Abstract: Based on the engineering approximate relation. in reference 1,between tearing instability stress and plastic collapse stress under simple loading for circumferential throughwall crack of pipes, a new approximate relation between them under combined loading is established. By the new approximate relation, the engineering assessments for 4 materials and 40 crack configurations and loading status are carried out. The results are in agreements with those of precise analgtical method in reference 2. It is believed that the new engineering assessment method can certainly play an important role in LBB stability analysis for pressure vessels and pipes.