Machine Safety: ISO 13849-1 is mandatory for conformity to the Machinery Directive in Europe but in the USA?

Can this mandatory standard in Europe help U.S. safety efforts? ISO 13849-1 is titled – Safety of Machinery – Safety Related Parts of Control Systems – Part 1: General Principles for Design.

11/04/2013


What does a mandatory standard in Europe mean for domestic machine safety compliance here in the United States? ISO 13849-1 is titled – Safety of Machinery – Safety Related Parts of Control Systems – Part 1: General Principles for Design.

A few questions come to mind.

  1. Will OSHA ever require compliance to ISO 13849-1?
  2. Will a domestic standard (ANSI, NFPA, NEMA, S2, ASTM, etc.) require compliance to ISO 13849-1?
  3. Will an international standard ever trump a domestic standard here in the U.S.?
  4. Will the U.S. adopt the international hierarchy for machine safety compliance?

If anyone has some insight to these (or additional) questions please add your comments at bottom.

As I recall, when safety PLCs came to market (around 2002) U.S. manufacturers could follow the supplier’s manuals for proper application in the machine control system. And, as long as the manuals were followed, very little engineering was required to achieve safety functions. Most of the components were safety rated for Category B, 1, 2, 3, or 4, and to mitigate a Cat 3 hazard every component in that circuit needed to be rated Cat 3. At times control reliable circuits needed to be applied which required multiple components. All of this drove some level of increased safety and a byproduct – reduced unplanned machine downtime. Industry coined this approach to machine safety as “qualitative.”

Now, on stage left is ISO 13849-1. This standard uses a “quantitative” statistical analysis approach to actually engineer the safety-related parts of the control system (SRP/CS). In other words, a probabilistic determination regarding the reliability of components, devices, software, and circuitry of the SRP/CS over time. To be compliant with this standard, users need to become familiar with terms like: PL – performance level, DC – diagnostics coverage, CCF – common cause failure, MTTFd – mean time to fail dangerous, B10d – the number of cycle to which 10% of the components fail to dangerous, and many more. As with the previous paragraph it is assumed that this approach will drive some level of increased safety.

What just happened regarding the above two paragraphs? Did ISO 13849-1 subtly just pull the capability to develop compliant safety circuits from a major portion of U.S. manufacturers? How many manufacturers across the U.S. have the finances or employees capable of performing the quantitative requirements of this standard? How many U.S. machinery manufacturers (OEM) will comply with this standard for fear that OSHA will require compliance prior to a domestic shipment? Throughout my career I haven’t found one OEM who experienced an OSHA inspection where OSHA inspected the machine being manufactured.

In Europe it’s against the law to manufacture an unsafe machine.

So, will compliance to ISO 13849-1 in the U.S. be driven by the threat of liability? Or is there some other driver? How will our small end user manufacturers ever comply? Will these manufacturers consider purchasing a new machine from Europe that’s not compliant to U.S. Categories? What will European machine manufacturers do when a U.S. purchase order specifies U.S. safety standards and Category certified safety components in their SRP/CS?

Has this presented you with any new perspectives? Do you have some specific topic or interest that we could cover in future blog posts? Add your comments or thoughts to the discussion by submitting your ideas, experiences, and challenges in the comments section below.

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



Heinz , OH, United States, 11/06/13 10:05 AM:

I disagree with the conclusion that an employer “could be cited by OSHA for not adopting one or more consensus standards…..” I believe that the process is a bit more circuitous than that.
As stated, the General Duty Clause comes into play. To be cited under it, four elements of proof must be in evidence, that is
1) Employer failed to keep his place of employment free of a hazard
2) Hazard was recognized by the employer individually or the employer’s industry in general
3) The recognized hazard was causing or is likely to cause serious physical harm or death
4) There was feasible means available that would eliminate or materially reduce the risk created by the hazard
As stated in OSHA’s Field Operator’s Manual, “General duty clause citations are not intended to allege that the violation is a failure to implement certain precautions, corrective actions, or other abatement measures but rather addresses the failure to prevent or remove a particular hazard”

The consensus standard, in addressing a specific hazard and its risk as well as prescribing a proposed means of risk reduction, is the element of proof for items 2 and 4 of the basis for the citation. I may be paraphrasing but, the OSHA reference to the specific consensus standard, perhaps even referencing the applicable clause, is based on “Following the consensus standard, among others, presents one feasible and acceptable means to control the hazard through which the employer could have provided the freedom from the recognized hazard as required”

The citation is for failure of the employer to mitigate the level of risk which the hazard represents to the employee(s) to an acceptable level. The citation is not for violation of the consensus standard which is referenced, nor for the failure to apply any other specific risk abatement measure. Any other equally effective risk reduction measure which reduces the hazard’s level of risk to an acceptable level would have prevented the citation.

It is the objective of the ANSI Consensus Standard Writing Sub-committees to provide sufficient awareness and guidance, that through the standards application, an acceptable level of risk will be achieved.
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