ASTM D4807 Standard Test Method for Sediment in Crude Oil by Membrane Filtration
5. Apparatus
5.1 Reservoir and Filter Support Assembly - an assembly designed to hold 47-mm diameter filters was used in the development of this test method (see Fig. 1).
5.1.1 Filter Reservoir - capable of holding from about 250 mL of solvent. The lower part of the reservoir has a 40-mm inside diameter and is designed to secure the 47-mm diameter filter against the filter support. The reservoir can be jacketed to facilitate heating the reservoir and sample during filtering.
NOTE 1 - Use of a glass reservoir should minimize the effect of static electricity when filtering.
5.1.2 Filter Support/Funnel - support base for the filter has a porous scintered glass center section about 40 to 43 mm in diameter. The support base is designed to fit securely against the reservoir holding the filter in place over the porous section. The stem of the funnel portion should be long enough to extend down into the filter flask such that the end is below the outlet for the vacuum.
5.1.3 Clamp Assembly - spring or screw type clamp to secure the reservoir to the filter support. The clamp should be tight enough to prevent the solvent from leaking through at the junction between the glass and filter membrane. The exterior dimensions of the reservoir and support/funnel are designed to facilitate clamping the two pieces together.
5.1.4 Rubber Stopper - a single-hole, capable of holding the lower stem of the filter support/funnel securely onto the filtering flask.
5.1.5 Vacuum Filtering Flask, 500 mL or larger.
5.2 Membrane Filter, nylon membrane filter, 47 mm in diameter with 0.45-µm pore size.
5.3 Oven, capable of maintaining a temperature of 105 +/- 2°C.
5.4 Vacuum Pump, capable of reducing and maintaining the pressure at 200 mm Hg (-80 KPA) during the filtering.
5.5 Analytical Balance, capable of measuring to the nearest 0.0001 g.
5.6 Heating Coil for Filter Assembly - copper tubing (1/8-in. diameter) wound around the reservoir on the filter apparatus and connected to a circulating bath to maintain the oil in the reservoir at 90 +/- 2°C (see Fig. 1). Alternative methods of heating the reservoir such as heating tape or glass thermal jacket could also be used.
5.7 Mixer - a nonaerating, high-speed mixer capable of meeting the homogenization efficiency test in Annex A1. Large volume dynamic mixing systems such as those used with automatic crude oil sampling receptacles are also acceptable providing they comply with Annex A1.
6. Reagents
6.1 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.
6.2 Toluene (Warning, Flammable).
NOTE 2 - Warning: Flammable.
7. Sampling, Test Specimens
7.1 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 and volume to allow mixing as described in 7.3.1. Mixing is required to properly disperse sediment as well as any water present in the sample.
7.2 Laboratory Sample - Use only representative samples obtained as specified in Practice D4057 or D4177 for this test method. Analyze samples within two weeks after taking the sample. Retaining samples longer may affect the results.
7.3 Test Samples - The following sample handling procedure shall apply.
7.3.1 Mix the test sample of crude oil at room temperature in the original container immediately (within 15 min) before analysis to ensure complete homogeneity. A test sample drawn directly from a large volume dynamic mixing system analyze within 15 min or else remix as follows:
NOTE 3 - Analysis should follow mixing as soon as possible. The 15-min interval mentioned above is a general guideline which may not apply to all crudes, especially some light crudes which do not hold water in suspension for even this short a time.
7.3.2 Mixing of the sample should not increase the temperature of the sample more than 10°C, or a loss of water may occur and this affects sample composition. The type of mixer depends on the quantity of crude. Before any unknown mixer is used, the specifications for the homogenization test, Annex A, must be met. The mixer must be re-evaluated following any changes in the type of crude, quantity of crude, or shape of the sample container.
7.3.3 For small test sample volumes, 50 to 300 mL, a nonaerating, high-speed, shear mixer is required. Use the mixing time, mixing speed, and height above the bottom of the container found to be satisfactory in Annex A1. Clean and dry the mixer between samples.
