System problems. According to official website information of Changyi Sanding Safety Education and Training Center, the online training of Changyi Sanding Safety Education and Training Center has 12 class hours. The reason why Changyi Sanding Safety Education and Training Center has no class hours is a system problem, and we just need to wait for the system update. Changyi Sanding Safety Education and Training Center has strong teachers, first-class teaching team and teaching level, good teaching quality and strict management. Deeply trusted and favored by students and parents.