Cableless (wireless) operator panels for machine applications, in my opinion, need special application considerations for appropriate and safe use. True, we often talk about how a wireless field bus and a wired field bus have many similarities. Even when they are safety certified for functional safety applications they continue to have many similarities.
Wireless operator panels (including cableless) for machine applications have been steadily growing over the past several years. The early versions of these portable operator panels were cabled for power and control/communication which limited their range via the length of the cable. The concept was for a panel builder or engineering group to design and build a conventional operator panel but that it needed to be portable and still conform to the same industry standards and regulations as fixed operator panels.
Machine Safety and “cableless” vs “wireless” has been an ongoing discussion over the past two years as this technology rapidly travels through its evolution cycles to the plant floor. Personally, I’ve sat in a dozen discussions over these two terms and how to choose a word that best describes the application as well as the issues. To wrestle this one to the ground it’s my recommendation that we choose an application like - cableless pendant control.
Machine Safety and Cableless Operator Stations with Safety! Did I just say all of that in the same sentence? Is this Doctor Spoc in Star Trek or is it the 21st Century? Well, beam me up Scotty because my radar screen sees something on the horizon. For several years now we’ve seen applications of safety functions being performed in machine architectures using safety certified and listed products where portions of the safety certified communications bus is wireless. So, does it make common sense that a natural migration of innovation would provide cableless operator stations with safety functions as added functionality?Cabled pendants in robot cells have been used for years and several years ago they evolved to cableless (meaning they have their own power source).
EN ISO 13849-1: 2006 was approved on or about October 2006 and simultaneously it was announced that EN 954-1: 1996 would cease to be an active standard at the end of 2008. Effectively this provided a two year period for industry (primarily in Europe) to transition to the new and incremental requirements of EN ISO 13849-1: 2006 for conformance to the Machinery Directive. Since then, the cessation of EN 954-1: 1996 has been extended twice and is currently scheduled for December of 2011.
In the world of machine safety it is commonly understood today that a risk analysis is required by the supplier and/or end user to identify and mitigate all hazards to acceptable levels. We get numerous questions on this process around the question of how to address the intent of the term “reasonably foreseeable misuse”? This term is actually defined in ANSI B11 - 2008, approved August 4, 2008 on page 16, clause 3.58 as: “reasonably foreseeable misuse: The use of a machine in a way not intended by the supplier or user, but which may result from readily predictable human behavior.” Furthermore, one can also find in Wikipedia a very thorough discussion with legal slant : https://en.wikipedia.org/wiki/Negligence. However, in the machine tool industry it mostly has to do with human behavior and applying thought to predicting certain possible actions. Quite commonly the life cycle of a machine is taken into account in identifying tasks and hazards as part of the risk assessment process because hazards not identified can create substantial unknown risks. The standards also say that reasonably foreseeable hazards that are not related to tasks shall also be identified. Some given examples often include “explosive environments, noise, instability, equipment failures or operational errors such as using an inappropriately sized workpiece, mechanical failure of a chuck, operating at incorrect speed, etc.” In addressing questions like this - [what is the intent of the term “reasonable foreseeable misuse?”] - my advice is always: Look up the term in several US machine tool standards Research the term on the internet Remember - interpretation is almost always required Some additional background information can be found at the following links: https://www.productsafetyletter.com/news/5569-1.html Before sale of a new product, every manufacturer should engage in a risk assessment of its product.
Residual risk is a term used for the past several years referring to a level of risk for a given hazard after applying protective measures (risk reduction measures). ANSI B11.TR3; 2000, ANSI B11 - 2008, ANSI / ISO 12100-1:2007, ISO 14121:2007, …..to mention a few, all tend to be harmonized on this definition. However, tolerable risk and acceptable risk are two additional terms also in the mix.
EN ISO 13849-1; 2006 is definitely on its way to US industry. It’s also true that there have been several delays for required compliance caused by extensions in Europe that have slowed broad acceptance here in the US. Last week in this blog I talked about the various segments of industry and what drives behavior to adopt or comply with safety standards. For example, don’t hold your breath for OSHA to enforce compliance to this International Standard any time this century.
Machine safety standards abound here in the US. And of course we also have OSHA regulations which form the basis for Federal enforcement. Book shelves are loaded with books and publications with the single theme of addressing these two sentences. We also have employee injuries & insurance companies, productivity & operating efficiencies, the legal thing, and just plain “Best Practices”….to mention a few. With all that said and for any company in the US, what drives domestic machine safety behavior? Let me offer one opinion. In my forty plus years of experience I would offer the following generalized priority: OSHA Regulations - because it’s the law, local regulations (i.e.: state, city, municipality, etc.), business demands/policy, and perhaps the legal threat. US based consensus standards, performance requirements in a purchase order, cost savings programs, and company safety policies. International standards influence, best practices, competition, and image. The purpose of this list is not to be absolutely accurate, but instead, to drive some thinking as to where a new international standard like EN ISO 13849-1; 2006 plays a role in my business.
On Monday of this week in Brussels the Official Journal of the European Union, 2009/C 321/09, announced the prolongation of EN 954-1 until Dec. 31, 2011. They also published a correction from EN ISO 13849-1:2006 to EN ISO 13849-1:2008.