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| of the emulsification that may have taken place. The second is a voltage breakdown test. In both tests, care should be exercised in taking the samples. The test receptacles should be rinsed first with some of the oil to be tested. The oil sample should be taken from the bottom, after the oil has been allowed to rest for a period of time. Several samples should be taken. |

| When using the color test set shown in Fig. 4-2, the oil sample is placed in the clear tube which is then inserted in the holder so that the oil may be viewed through the left center port. The circular color wheel is then inserted in the holder so that the rotation of the wheel permits the various colors on the wheel to be compared with the oil sample color at the right center port. When the color on the wheel is similar to the oil sample color, the numerical designation of the oil sample color appears in the port at the lower right side of the holder. |

| In the electric test using the portable dielectric test set shown in Fig. 4-3, the oil is tested between two, one-inch diameter circular electrodes set in a standard test cup. The electrodes are set, usually with a spacing between them of 0.1 (one-tenth) inch. The oil sample is put in the cup, rocked, and left to stand a few minutes to allow any bubbles that may have formed during the filling to dissipate. A voltage is applied and gradually raised until breakdown occurs. The process is repeated up to about five breakdowns for each cup of oil, and tests made on about 3 cups of oilfifteen readings in all. The breakdown values for good oil should never be less than 20,000 volts, and should average above that value. |

| Oil testing less than 20,000 volts should be removed from the tank and filtered through a paper press or a centrifuge before being put back in the tank. If there is evidence of sludge, the core, coils, and terminal board should be washed down with clean, hot oil under pressure, using the filter press pump and hose, before the tank is refilled with good clean filtered oil. |

| Figure 4-2 Oil color test set. |

| Figure 4-3 Typical portable dielectric test set. |

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