Machine Safety

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Machine safety: Does effective grounding include ancillary hand rails, fences, and more?

How inclusive is effective grounding for machine safety? Should safe machine grounding consider hand rails, walkways, and protective fencing?

April 29, 2013


How all encompassing is effective grounding for machine safety? Does this requirement really include things like hand rails, walkways and protective fencing?

 

The discussion regarding effective grounding is really broad and sometimes vague in my opinion. Certainly it’s intended to protect people from being electrically shocked and to guard against any false or unintended operation or movement of a machine. Some standards will have pages of requirements whereas other standards might have one paragraph “referencing” a manufacturer’s specifications. Most of these standards benefit by some level of interpretation by a knowledgeable person for the most effective grounding applications. Let’s look at one general description/requirement from NFPA 79; 2012:

 

8.2.1.2 Equipment Grounding. The machine and all exposed, non-current-carrying conductive parts, material, and equipment likely to be energized shall be effectively grounded. Where electrical devices are mounted on metal mounting panels that are located within nonmetallic enclosures, the metal mounting panels shall be effectively grounded. Where specified by the manufacturer, components and subassemblies shall be bonded to the equipment grounding (protective bonding) circuit in accordance with the manufacturer’s instructions.

 

The first sentence of this standard can easily be interpreted as though provisions like hand rails, walkways, and protective fencing probably don’t need grounding or bonding provisions.

 

However, if the walkway or hand rail connects a machine to another machine which also has an electrical control system and devices, industry experts have often recommended that these metallic non-current-carrying conductive parts be effectively grounded.

 

Does anybody know why?

 

J.B. Titus, CFSE

Has this presented you with any new perspectives? Add your comments or thoughts to the discussion by submitting your ideas, experiences, and challenges in the comments section below.

 

Related articles:

NFPA 79; 2012 – Electrical Standard for Industrial Machinery

ANSI B11.19 – 2012 Performance Criteria for Safeguarding

IEC 60204-1: 2005 Safety of machinery – Electrical equipment of machines

Contact: http://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.