ASTM D2416 Test Method for Coking Value of Tar and Pitch (Modified Conradson)
5. Apparatus
5.1 Crucible - Wide-form, a, either porcelain, glazed throughout, or silica, a; 29 to 31-mL capacity, 46 to 49 mm in rim diameter.
5.2 Skidmore Crucible - Iron crucible, b, flanged and ringed, 65 to 82-mL capacity, 53 to 57 mm inside and 60 to 67 mm outside diameter of flange, 37 to 39 mm in height, supplied with a cover without delivery tubes and having the vertical opening closed. The horizontal opening of about 6.5 mm shall be kept clean. The outside diameter of the flat bottom shall be 30 to 32 mm.
5.3 Metal Crucible - Spun sheet-iron or nickel crucible, c, with cover; 78 to 82 mm in outside diameter at the top, 58 to 60 mm in height, and approximately 0.8 mm in thickness. At the bottom of this crucible, and level before each test, shall be a layer of about 25 mL of sand, or enough to bring the Skidmore crucible, with cover on, nearly to the top of the sheet-iron crucible. The sand shall be dry and screened to pass through a 65-mesh screen and to be retained on a 200-mesh screen.
5.4 Wire Support - Triangle (65 mm) of bare Nichrome wire 1.5 to 2.0 mm in cross section, having an opening small enough to support the bottom of the metal crucible (see 5.3). The triangle, d, shall have its arms bent to form a cradle that will support the metal crucible with its bottom level with the bottom of the insulator (see 5.6).
5.5 Hood - Circular, sheet-iron, e, from 120 to 130 mm in diameter, the height of the lower perpendicular side to be from 50 to 53 mm; provided at the top with a chimney 50 to 60 mm in height and 50 to 56 mm in inside diameter, which is attached to the lower part having the perpendicular sides by a cone-shaped member, bringing the total height of the complete hood to 125 to 130 mm. The hood may be made from a single piece of metal, providing it conforms to foregoing dimensions. A bridge, g, made of approximately 3 mm iron or nichrome wire, and having a height of 50 mm above the top of the chimney, shall be attached to handle the chimney when positioning.
5.6 Insulator - Ceramic block or refractory ring, f, 150 to 175 mm in diameter if round, or on a side if square, 32 to 38 mm in thickness, provided with an inverted cone-shaped opening through the center; 83 mm in diameter at the bottom and 89 mm in diameter at the top.
5.7 Vertical Electric Furnace - Bore a hole in the bottom and insert the thermocouple of the pyrometer controller so that its junction is centered exactly 38 mm below the furnace opening.
5.8 Pyrometer Controller - The pyrometer controller should be checked periodically against a calibrated reference thermocouple, placed alongside but not touching, to ensure that the furnace is operating at the desired temperature. Appropriate changes in the controller circuit should be made, when necessary, to maintain the required temperature.
5.9 Sieve - U. S. Standard No. 30 (600-µm), conforming to Specification E 11.
