The bearing isolator is a permanent bearing protection device. It consists of a moving ring and a static ring. The two parts are combined into a whole, so the two parts will not be separated in operation. The moving ring rotates with the shaft, and the static ring is pressed into the bearing box for fixation. The dynamic ring and the static ring cooperate with each other to prevent foreign matters from entering the bearing box and the leakage of lubricating medium. The bearing isolator with the best performance is made of metal, usually copper, which combines the vapor blocking function to prevent the external water vapor from entering the bearing box when the equipment is stopped for cooling.