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.