E-Stop - a safety device or not?

Machine Safety - Tolerable Risk vs Acceptable Risk

Tolerable risk is the term used for the past several years referring to a level of residual risk for a given hazard after applying risk reduction measures. ANSI B11.TR3; 2000 further defines tolerable risk as: Risk that is accepted for a given task and hazard combination [hazardous situation]. However, as more focus continues to be directed at integrating the safety mindset into all phases from womb to tomb of a machine life cycle, a more current term has come to life replacing tolerable risk.

Acceptable risk is the new term that is currently appearing in updated standards and which more clearly represents the implied intent of both evaluation and mitigation. The assumption is that risk can never truly be totally eliminated from a hazard but that every risk should be evaluated for risk reductions and mitigated to the smallest amount possible. Therefore, more current standards are defining acceptable risk as the level at which further risk reduction will not result in significant reduction in risk or that additional expenditure of resources will not result in significant advances towards increased safety.

So, where’s this discussion going? Does it really matter? Maybe a good analogy is in order. For example, is a zebra white with black stripes or is it black with white stripes? Isn’t the whole bottom line of the risk analysis process really about consciously establishing the importance of reducing the risk of occupational injuries, illnesses, and fatalities? Of course the answer is – YES ! So, let’s get off our laurels and get on with the program

Which Has Machine Safety Priority - ANSI B11.000X or NFPA 79?

I often hear discussions about NFPA 79 (Electrical Standard for Industrial Machinery) having more importance than the ANSI B11 series of machine tool standards. Conversely, there’s an equal if not larger camp of user’s that profess the ANSI B11 series as “the rule of the land” inferring that NFPA 79 takes a back seat to ANSI.

In practice, we occasionally see customer specifications calling out requirements for these standards as well as some municipalities that have declared these standards as normative requirements. OSHA’s web site has a direct reference to the ANSI B11 series but only an indirect reference to NFPA 79.

Can anyone provide information clarifying this question?

Categories of Risk – Alive or Dead?

Yes it’s true, Europe has started a two year phase out of the risk categories; B, 1, 2, 3, & 4 as established by EN 954:1996 and hence referenced in numerous US based standards such as NFPA 79, ANSI B11, S2, ANSI B155.1, etc. to name a few. A  European standard, EN ISO 13849-1:2006, has recently been approved announcing a new system called Performance Level (PL_{a, b, c, d,} & _e) for determining risk levels on a machine replacing the Category system by 2009. So far, it doesn’t seem that any US based standards groups are mustering the troops to update recently modified standards that acknowledged the EN 954 Category system of 1996. The ink has barely dried for gosh sakes! Categories are a product of the task based objective risk assessment process currently still being introduced across the nation for discrete industries.

The PL system, on the other hand, is a quantitative based approach that (if adopted in the US) will require industries across the land to learn or acquire new skills in order to be compliant. One new requirement is calculating MTTF_d (mean time to fail dangerous) and another is PFH_d (probability of dangerous failure per hour). These values will need to be determined for components such as interlock switches and sensors. Does anyone believe that industry is ready for this tidal wave?

Or, will Categories live on………….?

Where's OSHA ??

We’ll – from where I stand it’s been since 1999 that the voluntary consensus standards began their migration march of updating approaches for machine safe guarding. That first standard was RIA 15.06 for industrial robots. One of many changes of this updated standard was the requirement to conduct a risk analysis on all robots within two years. The next major standard to update and provide new approaches to machine guarding was NFPA 79’s release in 2002. The major enhancements with this change include the opportunity to apply safety PLC’s, the ability to install e-stops on a safety certified bus, and the elimination of the mandate to hard wire all safety circuits. All of these changes are to some point driven by the desire for harmonization with European standards.

Since this beginning of the migration march for new opportunities in machine safe guarding, many more of our standards are falling in line and adopting these new concepts. Several that come to mind include:

1.      ANSI B11.TR3- 2000, Risk Assessment and Risk Reduction

2.      ANSI B11.TR4-2004, Selection of Programmable Electronic Systems (PES/PLC) for Machine Tools

3.      ANSI Z244.1-2003, Control of Hazardous Energy

4.      ANSI/PMMI B155.1-2006, Safety Requirements for Packaging Machinery

5.      NFPA 79-2007, Electrical Standard for Industrial Machinery

6.      SEMI S2, Safety Guidelines for Semiconductor Manufacturing Equipment

Several more consensus standards are in committee as we speak and will be publishing approved updates within months further confirming that a major paradigm shift has been underway for nearly eight years in the US. Throughout this time OSHA has done nothing I’m aware of to openly acknowledge any of these changes.

So – is there anyone out there who can write a comment into this blog and give us any clue to what OSHA is doing to update their 29CFR 1910 series of regulations?  

Simplified Machine Safety – Blah Humbug

How can this be? How could machine safety be more simple and easy than hard wiring 50 or 100 relays back to a machine control system? We’ve been doing it this way for over 30 years and our machine up time is above average at 68%!

How many of us have heard this story? We’ll, the safety landscape has changed! Industry has new options for safety compliance that are permitted by regulations. Companies can now ask themselves:

1.      Is the wiring still accurate for those 100 relays after 35 engineering changes?

2.      Are those relay jumpers for engineering changes or defective relay contacts?

3.      Is my safety compliance active or jumpered out of operation?

4.      Can I eliminate downtime caused by intermittent relays without diagnostics?

5.      Is an improvement to 90% machine up time really feasible?

6.      Can I eliminate 1500 lineal feet of conduit and 18,000 feet of home run wiring?

7.      Where’s Frank? He installed this system in 1972 and knows everything!

Wake up and smell the roses for gosh sakes! Frank retired in 2004 and hoola hoops are history. Today – trade journals are packed each month with articles supporting the changing landscape of machine safety. And, the industry regulations support these changes. How better can it get in these competitive times? Do you have a better idea? What’s holding you back?

Machine Safety Influence From Europe

Some folks in machine safety are off learning about European standards like IEC 60204, IEC 62061, and the October 2006 updated ISO 13849-1. These standards talk about the safe guarding of machines and use terms like; SIL (Safety Integrity Level), PL (Performance Level), MTTFD  (Mean Time To Fail dangerous), and SIL Claim Limit to mention a few! All of these terms are very deterministic and involve levels of mathematical calculations. It’s as though the European industry might be shifting away from a task based qualitative risk analysis process using categories of hazards (B,1,2,3,4) to a completely quantitative mathematical approach. What is the Safety Integrity Level for addressing hazards associated with the operator placing tote boxes too close to the machine?

Many end user’s and OEM’s here in the US are typically focused at our national consensus standards and OSHA regulations for compliance to machine safety requirements. These regulations occasionally “informatively” reference European standards and generally don’t require compliance to European standards. Is anyone aware of any of these European requirements emerging within the collaborative standards requirements of the US? What is your opinion? What are you doing to address these requirements?

Did anyone notice that we are about to enter a new paradigm in safety?

Did anyone notice that we are about to enter a new paradigm in safety?  I am fortunate enough to be on a committee that writes changes to regulations. The committee is a great group of people to work with, and we try very hard to make sure the regulations keep up with available technology. It’s been two years since NFPA 79, the Electrical Standard for Industrial Machinery, changed to allow businesses to leave hard-wired safety systems behind and implement integrated safety systems. The new standards open a wave (maybe even a flood) of new options that you’ve never had before in applying safety PLCs on the line.  But now I’m seeing stats that say 70% of the engineers out there don’t even know that they can do something different.  They see the old redundant systems in the plant – that was the first paradigm when no one trusted those “newfangled PLCs” 25 years ago – and don’t know they even have permission to do anything else.  It’s time for that to change.

The new regulations that allow integrated safety systems do more than just set you free from the hard wiring to relay logic.  Because of the diagnostics capabilities in integrated safety systems, you can troubleshoot much faster, reducing your maintenance costs and increasing uptime. Since I’m all about trying to reduce workload on the engineer, I can’t wait to see more companies talking about how the are ready to move away from their old stuff and replace it with safety that protects staff and actually improves productivity.  Are you dumping your old safety layer and integrating safety into your next system, or is your company relying on the old standby?  Let me know if you are part of the new paradigm, and what you are doing in your plant.

Have You Heard - Machine Safety ='s Cost Savings?

Has anyone noticed that we have entered a new paradigm in safety?  I am fortunate enough to be on several standards committees that write changes to regulations. The committees are great group of industry experts to work with, and we try very hard to make sure the regulations keep up with available technology. It’s been four years since NFPA 79, an Electrical Standard for Industrial Machinery, changed to allow businesses to leave hard-wired safety systems behind and implement integrated safety systems. The new standards open a wave (maybe even a flood) of new options that you’ve never had before in applying safety PLCs on the line.  But now I’m seeing stats that say 70% of the engineers out there don’t even know that they can do something different.  They see the old redundant systems in the plant – that was the first paradigm when no one trusted those “newfangled PLCs” 25 years ago – and don’t know they even have permission to do anything else.  It’s time for that to change.

The new regulations that allow integrated safety systems do more than just set you free from the hard wiring to relay logic.  Because of the diagnostics capabilities in integrated safety systems, you can troubleshoot much faster, reducing your maintenance costs and increasing uptime. Since I’m all about trying to reduce workload on the engineer, I can’t wait to see more companies talking about how the are ready to move away from their old stuff and replace it with safety that protects staff and actually improves productivity.  Are you dumping your old safety layer and integrating safety into your next system, or is your company relying on the old standby?  Let me know if you are part of the new paradigm, and what you are doing in your plant.