Functional Safety: Separation or Integration

There are different safety instrumented systems (SIS) and basic process control systems (BPCS) architectures available on the market. Integrated or separate functional safety systems are available from different suppliers in various form factors. In the past, there were always good reasons to keep SIS and BPCS separate and autonomous. Today, in the age of organized cybercrime attacks on industrial plants, this is becoming even more important.

Functional Safety Management defines all activities required during the functional safety lifecycle phases. As an operator, it is difficult to identify the shared components of an integrated safety system properly without external help. The fact that the operator must rely on external support complicates the compliance verification process.

The objective of functional safety is to reduce risks to an acceptable level to protect people, environment, and facilities. The objective of security is to protect operations from any possible negative influences. Current standards, such as IEC 61511 (safety) and IEC 62443 (security), provide a foundation for safety in the process industries and specify the separation of SIS and BPCS. In considering whether functional safety principles can be applied to security, both standards demand a sufficient segregation between protection layers. Each stipulates independence of control and safety, separation of technical and management responsibilities, and reduction of common-cause failures.

The White Paper “Secure Functional Safety: Why Separation or Integration is no Longer a Question” by ARC’s Thomas Menze explains the various architectures for functional safety solutions and describes why separation matters and how separate safety systems satisfy the requirements of industry standards and discuss the advantages of air-gapped and interfaced BPCS and SIS architectures. It also discusses automation security challenges faced by the process industry today. Thomas Menze concludes, “SIS operators are responsible for regularly proving the effectiveness of the protective measures. Fewer shared components (BPCS - SIS) simplify and accelerate this process.”

The ARC White Paper “Secure Functional Safety: Why Separation or Integration is no Longer a Question” can be downloaded here.