GB/T 7305-2003 Determination of water separation characteristics of petroleum and synthetic fluids

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Card type: Test method

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

• Standard number: GB/T 7305-2003
• Chinese title: Determination of water separation characteristics of petroleum and synthetic fluids
• English title: not provided in the available source (the main text only mentions modified adoption of ASTM D1401-1998 "Determination of water separation characteristics of petroleum and synthetic fluids", and does not give the English title of this standard)
• Replacement relationship: replaces GB/T 7305-1987 "Determination of demulsibility characteristics of petroleum and synthetic fluids"; GB/T 7305-1987 equivalent adoption of ASTM D1401-1967(1977)
• Adoption relationship: modified adoption of ASTM D1401-1998
• Main differences from ASTM D1401-1998:
  • Reagents for cleaning the graduated cylinder: ASTM specifies chromic acid cleaning solution, acetone, and tap water in sequence; this standard specifies chromic acid cleaning solution, tap water, and distilled water (because the cleaning effects of the two are equivalent, and acetone is more toxic)
  • Added a note supplementing "if required by research work, the test results may be observed and recorded at any time"
• Editorial modifications: deleted the keywords chapter in ASTM D1401-1998
• Main changes from GB/T 7305-1987:
  • The standard title was revised to "Determination of water separation characteristics of petroleum and synthetic fluids"
  • The 1987 version specifies that at test temperature 54℃±1℃ the test time is 60 min; this version specifies that at test temperature 54℃±1℃ the test time is 30 min (1987 version Chapter 1, this version Chapter 3)
  • Several descriptions of test result states were added to the test result reporting section
• Proposing department: former State Bureau of Petroleum and Chemical Industry
• Technical committee: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Lanzhou Lubricating Oil Research and Development Center of PetroChina Company Limited
• Main drafters: Wu Jin, Liu Ge, Han Jinxia
• Previous versions: GB/T 7305-1987

2. Scope of application and non-applicability

• 1.1 is applicable to the determination of the water separation characteristics of petroleum and synthetic fluids.
• Applicable to the determination of oils with kinematic viscosity of 40℃ 28.8 mm²/s～90 mm²/s, at a test temperature of 54℃±1℃.
• It may also be used for oils with kinematic viscosity exceeding 40℃ 90 mm²/s, but the test temperature is 82℃±1℃.
• For oils of higher viscosity, oil and water cannot be fully mixed; it is recommended to use the test method of GB/T 8022.
• Other test temperatures such as 25℃ may also be used.
• When the relative density of the synthetic fluid being tested is greater than that of water, the test procedure remains unchanged, but it should be noted that in this case water may float on the emulsion layer or on the synthetic fluid.
• 1.2 This standard involves certain hazardous materials, operations, and equipment, but it is not intended to address all safety issues associated with them. Users should establish appropriate safety and protective measures before using this standard, and determine applicable management systems.

3. Method principle

Place 40 mL of sample and 40 mL of distilled water in a graduated cylinder, and stir at 54℃ or 82℃ for 5 min, recording the time required for the emulsion to separate. After standing for 30 min or 60 min, if the emulsion has not completely separated, or the emulsion layer has not decreased to 3 mL or less, record the volumes of the oil layer (or synthetic fluid), water layer, and emulsion layer at that time.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 6.1.1 Petroleum ether: analytical reagent, 60℃～90℃
• 6.1.2 Anhydrous ethanol: analytical reagent
• 6.1.3 Distilled water: meets the specifications for grade two water in GB/T 6682

4.2 Materials

• 6.2.1 Cleaning solvent: light hydrocarbon compounds, such as petroleum ether, etc.
• 6.2.2 Chromic acid cleaning solution
• 6.2.3 Absorbent cotton, bamboo tweezers, litmus paper, glass rod wrapped with oil-resistant rubber

5. Apparatus and equipment

• 5.1 Graduated cylinder: capacity 100 mL, made of heat-resistant glass or other glass of equivalent chemical properties; graduations within the range of 5 mL～100 mL, with a division value of 1.0 mL; overall height 225 mm～260 mm; within the length from the top of the cylinder to a point 6 mm from the bottom, the inner diameter of the cylinder is within the range of 27 mm～30 mm; the graduation error at any point on the cylinder graduations shall not exceed 1 mL
• 5.2 Water bath: of sufficient size and depth to allow at least 2 test cylinders to be inserted into the water bath, and the water can immerse up to the 85 mL graduation mark of the cylinder; equipped with a support rack that can fix the position of the cylinder so that when the contents of the cylinder are stirred, the longitudinal axis of the blade corresponds to the vertical center line of the cylinder; the support rack should firmly hold the cylinder; the water bath temperature control accuracy is ±1℃
• 5.3 Stirrer: composed of a blade and a connecting rod made of chrome-plated steel or stainless steel; blade length 120 mm±1.5 mm, width 19 mm±0.5 mm, thickness 1.5 mm; connecting rod diameter approximately 6 mm, fixed to the blade and connected to the stirring device; the transmission device can make the blade rotate about its longitudinal axis at a speed of 1500 r/min±15 r/min; after the cylinder is fixed, insert the blade into the cylinder at a distance of 6 mm from the bottom of the cylinder, and then engage the connecting rod with the transmission device; during stirring, the wobble at the center of the bottom of the blade shall not exceed 1 mm from the center line of the rotating shaft; when not in use, the stirring rod may be raised vertically to facilitate cleaning of the top of the cylinder
• 5.4 Motor: speed 1500 r/min±15 r/min
• 5.5 Stopwatch

6. Recommended operating conditions

• Test temperature: 54℃±1℃ (routine); 82℃±1℃ (for oils with kinematic viscosity exceeding 40℃ 90 mm²/s); other test temperatures such as 25℃ may also be used
• Stirring speed: 1500 r/min±15 r/min
• Stirring time: 5 min
• Standing observation time: 30 min or 60 min
• Water bath temperature control accuracy: ±1℃
• Constant-temperature standing: usually stand for about 10 min so that the temperature of the oil and water in the cylinder is consistent with the water bath temperature; the heating time usually depends on the type of equipment, and shall not exceed 30 min at most

7. Sampling and sample preparation

• 7 Sampling: this test is very sensitive to a small amount of contamination, so sampling shall be carried out strictly in accordance with GB/T 4756.
• Sample volume: 40 mL, pour into the graduated cylinder to the 80 mL mark (first add 40 mL of reagent water, then add 40 mL of sample).
• Note 1: if the initial volume is measured at room temperature, the volume expansion caused by the increase to the test temperature shall be considered. For example, at 82℃, the total volume expands by 2 mL～3 mL; therefore, each volume reading at 82℃ needs to be corrected so that the total volume reading of oil (synthetic fluid), water, or emulsion does not exceed 80 mL. Another method that can be used for correction is to measure the initial volume at the test temperature.
• Note 2: when testing specific oils or fuels for ships, 1% sodium chloride solution or synthetic seawater (as specified in method GB/T 11143) may be used instead of distilled water.

8. Analytical procedure

• 8.1 Clean the graduated cylinder with cleaning solvent, then further clean the cylinder successively with chromic acid cleaning solution, tap water, and distilled water until no water droplets adhere to the inner wall of the cylinder.
• 8.2 Clean the stirring rod and blade successively with absorbent cotton and bamboo tweezers in petroleum ether and anhydrous ethanol, and air-dry. During cleaning, take care not to bend the stirring rod.
• 9.1 Heat the water bath to 54℃±1℃ (for relatively viscous oils, heat to 82℃±1℃), and keep it constant. Slowly pour 40 mL of reagent water into a clean graduated cylinder (see Note 1 and Note 2), then pour in 40 mL of sample to the 80 mL mark of the cylinder. Place the cylinder in a constant-temperature bath at 54℃±1℃ (or 82℃±1℃), then place the stirring blade into the cylinder and fix it with a metal clamp; usually stand for about 10 min so that the temperature of the oil and water in the cylinder is consistent with the water bath temperature. However, the heating time usually depends on the type of equipment, and shall not exceed 30 min at most.
• 9.2 Fix the graduated cylinder directly below the stirring blade, lower the blade to a distance of 6 mm from the bottom of the cylinder, engage the transmission device with the connecting rod, start stirring, observe and adjust the stirring rod to stir the sample at 1500 r/min±15 r/min for 5 min; after stopping stirring, lift the stirring rod, scrape the oil on the stirring blade into the cylinder with a glass rod wrapped with oil-resistant rubber, and at intervals of 5 min observe and record the volumes of separated oil, water, and emulsion layer in the cylinder. If necessary, remove the cylinder from the water bath, observe, and record.

9. Qualitative and quantitative determination and calculation formula

• 10.1 Record the time to reach the test range required by the product water separation performance or exceeding the water separation performance requirement (usually at 54℃±1℃ it is 30 min, at 82℃±1℃ it is 60 min, when the emulsion is 3 mL or less), and record the test results at intervals of 5 min (Note 1). The maximum volume reported for the oil layer is 43 mL (Note 2).
• Example of result reporting format:
  • 40-40-0(20): complete separation time is 20 min, at 15 min, the residual emulsion layer exceeds 3 mL
  • 39-38-3(20): complete separation did not occur, but the emulsion layer decreased to 3 mL, and the test ended
  • 39-35-6(60): after 60 min, the residual emulsion layer exceeds 3 mL, that is, 39 mL of oil, 35 mL of water, 6 mL of emulsion layer
  • 41-37-2(20): complete separation did not occur, but the emulsion layer decreased to 3 mL or less after 20 min
  • 43-37-0(30): after 30 min, the emulsion layer decreases to 3 mL or less. At 25 min, the emulsion layer exceeds 3 mL, for example, 0-36-44 or 43-33-4
• 10.2 The appearance of each layer is recorded using the following terms:
  • 10.2.1 Oil (oil-rich) layer: a) transparent; b) hazy (Note 3); c) cloudy (or milky) (Note 3); d) combined phenomena of a, b and c
  • 10.2.2 Water layer or water-rich layer: a) transparent; b) lacy or with bubbles, or both; c) hazy (Note 3); d) cloudy (or milky) (Note 3); e) combined phenomena of a, b, c and d
  • 10.2.3 Emulsion layer: a) indistinct lace; b) cloudy (or milky) (Note 4); c) creamy (Note 4); d) combined phenomena of a, b and c
• 10.3 The appearance of the oil/emulsion layer and water/emulsion layer interface is recorded using the following terms: a) interface clear and distinct; b) interface unclear, with bubbles; c) interface unclear, with lace
• 10.4 Report the test temperature other than 54℃ and the solution medium other than distilled water
• Note 1: If required for research work, the test results may be observed and recorded at any time
• Note 2: Some special oil samples may produce an indistinct oil layer. In this case, if two completely separated layers are observed, the upper layer is recorded as the oil layer; if it separates into two layers and the upper layer is greater than 43 mL, then the upper layer is identified as the emulsion layer
• Note 3: Hazy is defined as semi-transparent, cloudy is defined as opaque
• Note 4: The difference between cloudy and creamy is that the former is more uniform and may be unstable, while the latter is more viscous and may be stable. A cloudy emulsion will flow from a tilted surface, whereas a creamy emulsion will not
• Calculation formula: not provided in the available source

10. Precision

• 11.1 Precision: The precision of this test method was obtained using turbine oil with a kinematic viscosity of 40℃ at 28.8 mm²/s～90 mm²/s as the test oil, and when the test was completed, the emulsion layer was 3 mL or less. The precision is shown in Figure 1. This figure indicates the maximum deviation allowed for repeatability and reproducibility (95 confidence level) of the test results of the average emulsion layer of the oil product. However, this may not apply to other oil products or synthetic fluids.
• 11.2 Instructions for using Figure 1: In units of min, calculate the average measurement result. From the zero point A on the ordinate, move right to point B on the abscissa, and based on the average result of the test, calculate and find the error points C+ and C−. If the error points fall within the repeatability region, it indicates that the results are within the precision range.
  • Example: There is an oil sample with emulsibility of 40-40-0 (10 min) and 40-40-0 (15 min), the average time result of the test is 12.5 min (B), and the errors are +2.5 (C+) and −2.5 (C−). These points fall within the repeatability region.
  • This figure is also applicable to the determination of reproducibility results between different laboratories.
• 11.3 Bias: The test procedure for water separation performance of this test method has no bias, because the water separation performance measurement results are determined solely based on this method.
• Figure 1 specific values: not provided in the available source (source-text extraction image cannot read specific values)

11. Report

• 10.1 Record the time to reach the product water separation performance requirement or exceed the test range of the water separation performance requirement (usually when 54℃±1℃ is 30 min, when 82℃±1℃ is 60 min, the emulsion is 3 mL or less), and record the test results every 5 min
• The maximum volume number reported for the oil layer is 43 mL
• Result report format: oil layer volume-water layer volume-emulsion layer volume (time), see Section 9 for example
• 10.2 For the terms for recording the appearance of each layer, see Section 9
• 10.3 For the terms for recording the interface appearance, see Section 9
• 10.4 Report the test temperature other than 54℃ and the solution medium other than distilled water

12. Normative references

• GB/T 4756 Petroleum liquids—Manual sampling (GB/T 4756-1998, eqv ISO 3170:1988)
• GB/T 6682 Water for analytical laboratory use—Specification and test methods (GB/T 6682-1992, neq ISO 3696:1987)
• GB/T 8022 Determination of demulsibility characteristics of lubricating oils
• GB/T 11143 Test method for rust-preventing characteristics of inhibited mineral oil in the presence of water
• ASTM D1401-1998 Determination of water separability of petroleum oils and synthetic fluids (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 Q&A reference