GB/T 6539-1997 Determination of Electrical Conductivity of Aviation and Distillate Fuels

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Card type: Test method

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

• Standard number: GB/T 6539-1997
• Chinese full name: Determination of Electrical Conductivity of Aviation and Distillate Fuels
• English name: Standard test methods for electrical conductivity of aviation and distillate fuels
• Replacement relationship: replaces GB/T 6539-86 (91)
• Adoption relationship: equivalent adoption of ASTM D 2624—95 "Standard Test Method for Electrical Conductivity of Aviation and Distillate Fuels"
• Main differences from ASTM D 2624—95 (original foreword): the online continuous monitoring method provided in Chapter 13 is not adopted; the provision recommended in API RP 2003 that pumped fuel should stand for 30min after entering the storage tank is not adopted; the content of Appendix X is not adopted (discussion of the meaning of conductivity precision and the relationship between conductivity and temperature)
• Main revisions compared with GB/T 6539-86 (91) (original foreword): the standard name is changed to "Determination of Electrical Conductivity of Aviation and Distillate Fuels"; "Normative References" and "Terms" are added; mixed solvent is added; reproducibility data are added, and repeatability data are expanded from six levels 50pS/m–300pS/m to thirteen levels 1pS/m–1500pS/m; Appendix A Calibration of Conductivity Meters is added
• Appendix A is an appendix of the standard
• Approval/implementation: approved by the State Bureau of Technical Supervision 1997-12-11, implemented on 1998-07-01
• First issued: 1986 year 6 month, reviewed and confirmed in 1991
• Proposed/administrated/drafted by: proposed by China Petrochemical Corporation; administrated by the Petrochemical Research Institute of China Petrochemical Corporation; drafting organization: Petrochemical Research Institute of China Petrochemical Corporation; main drafter: Song Guangcheng

2. Scope of application and non-applicability

• 1.1 is applicable to the determination of the electrical conductivity of aviation and distillate fuels with or without antistatic additives; it gives the conductivity of the fuel when it is not charged, that is, the conductivity determined when the fuel is in an electrically static state (called static conductivity).
• 1.2 uses a portable instrument test method; it can be tested in field oil tanks and also in the laboratory; before testing, interference from residual charge should be minimized, and contamination of the fuel being tested should also be avoided.
• 1.3 values expressed in SI units are regarded as standard values.
• 1.4 this standard involves certain hazardous materials, operations, and instruments, but it is not intended to address all safety issues related thereto; users should establish appropriate safety and protective measures before use and determine applicable management systems; for special precautions, see the relevant clauses.
• 4.1 as long as the electrode size and current measuring instrument are correctly selected, this standard can be used to measure conductivity of 1pS/m or above; the conductivity meters mentioned in this standard can read 1000pS/m or 2000pS/m.
• 4.1.1 if it is necessary to measure conductivity below 1pS/m (such as when clay-treating fuel or refining hydrocarbon solvents), method GB/T 12582 may be used.
• 12.1 the precision data given in Table 1 do not include gasoline or solvents.
• Not applicable: no other explicit non-applicability clauses are provided in the available source.

3. Method principle

• 4.1 a direct-current voltage is applied between two electrodes immersed in the fuel, and the resulting current is expressed as the value of electrical conductivity; to avoid errors caused by ionic polarization, the current is measured instantaneously immediately after the voltage is applied.
• 3.2 static conductivity: the reciprocal of the resistivity of uncharged fuel when there is no ion loss and polarization; after a direct-current voltage is applied between the electrodes, the current measurement value at the initial instant is the conductivity.
• 5 significance and use: static charges are generated during fuel pumping and filtration operations; the ability to dissipate such charges is controlled by its conductivity, and conductivity depends on the form or amount of charged ions; if the conductivity is quite high, the charge dissipates quickly, sufficient to prevent accumulation of charge, and thus dangerous high potentials in receiving tanks can be avoided.

4. Reagents and materials (purity / preparation)

The following reagents are used as cleaning solvents. If water is suspected to be present, isopropanol may be used first, followed by toluene.

• 7.1 Isopropanol: analytical reagent. Note: isopropanol is flammable.
• 7.2 Toluene: analytical reagent. Note: toluene is flammable and its vapor is toxic.
• 7.3 n-Heptane: analytical reagent. Note: n-heptane is flammable and its vapor is toxic.
• 7.3 (last paragraph) A solvent mixed from 50% (V/V) isopropanol and 50% (V/V) n-heptane is used instead of toluene. (The original text here source-text extraction is "isopropanol" written with an unclear character, requires confirmation against the source standard (source-text extraction))

5. Instruments and equipment

• 6.1 Conductivity cell and current measuring instrument: any instrument that can instantaneously give conductivity after voltage is applied and can meet the precision requirements of this method.
• 6.2 Thermometer: a thermometer with an appropriate measurement range and capable of being used for field measurement.
• 6.3 Measuring container: a cylindrical container capable of fully immersing the conductivity cell, with a volume of not less than 1L. Note: see the content of Note 9.1.2.
• 4.1.1 this standard may use MAIHAK MLA type conductivity meter or EMCEE 1152 type conductivity meter.
• 10.2 for field measurement, MAIHAK MLA type conductivity meter or EMCEE 1152 type conductivity meter may be used; the above conductivity meters are all equipped with an extendable cable and a conductivity cell that can be inserted into the storage tank.

6. Recommended operating conditions

• 10.2 during measurement, both the conductivity meter and the conductivity cell should be kept in a stable state; otherwise, the precision of the measurement results will be reduced; when using the conductivity meter in hazardous locations, the relevant regulations of the safety department should also be followed.
• 10.2.1 connect the ground wire of the conductivity meter to the storage tank; immerse the clean, dry conductivity cell into the sample to be predicted, and move the conductivity cell up and down to expel air bubbles and residual oil retained from the previous test; during measurement, ensure that the conductivity cell is fully immersed in the sample, and take care to prevent the conductivity cell from contacting water.
• 10.2.1 sample standing time (original adoption note: the provisions of Note 4 of ASTM D 2624-95 are not adopted; this standard adopts the standing time specified in GB 13348): for road tank cars and railway tank cars, both are 2min; for storage tanks or oil compartments with a volume less than 5000m³, it is 10min; for storage tanks or oil compartments with a volume greater than 5000m³, it is 30min. (The original text source-text extraction is "5 000 m’" "5000 m"", the unit is suspected to be m³, requires confirmation against the source standard (source-text extraction))
• 10.2.2 after rinsing the conductivity cell, keep the conductivity cell stable; turn on the conductivity meter, and after initial stabilization, record the highest reading, which should be completed within 3s; when the conductivity meter has several ranges, select the range with the highest sensitivity; measure the sample temperature.
• 9.1.1 under hot and humid conditions, condensed water will form in the conductivity cell, so the zero point, calibration point, and sample reading will all be abnormal; to avoid this situation, the conductivity cell may be placed at a location 2℃–5℃ higher than the ambient temperature so as to obtain accurate measurement results. (The original text source-text extraction is "2C–5C", requires confirmation against the source standard (source-text extraction))
• A1.4 Note: it is known that early series conductivity meters cannot work normally at very low ambient temperatures, but if the exposure time is limited to within 30min, then even at temperatures as low as -29℃ (the original text source-text extraction is "one29C", requires confirmation against the source standard (source-text extraction)), series 3 and series 4 conductivity meters can also work normally.
• 12.2 the precision values in Table 1 are limited to application at room temperature; wider precision values (×2) may be applicable at a temperature of about -20℃. (The original text source-text extraction is "-20C", requires confirmation against the source standard (source-text extraction))

7. Sampling and sample preparation

• 9.1 the conductivity of the sample should preferably be measured in the field to avoid attenuation or contamination during sample transport; if the sample needs to be retained for future analysis, sampling should be carried out in accordance with GB/T 4756, and the following provisions should be observed.
• 9.1.1 if the conductivity cell contacts water, a full-scale reading will immediately appear when the instrument is started; if the conductivity cell has contacted water, it must be thoroughly rinsed with cleaning solvent, preferably first with isopropanol, and then dried with a stream of air.
• 9.1.2 the sample quantity should be as large as possible, at least not less than 1L. Note: since trace contamination can sensitively affect the test results of the sample in the sampling container, it is recommended to use the sampling container recommended in method SH/T 0616.
• 9.1.3 all sample containers should be thoroughly cleaned with cleaning solvent and blown dry with a stream of air; before sampling, all containers, including container lids, should be rinsed with the sample at least three times.
• 9.1.4 to avoid attenuation changes in sample conductivity, measurement should be carried out as soon as possible after sampling, and at the latest should not exceed 24h.
• 10.3.1 preparation of metal containers or glass containers: before sampling, ensure that all containers and measuring containers are cleaned thoroughly (see 9.1.3).

8. Analytical procedure

• 10.1 calibrate the conductivity meter according to the calibration procedure specified for the conductivity meter used.
• 10.2 for field measurement of railway tank cars, road refueling trucks, etc.: field measurement may use MAIHAK MLA type conductivity meter or EMCEE 1152 type conductivity meter.
• 10.2.1 calibrate the conductivity meter according to the calibration procedure specified for the conductivity meter used; connect the ground wire of the conductivity meter to the storage tank; immerse the clean, dry conductivity cell into the sample to be predicted, and move the conductivity cell up and down to expel air bubbles and residual oil retained from the previous test; during measurement, ensure that the conductivity cell is fully immersed in the sample, and take care to prevent the conductivity cell from contacting water; if the sample has just been pumped into the storage tank, wait until the sample has stood for a certain period (for road tank cars and railway tank cars, both are 2min; for storage tanks or oil compartments with a volume less than 5000m³, it is 10min; for storage tanks or oil compartments with a volume greater than 5000m³, it is 30min), and then immerse the conductivity cell.
• 10.2.2 after rinsing the conductivity cell, keep the conductivity cell stable; turn on the conductivity meter, and after initial stabilization, record the highest reading, which should be completed within 3s; when the conductivity meter has several ranges, select the range with the highest sensitivity; measure the sample temperature.
• 10.3 perform laboratory and field measurements on the sample.
• 10.3.2 Measurement: Thoroughly rinse the conductivity cell with the test sample to remove residual oil left on the conductivity cell from the previous test; transfer the test sample to a clean measurement container; calibrate the conductivity meter according to the calibration procedure specified for the conductivity meter used; completely immerse the conductivity cell into the test sample, taking care that the conductivity cell does not contact the bottom of the measurement container, so as to avoid causing reading errors; measure the conductivity of the test sample and the test sample temperature according to the procedure specified in 10.2.2.
• 8.1 The calibration procedure depends on the model of instrument used; for the calibration procedures of the MAIHAK MLA type conductivity meter and the EMCEE 1152 type conductivity meter, see Appendix A.

9. Qualitative and Quantitative and Calculation Formulas

• 4.1 A direct-current voltage is applied between two electrodes immersed in the fuel, and the resulting current is expressed as a conductivity value.
• 3.1 Conductivity unit picosiemens per meter (pS/m): 1 pS/m = 1×10⁻¹² Ω⁻¹·m⁻¹ = 1 CU = 1 picomho per meter. (The original source-text extraction is “1 pS/m=1×10-120-'m-'=1 CU=1 picomho per meter”, requires confirmation against the source standard (source-text extraction))
• 11.1 If the conductivity meter reading is zero, the measurement result may be reported as less than 1pS/m.
• Calculation formula: not provided in the available source.

10. Precision

• 12.1 The precision of this standard was determined by statistical analysis of test results obtained by combinations of operators and instruments at the same test location; the precision data given in Table 1 do not include gasoline or solvents.
• 12.1.1 Repeatability: For the same operator, in the same laboratory, using the same instrument, operating correctly according to the measurement method, and measuring samples at the same temperature, the difference between consecutive 20 measurement results is allowed to exceed the value listed in Table 1 only 1 times.
• 12.1.2 Reproducibility: For different operators, at the same test site (see 12.2), operating correctly according to the measurement method, and measuring samples at the same temperature, the difference between 20 measurement results is allowed to exceed the value listed in Table 1 only 1 times.
• 12.2 When an operator measures the conductivity of shipped fuel, the repeatability values are similar to those listed in Table 1, but the reproducibility values do not meet the requirements; it is recommended that the operator go to a large fuel storage depot and measure the conductivity of the entire batch of fuel or newly taken fuel according to the specified method, so as to ensure obtaining a sample consistent with the entire batch of fuel and to apply the precision values shown in Table 1.
• Table 1 Precision (unit pS/m):

• The precision values in Table 1 are limited to application at room temperature; wider precision values (×2) may be applicable at a temperature of about -20℃.
• 12.3 Bias: Since there is neither a recognized standard substance nor an appropriate test method to determine the bias of the conductivity measurement method, no bias value can be given.

11. Report

• 11.1 Report the conductivity of the test sample and the test sample temperature at the time of measurement; if the conductivity meter reading is zero, the measurement result may be reported as less than 1pS/m.
• 11.1 Note: It is well known that the conductivity of fuel varies greatly with temperature, and the variation relationships for various aviation fuels and distillate fuels are also different; if conductivity readings need to be calibrated to a specific temperature, each laboratory must establish the relationship between the fuel and the relevant temperature range.

12. Normative References

• GB/T 4756 Petroleum and liquid petroleum products sampling method (manual method)
• GB/T 12582 Determination of conductivity of liquid hydrocarbons (precision electrometer method)
• GB 13348 Electrostatic safety regulations for liquid petroleum products
• SH/T 0616 Determination of water separation index of jet fuels (portable separator method)
• Reference explanation (Chapter 2): The provisions contained in the following standards, through reference, constitute a part of this standard; unless otherwise expressly specified in the standard, the following referenced standards shall all be currently effective standards.

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