Are Safety Categories Obsolete?

Have you heard that Safety Categories are a thing of the past? That changing international standards have rendered Safety Categories redundant since the start of 2012? And that all new safety control systems for machinery must be designed to Performance Levels (PL) or Safety Integrity Levels (SIL)?

If so, here is some more information on the matter:

Yes, international standards have now moved to probabilistic methods, with two current standards as the options:
  1. IEC 62061 – Highly mathematical method where safety control systems are designed to a Safety Integrity Level (SIL)
  2. ISO 13849.1 2008 – Method based on the architecture of Safety Categories where safety control systems are designed to a Performance Level (PL)
However, Australian Standard AS 4024.1501 is a current machine safety standard where safety control systems can be designed to a Safety Category. So if you are comfortable using Safety Categories, you can continue to use this standard.

It is true that AS 4024.1 will eventually be updated to reflect current international standards, but AS 4024.1501 will remain unchanged for at least the next 3-4 years.

In my opinion, for simple safety systems, (i.e. systems using devices such as safety relays), Safety Categories is a good option that will result in a high level of integrity. If software is being designed, I would recommend following the software lifecycles available in IEC/AS 62061 or ISO 13849.1.
However, be aware that at some stage in the future our Australian Standards will transition to these probabilistic methods, but not in the immediate future.

Published: 4 April 2013