The Dow Chemical Company has written safety standards for critical instruments, which have been in effect for many years. Like many in the chemical industry, Dow's implementation of these standards has evolved into a Safety Instrumented Systems (SIS) approach. In 2000, Dow introduced Layers of Protection Analysis (LOPA) as the primary means of determining the need for and the integrity level of SIS. At that same time, Dow began to adopt globally the principles and methodology of industry standard IEC-61511 (later ISA S84-2004), even before it was finalized.

Dow first applied the industry standard to new projects. In 2002, as part of its overall process safety management strategy, Dow chose to use LOPA in its existing plants and to apply SIS protection layers as needed to manage risk. Applying new standards in existing plants and incorporating the “technology” of SIS for future projects in a way that is sustainable presents many challenges.

This paper describes how Dow has utilized Six Sigma methodology to implement SIS technology in new projects and existing plants. Specific areas of discussion will include tools, work processes, benchmarking, and organization.