The standards have provided an international referee that has given process plant managers the confidence that safety and control can run on the same platform without danger of either system corrupting the needs of the other.
IEC 61508 dates back a decade, while IEC 61511 was developed in the last three or four years. Simply put, IEC 61508 governs safety technology, while IEC 61511 dictates its use. “One regulation directs new technology and another directs implementation,” explains Duncan Schleiss, vice president of process systems for Emerson Process Management, in Austin, Texas. IEC 61508 defines the requirements that suppliers must meet for all process safety equipment. IEC 61511, which has been effective since 2002, presents the functional require-ments that end-users must meet in planning, implementing and maintaining a SIS [Safety Instrumented System], including risk analysis, performance-based design, operations and maintenance.”
Though the IEC standards are not compulsory by law, there is a continuing trend toward holding organization leaders responsible for operations management. The 2002 Sarbanes-Oxley Act governing conduct of corporate management is a clear example. Some believe responsible management can legally extend to the adoption of widely held industry standards. Thus, the IEC standards may as well be law. “In discussion with our North American and European customers, we are seeing the trend of personal liability,” says Schleiss. “A company used to be able to choose to follow certain standards or not. But with the current litigious society, plant managers are becoming more exposed than before to personal liability.” Thus, following IEC 61511 reduces risk to a level that management deems tolerable.