Application of standard IEC 62061 to a case study on hydraulic press

The standard IEC 62061 is a machine sector specification within the framework of IEC 61508. It is intended to facilitate the specification of the performance of safety-related electrical control systems in relation to the significant hazards of machines. Compliance with this standard provides one with means of conformity with the specified essential requirements given in Annex I of the EC Directive 2006/42/EC. This paper reports a case study on a press where an accident occurred. Through an appropriate risk analysis and reliability data a priority of interventions has been defined to reduce risks in the specific machine under investigation. The main target of the analysis was to test the applicability of most recent generation standards, that are not yet fully acquired by different industries, and to verify their effectiveness. A risk assessment was performed in order to verify the compliance with the essential requirements of the Machinery Directive 2006/42/EC. A risk assessment should include a look at each functional part in turn, making sure that every mode of operation and all phases of use are properly considered, including the human-machine interaction in relation to the identified functions or functional parts. For this reason the Hazard Identification approach (HazID) was chosen to investigate the criticalities of the bending tool. The HazId analysis was used as a support for the determination of the required Safety Integrity Level (SIL) of the safety-related functions that must be realized by a safety-related system. Once SIL has been assigned to Safety-Related Electrical Control System (SRECS), it was fundamental to calculate the SIL associated to that component and to verify if it is equal to the previously assigned SIL. This case study has shown that the performance of a safety instrumented system in the operational phase is influenced by many factors; not only by the system design and the related testing and maintenance strategies, but also by the operating conditions in the wider socio-technical system. For this reason it is important to account for the human factor in assigning integrity levels of safety systems (SIL) to the identified security functions.