Early consideration of risk and safety results in permanent and fundamental impacts on the reliability of processing plants. Integration of safety assessment into process design provides the opportunity to take preventive and proactive actions to eliminate possible hazards. The authors introduce a novel measure for risk and safety assessment based on Petri net modelling tool. This integrated approach relies on limited data which is available in the initial design phase and in the mean time the results are accurate to an extent to be usable as decision-making factors. Simplicity and flexibility are tow outstanding features which make this framework an applicable solution for industries.