ASTM D7157 Standard Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane Phase Separation; Optical Detection)
7. Apparatus
7.1 General - (See Fig. 1) This test method uses an integrated automated analytical measurement system comprised of a PC-based computer and three titration stations.
7.1.1 Computer, PC-based computer with associated software, capable of controlling up to three independent titration stations, controlling test sequencing, and acquisition of optical probe signal data. The associated software also provides for processing calculations and automatically produces a report of important test parameters.
7.1.2 Titration Stations:
7.1.2.1 Titration Unit, automatic computer controlled, adjustable motor-driven ceramic piston pump, capable of delivering solvent at a rate of 0.01 mL/s to 0.5 mL/s, with a volume dispensing accuracy of +/- 0.01 mL.
7.1.2.2 Magnetic Stirrer, adjustable from 200 r/min to 400 r/min.
7.1.2.3 Optical Probe, consisting of a system of three areas of light emitters (880 nm) and three areas of light receivers. The analytical measurement system will automatically select the optimum area, based on the level of translucency of the sample.
7.1.2.4 Titration Cell, of borosilicate glass, flat bottom, outside diameter 30 mm +/- 2 mm, volume 95 mL +/- 15 mL, fitted with a tapered ground glass joint (female).
7.2 Balance, capable of reading to 0.1 mg or better.
7.3 Dispenser, capable of delivering up to 10 mL of toluene with an accuracy of +/- 0.1 mL.
7.4 Condenser, double surface with a tapered ground-glass joint (male) at the bottom to fit the top of the titration cell.
7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from 100 r/min to 1000 r/min.
7.6 Stirring Bar, magnetic, PFTE-coated, 20 mm in length.
8. Reagents and Materials
8.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
8.1.1 Toluene. (Warning - Flammable. Health hazard. Vapor may cause flash fire.) (See Annex A1.)
8.1.2 n-Heptane. (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.) (See Annex A1.)
8.2 Quality Control Sample - A stable and homogeneous residual fuel oil having physical and chemical properties similar to those of typical sample fuels routinely tested.
