roll or drop-out是什么意思? The general procedure for line flushing and blowing is as follows: All instruments should be positively isolated from the lines. Wherever practical "roll" or "drop-out" all control valves to prevent pitting of the valve seats due to deposition of debris on the seat. 调节阀 有滚动或泄漏的 地方,应防止由于阀座上碎屑沉积而发生点蚀。 标红的地方该如何翻译?查看更多3个回答 . 1人已关注