NB/SH/T 0233-2024 Liquefied petroleum gas sampling 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 title / supersession relationship

• Standard number: NB/SH/T 0233—2024
• Chinese title: Liquefied petroleum gas sampling method
• English title: Method of sampling for liquefied petroleum gas
• Supersession relationship: supersedes SH/T 0233—1992 "Liquefied petroleum gas sampling method"
• Adoption relationship: modified adoption using the redrafting method of ISO 4257:2001 "Liquefied petroleum gas sampling method"
• Previous versions: first published in 1984 as SY 2084—1984, first revised in 1992 as SH/T 0233—1992; this is the second revision
• Publication/implementation: published on 2024-12-25, implemented on 2025-06-25
• ICS 75.160.30; CCS E 30
• Custodian: Subcommittee on Static Measurement of Petroleum and Light Hydrocarbons (SAC/TC280/SC2) of the National Technical Committee for Standardization of Petroleum Products and Lubricants
• Proposed by: China Petrochemical Corporation

2. Scope of application and non-applicability

• This document describes a method for obtaining liquefied petroleum gas (LPG) samples using sampling cylinders.
• Applicable to sampling of LPG under non-refrigerated conditions; sampling of LPG produced as a by-product in natural gas processing and coal chemical processes under non-refrigerated conditions may refer to this document.
• Not applicable to providing samples for trace analysis of low-boiling-point components in LPG.
• Note: ASTM D3700 gives the sampling method for samples used for trace analysis of LPG.

3. Method principle

LPG The liquid sample enters the sampling cylinder from the sample source through the sampling line. The sampling line and sampling cylinder are flushed with the sampled medium, the sampling cylinder is filled with liquid sample, the sampling cylinder is drained, and finally a liquid sample not exceeding 80% of the sampling cylinder volume is retained in the sampling cylinder.

Note: 80% The fill amount of the sampling cylinder volume is usually the fill amount at 15℃; for low-temperature samples, the fill amount of the sampling cylinder may need to be appropriately reduced on the basis of 80%.

4. Reagents and materials (purity / preparation)

• Volatile solvents: acetone and n-pentane are usually used in sequence as volatile solvents to clean the sampling cylinder (see 8.2 note).
• Gaseous propane: clean, dry gaseous propane, used to purge the sampling cylinder (see 8.2 d).
• Purity and specific specifications: not provided in the available source.

5. Apparatus and equipment

• 5.1 Sampling cylinder (7.1)
  • The inner wall should be passivated; the nominal volume should be selected according to the required amount of LPG sample (7.1.1).
  • A dual-cylinder-valve type with a reserved volume tube should be selected (see Figure 1); the end of the sampling cylinder where the reserved volume tube is installed should be clearly marked; the insertion depth of the reserved volume tube should allow the sampling cylinder to discharge at least 20% of the sampling cylinder volume of liquid (7.1.2).
  • Single-cylinder-valve sampling cylinders should not be used (7.1.3).
  • The sampling cylinder and its accessories should be made of metal materials; stainless steel cylinders are recommended, and aluminum cylinders should not be used; design, manufacture and testing should comply with the relevant provisions of cylinder product standards (6.3.1).
  • A pressure resistance test should be conducted and the maximum safe operating pressure marked; an airtightness test should be conducted (6.3.2). Note: sampling cylinders with a nominal working pressure not lower than 2.1 MPa are usually selected for filling LPG.
  • A protective cover (preferably a rectangular frame, see Figure 1) should be installed around the cylinder valve (6.3.4).
  • The following information should preferably be attached: sampling cylinder number, sampling location, ship name (if any), ship tank number (if any), shore tank number (if any), sampling method, sampling time, sampled product, sampling personnel, sampling cylinder destination, laboratory concerns (7.1.4).
• 5.2 Sampling line (7.2): metal tubing should be used, which should not leak LPG and should withstand the pressure encountered during sampling; Figure 2 gives an example of connecting a sampling line to a sampling cylinder.
• 5.3 Sampling cylinder connector (7.3): metal components should be used.
• 5.4 Closed sampling system (7.4): metal tubing should be used for the lines, which should not leak LPG and should withstand the pressure encountered during sampling; a pressure gauge, flow indicator and line control valves should be provided; Annex B gives an example of application of a closed system.
• 5.5 Automatic sampling system ASS (7.5): should comply with the design, manufacturing and other requirements for equipment used in explosive atmospheres; metal tubing should be used for the sampling line, which should not leak LPG and should withstand the pressure encountered during sampling; it is usually a closed system; Figure × gives a flow diagram of ASS (including sample inlet control valve, filter, pressure reducing valve, pressure controller, flow indicator, inlet automatic control valve, sampling solenoid valve, drain valve, vacuum pump, outlet automatic control valve, sample outlet control valve, explosion-proof controller, combustible gas alarm, sampling cylinder, sampling cylinder rotation drive system).

6. Recommended operating conditions

• After circulation or stirring before sampling, it is preferable to wait 30 min before sampling (5 c).
• When sampling from a flowing pipeline, the pipeline pressure should be greater than the vapor pressure of the sampled medium to avoid the appearance of gas and liquid two phases (5 d).
• Continuous flushing: use a liquid volume of not less than 10 times the sampling cylinder volume and flush the sampling cylinder within 5 min; during flushing, the pressure in the system should always be kept greater than the vapor pressure of LPG (9.2.2 b, 9.3.3.2, B.2.2).
• Sampling cylinder fill amount: retain a liquid sample not exceeding 80% of the sampling cylinder volume (Chapter 4, 9.2.3 b, 9.5).
• After sampling, the sampling cylinder should be quickly transferred to a cool environment, kept at low temperature or protected from drastic temperature changes (6.3.5).
• Other specific temperature and pressure values: not provided in the available source.

7. Sampling and sample preparation

• Preparation of the sampling cylinder (Chapter 8):
  • 8.1 If the previously contained sample is known and the residue does not affect subsequent analysis: drain the sampling cylinder and proceed as specified in 8.3.
  • 8.2 If the previously contained sample is unknown or the residue may affect subsequent analysis: a) drain the residual liquid; b) clean with volatile solvent; c) vacuum dry; d) purge with clean, dry gaseous propane, then close the cylinder valve and keep it closed.
  • 8.3 Connect the sampling cylinder to the sampling line or sampling system (ASS or closed system), and flush the sampling cylinder as specified in 9.2.2, 9.3.2.2 or 9.3.3.2.
• Representativeness precautions (Chapter 5): sample only from the liquid phase; avoid sampling at the bottom of the container; the medium in the tank may be non-uniform; when homogenization is impossible, note insufficient representativeness or take other measures, and if necessary, reach agreement among the relevant parties.

8. Analytical procedure

• 9.1 General: select automatic sampling or manual sampling according to conditions and equipment. Note: automatic sampling is the recommended method.
• 9.2 Automatic sampling
  • 9.2.1 Line flushing (purging): turn on the ASS line flushing function and fully flush the ASS sampling line with the sampled medium.
  • 9.2.2 Flushing the sampling cylinder: ASS flush the sampling cylinder by the system preset method, divided into a) flushing by times (refer to 9.3.2.2); b) continuous flushing (not less than 10 times the sampling cylinder volume of liquid, within 5 min, pressure always greater than the vapor pressure of LPG). After flushing, drain the residual liquid; ASS when vacuum capability is available, vacuum should preferably be applied.
  • 9.2.3 Sampling: a) ASS When there is no sampling amount adjustment function, fill the sampling cylinder with liquid sample, disconnect and remove the sampling cylinder; if a leak is found or any cylinder valve is open before adjusting the sampling amount, discard this sample. b) ASS When there is a sampling amount adjustment function, retain a liquid-phase sample of 80% of the sampling cylinder volume, disconnect and remove the sampling cylinder, and perform a leak check as specified in 9.5.
• 9.3 Manual sampling
  • 9.3.1 Sampling modes: usually include conventional sampling and closed sampling.
  • 9.3.2 Conventional sampling (using the sampling line in Figure 2)
    • 9.3.2.1 Flush the sampling line: connect the two ends of the sampling line safely to the sample source and the sampling cylinder valve C respectively; close control valve A, drain valve B and cylinder valve C; open the sample source end valve of the sampling line, control valve A and drain valve B, and flush the sampling line with the sampled medium.
    • 9.3.2.2 Flush the sampling cylinder: keep the sampling cylinder vertical with cylinder valve D at the top; close drain valve B and cylinder valve C, open control valve A; open cylinder valve C, slowly open cylinder valve D to partially fill the sampling cylinder with liquid-phase sample; close control valve A, discharge part of the gas-phase sample through cylinder valve D; close cylinder valve D, turn the sampling cylinder vertically 180 degrees; turn it vertical again with cylinder valve D at the top, open drain valve B to discharge the remaining liquid-phase sample; repeat the above flushing operation at least three times.
    • 9.3.2.3 Sampling: keep the sampling cylinder vertical with cylinder valve D at the top; close drain valve B and cylinder valve C, open control valve A and cylinder valve C, and fill the sampling cylinder with sample; close cylinder valve C and the sample source end valve; open drain valve B; after the sampling line is fully depressurized, disconnect and remove the sampling cylinder; if a leak is found or any cylinder valve is open before adjusting the sampling amount, discard this sample.
  • 9.3.3 Closed sampling
    • 9.3.3.1 Line flushing (purging): fully flush the sampling line of the closed system with the sampled medium; see Annex B for an example.
    • 9.3.3.2 Flush the sampling cylinder: flush with not less than 10 times the sampling cylinder volume of liquid, within 5 min, with pressure always greater than the vapor pressure of LPG; after flushing, drain the residual liquid; see Annex B for an example.
    • 9.3.3.3 Sampling: fill the sampling cylinder with sample; after the closed system line is fully depressurized, disconnect and remove the sampling cylinder; if a leak is found or any cylinder valve is open before adjusting the sampling amount, discard this sample; see Annex B for an example.
• 9.4 Adjusting the sampling amount: drain and adjust as soon as possible after sampling is completed. Keep the sampling cylinder vertical with the cylinder valve D where the reserved volume tube is installed at the top; slightly open cylinder valve D, the liquid-phase medium flows out, and when LPG evaporated gas appears, immediately close cylinder valve D; if no liquid-phase medium flows out, discard this sample and resample.
• 9.5 Leak check: after adjusting the sampling amount and retaining the liquid-phase sample in the sampling cylinder volume 80%, perform a leak check by an appropriate method, for example immersing the sampling cylinder in a water bath; if a leak is found, discard this sample; before the next sampling, repair or replace the leaking sampling cylinder.
• Appendix B Example of closed sampling:
  • B.2.1 Pipeline flushing (purging): confirm that valve A, valve B, valve E, cylinder valve C and cylinder valve D are all closed; cylinder valve D is connected to the sample source end, cylinder valve C is connected to the low-pressure end, the sampling cylinder is vertical and cylinder valve D is at the lower part; open valve A, valve E and valve B in sequence, and flush with the sampled medium for a certain time; when the requirements are met, close valve A, valve E and valve B in sequence.
  • B.2.2 Flush the sampling cylinder: confirm that all valves are closed; open valve A, valve B, cylinder valve D and cylinder valve C in sequence; flush with a liquid volume of not less than 10 times the sampling cylinder volume within 5 min, with the pressure always greater than the vapor pressure of LPG; close valve A, open valve E, cylinder valve C and cylinder valve D in sequence to fully release pressure, and close valve B; close cylinder valve C and cylinder valve D, disconnect and remove the sampling cylinder, confirm whether residual liquid is present, and if so, drain it.
  • B.2.3 Sampling: confirm that all valves are closed; cylinder valve C is connected to the sample source end, cylinder valve D is connected to the low-pressure end, the sampling cylinder is vertical and cylinder valve D is at the upper part; open valve A and cylinder valve C in sequence to fill the sampling cylinder with sample; close cylinder valve C and valve A in sequence; open valve E and valve B to fully release pressure in the pipeline, and close valve B; disconnect and remove the sampling cylinder; if a leak is found before adjusting the sampling amount or any cylinder valve is open, discard this sample.

9. Qualitative and Quantitative Determination and Calculation Formulas

• This document is a sampling method and does not provide qualitative and quantitative calculation formulas.
• Figure 1 gives the relationship: Vl = 4 × Vg (Vl is the liquid-phase volume, Vg is the gas-phase volume).
• Other calculations: not provided in the available source.

10. Precision

Not provided in the available source.

11. Report

Not provided in the available source (information that should be attached to the sampling cylinder is given in 7.1.4, not a test report format requirement).

12. Normative References

• GB/T 13005 Gas cylinder terminology (normative reference)
• References:
  • [1] GB/T 5099.4 Seamless steel gas cylinders — Part 4: Seamless stainless steel gas cylinders
  • [2] HG/T 20675 Design code for electrostatic grounding in chemical enterprises
  • [3] ASTM D3700 Standard practice for Obtaining LPG Samples Using a Floating Piston Cylinder
• Mentioned in notes: HG/T 20675 (note to 6.2.2), GB/T 5099.4 (note to 6.3.1), ASTM D3700 (note to Chapter 1)

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