Typical blast walls of offshore platform are stainless steel light-weight walls installed to contain the effect of an accidental explosion on the topside of an offshore installation. These walls are mostly designed using simplified analytical techniques like single degree of freedom (SDOF) method using global deformation or displacement as primary response parameter. Thin plate structures like stainless steel blast walls when subjected to high impulsive pressure loads, may damage severely in a particular region without experiencing a significant global deformation. This study presents realistic responses of offshore blast walls under various high impulsive pressure loads generated from accidental hydrocarbon explosions by using detailed non-linear finite element analysis (NFEA). The numerical models were verified against past experimental study on similar metal blast panels. An extensive parametric study was conducted using the verified finite element models to construct pressure-impulse (P-I) diagrams for different deformation levels. These P-I curves or iso-damage lines can be used as a quick assessment tool to determine possible level of damage of similar offshore blast walls due to different high impulsive pressure loading caused from different explosion scenarios. © 2016 The Authors.