HAZOP and SEQHAZ® methods as input data producers to Safety Integrity Level evaluations

Abstract: Today hazard studies are a self evident part of a project plan while creating a new process or making changes in an existing one in the chemical industry. Therefore it is important to make the hazard studies as efficient as possible. The objective for this thesis was to optimise the hazard study processes based on the main methods presently used at Neste Oil Oyj, Neste Jacobs Oy and Borealis Polymers Oy. This thesis focuses on SEQHAZ® and HAZOP methods as input data for safety integrity level (SIL) evaluation with risk graph and LOPA (layer of protection analysis) methods. The hazard study process has been investigated by interviews, participation in hazard studies, studying of hazard reports and a seminar day. Based on the results three models for optimising the process are suggested, two based on LOPA and the third based on risk graph. LOPA was found to be the best method for SIL evaluation and the suggested models are a step towards performing both the HAZOP/SEQHAZ® study and the SIL evaluation in the same session.