Control system: First, graded assessment, once a year for 15–20 years; once every six months for 20–25 years; principally scrapped over 25 years; Second, assessment content, structural safety, component life, safety devices, operation reliability; Third, hidden danger disposal, general hidden dangers rectified within time limit; serious hidden dangers suspended immediately; Fourth, approval process, for operation over 25 years, submit assessment report, renovation plan, insurance certificate, approved by provincial department; Fifth, accountability, fines of 50,000–200,000 yuan for operation without assessment or approval, pursue responsible person liability.