The rotating union housing is mounted on the fluid passage tube. The bearing, consisting of two sealed skeletons, is installed on the shaft formed by the rotating union housing via upper and lower clips. The rotating union housing has an internal thread and an external thread that match the outer wall of the fluid passage tube, respectively. A locking nut is mounted at the top of the rotating union housing, threaded onto the external thread of the fluid passage tube, securing the rotating union housing in one position on the tube. The skeleton seal is housed within the fluid passage tube. A layer of oil film provides lubrication and sealing. When air and liquid abrasive rise to the liquid surface, the air layer is compressed, hindering the upward climb of the liquid abrasive along the outer wall of the fluid passage tube.