Can IEC 61131 graphical languages be used for safety related PLC applications?

This paper reviews whether the IEC standards for PLC software (IEC 61131) and function blocks (IEC 61499) can be applied to the development of software for safety-related systems. The paper both outlines benefits from using these standards and highlights some shortcomings. The paper first considers the use of IEC 61131-compliant PLCs for safety-critical applications, reviews how it may be possible for graphical programs to be independently verified and then finally reviews the potential impact of the new function block standard IEC 61499.