The leakage factors of the bolted flanged connections were analyzed systematically and studied experimentally. The experimental system of sealing characteristics of bolted flanged connections was designed and constructed to study the influences of bolt loading method

preload and number of bolts on the sealing characteristics of flange connection. The results show that the loading method of JIS B 2251 can obtain more uniform preload

the gas leakage lasts longer than other methods up to 600s

and the workload is smaller; increasing the preload can increase the duration of the pressure drop

from 400s of 6.0kN to 540s of 7.5kN and 650s of 9.0kN. The increase in the number of bolts makes the leakage rate of the t=0 moment drop from 2.6cm3/s to 1.7cm3/s

thereby improving the sealing performance of the experimental piece. This study can provide a reference for the sealing characteristic analysis and structural design of bolted flanged connections.