Control FunctionsControl Reliability

European Commission Delays EN ISO 13849 – 1 Implementation

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 machinebuilding.net.

[More on the exten­sion of EN 954 – 1]

[More on the imple­ment­a­tion of EN 62061]

Background

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.

Rationale

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.

Implications

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]

One thought on “European Commission Delays EN ISO 13849 – 1 Implementation

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