5 For land based excavators to be used in removing wet material from small and narrow channels, which are not accessible to grab dredgers, tightly sealed closed grab excavators shall be used.
5 For land based excavators to be used in removing wet material from small and narrow channels, which are not accessible to grab dredgers, tightly sealed closed grab excavators shall be used.
当要清除细小而狭窄的水道内的湿物料时，因抓斗式挖泥机不能进入，便需使用地面挖土机，即密封式的抓斗挖土机。