Machine Safety: What are fault exclusions?

Where did the term “fault exclusions” derive? Can you simply choose any fault to exclude? Who would ever exclude a fault while trying to provide employees with appropriate safe machine guarding?

03/08/2013


Has anyone heard about “fault exclusions”? Where did this term emerge from? Can you simply choose any fault to exclude? Who in their right mind would exclude a fault while trying to provide employees with appropriate safe machine guarding?

 

Okay, now that I have your attention, let’s try to provide some background and understanding for this term.

 

Does a definition exist? I’ve examined several ANSI, NFPA, IEC and ISO standards. I found several uses of the term “fault exclusion” in IEC 62061, ISO 13849-1 and ISO 13849-2, however, I could not find the term in the definitions section of these standards. Additionally, I could not find the term used in NFPA 79, RIA 15.06, ANSI/PMMI B155.1 or any of the current ANSI B11 standards except one – ANSI B11.TR6 – 2010, Safety Control Systems for Machine Tools. Here’s the definition:

3.22 fault exclusion: The elimination from consideration of a specific identified failure within the Safety-Related Parts of the Control System because its probability is low relative to the systems‘ required performance, through design, selection of components, or implementation of additional measures.

 

Furthermore, in Clause 4 of the General Design Considerations section you’ll find the following additional clarifications for use:

4.6.2 Fault Exclusion

During the analysis, certain faults may be uncovered that cannot be detected during operation without undue economic costs. Further, the probability that these faults might occur may be extremely small, by using mitigating design, construction and installation. Under these conditions, the faults may be excluded from further consideration. This includes recommended maintenance procedures.

Fault exclusion can be based on but not limited to:

·  the low probability of occurrence of some faults;

·  tried and true (good) engineering safety practices;

·  application specific technical requirements for the specific hazard.

Detail justification shall be given in the technical documentation for any excluded faults.

 

ANSI B11.TR6 is a technical report and not a standard with normative requirements that “shall” be followed. ANSI standards are frequently referenced by OSHA via the General Duty Clause and therefore become law via enforcement by OSHA. As a technical report TR6 provides “guidance in understanding and implementing.”

 

Why doesn’t this term appear in any of our domestic normative standards? Since it’s used in several international standards why hasn’t it been defined and clarified? Can anyone help the rest of us with the background for “fault exclusion”? Will there be a trend for this term rolled into everyday life for safety professionals, end users and manufacturers?

 

J.B. Titus, CFSE

Have you encountered any of these issues? Add your comments or thoughts to the discussion by submitting your ideas, experiences, and challenges in the comments section below.

 

Related articles:

Inside Machines: Does adopting ISO 13849-1:2006 change the U.S. model for compliance and enforcement?

Machine Safety – does OSHA reference consensus standards for compliance?

Machine Safety: Is OSHA okay with my 'acceptable' risk mitigation?

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



CARLOS , Non-US/Not Applicable, Mexico, 04/01/13 06:33 PM:

Mr. Titus:
In section 4.6.2, the 3 fault exclusion you metion, are related with the RISC evaluation, which is low or reasonably accepted if the probability of the dangerous eevnt is very low, or if consequences are neglibles or can be containes by othe safety layer. In other words, Fault Exclusion mean a reasoable low enough RISC.
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
World-class maintenance: The three keys to success - Deploy people, process and technology; 2016 Lubrication Guide; Why hydraulic systems get hot
Your leaks start here: Take a disciplined approach with your hydraulic system; U.S. presence at Hannover Messe a rousing success
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Improving flowmeter calibration; Selecting flowmeters for natural gas; Case study: Streamlining assembly systems using PC-based control; CLPM: Improving process efficiency, throughput
Putting COPS into context; Designing medium-voltage electrical systems; Planning and designing resilient, efficient data centers; The nine steps of designing generator fuel systems
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me