GB/T 30517-2014 Test for free water in liquefied petroleum gas Visual method

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Card type: Test method

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

• Standard number: GB/T 30517-2014
• Chinese full title: Test for free water in liquefied petroleum gas Visual method
• English name: Test method for free water in liquefied petroleum gas—Visual inspection
• Replacement relationship: not provided in the available source (the foreword only states "adopted by redrafting method with modification from European Standard EN 15469:2007 'Petroleum products - Test for free water in liquefied petroleum gas - Visual method'", and does not mention replacing any previous version)
• Adoption relationship: modified adoption of EN 15469:2007; clause numbering comparison see Annex A (informative annex) Table A.1
• Publication/implementation: published on 2014-02-19, implemented on 2014-06-01
• Custodianship: National Technical Committee for Standardization of Petroleum Products and Lubricants, Subcommittee on Petroleum Fuels and Lubricants (SAC/TC 280/SC 1)
• Drafting organization: Sinopec Research Institute of Petroleum Processing

2. Scope of application and non-applicability

• Scope of application: This standard specifies a test method using the visual method to determine the presence of free water in liquefied petroleum gas below 0°C; applicable to liquefied petroleum gas (LPG).
• Note: Usually the test temperature is not lower than -5°C (the original text "not lower than one unit CC" is source-text extraction noise, judged according to 6.3 Note "usually the test temperature is controlled not lower than -5°C", requires confirmation against the source standard (source-text extraction)).
• Non-applicability: not provided in the available source explicitly listing non-applicable objects. 6.3 Note points out that "low-temperature cooling water bath is not applicable to this standard".

3. Method principle

• Transfer the liquefied petroleum gas sample to a transparent pressure-resistant test cell, with the sample amount occupying 50% of the container volume, then place the test cell in a cold bath below 0°C and cool for not less than 1 h, and observe whether ice crystals form in the sample.
• Result determination: when there are no ice crystals, the test result is "pass"; when ice crystals are present, the test result is "fail".
• Principle explanation: when the LPG sample contains dissolved water or free water, under saturated vapor pressure and at temperatures above 0°C, it is transparent and not cloudy, and the two liquid phases are difficult to distinguish; LPG and water are both colorless, and at room temperature it is very difficult to determine the separation interface of the two liquid phases; only by using a transparent container and under suitable light can it be distinguished. Ice is much less transparent than water and is easier to observe; after water freezes into ice, its visibility increases.

4. Reagents and materials (purity / preparation)

• Cleaning solvent: anhydrous ethanol or isopropanol (used to clean the test cell, see Chapter 7).
• Drying gas: nitrogen or dry air (used to dry the test cell).
• Dry gaseous butane (used to release the vacuum in the test cell).
• Water: used for verification tests (add 1 mL water to the sample cell, see 9.2.4).
• Purity specifications and specific preparation methods: not provided in the available source.

5. Apparatus and equipment

• 6.1 Sample cell: equipped with a bottom valve; the valve stem should be as short as possible to prevent possible retention of free water during transfer to the test cell; if such equipment is not available, a conventional sample cell may be used and operated according to 9.1.2.
• 6.2 Test cell: transparent, with a volume of 250 mL. It should be equipped with a thermocouple to measure the liquid temperature, and should also be equipped with a bottom valve and a top vent valve.
  • Note: The transparent liquefied petroleum gas test cell is made of glass or plastic, such as the hydrometer cylinder described in SH/T 0221 or another glass or plastic container that is pressure-resistant and equipped with a bottom valve and a top vent valve.
• 6.3 Cold bath: capable of controlling the temperature below 0°C.
  • Note: Usually the test temperature is controlled not lower than -5°C; a low-temperature cooling water bath is not applicable to this standard.
• Sampler (see Chapter 8): should be made of stainless steel of a suitable grade, and may be single-valve or double-valve, with a discharge tube or without a discharge tube; the size may be determined according to the amount required for the test; it should be able to withstand pressure above 3.1 MPa, and should periodically undergo 2.0 MPa airtightness testing.

6. Recommended operating conditions

• Cold bath temperature: below 0°C; usually controlled not lower than -5°C (6.3 Note).
• Test cell pre-cooling: place the test cell in the cold bath for at least 30 min (9.1.1).
• Sample amount: fill to the 50% position of the test cell volume (9.1.4).
• Cooling time: place the test cell containing the sample horizontally in the cold bath for not less than 1 h (9.2.1); Note: when the test cell volume or sample amount is large, the cooling time may need to exceed 1 h.
• Other operating conditions: not provided in the available source.

7. Sampling and sample preparation

• Sampling of liquefied petroleum gas shall be carried out in accordance with SH/T 0233 (Chapter 8).
• Sampler requirements: made of stainless steel of a suitable grade, single-valve or double-valve, with a discharge tube or without a discharge tube; size determined according to the amount required for the test; should be able to withstand pressure above 3.1 MPa, and should periodically undergo 2.0 MPa airtightness testing.
• Apparatus preparation (Chapter 7): before cleaning the test cell, residual LPG sample in the cell should be drained in liquid form to prevent gaseous draining from causing LPG to remain on the cell wall. The test cell should be carefully cleaned with a suitable cleaning solvent (anhydrous ethanol or isopropanol), and then dried with nitrogen or dry air. Remove nitrogen and air from the test cell by vacuuming, then introduce dry gaseous butane into the cell to release the vacuum. Before use, the test cell should be sealed and stored under dry conditions, ensuring that no liquid (water and solvent) remains inside the bottom valve.
• Warning: Gaseous butane is flammable and explosive. During the operation of introducing butane to release the vacuum, safety measures for removing vapors should be in place.

8. Analytical procedure

9.1 Introduction of the sample

• Warning: Operators should avoid liquefied petroleum gas contacting the skin, should wear gloves and protective glasses, and avoid inhaling vapors.
• 9.1.1 Before transferring the sample to the test cell, place the test cell in the cold bath (see 6.3) for at least 30 min.
• 9.1.2 To prevent water from remaining at the bottom valve of the sample cell, shake the sample cell vigorously so that water droplets are uniformly dispersed in the LPG liquid phase.
• 9.1.3 Connect the bottom valve of the sample cell containing the sample to be tested (placed vertically) to the test cell. The diameter of the connecting line should be as small as possible to prevent introducing a large amount of air into the test cell, ensure that the entire connection line does not leak, and then open the bottom valve of the sample cell.
• 9.1.4 Open the inlet valve of the test cell to allow the sample to flow in. If necessary, gently open the vent valve of the test cell and fill LPG to the 50% position of the test cell volume.
• 9.1.5 Close all valves and separate the test cell from the sample cell.
• 9.1.6 After closing all valves, check whether the test cell leaks: if it leaks, discard the sample and resample after the test cell is repaired.
• Warning: Liquefied petroleum gas is flammable and explosive. When fog spots, cracks, rupture, or corrosion marks are found on the test cell, it should be replaced to prevent the test cell from bursting and liquefied petroleum gas from leaking.

9.2 Testing

• 9.2.1 Place the test cell containing the sample horizontally in the cold bath for not less than 1 h. Note: when the test cell volume or sample amount is large, the cooling time may need to exceed 1 h.
• 9.2.2 (the original numbering is missing; based on the meaning of the text) Remove the test cell from the cold bath and immediately observe to check whether ice crystals are present at the bottom of the sample or the bottom of the test cell.
• 9.2.3 Due to moisture in the air, the outer surface of the test cell will quickly be covered with a frozen layer, making observation impossible. If this occurs, quickly wipe off the frozen layer and observe again.
• 9.2.4 The appearance of any ice crystals should be recorded. By adding 1 mL water to the sample cell and carrying out the same test procedure, it can be verified whether free water in the sample cell is present but undetected.
  • Note: As a training process for the test operator, it is useful to repeat the entire test procedure by adding 1 mL water to the test cell to simulate a "fail" test. In this case, ice crystals are easily detected; thus the operator can observe the phenomenon that occurs when free water is present under low-temperature test conditions.

9. Qualitative and quantitative determination and calculation formulas

• This method is a qualitative (visual) determination and has no calculation formula.
• Determination rule: if no ice crystals appear, the test result is reported as "pass"; if ice crystals appear, the test result is reported as "fail" (Chapter 10).

10. Precision

• The precision of the test procedure cannot be determined because the test result is "pass" or "fail", rather than a quantitative determination (Chapter 11).

11. Report

• If no ice crystals appear, the test result is reported as "pass"; if ice crystals appear, the test result is reported as "fail" (Chapter 10).
• Other report content requirements: not provided in the available source.

12. Referenced documents

• SH/T 0233 Liquefied petroleum gas sampling method (normative referenced document, Chapter 2)
• Bibliography: [1] SH/T 0221 Determination of density or relative density of liquefied petroleum gas (pressure hydrometer method)
• Annex A (informative annex): clause numbering comparison table between this standard and EN 15469:2007 (Table A.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 Q&A