Abstract :
BS EN IEC 61511 provides the guidance to Control and Safety Integration and it states: ‘.....Wherever practicable, the safety instrumented functions should be separated from the non-safety instrumented functions.’ ‘.... the basic process control system shall be designed to be separate and independent to the extent that the functional integrity of the safety instrumented system is not compromised.’ ‘.... Adequate independence means that neither the failure of any non-safety functions nor the programming access to the non-safety software functions is capable of causing a dangerous failure of the safety instrumented function‘ If we want to share common items between the safety system and the basic process control system then can we? For new installations can we design for this? For existing installations (called ‘Legacy’ installations) this requirement has often neither been present nor covered properly.
