第一部分 翻译

1)Spheres are normally used to separate one fluid from another in a pipeline, either during hydrostatic testing of the line or during operation.

2)Differential pressure required to move a pig or sphere through the pipeline overcomes the friction of the pig with the inside wall of the pipe.

3)Cleaning pigs are used in all types of pipelines to increase efficiency and avoid problems at pump or compressor stations that could result from the presence of unwanted materials.

第二部分 听力

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第三部分

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