EU changes direction on EN ISO 13849-1

Update on EN ISO 13849-1 mandatory implementation date.

In a post on 15-Sep I reported that the European Union had decided to delay the mandatory implementation date of  EN ISO 13849-1 for an additional three years. This report was based on information obtained from an internal source at the European Commission and has since been reversed by that same source.

Mr. Glyn Garside provided the following update to this important story:

It has been widely reported, but never confirmed, that the EU commission had accepted the CEN proposal to extend the date of cessation of presumption of conformity of EN 954-1:1996 until the end of 2012. THESE REPORTS HAVE NOW BEEN AUTHORITATIVELY DENIED.

(By the way, this discussion of dates of cessation of presumption of conformity only affects the European standards, EN 954-1 and EN ISO 13849-1. International standard ISO 13849-1 is obviously controlled by ISO and not by CEN or the EU. The current edition of ISO 13849-1 is 2006, essentially identical to EN ISO 13849-1 : 2008.)

At this point the possibility of an extension of the transition from EN 954-1 to EN ISO 13849-1 remains controversial, confused and IMHO uncertain. (There’s been approx 3 years transition period already.) If I were still a manufacturer, I would not want to wait until Dec 29th to find out if I could still ship my product using EN 954-1!

The reports of an extension were based on an email sent earlier this month (3rd Sept) by a CEN employee. However, the EU Commission never confirmed the report, and on September 24th the same CEN employee, Marie Poidevin, has written,
—————–
> “We have been informed today by the European Commission […] that contrary to what was expressed in
> my previous message sent on the 3rd of September, EN 954-1 will not give presumption of conformity
>  to the new MD 2006/42/EC until further notice.
> “Indeed, due to discussions following the announcement made below, the EC wishes to gather experts’
> views and, therefore, this issue will be discussed at the next Machinery Working group to be held on
> the 7-8th December.”
—————–

A related email from Ian Fraser (“EC Policy Director for the Machinery Directive”), dated 2009-09-18 states,
—————–
“Following the discussion at the meeting of the Machinery Working Group held on 7 and 8
July 2009, we have received a number of questions concerning the transition from standard
EN 954-1 to standard EN ISO 13849-1 on safety-related parts of control systems.
At the meeting of the Machinery Working Group, there was general agreement on two
aspects:
1. Manufacturers who apply standard EN ISO 13849-1 benefit from a presumption of
conformity, even if the harmonised C-type standard relating to the machinery concerned still
refers to the categories of EN 954-1;
2. Harmonised C-type standards that refer to the categories of EN 954-1 continue to confer a
presumption of conformity until they are amended to refer to standard EN ISO 13849-1.
These conclusions will be recorded in the minutes of the meeting.

During the discussion, several participants indicated that more time was needed for the
industry, and in particular for SMEs, to adapt to the new standard. As Chairman of the
meeting, I asked whether it might not be preferable to postpone the date of cessation of
presumption of conformity for EN 954-1.
In response to this suggestion, on 30 July 2009, Mr. Steiger wrote to the Commission, on
behalf of the CEN Machinery Sector, to request that the date of cessation of presumption of
conformity for EN 954-1 be exceptionally postponed until 31 December 2012 […].
The Commission will reply to this request from CEN. However, given the complexity of the
issues involved, the Commission intends to consult experts and to seek the opinion of the
Machinery Working Group to be held on 7 and 8 December 2009, before reaching a final
decision.
Kind regards,
Ian FRASER”
—————

Thanks again to Glyn Garside and the EMC-PSTC List Server!

Why Conventional EMC Testing is Insufficient for Functional Safety

At the recent PSES Symposium, I attended a couple of interesting workshops on EMC and Functional Safety. One was called “Workshop on EMC & Functional Safety” presented by Keith Armstrong, Bill Radasky and Jacques Delaballe. The other was a paper presentation called “Why Conventional EMC Testing is Insufficient for Functional Safety” presented by Keith Armstrong.

For readers who are new to the idea of Functional Safety, this field deals

At the recent PSES Symposium, I attended a couple of interesting workshops on EMC and Functional Safety. One was called “Workshop on EMC & Functional Safety” presented by Keith Armstrong, Bill Radasky and Jacques Delaballe. The other was a paper presentation called “Why Conventional EMC Testing is Insufficient for Functional Safety” presented by Keith Armstrong.

For readers who are new to the idea of Functional Safety, this field deals with the ability of a product or system to function in it’s intended use environment, or in any foreseeable use environments, while reliably providing the protection required by the users. Here’s the formal definition taken from IEC 61508-4:1998:


3.1.9
functional safety
part of the overall safety relating to the EUC and the EUC control system which depends on the correct functioning of the E/E/PE safety-related systems, other technology safety-related systems and external risk reduction facilities

3.2.3
equipment under control (EUC)
equipment, machinery, apparatus or plant used for manufacturing, process, transportation, medical or other activities

NOTE – The EUC control system is separate and distinct from the EUC.

Table 1: (E/E/PE) electrical / electronic / programmable electronic

Reliability requirements are found in two key standards, ISO 13849 and IEC 61508. These two standards overlap to some degree, and do not define reliability categories in the same way, which frequently leads to confusion. In addition there is a Machinery Sector Specific standard based on IEC 61508, called IEC 62061, Safety of machinery – Functional safety of safety-related electrical, electronic and programmable electronic control systems. These three standards make reference to EM effects on systems but do not provide guidance on how to assess these phenomena. This is where IEC TS 61000-1-2 comes into play.

All three experts are members of IEC TC 77 and are directly engaged in writing the second edition of IEC TS 61000-1-2 (more info on this at the bottom of this post). This IEC Technical Specification deals with electromagnetic (EM) effects on equipment that result in functional safety problems, like failures in guarding circuits, or failures in some of the new programmable safety systems. This is becoming an increasingly important issue as programmable controls migrate into the traditionally hardwired safety world. In fact, Keith pointed out that EM effects are present even in many of our “tried and true” circuits, but the failures have been incorrectly attributed to other phenomena because most electrical engineers have not been used to thinking about these phenomena, especially in 24Vdc relay-based control circuits.

In the workshop, the presenters discussed a typical product life cycle, then went on to explore the typical environments that a product may be exposed to, including the EM and physical environments. They went on to discuss the need for an EMC-related Risk Assessment and then finished up by looking at Electromagnetic Safety Planning. The whole workshop took the entire second day of the Symposium.

A key point in the workshop is that conventional EMC testing cannot practically prove that systems are safe. This is due to the structure of the EMC tests that are normally undertaken, including the use of fixed modulation frequencies during immunity testing, failure to assess intermodulation effects and many other issues. In addition, EMC testing does not and cannot test for aging effects on performance, wear & tear and other use-related conditions. The presenters discussed a number of ways that these problems could be addressed and ways that testing could be extended in selective ways to attack predicted vulnerabilities. EMC testing does not consider the reliability requirements of the tested product (i.e. IEC 61508-1 SIL-3 or SIL-4).

On the following morning, Keith Armstrong presented his paper. In this paper, Mr. Armstrong went into considerable detail on the shortcomings of conventional EMC testing when it comes to Functional Safety. He suggested some approaches that could be used by manufacturers to address these issues in safety critical applications.

The workshop presentations and Mr. Armstong’s paper can be purchased through IEEE Xplore for those that did not attend the Symposium.

The IET has published a new book, available for free from their web site, entitled Electromagnetic Compatibility for Functional Safety. This guide will be reviewed in a future post, so keep reading!

Keith Armstrong, Bill Radasky and Jacques Delaballe are members of IEC Technical Committee 77, writing IEC TS 61000-1-2 Ed 2.0, ELECTROMAGNETIC COMPATIBILITY (EMC) – PART 1-2: GENERAL – METHODOLOGY FOR THE ACHIEVEMENT OF THE FUNCTIONAL SAFETY OF ELECTRICAL AND ELECTRONIC EQUIPMENT WITH REGARD TO ELECTROMAGNETIC PHENOMENA. Edition 2 of this standard should be published by Mar-2009 according to the IEC.

Keith Armstrong is Principal Consultant at Cherry Clough Consultants in Brocton, UK.

Bill Radasky works with Metatech Corporation from his office in Goleta, California.

Jacques Delaballe works for Schneider Electric Industries SAS in Grenoble, France.

2008 IEEE PSES Symposium On Product Compliance Engineering

What a great Symposium! Dr. June Andersen kicked it off with a great keynote, and the rest of the sessions were excellent!

Last week I was at the 2008 PSES Symposium in Austin Texas.

This was one of the most successful Symposia held by the PSES, with 180 in attendance and 15 exhibitors in the hall. Attendees came from as far as Argentina, the UK and Israel!

Dr. June Andersen gave a great keynote address on Monday morning, showing the group how IBM manages worldwide compliance in more than 180 different markets. Dr. Andersen’s background is impressive, and a bit intimidating. I found her to be a warm, friendly and interesting person when we shared breakfast together before the conferece opened. Dr. Andersen’s presentation will be made available through the PSES web site to members, so if you would like a copy and you’re not a member, now is a great time to join!

Keith Armstrong of Cherry Clough Consultants, along with his colleagues Jacques Delaballe and Bill Radasky presented an interesting one-day workshop on EMC and Functional Safety, discussing the effects of EMC on the safety related parts of control systems. On Wednesday, Keith completed the series with a short presentation on the shortcomings of conventional EMC testing in revealing safety-related design problems. Definitely a worthwhile series! Armstron, Delaballe and Radasky are planning a new workshop for next-year’s Symposium in Toronto that will carry on from this year, so if you are interested in this area, plan to attend!

There were several sessions on batteries and the on-going work that the battery companies and the main battery consumers are undertaking to resolve the design and manufacturing problems that led to the notebook and cell phone fires in the past year. These sessions were packed and well reviewed by everyone I spoke with.

There were lots of other presentations that I didn’t get a chance to attend – with 40 presentations and only one me, it was impossible to get to every one.

If you missed this year’s Symposium, start plannng for next year’s in Toronto – it’s going to be great!