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Page 166

| In the case of large circuit breakers, contacts and arcing devices may be reached through a removable cover plate after sufficient oil has been drained to uncover them. |

| Oil. |

| The oil in a circuit breaker should be frequently checked to ascertain its condition and that of the breaker. The condition of the oil may be determined on the site by simple tests. Oil samples may be obtained through the drain valve at the bottom of the tank. If the oil shows signs of moisture, carbonization, or dirt, it should be filtered through a paper press or centrifuge before being put back in the tank. |

| The task of draining oil from circuit breaker tanks may be a long and cumbersome one since some of the larger circuit breakers may require thousands of gallons of oil. For smaller breakers, oil may be drained into drums or barrels; for larger breakers, oil may be drained into plastic storage bags of rather large dimensions or pumped into truck-mounted tanks such as those used for oil or gasoline deliveries (Fig. 9-8). |

| If there is evidence of carbon, the tank and other parts of the breaker, insulating barriers, partitions and spacers, lift-rods, and the like, should be washed down with clean hot oil under pressure and checked for cracks or deformities before the tank is refilled with clean filtered oil. |

| It is good practice to pass even new oil through filter presses before filling the circuit breakers. Oil levels in tanks should be maintained at proper |

| Figure 9-8 Portable plastic tank. |

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