SH/T 0658-1998 Determination of Hydrogen Content in Jet Fuels (Low-Resolution Nuclear Magnetic Resonance Method)

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Standard number: SH/T 0658-1998 (confirmed in 2004)
• Chinese name: Determination of Hydrogen Content in Jet Fuels (Low-Resolution Nuclear Magnetic Resonance Method)
• English name: Standard test method for hydrogen content of jet fuels by low resolution nuclear magnetic resonance spectrometry
• Replacement relationship: not provided in the available source (only equivalent adoption of ASTM D3701-92 is mentioned; no replaced standard number is listed)
• Adoption relationship: equivalent adoption of ASTM D3701-92 "Determination of Hydrogen Content in Jet Fuels (Low-Resolution Nuclear Magnetic Resonance Spectroscopy Method)"
• Main differences from ASTM D3701-92: ASTM D3701-92 specifies that the hydrogen content of other petroleum liquids is determined by ASTM D4808; because China has not yet established a corresponding similar standard to ASTM D4808, this standard does not include content related to this in either the scope or the referenced standards
• Approval/implementation: approved by China Petrochemical Corporation 1998-06-23, implemented on 1998-12-01
• Proposed by: Sinopec Jinling Petrochemical Company
• Centralized management unit: Petrochemical Research Institute of China Petrochemical Corporation
• Drafting unit: Refinery of Sinopec Jinling Petrochemical Company
• Main drafter: Liu Qingxia

2. Scope of application and non-applicability

• 1.1 This standard specifies a method for determining the hydrogen content of samples by low-resolution nuclear magnetic resonance.
• 1.2 This standard applies to jet fuels.
• Not applicable: other petroleum liquids (the content in ASTM D3701-92 determined by ASTM D4808) are not included in this standard; no other explicit non-applicability clauses are provided in the available source.
• 1.3 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 and determine applicable management systems before using this standard. Some special precautionary instructions are given in Chapter 6.

3. Method principle

Using analytical reagent grade n-dodecane as the standard sample, a low-resolution nuclear magnetic resonance instrument is used to measure the nuclear magnetic resonance signal integral values generated by the standard sample and the test sample; this value represents the absolute amount of hydrogen atoms in the standard sample and the test sample. Based on the mass of the standard sample and its theoretical hydrogen content and the mass of the test sample, the hydrogen content of the test sample (mass percentage) can be obtained.

4. Reagents and materials (purity / preparation)

• n-Dodecane: analytical reagent grade, used as the standard sample. Note: flammable.
• Other reagents: not provided in the available source.

5. Apparatus and equipment

• 5.1 Low-resolution nuclear magnetic resonance instrument: a low-resolution continuous-wave instrument capable of measuring the nuclear magnetic resonance signal generated by hydrogen atoms in the sample. The instrument includes:
  • 5.1.1 Excitation coil and detection coil: sized to accommodate a glass test tube.
  • 5.1.2 Electronic components: used to control and monitor the magnet and coils, and equipped with circuits for adjusting radio frequency and audio frequency gain and an integration counter.
  • Note: Instruments with performance equivalent to this standard may also be used.
• 5.2 Adjustment block (aluminum block bath): see Figure 1. An aluminum alloy block with holes for holding glass test tubes. The height of the sample in the glass test tube should be at least 20mm below the top of the adjustment block.
• 5.3 Glass test tube: flat bottom, capacity about 100mL, outer diameter 33.7mm±0.5mm, inner diameter 31.0mm±0.5mm. There is a ring mark at 51mm from the bottom of the tube.
• 5.4 Polytetrafluoroethylene stopper: used to seal the glass test tube.
• 5.5 Insertion rod: see Figure 1. A metal rod with a threaded end, used for installing and removing the polytetrafluoroethylene stopper.
• 5.6 Balance: sensitivity 0.01g.
• 5.7 Pipette: 25mL.

6. Recommended operating conditions

• 8.2 Adjust the instrument according to the following conditions:
  • On a new nuclear magnetic resonance instrument with variable gating, the gating should be set at 1.5GS( gauss) so as to be consistent with instruments with non-variable gating.
  • Radio frequency level: 20VA
  • Audio frequency gain: 50( on the dial)
  • Integration time: 128s
• 8.3 Turn on the instrument power and preheat the instrument for more than 1h.
• 8.1 Before testing, read the instrument instruction manual in detail, and take care to prevent direct sunlight or direct wind from blowing on the instrument, so as to avoid rapid fluctuations in the temperature of the instrument and the adjustment block during the measurement. Throughout the measurement process, magnetic materials should not be brought close to the instrument, to eliminate errors caused by changes in the magnetic environment.
• 10.1 Before testing, place the glass test tubes containing the standard sample and the test sample in the adjustment block for at least 30min to ensure that their temperatures are uniform and consistent, that is, room temperature.

7. Sampling and sample preparation

• 7 Sampling: sample according to GB/T 4756 to obtain a homogeneous sample.
• 9 Preparation of standard sample and test sample:
  • 9.1 Take a clean, dry glass test tube and a polytetrafluoroethylene stopper, weigh them together, weigh to the nearest 0.01g, and record the mass. Carefully add 30mL±1mL of the standard sample to the glass test tube with a pipette, taking care to prevent liquid from splashing above the ring mark.
  • 9.2 Use the insertion rod to slowly screw the polytetrafluoroethylene stopper vertically into the glass test tube until it just reaches above the liquid surface. Twisting slightly while inserting the stopper helps air escape from the glass test tube and ensures that the bottom of the stopper is raised all around, which prevents changes in results caused by rapid evaporation of the sample.
    • Note: When inserting the stopper, a metal wire with a diameter smaller than 0.2mm may be inserted along the inner wall of the test tube until about 38mm from the ring mark. After the stopper is pushed in, pull out the metal wire.
  • 9.3 The bottom edge of this stopper should be at or slightly below the 51mm ring mark of the glass test tube; carefully pull out the insertion rod without damaging the stopper.
  • 9.4 Weigh the glass test tube, standard sample, and stopper together, weigh to the nearest 0.01g, record the mass, and obtain the mass of the standard sample.
  • 9.5 Place the glass test tube containing the standard sample in the adjustment block.
  • 9.6 When determining the test sample, repeat the steps from 9.1 to 9.5, replacing only the standard sample with the test sample.

8. Analysis procedure

• 8 Instrument preparation:
  • 8.1 See Section 6.
  • 8.2 See Section 6.
  • 8.3 See Section 6.
  • 8.4 Place the glass test tube containing the test sample in the excitation coil, and adjust the tuning knob until the two resonance waves on the oscilloscope coincide. It may be necessary to readjust this set value during measurement.
  • 8.5 Remove the glass test tube from the excitation coil and observe the signal; at this time, whether it is zero ±3 digits. During a series of tests, periodic checks should be made to ensure that the excitation coil has not been contaminated.
• 10 Test procedure:
  • 10.1 Before testing, place the glass test tubes containing the standard sample and the test sample in the adjustment block for at least 30min to ensure that their temperatures are uniform and consistent, that is, room temperature.
  • 10.2 Carefully place the glass test tube containing the standard sample into the excitation coil. When the glass test tube is fully inside the excitation coil, the top of the glass test tube is slightly higher than the instrument cover plate.
  • 10.3 Check whether the peaks on the oscilloscope coincide. If they do not coincide, adjust the tuning knob to make them coincide.
  • 10.4 After the standard sample has been placed in the excitation coil for 3s, press the reset switch.
    • Note: The placement time may be extended so that the hydrogen nuclei are fully polarized in the magnetic field.
  • 10.5 After the counting time of 128s, the digital display will stop at its final value; record the integrator reading, press the reset switch again and record a second reading, and calculate the measured average integral value of the standard sample.
  • 10.6 Weigh the test tube containing the standard sample again and record the total mass (if the change from the mass weighed in 9.4 is greater than 0.01g, the cause should be identified and corrected).
  • 10.7 Place the standard sample back into the adjustment block.
  • 10.8 Repeat the steps from 10.2 to 10.5 for the test sample to be determined. Obtain two similar integral readings and calculate the measured average integral value of the test sample.
    • Note: Temperature changes between the standard sample and the test sample, as well as mass changes caused by evaporation loss, will affect the accuracy of the determination. Therefore, when determining a series of results, the test sample and standard sample should be determined, weighed, and calculated in pairs. When not performing determinations, the glass test tubes containing the standard sample and test sample must be placed in the adjustment block.

9. Qualitative and quantitative determination and calculation formula

The hydrogen content of the test sample x[%(m/m)] is calculated according to formula (1):

x = (ST / SR) × (WR / WT) × 15.39 ………………(1)

Where:

• ST—— measured average integral value of the test sample;
• SR—— measured average integral value of the standard sample;
• WT—— mass of the test sample, g;
• WR—— mass of the standard sample, g;
• 15.39—— hydrogen content of the n-dodecane standard sample, %(m/m).

10. Precision

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

• 13.1 Repeatability: the difference between two results obtained by the same operator, using the same instrument, on the same sample, under unchanged operating conditions, should not exceed 0.09%(m/m).
• 13.2 Reproducibility: the difference between two results obtained by different operators in different laboratories on the same sample under the same conditions should not exceed 0.11%(m/m).
• 13.3 Bias: according to the American Society for Testing and Materials ASTM 1977 annual research report, for the expected value of pure known substances, the hydrogen content determined by this standard is somewhat high.

11. Report

The hydrogen content result of the test sample is reported to 0.01%(m/m).

12. Referenced documents

• GB/T 4756 Manual sampling method for petroleum liquids

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 Q&A