单项选择题 For many years marine centrifuges were designed for （） operation, that is the machines were run for a period during which solids accumulated in the bowlThe machine was stopped when the accumulated solids began to impair its performance.

单项选择题 When a clarifier is running the impurities and water collect at the bowl （）.

单项选择题 A centrifuge arranged to separate impurities and small amounts of water from oil is known as （）.