Confused on safety and machinery control systems? Take this survey
Machinery controls have evolved from simple hard wired circuits to evermore complex hardware and software systems. Whenever machinery controls are used to reduce risk, they become what is known as “safety related parts of the control system” and the system reliability must be properly assessed. Determining just how reliable a safety circuit or system is demands a comprehensive approach. As safety PLCs replace relays, mechatronic actuators drive hazardous motion and software driven safety features like “safe speed” and “safe position” become prevalent, analyzing safety system reliability becomes a complex task indeed. When control systems fail to perform as expected, machines can move unexpectedly or not stop when expected – this can result in injuries to personnel or damage to equipment or products. The more complex the system(s), the greater the difficulty in identifying and preventing unintended consequences.
The standards writing community has tried to keep pace with the technological advances, and we have seen the now familiar “Category” system from EN 954-1(1996) evolve into the much debated ISO 13849-1 (2006) and IEC 62061 (2005). Adding to the confusion, the term “control reliability” has been used in the U.S. for several years but there has been confusion as to exactly what the term means.
In 2006, the latest revision of ISO 13849-1 introduced a probabilistic determination of potential control system failures. The 2006 standard intended to replace the categories of the 1999 version with newer “Performance Levels” as the metric used to discuss control systems. Yet a third methodology appears in IEC 62061 which uses “Safety Integrity Levels” (SILs), and applies only to electronic systems and tends to be used frequently in the processing industries.
In 2011, ISO Technical Committee 199 (responsible for the ISO 13849 standard) and IEC Technical Committee 44 (responsible for the IEC 62061 standard) formed a Joint Working Group (JWG) of ISO and IEC “experts” to evaluate developing a new standard for safety related control systems. One suggestion being considered is merging the contents of ISO 13849-1 and IEC 62061 to include the methods of PLs and/or SILs (one, the other, or both). Another suggestion is to create a yet another new method different from PLs and SILs to be used for control systems.
Such proposed changes can have significant impacts to the engineering development and use of machinery builders and end users. In an attempt to try to assess that impact, the JWG has developed a brief survey requesting that machinery builders and end users of machinery share their views on this topic. This is time-sensitive as the survey will close by end of August to allow the results to be compiled for discussion at a meeting scheduled for this September. This is your opportunity to impact the standards development work – let your voice be heard!
SAE holds international training event
SAE International held their Section Officer Leadership Seminar (SOLS) North American training conference this past month. SOLS brings volunteers from SAE International North American sections representing manufacturing, engineering, academia and workforce development together to hear from peers and colleagues about best practices to support more effective SAE sections. The members of these sections support regional, local Mobility Engineering industries in Aerospace, Automotive and Commercial Vehicles.
SOLS provided four main sessions. AMT’s Tim Shinbara led teams that provided content for two of the sessions: engaging membership (providing the value proposition to members and industry); and improving communications (applying the right message, at the right time, to the right audience).
If anyone is interested in learning more about the SOLS conference, please contact Tim at 703-827-5243.
Future B11 Standards meeting
– July 23-24, 2012 – Seattle, Wash. If you have an interest in participating in this meeting or would like more information, contact David Felinski at dfelinski@B11standards.org.