The IEC61508 standard for safety-related systems that involve electrical.
electronic or programmable electronic devices this year superseded all
other conflicting national standards. To help users assess their process
safety and the design measures required to meet the new standard, ABB has
published a step-by-step wall chart explaining the key measures that must
be taken and how to implement them. There is also guidance on how to
carry out a hazard and risk analysis in order to determine appropriate
Safety Integrity Levels. The wall chart is free on application by email.