Machine Safety

An ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis, operating efficiencies and cost savings, as well as all relevant safety standards, such as those from NFPA, ANSI, RIA, IEC, ISO and OSHA. About J.B. Titus.

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Machine safety and degrading component reliability

Is your machine downtime sometimes a surprise? Did a component in a safety circuit fail because it simply wore out and nobody knew it was about to fail? Well, maybe help has just arrived. Has anyone heard about EN ISO 13849-1; 2008? See "4 ways to reduce surprise downtime."

July 14, 2011


JB Titus, CFSEIs your machine downtime sometimes a surprise? Did a component in a safety circuit fail because it simply wore out and nobody knew it was about to fail? Well, maybe help has just arrived. Has anyone heard about EN ISO 13849-1; 2008?

   This new standard (Safety of machinery, Safety-related parts of control systems) has arrived and the Machinery Directive in Europe has established its effective date as Jan. 1, 2012. Since the US is part of the ISO (International Standards Organization) many companies in the US are making plans to or have already adopted this new standard. In my opinion, 13849-1 improves machine safety because it moves machine safety from qualitative Categories to quantitative Performance levels. Compliance requirements in this new standard will now address all of the components in a safety circuit while determining that circuit’s Performance Level. As such, the expected life of a component is determined and documented relative to its expected number of cycles during machine operation. Therefore, the weak links can be identified and flagged early on during the design stage. This is particularly important for those components that are electro/mechanical, such as contactors or safety relays, and have moving parts or points that wear out over time. This wearing out over time is what many people refer to as “degrading component reliability”.

   OK, great! Does anyone have an idea with this information how to reduce the surprise downtime (and possible hazard) related to this type of component failure?

4 ways to reduce surprise downtime

   Several thoughts I have are as follows:

1.)   Identify and document these components in your risk assessment for the machine.

2.)   Add these components to your preventive maintenance plan.

3.)   Plan for routine machine maintenance to replace these components before their expected failure.

4.)   Update your risk assessment for the machine.

   I have barely touched on the comprehensive approach for Functional Safety addressed by EN ISO 13849-1; 2008. Several companies and consultants offer two and three day classes on the new compliance requirements embedded in this new standard. In my opinion, to fully understand these compliance requirements you should consider contacting these sources and consider enrolling in one of their classes.

   Your comments or suggestion are always welcome so please let us know your thoughts. Submit your ideas, experiences, and challenges on this subject in the comments section below. Click on the following text if you don't see a comments box, then scroll down: Machine Safety & Degrading Component Reliability.

   Did you see the Safety Integration Webcast?

   Related articles:

EN ISO 13849-1; 2008 - Are We Ready? - Part 2

Trouble Implementing ISO 13849-1; 2006 per the European Machinery Directive

B10s at work for machine guarding

Contact: www.jbtitus.com for “Solutions for Machine Safety”.



For more than 30 years, J.B. Titus has advised a wide range of clients on machine functional safety solutions, including Johnson + Johnson, Siemens, General Motors, Disney, Rockwell Automation, Bridgestone Firestone, and Samsung Heavy Industries. He holds a Bachelor of Business Administration degree from Oklahoma University in industrial management and an MBA from Case Western Reserve University in marketing and finance. He is a professional member of the American Society of Safety Engineers and is OSHA-certified in machine guarding. Titus is also TUV-certified as a Functional Safety Expert and serves on several American National Standards Institute, National Fire Protection Association, and National Electrical Manufacturers Association national safety and health standards committees. Reach him at jb(at)jbtitus.com and via www.jbtitus.com.