IEC 61511-1:2016+A1:2017 gives requirements for the specification, design, installation, operation and maintenance of a safety instrumented system (SIS), so that it can be confidently entrusted to achieve or maintain a safe state of the process. IEC 61511-1 has been developed as a process sector implementation of IEC 61508:2010. The contents of the corrigendum of September 2016 have been included in this copy. This consolidated version consists of the second edition (2016) and its amendment 1 (2017). Therefore, no need to order amendment in addition to this publication.