To ensure tight closure, and the valve seat valve sealing surface of the ground.

为了保证关闭严密，阀瓣与阀座密封面进行的研磨。

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To ensure tight closure, and the valve seat valve sealing surface of the ground.

为了保证关闭严密，阀瓣与阀座密封面进行的研磨。

youdao