洗涤塔设备图上的这句英语怎么解释?

All internal except swirl plate and N9 shall pass through manhole OD I.D. 470mm 这句话怎么解释呢？ 紧接着下面一句是：swirl plate and N9 shall pass through column ID 3000mm 这pass through 怎么解释啊？