The fan was usually controlled by hand in the small cement grinding station; the required air of the bill was regulated by adjusting the fan opening value, which wasted a mount of electric energy.

在小型水泥粉磨站中，风机通常采用人工手动进行控制，即手动调节风机阀门开度来调节球磨机的需风量，此种控制方式造成了电能被大量的损耗。

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