GB/T 4985-2021 Determination of Needle Penetration of Petroleum Waxes

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Card type: Test method

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

• Standard number: GB/T 4985—2021
• Chinese title: Determination of Needle Penetration of Petroleum Waxes
• English title: Standard test method for needle penetration of petroleum waxes
• Replacement relationship: replaces GB/T 4985—2010
• Previous versions: first published in 1985 as GB/T 4985—1985, first revision in 1998, second revision in 2010, this is the third revision
• Publication/implementation: published on 2021-10-11, implemented on 2022-05-01
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280)
• Main technical changes compared with GB/T 4985—2010 (foreword):
  • a) added content on Fischer-Tropsch wax, synthetic wax, and biological wax (see Chapter 1)
  • b) added content on automatic penetrometer (see 5.1.3)
  • c) changed "laboratory or test chamber: capable of maintaining at 23.9℃±2.2℃" to "laboratory or test chamber: capable of maintaining at 24.0℃±2.0℃" (see 5.5, 2010 version of 5.5)
  • d) added content on reagents (see 5.9)
  • e) added content on test procedure for automatic penetrometer (see 7.2)
  • f) added content on quality control (see Chapter 9)
  • g) changed repeatability at test temperature 25℃ (see 10.1.2, 2010 version of 9.1.1), added repeatability at test temperature 35℃ (see 10.1.2), added repeatability at test temperature 40℃ (see 10.1.2), changed reproducibility at test temperature 25℃ (see 10.1.3, 2010 version of 9.1.2), added reproducibility at test temperature 35℃ (see 10.1.3), added reproducibility at test temperature 40℃ (see 10.1.3)
  • h) changed repeatability and reproducibility corresponding to typical penetration values in Table 1 (see Table 1, Table 1 of the 2010 version)

2. Scope of application and non-applicability

• This document describes a method for evaluating wax hardness by measuring the depth of penetration of a standard needle into a wax test specimen.
• Applicable to petroleum waxes with a needle penetration value not greater than 250 1/10 mm.
• It can also be used to determine Fischer-Tropsch wax, synthetic wax, biological wax, etc.
• Not applicable/not provided: This document does not provide precision for the determination of synthetic wax and biological wax, etc.

3. Method principle

Heat the test specimen to at least 17℃ above its expected freezing point or melting point to melt it, then pour it into a former, cool it in air under specified conditions to form, then in a water bath control the temperature of the formed specimen to the test temperature, use the standard needle of a penetrometer under a load of 100 g to penetrate the specimen for 5 s, and measure its needle penetration. The test temperature can be selected as any temperature within the range of 25℃ to 55℃, and commonly used are 25℃, 35℃, 40℃, 45℃, or 55℃.

4. Reagents and materials (purity / preparation)

• 5.9 Reagent: glycerin aqueous solution (volume fraction 50%).
• 5.8 Brass plate: dimensions are length 63.5 mm±1.6 mm, width 38.0 mm±1.6 mm, thickness 6.4 mm±1.6 mm, used to support the specimen during sample preparation and forming; this plate is placed on an insulating material such as a cork or rubber stopper during sample cooling.
• Other purity and preparation details: not provided in the available source.

5. Apparatus and equipment

• 5.1 Penetrometer
  • 5.1.1 Penetrometer: schematic diagram as shown in Figure 1, in this document a standard needle is used to determine the hardness of the wax specimen, the total load includes the standard needle, the plunger, and a 50 g weight, totaling 100 g.
  • 5.1.2 Manual penetrometer: used to bring the standard needle into contact with the specimen surface and to measure the depth of penetration of the standard needle into the specimen when the test is completed. When the indicator reading of the manual penetrometer is "zero", the needle tip should be accurately positioned on the surface of the wax specimen by an adjustment device. One type of adjustment device is an adjustable test table, and the other is an adjustable needle assembly; either one may be chosen. The instrument is equipped with leveling screws and a spirit level to ensure that the plunger axis is in a vertical position; when the loaded standard needle is released, the standard needle should fall without obvious resistance. The indicator scale should be calibrated in 1/10 mm, and the scale range should be not less than 250 1/10 mm.
  • 5.1.3 Automatic penetrometer: used to bring the standard needle into contact with the specimen surface; at the start of measurement, the penetration time is controlled by an automatic timing device, and the needle penetration value is automatically measured and reported, in units of 1/10 mm, with a measurement range not less than 250 1/10 mm. The automatic penetrometer is equipped with an adjustable needle assembly, by which the needle tip should be accurately positioned on the surface of the wax specimen. It is equipped with leveling screws and a spirit level to ensure that the plunger axis is in a vertical position; when the loaded standard needle is released, the standard needle should fall without obvious resistance. It is equipped with an automatic timing device and an automatic device for measuring the depth of penetration of the standard needle into the specimen.
• 5.2 Timer: the automatic timing device attached to the penetrometer may be used, or a stopwatch with an accuracy of 0.1 s may be selected.
• 5.3 Standard needle and plunger: the dimensions of the standard needle are as shown in Figure 2, and the needle length is about 83 mm. One end of the needle is symmetrically tapered into a cone, and the cone angle of the entire cone length should be within the range of 8°55′ to 9°25′; the cone axis coincides with the needle shaft axis, and the maximum eccentricity (maximum deviation) is within 0.13 mm. The cone part shall be made of fully hardened and tempered stainless steel, grade 440C or equivalent, with a Rockwell hardness value of 57 HRC to 60 HRC. After the cone is tapered, the tip is ground off to form a truncated cone, and the cross-sectional diameter of the small end is 0.14 mm to 0.16 mm. The cross-section is at right angles to the needle axis, with an allowable deviation within 2°; the edge should be sharp without burrs; the finish of the conical surface and the top of the cross-section is 0.2 μm (rms). The actual mass of the standard needle is 2.5 g±0.05 g (achieved by drilling the rod and adjusting the length to reach the specified mass), the total mass of the plunger is 47.5 g±0.05 g, and a 50 g±0.05 g weight is added to the plunger. The standard needle, plunger, and weight shall be verified to meet the above requirements.
• 5.4 Specimen former: a brass cylinder open at both ends, inner diameter 25.4 mm±1.6 mm, height 31.8 mm±1.6 mm, wall thickness 3.2 mm±1.6 mm; to prevent hard wax samples from slipping, a small amount of threads or grooves are cut in the center of the inner wall of the cylinder. When forming the specimen, place the former on a brass plate moistened with glycerin aqueous solution.
• 5.5 Laboratory or test chamber: capable of maintaining at 24.0℃±2.0℃.
• 5.6 Water bath: the volume of the water bath is not less than 10 L, and it can maintain the test temperature accurate to ±0.1℃. It should be able to immerse the specimen to a depth of not less than 102 mm, and support the specimen by a perforated adjustable rack not less than 51 mm from the bottom of the water bath; the water bath should also be equipped with a rigid perforated specimen rack at about 51 mm below the water surface to fix the specimen when the needle penetrates; or alternatively, a water bath that can be placed on the penetrometer test table may be selected, maintaining the water temperature in the water bath at the test temperature (within ±0.1℃) and the necessary water circulation above and below the specimen; the formed specimen is placed on the perforated specimen rack, ensuring that the water bath surface is at least 25 mm above the upper surface of the specimen; the water bath is made of glass or other suitable transparent material, or has a viewing window through which the specimen can be observed horizontally.
• 5.7 Thermometer: a precision thermometer for measuring the water bath temperature, full immersion type, scale range 25℃ to 55℃. It meets the requirements for thermometer number GB-71 specified in GB/T 514—2005.
• 5.8 Brass plate: see Section 4.
• 5.9 Reagents: see Section 4.

6. Recommended operating conditions

• Test temperature: any temperature within the range of 25℃ to 55℃ may be selected, and commonly used are 25℃, 35℃, 40℃, 45℃, or 55℃.
• Load: 100 g (standard needle, plunger, and 50 g weight totaling 100 g; 7.1.3 specifies adding a 50 g weight to the standard needle so that the total mass of the standard needle and its accessories is 100 g±0.15 g).
• Penetration time: 5 s±0.1 s.
• Laboratory or test chamber temperature: 24.0℃±2.0℃.
• Water bath temperature control: test temperature ±0.1℃.
• Cooling time: cool at 24.0℃±2.0℃ for 1 h.
• Time in water bath: 60 min.
• Other conditions: not provided in the available source.

7. Sampling and specimen preparation

• 6 Specimen preparation: heat the wax specimen to at least 17℃ above its expected freezing point (determined by method SH/T 0132) or melting point (determined by method GB/T 2539) to melt it, prevent local overheating, and ensure the wax specimen is uniform and free of bubbles.
• In a laboratory or test chamber at 24.0℃±2.0℃ (5.5), place the brass plate (5.8) on a stable support such as a rubber stopper or cork, then moisten the upper surface of the brass plate with the reagent (5.9).
• Place the specimen former (5.4) on the brass plate, then pour the molten wax specimen into the specimen former so that it forms a convex meniscus.
• Cool it at a temperature of 24.0℃±2.0℃ for 1 h.
• Scrape off excess wax specimen from the top of the specimen former, remove the brass plate, place the surface of the wax specimen that was in contact with the brass plate facing up on the perforated specimen rack, and place it in a water bath (5.6) at the test temperature ±0.1℃ for 60 min.
• Very hard wax sometimes separates from the specimen former due to shrinkage; in this case, it is permissible to use wedges to wedge the wax sample tightly in the former.
• Sampling amount, sampling tools, etc.: not provided in the available source.

8. Analysis procedure

• 7.1 Manual penetrometer
  • 7.1.1 Place the head of the manual penetrometer at the edge of the water bath (5.6) and above the porous sample holder that supports the specimen. A weight may be placed on the penetrometer base to balance the head. Adjust the penetrometer and the porous sample holder in the water bath to horizontal.
  • 7.1.2 Ensure that during the test the specimen former and the porous sample holder do not shake; adjust the water bath water surface to be at least 25 mm above the upper surface of the specimen, maintain within the test temperature (within ±0.1℃), and before measuring each sample, measure the temperature of the water bath with the thermometer specified in 5.7.
  • 7.1.3 Add a 50 g weight to the standard needle so that the total mass of the standard needle and its attachments is 100 g±0.15 g. Check whether the release device is stuck on the rod; the indicator should be at the "zero" position. According to the different types of adjustment devices, adjust the needle assembly or adjust the test table so that the tip of the standard needle almost touches the surface of the specimen, with the needle tip located on a circumference at least 3.2 mm from the edge of the specimen former and with the four test positions at approximately equal intervals (separated by not less than 12.7 mm); securely lock the movable assembly at this position.
  • 7.1.4 Fine-tune so that the tip of the standard needle just contacts the surface of the wax specimen; observing the projection of the standard needle tip helps accurate adjustment. After confirming that the water bath temperature is within the specified range, release the sliding rod and continue for 5 s±0.1 s, using an automatic timing device or a stopwatch with an accuracy of 0.1 s. Gently press down the indicator rod until it is stopped by the sliding rod, and read the penetration value from the indicator dial.
  • 7.1.5 Carry out the determination at the remaining three test positions in accordance with the requirements of 7.1.3 and 7.1.4; before each determination, carefully wipe in the direction of the needle tip with a clean dry cloth to remove all adhering wax specimen.
• 7.2 Automatic penetrometer
  • 7.2.1 Place the adjustable needle assembly of the automatic penetrometer above the water bath (5.6) and above the porous sample holder that supports the specimen, and carry out in accordance with 7.1.2.
  • 7.2.2 Set up the penetrometer according to the instrument instructions, and test the penetration value in accordance with the requirements in 7.1.3 to 7.1.5.

9. Qualitative and quantitative and calculation formulas

• 8 Reporting of results: record the measured values at 4 test positions of the specimen, calculate the average as the test result, round to an integer, and also report the test temperature, such as 85 1/10 mm (35℃).
• Precision calculation formulas:
  • Repeatability:
    • r₂₅℃ = 1.72[10^(0.00524(X))] …………………………(1)
    • r₃₅℃ = 0.03304(X)^1.2089 …………………………(2)
    • r₄₀℃ = 0.09905(X)^1.1175 …………………………(3)
    • Where: X—— is the average of two test results, in units of one tenth of a millimeter (1/10 mm); r₂₅℃—— repeatability at test temperature 25℃; r₃₅℃—— repeatability at test temperature 35℃; r₄₀℃—— repeatability at test temperature 40℃.
  • Reproducibility:
    • R₂₅℃ = 4.81[10^(0.00442(X))] …………………………(4)
    • R₃₅℃ = 0.1812(X)^1.0584 …………………………(5)
    • R₄₀℃ = 0.1746(X)^1.1175 …………………………(6)
    • Where: X—— is the average of two independent test results, in units of one tenth of a millimeter (1/10 mm); R₂₅℃—— reproducibility at test temperature 25℃; R₃₅℃—— reproducibility at test temperature 35℃; R₄₀℃—— reproducibility at test temperature 40℃.
• Note: In formula (1), the exponent part source-text extraction is "１００．００５２４([unreadable variable])", which is suspected to be 10^(0.00524(X)), requires confirmation against the source standard (source-text extraction); in formula (4), the exponent part source-text extraction is "１００．００４４２([unreadable variable])", which is suspected to be 10^(0.00442(X)), requires confirmation against the source standard (source-text extraction).

10. Precision

• 10.1.1 Overview: Judge the reliability of the results according to the following provisions (95% confidence level), in which the precision of 35℃ is based on the requirements of the GB/T 6683 method and was obtained by cooperative testing of 10 samples by 6 laboratories.
• 10.1.2 Repeatability: In the same laboratory, by the same operator using the same instrument and equipment, according to the same test method, and within a short time on the same sample, the difference between two repeated test results obtained shall not be greater than the value calculated in formula (1) or formula (2) or formula (3). The repeatability corresponding to typical penetration values is shown in Table 1.
• 10.1.3 Reproducibility: In different laboratories, by different operators, using different instruments and equipment, according to the same test method, on the same sample, the difference between two single, independent test results obtained shall not be greater than the value calculated in formula (4) or formula (5) or formula (6). The reproducibility corresponding to typical penetration values is shown in Table 1.
• Table 1 Repeatability and reproducibility corresponding to typical penetration values (in units of one tenth of a millimeter):

• 10.2 Bias: At present there is no reference material that can be used for the bias of this method, so this method does not give bias.

11. Report

• 8 Reporting of results: record the measured values at 4 test positions of the specimen, calculate the average as the test result, round to an integer, and also report the test temperature, such as 85 1/10 mm (35℃).
• Other reporting requirements: not provided in the available source.

12. Referenced documents

• GB/T 514—2005 Technical conditions for glass liquid thermometers for petroleum product testing
• GB/T 2539 Determination of melting point of petroleum wax - Cooling curve method
• NB/SH/T 0843 Statistical technical method for evaluation of petrochemical industry analytical testing systems
• SH/T 0132 Determination of freezing point of petroleum wax
• References: [1] GB/T 6683 Method for determining precision data of petroleum product test methods

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