Abstract: Based on the characteristic analysis results and the concept of inherent safety, a hierarchical supervision route is systematically established for pressure vessels that have reached their design service life (over-limit vessels for short). The route consists of pre-assessment screening→safety assessment→alteration of usage registration→risk assessment→risk level assignment→classified supervision. Concurrently, four sufficient conditions for over-limit vessels to enter the safety assessment procedure are defined. For typical scenarios that may arise after safety assessment, this paper adopts the risk matrix method and establishes a risk assessment model for over-limit vessels, thereby achieving quantitative evaluation of risk levels under different operating conditions. And based on the assessment results, differentiated supervision strategies are proposed for over-limit vessels with distinct risk levels. The proposed supervision route and strategies can provide systematic references and practical foundations for safety supervision and risk management of over-limit pressure vessels.

Key words: over-limit pressure vessel, safety assessment, risk level, supervision strategies