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Home >Safety Standards - the same but different

Safety Standards - the same but different

02 March 2015

There have been many changes in safety standards in recent years, both to harmonise standards on an international level, and to update them to reflect modern automation practices. Andy Pye discusses some of the implications

EN ISO 12100 and the North American machinery safety standard ANSI B11.0-2010 and are similar in many ways, yet they also differ. While the ISO 12100 standard is geared more toward original equipment manufacturers (OEMs), ANSI B11.0 covers machinery safety and end user safety.

This means there may be some subtle terminology in ANSI B11.0 geared for end users that may not have a direct correlation with the ISO standards. Other than that, the risk assessment principals and requirements documentation are almost identical.

What this means is that should a builder design a machine to ANSI B11.0 and ships it to Europe or any non-North American country, it would, for all practical purposes, have met ISO 12100 or EN ISO 12100 requirements because of the harmonisation. And conversely, the same is true for machines built to ISO 12100 specifications before being shipped to North America. Both standards are globally recognised.

Control systems

Amongst sub-systems, for controllers, EN 954-1 was replaced at the end of 2011. This was because programmable electronic systems had overtaken it - for example, the time response (testing intervals, life cycles) and the failure probability of components were not considered. It was replaced by EN 13849-1 (safety of machines – safety-related parts of control systems, part 1: General design principles) and EN 62061 (safety of machines – functional safety of electrical, electronic and programmable electronic control systems).

EN 954-1 demanded a risk analysis with the resulting safety categories (B, 1, 2, 3, 4). B stands for low and almost no safety respectively, 4 stands for high safety. The safety devices for a system were chosen with the safety category.

With EN ISO 13849-1, a risk diagram was introduced. Instead of categories, where hierarchically graduated Performance Levels (PL) are defined. EN 62061 uses the "Safety Integrity Level” (SIL) to classify risks. This is a quantified measure for the safety-related performance of a safety function. The necessary SIL is determined according to the principle of risk assessment according to EN ISO 14121.

Now, EN ISO 13849 and IEC 62061 are themselves scheduled to merge into one global standard by IEC/ISO 17305, by 2016. For machinery and equipment suppliers (OEMs), preparing now will help them take advantage of advanced technologies and eliminate trade barriers.

"For OEMs, preparing now is easier than they might think, and it will help them build safer, higher performing and internationally competitive machinery while helping to take cost out of the multinational safety-compliance process," says Derek Jones, Functional Safety Engineer, TÜV Rheinland. "The adoption target of 2016 allows two years of transition to 2018, although the standards organisations may need additional time to finalise IEC/ISO 17305. The target date for completion is seen by some to be too optimistic and 2018 might be more realistic."

Type C Standards (Product-Specific)

Amongst the specialist standards for specific requirements on specific machines (Type C on Table 1), EN16500:2014 is a new set of safety standards designed to rigorously protect users through all operational aspects of a vertical baler. These standards cover all aspects of use including but not exclusive to the bale chamber, the bale ejection area, the controls actuators and devices, emergency stop systems, noise reduction, instruction manuals and labels and any other potential hazards a user could face.

Automation controllers

The principle of risk classification as embodied in the new standards is reflected in Siemens' new range of Simatic automation controllers.

There are four failsafe CPUs with different performance levels for supplementing the Simatic S7-1500 Advanced Controller: CPU 1517F is suitable for average to sophisticated safety applications, while the CPUs 1511F, 1513F and 1515F are designed for less complex tasks.

The first 1510SP F and 1512SP F CPUs with distributed controllers are also available. With the new SP1 version of the Step 7 Safety Advanced V13 engineering tool, which has been enhanced with additional failsafe functions, users can create programs using the same engineering and operating concept for both standard and safety-related tasks.