ASTM D1837 Standard Test Method for Volatility of Liquefied Petroleum (LP) Gases
5. Apparatus
5.1 Weathering Tube - A centrifuge tube, cone-shaped, conforming to the dimensions given in Fig. 1 and made of thoroughly annealed heat-resistant glass. The shape of the lower tip of the tube is especially important. The taper shall be uniform and the bottom shall be rounded as shown in Fig. 1. The tubes shall comply in wall thickness to ASTM centrifuge tube requirements (Note 1). The graduation tolerances are given in Table 1.
NOTE 1 - Requirements for centrifuge tubes appear in Test Methods D96 and D1796.
5.2 Tube Support - Means shall be provided for supporting the weathering tube by its neck in a vertical position.
5.3 Water Bath (for use in tests on butane and propane-butane mixture types of liquefied petroleum gas only). A shallow container filled with clean water having a maintained temperature ranging from 15 to 21°C (60 to 70°F) and a depth of 38 mm (1 1/2 in.).
5.4 Thermometer - ASTM Armored Weathering Test Thermometer having a range from -50 to 5°C (-58 to 41°F) and conforming to the requirements for Thermometer 99C-92 (99F-86) as prescribed in Specification E1. Do not remove the armor from the thermometer.
5.5 Sampling Precooling Equipment:
5.5.1 Cooling Vessel - Any suitable wide-mouthed metal container or Dewar flask at least 64 mm (2 1/2 in.) in inside diameter by 292 mm (11 1/2 in.) deep.
5.5.2 Cooling Coil - Approximately 6 m (20 ft) of 4.8-mm (3/16 -in.) outside diameter soft copper tubing, wound around a hollow mandrel at least 54 mm (2 1/8 in.) in outside diameter, with adjacent turns touching. Run the lower end of the tube up through the center of the mandrel before winding so that the finished coil will fit snugly inside the cooling vessel. When assembled, the top of the coil shall be at least 25 mm (1 in.) below the top of the cooling vessel and the open ends of the coil shall not be more than 100 mm (4 in.) above. Connect the downstream end of the coil to a 3.2 mm (1/8 in.) needle valve having an outlet connection not more than 76 mm (3 in.) long (see Fig. 2).
5.5.3 Precoolant - This can be the liquefied petroleum gas from the same container from which a sample is to be taken. Other refrigerants having a boiling point lower than the initial boiling point of the sample can be used. Use a nonflammable precoolant if required.
5.6 Charcoal - Four grains of activated charcoal, approximately 6 to 14 mesh in size, are required. The four grains shall be similar in size (Note 2).
NOTE 2 - Grains of charcoal are used as a boiling aid which reduces the tendency for the propane or butane to overflow the weathering tube as the propane or butane evaporates.
