An attempt was made to define the safety grade of flanged connections according to target leakage rates described in domestic gasket standards and tightness rates of joints stated in PVRC of ASME.

The rules of measurement function for grade of target threat were established, evaluate matrix was defined to obtain multi-parameters unascertained measurement.

Based on fuzzy set theory target recognition method, through CCD image collection, the difference between target and bullet track gradation were used to evaluate the firing grade.