Machine builders, integrators get help with machinery directive update
Effective January 1, 2012, machine builders and integrators must use EN ISO 13849-1:2008 to prove presumption of conformity with the Machinery Directive. On January 1, 2012, EN 954-1:1996 and EN ISO 13849-1:1999 may no longer be used for this purpose. Omron STI has reportedly made their resources available to help machine builders and integrators successfully make the transition.
“ISO 13849-1 is the most important standard for regulating the basic principles and performance required of a safety control system for machines and devices. The 2006 revision to this standard are causing major changes to the fundamentals of safety system design, and machine builders and integrators will need to be using this standard as the baseline to prove conformity with the machinery directive by January 1, 2012,” said Frank Webster, vice president standards development, Omron STI. Webster is a member of Working Groups for Machine Safety in IEC/TC44 and ISO/TC199 and is the Convener of IEC/TC44/WG10 developing a new set of standards for Vision Based Protective Devices.
Background: Risk reduction
In considering safety protection and measures to reduce machine risks, it has long been common practice to evaluate levels of risk reduction and the performance of a safety-related parts of control system in terms of Categories as specified in the international standard ISO 13849-1:1999 (based on the European standard EN 954-1). The latest version of ISO 13849-1:2006 combines the straightforward deterministic features of EN 954-1’s Categories with IEC 62061’s probabilistic and systematic design consideration (a reliability model). This means that the revised version of ISO 13849-1 selects the architecture models in IEC 62061 that match the definitions of the Categories, and applies reliability models. This version can be called a functional safety standard in its simplified version.
“The question is whether or not this is a correct concept considering that every machine can fail at some future time. The components comprising the safety control system will also deteriorate and can fail at some future time, so it is important to figure out the mode in which the system will encounter a failure at such times,” explained Webster.
When a machine experiences a failure that causes the expected safety function to fail, if the failure is not detected it is equal to non-performance of safety functions. But definitions only based upon deterministic theory cannot cover such time related elements.
Omron STI’s Future Safety Design manual
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– Edited by Chris Vavra, Control Engineering, www.controleng.com