Abstract: In order to improve the accuracy and instability of the test results of the complicated on-line checking and judging process of safety valve, we studied the operation principle of the on-line checking method and process of safety valve.Proposed a new on-line checking method named “valve displacement method”, and obtain the theoretical formula of “valve displacement method” by calculation and deduction.The experimental results show that the “valve displacement method” is feasible as on-line checking method of the safety valve, and improves the accuracy and stability of the test results while simplifying the on-line checking process.

Key words: safety valve, on-line calibration, valve displacement