This paper will discuss how systematic safety assessments should be performed at regular intervals in operating plants and also when changes in operating procedures or configuration is implemented. For illustration, this paper will describe one of several possible ways to perform a safety audit in accordance with IEC 61511 in a running plant. Finally some case stories are presented showing learning points that were found after Hazard and Operability Study (HAZOP) and Safety Integrity Level (SIL) analysis at the Geleen ammonia facilities of Orascom Construction Industries.