GDHigh Vacuum Flapper Valve GD high vacuum flapper valve is used to put through or cut off the airflow in vacuum pipeline.是什么意思_GDHigh Vacuum Flapper Valve GD high vacuum flapper valve is used to put through or cut off the airflow in vacuum pipeline.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句