A chemical plant cracking furnace induced draft fan using a traditional lip seal, oil seal and fan shaft wear each other in the work of the oil seal damage, harmful substances in the atmosphere such as dust, water leakage into the bearing box, causing premature grease failure, accelerated bearing The wear reduces the service life of the bearing. According to the actual needs of the development of bearing protection device to replace the traditional oil seal, do not wear the rotor, sealing effect is good, after application can be quickly installed without dismantling equipment, prolong bearing life, improve maintenance efficiency, and achieved a good transformation effect