Functional safety IEC 61508 / IEC 61511 the impact to certification and the user

The functional safety standards IEC 61508 "functional safety of electrical/electronic/programmable electronic safety related systems" and IEC 61511 "functional safety of safety instrumented systems for the process industry sector" have gained a widespread acceptance and are becoming daily practice in many countries and industries. Since their inception in the late 90\´s they have affected end users and system integrators as well as product manufacturers. For the first time, end users and system integrators have standards which are accepted worldwide and guide them throughout the safety life-cycle of their facilities. For product manufacturers the standard IEC 61508 provides a guideline for the design of safety related equipment. The purpose of this paper is to discuss practical experience concerning the use of the standards. Benefits and problems for manufacturers, users and certification agencies are discussed in relation to the approval, assessment and certification of safety-related equipment and systems. The paper address the use of reliability data, the need for measures and techniques for avoidance and control of failures, and the positive effects of having functional safety management and qualified engineers/experts in place. The paper also discuss the relation between IEC 61511 (specific to the process industry) and IEC 61508.