More flip-​flopping on EN 954 – 1?

In recent posts I’ve been dis­cuss­ing the changes in the use of EN 954 – 1, Safety of Machinery – Safety Related Parts of Control Systems. Part 1: General Principles for Design. The EU ori­gin­ally announced that this stand­ard was to be with­drawn on 31-​Dec-​09, being replaced by EN ISO 13849 – 1. As you may know, there are sig­ni­fic­ant dif­fer­ences in these two standards. 

A later announce­ment from the European Commission repealed

In recent posts I’ve been dis­cuss­ing the changes in the use of EN 954 – 1, Safety of Machinery – Safety Related Parts of Control Systems. Part 1: General Principles for Design. The EU ori­gin­ally announced that this stand­ard was to be with­drawn on 31-​Dec-​09, being replaced by EN ISO 13849 – 1. As you may know, there are sig­ni­fic­ant dif­fer­ences in these two standards.

A later announce­ment from the European Commission repealed the with­draw­al of EN 954 – 1, extend­ing its use until 31-​Dec-​12. This announce­ment was itself withdrawn.

So where do we stand today? Currently, EN 954 – 1 will be with­drawn on 31-​Dec-​09 and will be replaced by EN ISO 13849 – 1, UNLESS this decision is again reversed by the EC in con­sulta­tion with the EC Machinery Working Group. A meet­ing is planned for 7/​8-​Dec-​09 to dis­cuss this situ­ation and to resolve the confusion.

As a machine build­er, there is only one prudent course of action – imple­ment EN ISO 13849 – 1 in your designs. If the decision remains as it cur­rently stands, then your products will con­form to the require­ments on 31-​Dec-​09 and you will be able to con­tin­ue to ship product to the EU. If the decision is reversed by the EC and EN 954 – 1 remains in use until 2012, then you are three years ahead of the require­ment and should be using that to full advant­age in your mar­ket­ing and sales efforts.

My friend Jon Severn has a post related to this on his blog at MachineBuilding​.net.

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
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
Kind regards,
— —  —  — —

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

European Commission Delays EN ISO 13849 – 1 Implementation

The EC has decided to extend the trans­ition peri­od for EN 954 – 1 from 31-​Dec-​09 to 31-​Dec-​12, delay­ing the man­dat­ory imple­ment­a­tion of EN ISO 13849 – 1. How will this affect machine build­ers and con­trols manufacturers?

I recently read that the European Commission has decided to delay the man­dat­ory imple­ment­a­tion of EN ISO 13849 – 1 2008 and EN 62061. The 2006 edi­tion of ISO 13849 – 1 moves the bar con­sid­er­ably high­er for machine build­ers, requir­ing much more extens­ive ana­lys­is of con­trol reli­ab­il­ity require­ments as part of the design cycle. EN 62061 provides a machinery spe­cif­ic imple­ment­a­tion of IEC 61508 for  sys­tems includ­ing pro­gram­mable equip­ment in the safety related parts of the con­trol sys­tem. The ori­gin­al man­dat­ory imple­ment­a­tion date for these stand­ards was 31-​Dec-​2009. This has now been pushed out to 31-​Dec-​2012 accord­ing to machineb​uild​ing​.net.

[More on the exten­sion of EN 954 – 1]

[More on the imple­ment­a­tion of EN 62061]


European Union

When EN 954 – 1 was intro­duced in 1996, it set out a whole new cri­ter­ia for the eval­u­ation of safety sys­tem con­trol reli­ab­il­ity in machinery. This stand­ard intro­duced the idea of the famil­i­ar Reliability Categories, B, 1 – 4. This stand­ard ended the days where a single chan­nel cir­cuit with any con­veni­ent sens­ing device could be con­sidered to be accept­able for safety applic­a­tions in most indus­tri­al applications.

The next few years were chal­len­ging ones for machine build­ers and design­ers as they learned to imple­ment these require­ments in their products. The con­trol com­pon­ents man­u­fac­tur­ers intro­duced broad arrays of con­trol com­pon­ents, like guard mon­it­or­ing relays, emer­gency stop relays and enabling-​device relays to assist design­ers by provid­ing build­ing block com­pon­ents to sim­pli­fy designs and reduce costs.

The first edi­tion of ISO 13849 – 1 was pub­lished in 1999. The new ISO stand­ard was essen­tially a straight adop­tion of EN 954 – 1, bring­ing the doc­u­ment into the ISO devel­op­ment mod­el. Stakeholders were aware that changes to the doc­u­ment were needed, and that addi­tion­al clar­ity was required to assist design­ers in cor­rectly imple­ment­ing the stand­ard. Additional tools were envi­sioned to help users bet­ter apply reli­able con­trol design prin­ciples in their products.

In 2006, the second edi­tion of ISO 13849 – 1 was pub­lished, and in May 2007 noti­fied in the Official Journal of the European Union, see OJ 2007/​C 104/​01. The man­dat­ory imple­ment­a­tion date was set to 31-​Dec-​2009, and the two-​year trans­ition peri­od began. During this peri­od either the 1999 edi­tion or the 2007 edi­tion could be applied and com­pli­ance with the rel­ev­ant por­tions of the EU Machinery Directive could be claimed.

North America

It took a bit longer for con­trol reli­ab­il­ity to creep into the North American designer’s con­scious­ness. Manufacturers who were mar­ket­ing product in the EU became aware of EN 954 – 1 as they worked on com­pli­ance with the CE Marking dir­ect­ives that applied to their products. In the USA, ANSI RIA R15.06 intro­duced con­trol reli­ab­il­ity require­ments in the 1999 edi­tion, and soon after CSA pub­lished CSA Z434 which closely fol­lowed RIA’s stand­ard with some small but sig­ni­fic­ant changes. These stand­ards intro­duced the SIMPLE, SINGLE-​CHANNEL, MONITORED SINGLE-​CHANNEL and CONTROL RELIABLE defin­i­tions into robot sys­tem design­ers thinking.

These con­cepts were later included in CSA Z432, Safeguarding of Machinery, and are being incor­por­ated into the ANSI B11 fam­ily of machinery safety stand­ards. ANSI’s soon-​to-​be-​published  B11-​GSR, General Safety Requirements, stand­ard will fur­ther embed these con­cepts into US machinery safety standards.

Recent amend­ment of ANSI RIA 15.06 by ANSI RIA ISO 10218 – 1 brings ISO 13849 – 1 into the North American mar­ket by asso­ci­ation, since the ISO robot­ic stand­ard dir­ectly ref­er­ences the ISO con­trol reli­ab­il­ity stand­ards. How long it will take for Canada to fol­low suit is unknown at this time, but CSA Z434 is just start­ing review and may be har­mon­ized with the US, the EU and the International standards.

Need to know more about the US amend­ment of R15.06 by 10218 – 1? See Jeff Fryman’s report on the RIA web site.


According to MachineBuilding​.net, “…many man­u­fac­tur­ers are not yet ready to apply the replace­ment stand­ard EN ISO 13849 – 1.” Sources in the UK have long been con­cerned that many small and medi­um enter­prises were hav­ing dif­fi­culty apply­ing EN 954 – 1, without increas­ing the bur­den by adding sig­ni­fic­antly more ana­lys­is to the design task. Consultations between the EC Machinery work­ing group and the European Commission led to the decision to post­pone the date.


What are the implic­a­tions of this delay?

First, I think that many machine build­ers will heave a sigh of relief, hav­ing gained a bit more than three years grace on the dead­line. This will give them more time to work on their designs and to com­plete third-​party eval­u­ations used to sup­port their Declaration of Conformity. This will also allow those who are inclined to “slide” three more years to delay doing anything.

On the oth­er hand, the con­trols man­u­fac­tur­ers spent at least the last two years gear­ing up their products to meet design­ers require­ments under the new stand­ard. One of the sig­ni­fic­ant require­ments is the pro­vi­sion of fail­ure rate data for com­pon­ents from inter­lock switches to relays and light cur­tains to emer­gency stop but­tons. Significant test­ing is required to be able to provide MTTFd or B10d num­bers usable in the design analysis.

For com­pan­ies that provide train­ing in this area, more time is now avail­able to get cli­ents trained, but some of the urgency has been removed, poten­tially extend­ing the return on invest­ment in devel­op­ment of courses on this standard.

Ultimately, the losers are the users of the equip­ment. This stand­ard provides an oppor­tun­ity to sig­ni­fic­antly improve the reli­ab­il­ity of the safety sys­tems on indus­tri­al machines. The exten­sion only delays this needed improve­ment by three years, and by an untold num­ber of oth­er­wise pre­vent­able injur­ies. While I under­stand the pres­sures that the old dead­line put on man­u­fac­tur­ers, it is my exper­i­ence that this kind of pres­sure is fre­quently neces­sary to drive the changes that soci­ety demands. While these changes dir­ectly affect those mar­ket­ing in the EU today, the changes to the North American stand­ards mean that this import­ant stand­ard will soon be a part of North American designer’s think­ing as well. It will be inter­est­ing to see what oth­er effects this change has over the next three years.

Many thanks to Glyn Garside for send­ing me a few cor­rec­tions to the ori­gin­al post! Mr. Garside is a reg­u­lar read­er and con­trib­ut­or to the EMC-​PSTC list serv­er main­tained by the IEEE Product Safety Engineering Society.

[More inform­a­tion on the List Server]

[More inform­a­tion on the Society]