EXPERIENCES WITH THE APPLICATION OF IEC 61511 IN THE PROCESS INDUSTRY IN AUSTRIA

Within this paper different approaches of handling the requirements of IEC 61511 (starting from risk analysis up to the Safety Integrity Level (SIL) verification) are discussed. If pressure equipment is protected against exceeding the design limits (pressure, temperature) by means of a Safety Instrumented Function (SIF), this SIF has to undergo a conformity assessment procedure according to the PED. The corresponding requirements of TUV Austria, acting as a notified body for pressure equipment, on the risk analysis resulting in SIL classification of such SIF are given. Due to a lack of acceptance of semi-quantitative methods in risk analysis of some Austrian authorities, the risk graph as given in IEC 61511-3 Annex E is sometimes required, whereby other approaches seem to be much more comprehensible. Regarding explosion protection issues, an overview of the SIF requirements for ignition protection of non-electrical equipment and safety devices used for the control of ignition hazards is given. Furthermore, a concept for handling primary explosion protection in SIL classification is proposed. Many vendors of equipment used in SIF do not have SIL certificates, PFD/PFH-values, SFF values, etc. available since often the components are unique, specially designed or purely mechanical devices. Thus, alternatives proving an equivalent level of safety of a SIF, or using B10-values for pneumatic and electro-mechanical components may be used in such cases. Finally some practical recommendations on SIF component selection and signal transmission are presented.