ASTM D96 Water and Sediment in Crude Oil by Centrifuge Method (Field Procedure)
9. Calculation and Report
9.1 Compare the readings of the two tubes. If the difference between the two readings is greater than one subdivision on the centrifuge tube (see Table 2 or 3) or 0.025 mL (0.05 % for 200-part tubes) for readings of 0.10 mL (0.20 % for 200-part tubes) and below, the readings are inadmissible and the determination shall be repeated.
9.2 If tubes graduated in 100 mL have been used for the determination, record the sum of the final volumes of sediment and water in each tube obtained, as specified in Section 8, and report this sum as the percentage of sediment and water (see Fig. 3 for reading and reporting sediment and water when using 100-mL cone-shaped centrifuge tubes). Report the results as shown in Table 6.
9.3 If direct-reading 200-part tubes have been used for the determination, the percentage of sediment and water is the average, to three decimal places, of the values read directly from the two tubes. The percentage can only be read directly from a 200-part tube if the tube contains 50 mL or 100 parts of oil.
9.4 If the volume of oil is greater or less than 50 mL, or 100 parts, calculate the percentage of sediment and water as follows:
Sediment and water, percent = (S/V) x 100
where:
S = volume of sediment and water, mL or parts and
V = volume of oil tested, mL or parts.
For example, if the total volume of oil tested (V) is 20 mL and the volume of sediment and water (S) is 0.15 mL:
Sediment and water, % = (0.15/20) x 100 = 0.75
9.5 If the test conditions outlined in Section 6 are not followed exactly, the following must also be reported:
9.5.1 The solvent used and the water saturation temperature.
9.5.2 The type and amount of demulsifier (if used).
9.5.3 The temperatures of the sample and solvent, the preheater temperature, the centrifuge temperature, and the temperature of the final mixture after centrifuging.
9.5.4 The number of samples or tubes used in the determination.
10. Precision and Bias
10.1 Precision - The precision of this test method is being determined.
10.2 Bias - Since there is no accepted reference material suitable for determining the bias, no statement about bias is being made.
11. Keywords
11.1 centrifuge; centrifuge tube; crude oil; field procedure; sampling; sediment and water; solvent
