ASTM D5002 for density and relative density of crude oils by digital density analyzer
6. Apparatus
6.1 Digital Density Analyzer - A digital analyzer consisting of a U-shaped, oscillating sample tube and a system for electronic excitation, frequency counting, and display. The analyzer must accommodate the accurate measurement of the sample temperature during measurement or must control the sample temperature as described in 6.2 and 6.5. The instrument shall be capable of meeting the precision requirements described in Test Method D4052.
6.2 Circulating Constant-Temperature Bath, capable of maintaining the temperature of the circulating liquid constant to more or less 0.05°C in the desired range. Temperature control can be maintained as part of the density analyzer instrument package.
6.3 Syringes, at least 2 mL in volume with a tip or an adapter tip that will fit the inlet of the density analyzer.
6.4 Flow-Through or Pressure Adapter, for use as an alternative means of introducing the sample into the density meter.
6.5 Thermometer, calibrated and graduated to 0.1°C, and a thermometer holder that can be attached to the instrument for setting and observing the test temperature. In calibrating the thermometer, the ice point and bore corrections should be estimated to the nearest 0.05°C. Precise setting and control of the test temperature in the sample tube is extremely important. An error of 0.1°C can result in a change in density of one in the fourth significant figure.
7. Reagents and Materials
7.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated it is intended that all reagents shall 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.
7.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type II of Specification D1193.
7.3 Water, redistilled, freshly boiled and cooled reagent water for use as a primary calibration standard.
7.4 Acetone, for flushing and drying the sample tube. (Warning - Extremely flammable.)
7.5 Petroleum Naphtha, for flushing viscous petroleum samples from the sample tube. (Warning - Extremely flammable.)
NOTE 1 - Suitable solvent naphthas are marketed under various designations such as "petroleum ether", "ligroine", or "precipitation naphtha".
7.6 n-Nonane, n-tridecane or cyclohexane, 99 % purity or better, or similar pure material for which the density is known precisely from literature references or by direct determination in accordance with Test Method D941 or D1217. (Warning - Extremely flammable.)
8. Sampling, Test Specimens, and Test Units
8.1 Sampling is defined as all the steps required to obtain an aliquot of the contents of any pipe, tank or other system, and to place the sample into the laboratory test container. The laboratory test container and sample volume shall be of sufficient dimensions to allow mixing as described in 8.3.1. Mixing is required to obtain a homogeneous sample for analysis.
8.2 Laboratory Sample - Use only representative samples obtained as specified in Practices D4057 or D4177 for this test method.
8.3 Test Specimen - The aliquot of sample obtained from the laboratory sample and delivered to the density analyzer sample tube. The test specimen is obtained as follows:
8.3.1 Mix the sample of crude oil to homogenize any sediment and water present. The mixing may be accomplished as described in Practice D4177 or Test Method D4377. Mixing at room temperature in an open container can result in the loss of light ends, so mixing in closed, pressurized containers or at sub-ambient temperatures is recommended.
8.3.2 Draw the test specimen from a properly mixed laboratory sample using an appropriate syringe. Alternatively, if the proper density analyzer attachments and connecting tubes are used then the test specimen can be delivered directly to the analyzer's sample tube from the mixing container.
