GB/T 3535-2006 Determination of pour point of petroleum products

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Card type: Test method

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

• Standard number: GB/T 3535—2006
• Chinese title: Determination of pour point of petroleum products
• English title: Petroleum products—Determination of pour point
• Adoption relationship: modified adoption of ISO 3016:1994 (MOD)
• Replacement relationship: replaces GB/T 3535—1983 "Determination of pour point of petroleum oils"
• Publication/implementation: published on 2006-01-23, implemented on 2006-10-01
• Responsible organization: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Guo Tao, Chen Jie
• Appendix: Appendix A is a normative appendix

2. Scope of application and non-applicability

• This standard specifies a method for determining the pour point of petroleum products.
• It also describes test procedures for determining the pour point of fuel oils, heavy lubricant base stocks, and products containing residual fuel components (see 6.10).
• Note: A dedicated method for determining the pour point of crude oil is under study, but the general test procedures described in this standard can also be used to determine the pour point of crude oil. Note that some crude oils require special pretreatment to avoid loss of volatile substances.
• The precision of this standard was established on a basis that does not include crude oil samples (see the note to Chapter 8).
• No explicit "non-applicability" clause is provided in the available source (the non-applicability of precision to crude oil has already been explained in the note).

3. Method principle

After the test specimen is preheated, it is cooled at a specified rate, and the fluidity of the test specimen is checked every 3 ℃. The lowest temperature at which the test specimen is observed to be capable of flowing is recorded as the pour point.

4. Reagents and materials (purity / preparation)

• 4.1 Sodium chloride (NaCl): crystalline.
• 4.2 Calcium chloride (CaCl₂): crystalline. (The source text source-text extraction is "CaCl", requires confirmation against the source standard (source-text extraction))
• 4.3 Carbon dioxide (CO₂): solid. (The source text source-text extraction is "COs", requires confirmation against the source standard (source-text extraction))
• 4.4 Cooling liquid: acetone, methanol, or naphtha.
• 4.5 Wiping liquid: acetone, methanol, or ethanol.
• Preparation of coolants (5.7 Note):
  1. 9 ℃ (The source text source-text extraction is "9CC", requires confirmation against the source standard (source-text extraction)): ice and water (can be used to prepare the 0 ℃ bath specified in the standard); 2)-12 ℃: crushed ice and sodium chloride (can be used to prepare the -18 ℃ bath specified in 6.8); 3)-27 ℃: crushed ice and calcium chloride (can be used to prepare the -33 ℃ bath specified in 6.8); 4)-57 ℃ (The source text source-text extraction is "57C", requires confirmation against the source standard (source-text extraction)): carbon dioxide and cooling liquid (can be used to prepare the -51 ℃ and -69 ℃ baths specified in 6.8).
• Footnote 1: This mixture can be prepared as follows: in a covered metal beaker, cool an appropriate amount of cooling liquid to -12 ℃ or below -12 ℃ (by the ice-salt mixture method). Then, add sufficient carbon dioxide to the already cooled cooling liquid to obtain the required temperature.

5. Apparatus and equipment

• 5.1 Test tube: made of flat-bottomed, cylindrical transparent glass, with an inner diameter of 30.0 mm–32.4 mm, an outer diameter of 33.2 mm–34.8 mm, a height of 115 mm~125 mm, and a wall thickness not greater than 1.6 mm. A long graduation line is marked at 54 mm±3 mm from the inner bottom of the test tube, indicating the height of the liquid level of the contents.
• 5.2 Thermometer: partial immersion type, meeting the requirements of Appendix A.
• 5.3 Cork stopper: for use with the test tube, with a hole drilled in the center of the stopper for inserting the thermometer.
• 5.4 Sleeve: made of flat-bottomed, cylindrical metal, leakproof, cleanable, with an inner diameter of 44.2 mm~45.8 mm, a wall thickness of about 1 mm, and a height of 115 mm±3 mm. The sleeve should be able to maintain an upright position in the cooling bath, and its height above the cooling medium must not exceed 25 mm.
• 5.5 Disc: made of cork or felt, about 6 mm thick, with a diameter the same as the inner diameter of the sleeve.
• 5.6 Gasket: made of rubber, leather, or other suitable material. Ring-shaped, about 5 mm thick, with a certain degree of elasticity, required to fit tightly against the outer wall of the test tube while remaining loose against the inner wall of the sleeve. The gasket is also required to have sufficient hardness to maintain its shape. Note: The purpose of the ring-shaped gasket is to prevent direct contact between the test tube and the sleeve.
• 5.7 Cooling bath: its type should be suitable for reaching the temperatures specified in this standard. The size and shape of the cooling bath are arbitrary, but it must be able to firmly fix the sleeve in a vertical position. The bath temperature should be monitored with a suitable thermometer immersed to the correct immersion depth. When determining the pour point of oils with a pour point below 9 ℃, two or more cooling baths are required. The required bath temperature can be maintained by a refrigeration device or a suitable coolant. The bath temperature of the cooling bath is required to be maintained within the range of ±1.5 ℃ of the specified temperature.
• 5.8 Timer: the maximum error in measuring 30 s must not exceed 0.2 s.
• Figure 1 Pour point tester (the source contains a figure, source-text extraction dimension annotations: inner φ30.0–32.4, outer φ33.2–34.8, maximum 25, 115~125, etc., requires confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• 6.1 Pour the clean test specimen into the test tube up to the graduation line. If necessary, the test specimen may first be heated in a water bath until it flows, and then poured into the test tube. Samples known to have been heated above 45 ℃ within 24 h before the test, or samples whose heating history is unknown, must be left at room temperature for 24 h before testing.
• 6.2 Stopper the test tube with a cork stopper inserted with a thermometer for high cloud point and high pour point. If the expected pour point of the test specimen is higher than 36 ℃, use a melting point thermometer (see Appendix A). Adjust the positions of the cork stopper and thermometer so that the cork stopper tightly seals the test tube, and the thermometer and test tube are required to be on the same axis. Let the test specimen immerse the thermometer bulb so that the starting point of the thermometer capillary is immersed at 3 mm below the liquid level of the test specimen.
• 6.4 Test specimens with a pour point higher than -33 ℃ should be handled as follows.
  • 6.4.1 Without stirring, place the test specimen in a bath maintained at 12 ℃ above the expected pour point, but at least 48 ℃, and heat the test specimen to 45 ℃ or 9 ℃ above the expected pour point (choose the higher).
  • 6.4.2 Transfer the test tube to a bath maintained at 24 ℃±1.5 ℃.
  • 6.4.3 When the test specimen reaches 9 ℃ above the expected pour point (estimated as a multiple of 3 ℃), begin checking the fluidity of the test specimen as specified in 6.7. If the test specimen is still capable of flowing when its temperature has reached 27 ℃, carefully remove the test tube from the bath, wipe the outer surface of the test tube with a clean cloth moistened with wiping liquid, and then place the test tube in a bath at 0 ℃ as specified in 6.6. Observe the fluidity of the test specimen as specified in 6.7, and cool according to the procedure specified in 6.8.
• 6.5 Test specimens with a pour point of -33 ℃ and below -33 ℃ should be handled as follows. (The source text source-text extraction is "pour point is 33°C and below -33°C", requires confirmation against the source standard (source-text extraction))
  • 6.5.1 Without agitation, heat the test specimen in a bath at 48 ℃ to 45 ℃, then place it in a bath at 6 ℃±1.5 ℃ to cool to 15 ℃.
  • 6.5.2 When the temperature of the test specimen reaches 15 ℃, carefully remove the test tube from the water bath, wipe the outer surface of the test tube with a clean cloth moistened with wiping liquid, then remove the thermometer for high cloud point and high pour point and replace it with a thermometer for low cloud point and low pour point. Place the test tube in a bath at 0 ℃ as specified in 6.6, and then sequentially transfer the test tube to each low-temperature bath according to the procedure specified in 6.8.
  • 6.5.3 When the temperature of the test specimen reaches 9 ℃ above the expected pour point, observe the fluidity of the test specimen as specified in 6.7.
• 6.6 Ensure that the disc, gasket, and inner wall of the sleeve are clean and dry, and place the disc at the bottom of the sleeve. Before inserting the test tube, the disc and sleeve should be placed in the cooling medium for at least 10 min. Place the gasket on the outer wall of the test tube, about 25 mm from the bottom, and insert the test tube into the sleeve. Except for the 24 ℃ and 6 ℃ baths, in all other cases the test tube must not be placed directly into the cooling medium.
• 6.7 Observe the fluidity of the test specimen.
  • 6.7.1 Starting from the first observation temperature, for every decrease of 3 ℃, the test tube should be removed from the bath or sleeve (depending on actual use), and the test tube should be tilted sufficiently to determine whether the test specimen flows. The entire operation of removing the test tube, observing the fluidity of the test specimen, and returning the test tube to the bath is required to take no more than 3 s.
  • 6.7.2 Starting from the first observation of the fluidity of the test specimen, for every decrease in temperature of 3 ℃, the fluidity of the test specimen should be observed. Special care must be taken not to agitate lumps in the test specimen, and the thermometer must not be moved after the test specimen has cooled sufficiently to form paraffin crystals. This is because agitating the porous network of crystals in the paraffin can lead to low or erroneous results. Note: At low temperatures, condensed water mist can hinder observation; a clean cloth moistened with wiping liquid close to the cooling bath temperature can be used to wipe the test tube to remove water mist on the outer surface.
  • 6.7.3 When the test tube is tilted and the sample does not flow, the test tube should immediately be placed in a horizontal position 5 s (measured with a timer), and the surface of the sample should be carefully observed. If the sample shows any movement, the test tube should immediately be returned to the bath or jacket (depending on the actual use), and when the temperature is lowered again by 3 ℃, the flowability of the sample should be observed again.
  • 6.7.4 Continue operating in this manner until the test tube is placed in a horizontal position 5 s; if the sample in the test tube does not move, record the thermometer reading observed at this time.
• 6.8 If the sample is still flowing when the temperature reaches 9 ℃, transfer the test tube to the next lower-temperature bath, and carry out the same transfer at -6 ℃, -24 ℃ and -42 ℃ according to the following procedure.
  1. When the sample temperature reaches 9 ℃, transfer to the -18 ℃ bath;
  2. When the sample temperature reaches -6 ℃, transfer to the -33 ℃ bath;
  3. When the sample temperature reaches -24 ℃, transfer to the -51 ℃ bath;
  4. When the sample temperature reaches -42 ℃, transfer to the -69 ℃ bath.
• 6.9 For oils whose pour point specification value is not a multiple of 3 ℃, the determination may also be carried out as specified below. Begin checking the flowability of the sample when the sample temperature is 9 ℃ above the pour point specification value, then observe the sample at intervals of 3 ℃ according to the procedures described in 6.7 and 6.8, until the specification value of the sample. Report whether the sample passes or fails the specification value.
• 6.10 For fuel oils, heavy lubricating base oils and products containing residual fuel components, the result obtained by the procedure described in 6.1–6.8 is the upper (maximum) pour point of the sample. If it is necessary to determine the lower (minimum) pour point of the sample, the sample may first be heated to 105 ℃ with stirring, then poured into the test tube, and the lower (minimum) pour point of the sample determined according to the procedure described in 6.2–6.8.
• 6.11 If an automatic pour point tester is used, users are required to strictly follow the manufacturer's instructions for calibration, adjustment and operation of the instrument. Since the precision of automatic pour point testers has not been established, in case of dispute the manual method described in this standard shall be used as the referee test method.

7. Sampling and sample preparation

• Sampling: no independent "sampling" section is provided in the available source; for sample preparation see 6.1, 6.4, 6.5, 6.10.
• 6.1 Pour the clean sample into the test tube up to the etched line. If necessary, the sample may first be heated in a water bath until it flows, and then poured into the test tube. Samples known to have been heated above 45 ℃ within 24 h before the test, or samples whose heating history is unknown, must be left at room temperature for 24 h before the test can be carried out.
• 6.4, 6.5 specify pretreatment for different expected pour point ranges.
• 6.10 specifies the sample pretreatment for lower pour point determination (heating to 105 ℃).

8. Analytical procedure

See Section 6 (6.1~6.11).

9. Qualitative and quantitative determination and calculation formulas

• 7 Expression of results: add 3 ℃ to the results recorded at 6.7.4 and 6.10, as the pour point or lower pour point of the sample (depending on the actual use), and take the average of two results from duplicate determinations as the test result.
• 6.9 Report whether the sample passes or fails the specification value.
• No other calculation formulas are provided in the available source.

10. Precision

Judge the reliability of the test results according to the following provisions (confidence level of 95%).

• 8.1 Repeatability: the difference between two consecutive test results obtained by the same operator, using the same instrument, with the same method, on the same sample shall not be greater than 3 ℃.
• 8.2 Reproducibility R: the difference between two test results obtained by different operators, using different instruments, with the same method, on the same sample shall not be greater than 6 ℃.
• Note: The precision was established by 10 new (unused) mineral oil-type lubricating oils and 16 blended fuel oils in 12 cooperating laboratories. The pour point range of the mineral oil-type lubricating oils is -48 ℃~6 ℃, and the pour point range of the fuel oils is 33 ℃~51 ℃ (the original source-text extraction is "fuel oil point range is 33C～51C", requires confirmation against the source standard (source-text extraction)), and the following precision was obtained.
• The specific precision values after "mineral oil-type lubricating oils" in the original: not provided in the available source (source-text extraction missing).

11. Report

The test report shall include at least the following:

1. complete information on the product tested;
2. a statement that this standard is referenced;
3. the test results;
4. any differences from the test procedure of this standard as agreed or otherwise specified shall be noted;
5. the test date;
6. a statement of whether an automatic instrument was used for the determination test.

12. Referenced documents

• ISO 3016:1994 "Determination of pour point of petroleum products" (modified adoption)
• GB/T 3535—1983 "Determination of pour point of petroleum" (superseded)
• Annex A (normative annex) Thermometer specifications: ASTM 6C/IP 2C (thermometers for low cloud point and low pour point), ASTM 5C/IP 1C (thermometers for high cloud point and high pour point), ASTM 61C/IP 63C (thermometers for melting point)
• No other list of normative referenced documents is provided in the available source.

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