The rotary union housing is fitted over the fluid conduit. The bearing, composed of two sealing skeletons, is mounted on the shaft formed by the rotary union housing via upper and lower clips. The rotary union housing and the outer wall of the fluid conduit are respectively fitted with an internal spline and an external thread to match. A locking nut is placed at the top of the rotary union housing, threaded onto the external thread of the fluid conduit, securing the housing in one position on the conduit. The skeleton sealing sleeve is inserted into the fluid conduit. 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 ascent of the liquid abrasive along the outer wall of the fluid conduit.