6. Apparatus
6.1 Centrifuge Tube, cone-shaped, conforming to the dimensions given in Fig. 1, and made of thoroughly annealed glass. The graduations, numbered as shown in Fig. 1, shall be clear and distinct and the mouth constricted in shape for closure with a cork. Scale error tolerances and smallest graduations between various calibration marks are given in Table 1 and apply to calibrations made with air-free water at 20°C.
6.2 Centrifuge, meeting all safety requirements for normal use and capable of whirling two or more filled centrifuge tubes at a speed that can be controlled to give a relative centrifugal force (rcf) between 600 and 700 at the tips of the tubes. The revolving head, trunnion rings, and trunnion cups, including the rubber cushion, shall be soundly constructed to withstand the maximum centrifugal force capable of being delivered by the power source. The trunnion cups and cushions shall firmly support the tubes when the centrifuge is in motion. The centrifuge shall be enclosed by a metal shield or case strong enough to eliminate danger if any breakage occurs. Calculate the speed of the rotating head as follows:
where:
rcf = relative centrifugal force, and
d = diameter swing, mm, measured between tips of opposite tubes when in rotating position.
Table 2 shows the relationship between the diameter of swing, ref and rpm.
6.3 Oven, explosion-proof, capable of maintaining a temperature of 105 +/- 3°C.
6.4 Balance, having a sensitivity of 0.5 mg for weighing the 100-mL beaker and centrifuge tube, and a balance having a sensitivity of 0.1 g for weighing the oil sample.
7. Reagents and Solvents
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 water in accordance with Specification D1193, Type IV.
7.3 n–butyl diethanolamine (2,2- (butylimino) diethanol) (Warning - see Note 5).
7.4 Ethanol, denatured, (Warning - see Note 3) conforming to either Formula 30 or 3A of the US Bureau of Internal Revenue.
7.5 Pentane (Warning - see Note 4).
7.6 Propan-2-ol (isopropyl alcohol), (Warning - see Note 3).
7.7 Toluene (Warning - See Note 2).
NOTE 2 - Warning: Flammable. Vapor harmful.
7.8 Toluene-Alcohol Solution, wash solvent, made by mixing 1 volume of toluene (7.7) with 1 volume of denatured ethanol (Warning - See Note 3) conforming to either Formula No. 30 or 3A of the U.S. Bureau of Internal Revenue.
NOTE 3 - Warning: Flammable. Denatured. Cannot be made nontoxic.
NOTE 4 - Warning: Extremely flammable. Vapors may cause flash fires.
7.9 Pentane-Coagulant Solution - Add 50 mL of n-butyl diethanolamine (Warning - see Note 6) and 50 mL of isopropyl alcohol (2-propanol) (Warning - See Note 7) to 1 L of n-pentane ( Warning - See Note 5) and mix.
NOTE 5 - Warning: May be harmful if inhaled or swallowed.
NOTE 6 - Warning: Flammable.
8. Sampling
8.1 Obtain a sample using either Practice D4057 or D4177.
8.2 Heat the sample of used oil to 60 +/- 5°C in the original container and agitate until all sediment is homogeneously suspended in the oil (Note 2). If the original container is of opaque material, or if it is more than three-fourths full, transfer the entire sample to a clear glass bottle having a capacity at least one third greater than the volume of the sample, and transfer all traces of sediment from the original container to the bottle by violent agitation of portions of the sample in the original container. After complete suspension of all sediment, strain the sample or a convenient aliquot through a 150-µm (No. 100) sieve to remove large contaminating particles.
NOTE 7 - As used oil may change appreciably in storage, samples should be tested as soon as possible after removal from the lubricating system and the dates of sampling and testing should be noted.