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: Does a risk assessment need to be updated for a minor machine modification?

We’ve made some minor changes to several machines over the past six months but none of these modifications included the safety system. Our engineer said that there was no change in operator safety. Do we have to update the risk assessments anyway? See ANSI B11.0 – 2010 Safety of Machinery – General Requirements and Risk Assessment; OSHA recommended.

May 07, 2012


J.B. Titus, CFSE"We’ve made some minor changes to several machines over the past six months but none of these modifications included the safety system. Our engineer said that there was no change in operator safety. Do we have to update the risk assessments anyway?"

   The long and short answer is – yes! This is one of the most frequently asked questions at Machine Safety seminars. Just think about the consequences for a moment. Let’s say a modification was made to the protective fencing moving a man entry gate six feet. The modification was simple enough and the existing door interlock switch continues to work just fine after being re-wired. The operator is unaffected by this change because he/she is not required to access this door. So, operator safety is unaffected as the engineer had said.

   However, if the new door location is now six feet closer to a hazard point the time distance calculations may reflect the need to raise the hazard level from Cat 3 to Cat 4. This will undoubtedly require different hazard mitigation techniques to reach the same reduced level of hazard (acceptable risk). And, how would we discover that this simple modification resulted in a serious change to overall machine safety? An updated risk assessment! This is why any modification to a machine requires that the risk assessment must be updated.

ANSI B11.0 – 2010 Safety of Machinery – General Requirements and Risk Assessment. Cover image used with permission. Courtesy: ANSI   In my opinion, referring to ANSI B11.0 – 2010 Safety of Machinery – General Requirements and Risk Assessment will answer this question in Clause 4.11 (page 27) as follows:

 4.11 Modifying and/or rebuilding a machine

   Non-standard uses or modifications of the machine, machine control system or the safeguarding can create additional hazards. A modifier and/or rebuilder of machinery shall use the risk assessment process to ensure that risks are reduced to an acceptable level. Modifiers and/or rebuilders shall, where practicable, solicit the original supplier’s recommendations regarding any proposed modification to a machine that may affect the safe operation prior to making any such changes.

   Where modifications are made to the machine/system (for example, intended use, tasks, hardware, and software), a risk assessment / risk reduction process shall be repeated for those parts of the machine/system being modified or affected.

   Within the United States I strongly recommend that manufacturers use ANSI B11.0 as one of your core industry standards for machine safety compliance. Also, it’s actually recommended by OSHA.

   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: Does a risk assessment need to be updated for a minor machine modification?

Related articles:

Updating Minds About Machine Safety

Machine Guarding & The Hierarchy of Measures for Hazard Mitigation

Machine Safety – the myths of safety cultures.

   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.