Many machine designers think of interlocks as exclusively electrical devices; a switch is attached to a movable mechanical guard, and the switch is connected to the control system. Trapped Key Interlocking is a way to interlock guards that is equally effective, and often more appropriate in difficult environmental conditions. Continue reading “Trapped Key Interlocking”
During the Free Safety Talks that we did with Schmersal Canada and Franklin Empire, we had a “hot question” come up regarding Category 2 architecture and the testing interval requirement. In the short video below, Doug answers that question.
If you have more questions or felt something wasn’t clear in the video, leave us a comment and we will get back to you!
If you are having problems with developing your safety function, please get in touch with Doug directly.
 “The Bathtub Curve and Product Failure Behavior (Part 2 of 2)”, Weibull.com, 2018. [Online]. Available: http://www.weibull.com/hotwire/issue22/hottopics22.htm. [Accessed: 13- May- 2018].
 German Social Accident Insurance (DGUV) — Institute for Occupational Safety and Health (BGIA), “Functional safety of machine controls — Application of ISO 13849–1 — Report 2/2008e”, Institute for Occupational Safety and Health (BGIA), Sankt Augustin, DE, 2008.
 “Safety Circuit Examples of Safety Components | Technical Guide | Australia | Omron IA”, Omron.com.au, 2018. [Online]. Available: http://www.omron.com.au/service_support/technical_guide/safety_component/safety_circuit_example.asp. [Accessed: 14- May- 2018].
Reason #1 — Free Safety Talks
You can’t argue with Free Stuff! Last week we partnered with Schmersal Canada and Franklin Empire to put on three days of Free Safety Talks. We had full houses in all three locations, Windsor, London and Cambridge, with nearly 60 people participating.
We had two great presenters who helped people understand Pre-Start Health and Safety Reviews (PSRs) , CSA Z432-2016 , Interlocking Devices  and Fault Masking .
Franklin Empire provided us with some great facilities and breakfast to keep our minds working. Thanks, Franklin Empire and Ben Reid who organized all of the registrations!
Reason #2 — Understanding Interlocking Devices
Mr Kartik Vashi, CFSE, discussed the ISO Interlocking Device standard, ISO 14119. This standard provides readers with guidance in the selection and application of interlocking devices, including the four types of interlocking devices and the various coding options for each type. Did you know that ISO 14119 is also directly referenced in CSA Z432-16 ? That means this standard is applicable to machinery built and used in Canada as of 2016. If you don’t know what I’m talking about, you can contact Mr Vashi to get more information.
Reason #3 — Understanding Fault Masking
Mr Vashi also talked about fault masking, an important and often misunderstood situation that can occur when interlocking devices or other electromechanical devices, like emergency stop buttons, are daisy-chained into a single safety relay or safety input on a safety PLC. Mr Vashi drew from ISO/TR 24119 to help explain this phenomenon. If you don’t understand the impact that daisy-chaining interlocking devices can have on the reliability of your interlocking systems, Mr Vashi can help you get a handle on this topic.
Reason # 4 — Pre-Start Health and Safety Reviews
Mr Nix opened his presentation with a discussion of some commonly asked questions about Pre-Start Health and Safety Reviews (PSRs). There are many ways that people become confused about the WHY, WHAT, WHEN, WHERE, WHO and HOW of PSRs, and Mr Nix covered them all. This unique-to-Ontario process requires an employer to have machines, equipment, racking and processes reviewed by a Professional Engineer or another Qualified Person when certain circumstances exist (see O. Reg. 851, Section 7 Table). If you are confused by the PSR requirements, contact Mr Nix for help with your questions.
Reason #5 — Understanding the changes to CSA Z432
CSA Z432  was updated in 2016 with many changes. This much-needed update came after 12 years experience with the 2004 edition and many changes in machinery safety technology. Mr Nix briefly explored the many changes that were brought to Canadian machine builders in the new edition, including the many new references to ISO and IEC standards. These new references will help European machine builders get their products accepted in Canadian markets. Both Mr Vashi and Mr Nix sit on the CSA Technical Committee responsible for CSA Z432.
Reason #6 — Hot Questions
We like to over-deliver, so here’s the bonus reason!
We had some great questions posed by our attendees, two of which we are answering in video posts this week. If you have ever considered using a programmable safety system for lockout, our first video explains why this is not yet a possibility. Mr Nix gets into some of the reliability considerations behind the O.Reg. 851 Sections 75 and 76 and CSA Z460 requirements.
Mr Nix posted a second video discussing ISO 13849–1  Category 2 architecture requirements and particularly Testing Intervals. This video explains why it is not possible to meet the testing requirements using a purely electromechanical design solution.
A case in the UK illustrates the dangers of bypassing interlocking systems. A worker was killed by a conveyor system in a pre-cast concrete plant when he was working in an area normally protected by a key-exchange system. Here’s the link to the article on OHSOnline.com. Allowing workers into the danger zone of a machine without other effective risk reduction measures may be a death sentence.