ASTM D4007 standard test method for water and sediment in crude oil
ASTM D4007 standard test method for water and sediment in crude oil by the centrifuge method (laboratory procedure)
9. Calculation
9.1 Record the final volume of water and sediment in each tube. If the difference between the two readings is greater than one subdivision on the centrifuge tube (see Table 1) or 0.025 mL for readings of 0.10 mL and below, the readings are inadmissible and the determination shall be repeated.
9.2 Express the sum of the two admissible readings as the percent by volume of water and sediment; report the results as shown in Table 2.
10. Precision
10.1 The precision of this method, as obtained by statistical examination of interlaboratory test results in the range from 0.01 to 1.0 %, is described in 10.1.1 and 10.1.2.
10.1.1 Repeatability - The difference between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
From 0.0 % to 0.3 % water, see Fig. 3.
From 0.3 % to 1.0 % water, repeatability is constant at 0.12.
10.1.2 Reproducibility - The difference between two single and independent test results obtained by different operators working in different laboratories on identical test material, would, in the long run, in the normal and correct operation of the test method, exceed the following value in only one case in twenty:
From 0.0 % to 0.3 % water, see Fig. 3.
From 0.3 % to 1.0 % water, reproducibility is constant at 0.28.
11. Keywords
11.1 centrifuge; centrifuge tube; crude oil; laboratory procedure; sampling; sediment and water; solvent
