The industrial manufacturing environment is constantly evolving – driven by the need to achieve a competitive edge.
Derek Jones, manager safety business development, Rockwell Automation, discusses the apparent lack of evolution of the accompanying safety standards.
One of the most decisive factors for success is the automation of machinery and processes to facilitate powerful, flexible and reliable operation. This requires the intensive use of complex, programmable technologies linked through communication networks to faster, accurate and powerful actuators.
What has changed?
“It was realised some time ago that the standards that deal with the safety of machinery had not kept pace with developments in the automation of machinery,” says Jones. In order to help provide both the safety and productivity of contemporary machinery, safety related control systems themselves often need to use complex and programmable technologies. Machinery safety related control system standards, such as EN 954-1 (ISO 13849-1: 1999), have served us well for many years, but are now too simplistic to cope with the technology. This means a change to the familiar system of ‘Categories’.
There are two new-generation standards for machine safety related control systems, IEC/EN 62061 and EN ISO 13849-1:2008, both of which can be used to show conformity with the European Machinery Directive. They both have new system classifications: IEC/EN 62061 uses Safety Integrity Level (SIL) and EN ISO 13849-1 uses Performance Level (PL). SIL and PL can be said to be variations on the same theme and the decision on which standard to use is governed by what is best for an application. In general terms, if familiar with the use of the EN 954-1 Categories and using relatively straightforward conventional safety functions, then EN ISO 13849-1 (PLs) is probably better.
“If you are specifically required to use SIL, or if your application uses complex multiconditional safety functionality, then EN/IEC 62061 may be the most suitable. Note that EN ISO 13849-1 covers all technologies, whereas EN/IEC 62061 only covers electrical-based systems,” says Jones.
Where to now?
The ideal first step is for engineers to read both standards in order to understand their requirements and implications. Perhaps the most daunting aspect of both standards is the fact that they require some calculations based on reliability data that the safety component manufacturers should supply. Help is at hand in the form of software tools for the calculation. The BGIA in Germany provides a comprehensive calculation tool for EN ISO 13849-1 called SISTEMA. It is available for free on the BGIA website.
“A link to the SISTEMA tool is available through the Rockwell Automation website where you can also register and download free the Rockwell Automation product ‘data library’ for use in the SISTEMA tool,” notes Jones.
For EN/IEC 62061, TUV Rheinland is coordinating the production of a calculation tool which should be available in 2009. Both of these tools have the advantage of the credibility of experience and commercial independence.
For more information contact Jeff Sandison, Rockwell Automation, +27 (0)11 654 9700, [email protected], www.rockwellautomation.co.za
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