling bath. Warning: flammable, vapor is harmful, and if swallowed or inhaled may cause blindness or death.
• 7.2 Cleaning solvent: petroleum ether, analytical grade, or naphtha, used to clean and dry the pour point tube and probe. Warning: flammable, the liquid can cause eye burns, vapor is harmful.
• 6.6 Cork disk: thickness 6 mm±0.2 mm, placed with appropriate looseness inside the pour point tube jacket; felt may also be used, but special care must be taken to avoid moisture inside the felt, and before each measurement it must be ensured that the felt is dry.
• 6.7 Cork gasket: can be properly fitted around the outside of the pour point tube and placed exactly inside the pour point tube sleeve; the purpose is to prevent the pour point tube from contacting the cooled pour point tube sleeve.

5. Instruments and equipment

• 6.1 Optical automatic pour point tester
  • 6.1.1 Computer controller: capable of controlling 1 or more independent test cells.
  • 6.1.2 Cooling supply source: capable of cooling according to the specified cooling steps and independently controlling each test cell.
  • 6.1.3 Monitor: continuously monitors the test sample temperature.
  • 6.1.4 Sensor: determines slight movement of the test sample during tilting.
  • 6.1.5 The instrument should satisfy the cooling steps in Table 1 and Figure 1 and the test procedure in chapter 11, and be operated according to the manufacturer's instructions.
• 6.2 Temperature detector: IEC 60751 grade A: ΔT=± (0.15+0.0021|T|), capable of normal operation from +70 ℃ to -80 ℃. The temperature detector is inside the pour point tube during testing, and the tip of the platinum resistance is immersed 3 mm below the oil surface.
• 6.3 Pour point tube: cylindrical glass material, flat bottom, outer diameter 34 mm±0.5 mm, wall thickness 1.4 mm±0.15 mm, height 120 mm±0.5 mm, bottom thickness 2.0 mm±0.5 mm, with a line engraved at 54 mm±0.5 mm from the inner bottom of the pour point tube to indicate the test sample height.
• 6.4 Pour point tube sleeve: made of copper, cylindrical, flat bottom, depth 113 mm±0.2 mm, inner diameter 45 mm±0.1 mm.
• 6.5 Cooling system: an external cooling system equipped with a circulation pump, which can maintain the temperature of the cooling bath at least 10 ℃ lower than the pour point tube sleeve temperature, or an internal cooling system capable of maintaining the required sleeve temperature (see Table 1 and Figure 2).
• 6.6 Cork disk (see section 4)
• 6.7 Cork gasket (see section 4)
• 10.1 Probe simulator: an electronic product that uses a precision resistor to replace the temperature probe of PT 100 to calibrate the pour point tube jacket and test sample temperature.

6. Recommended operating conditions

• Table 1 Cooling program for sample and sleeve (sample temperature ST / sleeve temperature):
  • +27 ≥ ST > +9: sleeve temperature 0±0.5 ℃
  • +9 ≥ ST > -6: sleeve temperature -18±0.5 ℃
  • -6 ≥ ST > -24: sleeve temperature -33±0.5 ℃
  • -24 ≥ ST > -42: sleeve temperature -51±0.5 ℃
  • -42 ≥ ST > -60: sleeve temperature -69±0.5 ℃
  • -60 ≥ ST > -78: sleeve temperature -87±0.5 ℃
• Figure 1 Cooling program (original graphic data, presented as source-text extraction): sample temperature 27, 24, 0, -18, -24, -33, -42; sleeve temperature -69, -87, -60, -105, -90; labeled “expected pour point > -33 ℃” “expected pour point ≤ -33 ℃”. (The specific correspondence of Figure 1 requires confirmation against the source standard (source-text extraction))
• Figure 2 Automatic pour point test cell and cooling system: sleeve temperature control device -59 ℃, sleeve temperature -69 ℃, -79 ℃, external or internal cooling system. (requires confirmation against the source standard (source-text extraction))
• 11.8: In order to lower the sleeve temperature to -52 ℃, the time for the pour point tube sleeve temperature to be adjusted from one level to the next lower level shall not exceed 200 s.
• 11.8 Note: In order to obtain a lower sleeve temperature, the time from one sleeve temperature to another sleeve temperature shall not exceed 300 s; keep the cooling system temperature as low as possible to reach the required sleeve temperature in a short time, while using the cooling capacity of the cooling system to achieve application of the lowest temperature.
• 5.3 The resolution of pour point determination in this standard is 1.0 ℃.
• 5.4 The determination result is determined by the selected measurement temperature interval (interval 1 ℃ or interval 3 ℃).

7. Sampling and test sample preparation

• 8.1 Sample according to GB/T 4756 or SY/T 5317.
• 8.2 Particularly viscous test samples may be heated until they can flow before transfer; the sample should not be heated above the required heating temperature. The sample may be heated or transferred into the pour point tube only when the sample temperature is at or below 70 ℃. Note: if the test sample has already been heated above 70 ℃, the test sample should be cooled to at least 70 ℃ before transferring the sample.
• 8.3 If the residual fuel has been heated above 45 ℃ before testing, or its heating history is unknown, it must be left at room temperature for 24 h before testing.
• 11.1 Pour the test sample into the pour point tube to the engraved line. If necessary, heat the test sample in a hot bath or oven until it just flows, then pour the test sample into the pour point tube. When the expected pour point of the test sample is above 36 ℃ or the test sample is solid at room temperature, it may be heated above 45 ℃, but heating must not exceed 70 ℃.
• 11.2 Carry out pretreatment of the test sample or choose to use the instrument's automatic preheating. Note: residual fuel is relatively sensitive to heating history; before determination, for the handling of the relevant sample see clause 8.3.
  • 11.2.1 When the expected pour point of the test sample is ≤ -33 ℃, heat the test sample in a constant-temperature bath or oven at 48 ℃ to 45 ℃.
  • 11.2.2 When the expected pour point of the test sample is > -33 ℃, heat the test sample to 9 ℃ above the expected pour point, or above 45 ℃, but not higher than 70 ℃.

8. Analysis procedure

• 9.1 Check the instrument so that it can be operated according to the operating instructions.
• 9.2 According to the manufacturer's provisions, clean and dry the probe and pour point tube with a suitable solvent.
• 9.3 When an external cooling system is used, adjust the set point of the circulating refrigerator to an appropriate temperature so that the pour point tube sleeve is cooled to the required temperature. Note: when an external cooling system is used, most application software sets the circulating refrigerator to the lowest operating temperature.
• 10.1 Confirm that all steps for instrument calibration, checks, and operation are performed according to the instructions provided by the instrument manufacturer. Use a probe simulator to calibrate the instrument. The probe simulator is an electronic product that uses precision resistors in place of the temperature probe of PT 100 to calibrate the pour point tube jacket and specimen temperature; use it in accordance with the manufacturer's calibration operating instructions.
• 10.2 A pour point sample with an assigned value may be used to verify instrument performance; in addition, samples that have previously been extensively tested between laboratories may also be used to calibrate the instrument.
• 11.3 Place a disc at the bottom of the pour point tube jacket, and fit a cork gasket onto the pour point tube. The cork gasket should be 25 mm±3 mm from the bottom of the pour point tube.
• 11.4 Place the pour point tube into the selected test cell, and connect the probe according to the manufacturer's operating manual.
• 11.5 Select the test interval temperature (1 ℃ or 3 ℃).
• 11.6 Enter the expected pour point; if the selected test interval temperature is 3 ℃, the entered expected pour point should be a multiple of 3 ℃.
• 11.7 Start the test according to the instrument's operating manual.
• 11.8 The instrument uses an optical detector to monitor the specimen, adjusts the temperature of the pour point tube jacket to the first temperature level, and measures the specimen temperature. The instrument will automatically adjust the temperature of the pour point tube jacket according to the specimen temperature (see Table 1). When the specimen temperature is 9 ℃ above the expected pour point, the instrument begins to tilt the specimen in the specified manner (without moving within the pour point tube jacket). If the specimen moves when tilted, the no-flow point has not been reached, and the pour point tube jacket returns to the vertical position to wait for the next test. Testing continues until the pour point tube jacket is completely horizontal and the detector detects no movement of the specimen within 5 s. The temperature of the no-flow point plus 1 ℃ or 3 ℃ (depending on the selected test interval temperature) is the pour point of the specimen (see Figure 3). When the pour point is determined, the instrument will display the pour point result and begin reheating the test specimen.
• 11.9 If the instrument detects a no-flow point at the first tilt (expected pour point +9 ℃), discard that result and restart with a higher expected pour point.
• 11.10 Record the result as the pour point. Note: For residual fuel oils, it is not known whether they have been heated; if measurement is required, refer to 8.3 for relevant sample handling.
• Figure 3 Optical detection system: L light emitter; R light receiver; test vertical position; tilt specimen; sample is liquid, returns to vertical position; sample is solid, no surface movement detected; pour point = sample temperature + 3 ℃ (*when 3 ℃ test interval is selected).

9. Qualitative and Quantitative and Calculation Formulas

• Definition of pour point (3.1): Under specified conditions, the lowest temperature at which the observed specimen can flow.
• Definition of no-flow point (3.2): Under test conditions, the temperature at which the specimen, due to wax structure, increased viscosity, or both acting simultaneously, prevents movement of the specimen surface. Note: When the no-flow point occurs, the observation instrument no longer detects movement of the sample surface under the test conditions; the previous test temperature, i.e., the last test temperature at which the specimen could move, is the pour point.
• Definition of tilt (3.3): The movement technique in which the pour point tube is moved from a vertical position toward a horizontal position, causing the specimen to move. Note: When the pour point tube is tilted and held in the horizontal position for 5 s, the temperature at which the specimen still does not move is the no-flow point, and the test is then completed.
• Calculation of results: The temperature of the no-flow point plus 1 ℃ or 3 ℃ (depending on the selected test interval temperature) is the pour point of the specimen (11.8, Figure 3).
• Calculation formula: not provided in the available source (no independent formula).

10. Precision

• Note: Precision and relative bias are based on interlaboratory statistical tests conducted in 1998. Used for analysis were: two sets of diesel fuel oils, five sets of base oils, three sets of multigrade lubricating oils, and one set of hydraulic oil and automatic transmission fluid, each set consisting of two identical samples, with all samples within the range of -51 ℃ to -11 ℃. Eight laboratories participated in the tests using automated instruments, and all tests were conducted at 1 ℃ intervals and 3 ℃ intervals. Seven laboratories participated in the tests using the manual method according to ASTM D97. In addition, in 1992 only interlaboratory statistical tests from -39 ℃ to 6 ℃ were completed, and in 1998 interlaboratory statistical tests from -51 ℃ to -11 ℃ were completed. The interlaboratory statistical test results conducted for this standard in 1998 have better repeatability and reproducibility than GB/T 3535, which is equivalent to ASTM D97/IP15.
• 13.1 Precision: Judge the reliability of test results according to the following provisions (95% confidence level).
  • 13.1.1 Repeatability: For determinations of the same sample by the same operator using the same instrument according to the same method, the difference between two results obtained shall not exceed the requirement of Table 2:
    • Table 2 Repeatability data: 3 ℃ test temperature interval, repeatability r = 3.9 ℃; 1 ℃ test temperature interval, repeatability r = 2.7 ℃.
  • 13.1.2 Reproducibility: For determinations of the same sample by different operators in different laboratories according to the same method, the difference between two single, independent results obtained shall not exceed the requirement of Table 3:
    • Table 3 Reproducibility data: 3 ℃ test temperature interval, reproducibility R = 6.1 ℃; 1 ℃ test temperature interval, reproducibility R = 4.5 ℃.
• 13.2 Bias: Since there is no recognized standard material to determine the bias of this standard, no bias has been established for this standard.
• 13.3 Relative bias:
  • 13.3.1 Comparing the pour point test results of this standard at 3 ℃ intervals with the results of GB/T 3535 equivalent to ASTM D97/IP15, possible relative bias may be found for certain samples, but the relative bias is not systematic. Note 1: In the interlaboratory determination process in 1998, sample types with bias equivalent to GB/T 3535 of ASTM D97/IP15 were not included. Note 2: In the interlaboratory test study in 1998, it was found that for different test methods, when measuring high-sulfur winter diesel samples, there were relatively large differences in test results. During the cooling process, the sample forms a very thin, very large disc-shaped crystal layer. In addition to covering the sample surface, these crystals also exist at the contact surface between the sample and the glass. In the entire sample, except for this thin crystal layer, the other liquid has obvious low-viscosity characteristics. At this time, if the sample is handled gently, the sample will not pour out; but if the sample is handled forcefully, the crystal-wrapped shell will break, and the sample will pour out easily. It is recommended that when this phenomenon occurs during testing, attention should be paid to differences in test results among different methods.
  • 13.3.2 When the measurement results of this standard at 1 ℃ intervals are compared with those at 3 ℃ intervals, there may be an average bias of 1.1 ℃. It should be noted that when testing samples at 3 ℃ intervals compared with testing samples at 1 ℃ intervals, the statistical results have a difference of 1 ℃. This is due to the increased number of tests and different reporting formats. If the difference in a large number of test results is greater than 1 ℃, then other causes exist. During the interlaboratory testing process, the test results at 1 ℃ intervals were on average lower by 1.1 ℃ than the measurement results at 3 ℃ intervals.

11. Report

According to this standard, report the pour point result of the sample according to the temperature recorded in 11.10, the test temperature interval, and the instrument model.

12. Referenced Documents

• GB/T 3535 Standard Test Method for Pour Point of Petroleum Products (GB/T 3535-2006, ISO 3016:1994, MOD)
• GB/T 4756 Standard Practice for Manual Sampling of Petroleum Liquids (GB/T 4756—1998, eqv ISO 3170:1998)
• SY/T 5317 Standard Practice for Automatic Sampling of Petroleum Liquids in Pipelines (SY/T 5317—2006, ISO 3171:1988, IDT)
• IEC 60751 Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors
• ASTM D97 Standard Test Method for Pour Point of Petroleum Products
• IP 15 Standard Test Method for Pour Point of Petroleum Products
• GB/T 1.1—2009 (mentioned in the foreword, as the basis for drafting rules)

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