Previous investigation proposed the mechanical definition of plastic collapse for pressure vessel components as the turning point of the plastic strain increment ratio at the maximum stress point of the components. The applicability of the definition is confirmed for the small end and the large end of cone-cylinder junctions and for the practical tori-spherical head of SUS 304 material with actual geometrical change. Finally, collapse pressure determined practically by using pressure-deflection curve is proposed as the pressure at the 4 times the deflection of the first yield. The practical validity of the proposed determination method is verified by comparing with various proposed methods.