Abstract: A device for fixing an external part to a shaft, which clam a boll and roller bearing by a washer and a nut. The washer is provided with a plurality of projecting engageable pawls on the outer periphery thereof and a projecting tongue piece on the inner periphery thereof. This tongue piece is inserted into an engageable groove formed in an externally threaded portion of the shaft. The nut has engageable grooves for receiving the engageable pawls of the washer, on the outer periphery thereof. This nut is threadably coupled onto the externally threaded portion of the shaft, thereby the ball and roller bearing is clamped interposing the washer between the bearing and the nut. The tongue piece of the washer is formed in such a manner that, out of the opposite ends in the circumferential direction of the tongue piece, at least the forward end in a direction of rotation of fastening the nut is positioned on the center line or thereabout of the engageable pawl. The shaft may be a hollow shaft.

Abstract: A bubble cap assembly is provided with keyways and a special keyed lock washer with locking tabs to securely fasten the bubble cap during operation in a reactor. The unique arrangement also accommodates simple removal for easy maintenance and decoking without damaging the bubble cap assembly.