ISO 13849 – 1 Analysis — Part 1: Start with Risk Assessment

This entry is part 1 of 9 in the series How to do a 13849 – 1 analysis

I often get ques­tions from cli­ents about how to get star­ted on Functional Safety using ISO 13849. This art­icle is the first in a series that will walk you through the basics of using ISO 13849. Keep in mind that you will need to hold a copy of the 3rd edi­tion of ISO 13849 – 1 [1] and the 2nd edi­tion of ISO 13849 – 2 [2] to use as you go along. There are oth­er stand­ards which you may also find use­ful, and I have included them in the Reference sec­tion at the end of the art­icle. Each post has a Reference List. I will pub­lish a com­plete ref­er­ence list for the series with the last post.

Where to start?

So you have just learned that you need to do an ISO 13849 func­tion­al safety ana­lys­is. You have the two parts of the stand­ard, and you have skimmed them, but you are feel­ing a bit over­whelmed and unsure of where to start. By the end of this art­icle, you should be feel­ing more con­fid­ent about how to get this job done.

Step 1 – Risk Assessment

For the pur­pose of this art­icle, I am going to assume that you have a risk assess­ment for the machinery, and you have a copy for ref­er­ence. If you do not have a risk assess­ment, stop here and get that done. There are sev­er­al good ref­er­ences for that, includ­ing ISO 12100 [3], CSA Z432 [4], and ANSI B11.TR3 [5]. You can also have a look at my series on Risk Assessment.

The risk assess­ment should identi­fy which risks require mit­ig­a­tion using the con­trol sys­tem, e.g., use of an inter­locked gate, a light cur­tain, a two-​hand con­trol, an enabling device, etc.See the MS101 gloss­ary for detailed defin­i­tions. Each of these becomes a safety func­tion. Each safety func­tion requires a safety require­ments spe­cific­a­tion (SRS), which I will describe in more detail a bit later.

Safety Functions

The 3rd edi­tion of ISO 13849 [1] provides two tables that give some examples of safety func­tion char­ac­ter­ist­ics [1, Table 8] and para­met­ers [1, Table 9] and also provides ref­er­ences to cor­res­pond­ing stand­ards that will help you to define the neces­sary para­met­ers. These tables should not be con­sidered to be exhaust­ive – there is no way to list every pos­sible safety func­tion in a table like this. The tables will give you some good ideas about what you are look­ing for in machine con­trol func­tions that will make them safety functions.

While you are identi­fy­ing risk reduc­tion meas­ures that will use the con­trol sys­tem for mit­ig­a­tion, don’t for­get that com­ple­ment­ary pro­tect­ive meas­ures like emer­gency stop, enabling devices, etc. all need to be included. Some of these func­tions may have min­im­um require­ments set by Type B2 stand­ards, like ISO 13850 [6] for emer­gency stop which sets the min­im­um per­form­ance level for this func­tion at PLc.

Selecting the Required Performance Level

ISO 13849 – 1:2015 provides a graph­ic­al means for select­ing the min­im­um Performance Level (PL) required for the safety func­tion based on the risk assess­ment. A word of cau­tion here: you may feel like you are re-​assessing the risk using this tool because it does use risk para­met­ers (sever­ity, frequency/​duration of expos­ure and pos­sib­il­ity to avoid/​limit harm) to determ­ine the PL. Risk assess­ment This tool is not a risk assess­ment tool, and using it that way is a fun­da­ment­al mis­take. Its out­put is in terms of per­form­ance level, which is fail­ure rate per hour of oper­a­tion. For example, it is entirely incor­rect to say, “This machine has a risk level of PLc” since we define PLs in terms of prob­able fail­ure rate per hour.

ISO 13849-1 graphical selection tool for determining PLr requirement for a safety function
Graphical Performance Level Selection Tool [1]
Once you have assigned a required Performance Level (PLr) to each safety func­tion, you can move on to the next step: Developing the Safety Requirements Specification.

Book List

Here are some books that I think you may find help­ful on this journey:

[0]     B. Main, Risk Assessment: Basics and Benchmarks, 1st ed. Ann Arbor, MI USA: DSE, 2004.

[0.1]  D. Smith and K. Simpson, Safety crit­ic­al sys­tems hand­book. Amsterdam: Elsevier/​Butterworth-​Heinemann, 2011.

[0.2]  Electromagnetic Compatibility for Functional Safety, 1st ed. Stevenage, UK: The Institution of Engineering and Technology, 2008.

[0.3]  Overview of tech­niques and meas­ures related to EMC for Functional Safety, 1st ed. Stevenage, UK: Overview of tech­niques and meas­ures related to EMC for Functional Safety, 2013.

References


[1]     Safety of machinery — Safety-​related parts of con­trol sys­tems — Part 1: General prin­ciples for design. 3rd Edition. ISO Standard 13849 – 1. 2015.

[2]     Safety of machinery – Safety-​related parts of con­trol sys­tems – Part 2: Validation. 2nd Edition. ISO Standard 13849 – 2. 2012.

[3]      Safety of machinery – General prin­ciples for design – Risk assess­ment and risk reduc­tion. ISO Standard 12100. 2010.

[4]     Safeguarding of Machinery. CSA Standard Z432. 2004.

[5]     Risk Assessment and Risk Reduction- A Guideline to Estimate, Evaluate and Reduce Risks Associated with Machine Tools. ANSI Technical Report B11.TR3. 2000.

[6]    Safety of machinery – Emergency stop func­tion – Principles for design. ISO Standard 13850. 2015.

The Brexit Vote and CE Marking: What’s it going to mean for Canadian Exporters?

Shocked and Amazed by Brexit

UK and EU Flags against a blue sky during the Brexit VoteThis morn­ing I am shocked and amazed to learn that one of the founders of the European Union has chosen to leave that Union. Joining the EEC in 1973, the UK and oth­er European coun­tries moved toward the form­a­tion of the EU, first as an eco­nom­ic treaty, and even­tu­ally as a polit­ic­al uni­on. Today, the sep­ar­a­tion begins.

What now?

Starting today, the UK will need to determ­ine how best to get its house in order before trig­ger­ing Article 50 of the Lisbon Treaty. This is expec­ted to take at least a couple of years. In that time, there is a pos­sib­il­ity that Scotland may hold anoth­er exit ref­er­en­dum from the UK, and may then choose to apply to join the EU. This may also hap­pen in Ireland, fur­ther dimin­ish­ing the size of the UK. We will have to wait and see what these coun­tries will choose to do in com­ing months.

What effect does this have on Canadian and US Exporters?

If you export to the EU and you have European branch offices in the UK and oth­er European coun­tries, the exit of the UK from the EU will have little effect, oth­er than on the ques­tion of lan­guage. Unless Scotland or Ireland choose to leave the UK and join the EU, AND they choose to include English as one of their offi­cial lan­guages, it’s pos­sible that English may no longer be an offi­cial lan­guage of the European Union. This could mean that instruc­tions, manu­als, oper­at­or screens, haz­ard warn­ings and oth­er text-​based inform­a­tion on your products that are provided primar­ily in English may no longer be permitted.

If you are using the ser­vices of a com­pany that provides ser­vices to “com­pile the tech­nic­al file” for your product, and that com­pany is loc­ated in the UK, you will have to find anoth­er com­pany to provide these ser­vices. This would also be true for com­pan­ies using ser­vices of com­pany act­ing as Authorized Representatives. Again, I recom­mend tak­ing a deep breath and wait­ing to see what Scotland and Ireland will do.

If a change in Authorized Representative, or per­son “author­ised to com­pile” is required, this will also impact the inform­a­tion on the name­plates on your products since the Authorized Representative’s or person-authorised-to-compile’s name and con­tact coordin­ates must be on the name­plate along with the manufacturer’s inform­a­tion. This same change will also be required on the product Declaration of Conformity or Incorporation.

What now?

Young Woman Meditating on the grassTake a deep breath. Wait.

We need to give the UK and the EU some time to determ­ine how they are going to organ­ise their divorce. This is a world chan­ging decision, and the changes will not be done without due care and atten­tion. In the mean time, we must watch and wait. Here at Compliance inSight Consulting and the Machinery Safety 101 blog, we will be watch­ing and talk­ing to our col­leagues in Europe, and we will keep you up to date as we know more.

Now, with me… breathe deeply…

New Directions in Plastics Machinery

Canada’s Participation in ISO TC 270

SCC Standards Council of Canada LogoIn February of 2016, Canada formed the SCC Mirror Committee (SMC) to ISO TC 270, Rubber and Plastics Machinery. This inter­na­tion­al tech­nic­al com­mit­tee is cur­rently devel­op­ing ISO 20430, the first inter­na­tion­al plastic injec­tion mould­ing machine stand­ard. Until the pub­lic­a­tion of ISO 20430, two stand­ards have been fight­ing for dom­in­ance: EN 201, Plastics and rub­ber machines — Injection mould­ing machines — Safety require­ments, and ANSI B151.1, American National Standard for Plastics Machinery – Horizontal Injection Moulding Machines – Safety Requirements for man­u­fac­ture, Care and Use.

Canada has a strong plastic and rub­ber industry, with key equip­ment man­u­fac­tur­ers like Athena Automation, Husky Injection Molding Systems, Mold Masters and GN Plastics among oth­ers pro­du­cing world class machinery for the industry. The industry is rep­res­en­ted nation­ally by the Canadian Plastics Industry Association. Despite this, Canada has nev­er had its own stand­ard for this type of machinery.

Involvement in ISO TC 270 allows Canada’s plastics industry to have a voice in devel­op­ing the inter­na­tion­al stand­ards for the machinery they design and build, and which ever more com­monly, they buy and use.

The com­mit­tee needs your help to know which way Canadian industry wants us to focus our efforts as the work on ISO 20430 wraps up in com­ing months. We have a short sur­vey, just three ques­tions long, where you can rank five pos­sible top­ics we can focus on. We will be sub­mit­ting our com­mit­tee vote in early August on the top­ic, so you have a month or so to answer the ques­tion­naire. Let us know your preferences.

Why now?

ISO LogoUntil the pub­lic­a­tion of ISO 20430, two stand­ards have been fight­ing for dom­in­ance: EN 201 in Europe, and ANSI B151.1 in North America. Until the rel­at­ively recent form­a­tion of ISO TC 270 in 2012, there were NO inter­na­tion­al stand­ards for this type of machinery. While there have been some efforts to har­mon­ise the European and ANSI stand­ards, there are still some sig­ni­fic­ant gaps between these stand­ards. In addi­tion, ANSI’s B151 com­mit­tee has a num­ber of addi­tion­al stand­ards for aux­il­i­ary equip­ment for items like robots designed to unload molds, that are not dir­ectly addressed in EN standards.

Canada was giv­en a chance to par­ti­cip­ate through our ongo­ing friend­ship with ANSI and the USA, so between 2012 and 2015, Canadian del­eg­ates atten­ded ISO TC 270 work­ing group meet­ings inform­ally, and put Canada’s per­spect­ive for­ward through the US ANSI TAG com­mit­tee, but in 2016 it became clear that we needed to form our own com­mit­tee. If you are involved in the industry and you are a mem­ber of one of these gen­er­al groups and would like to get involved with stand­ards devel­op­ment, please go to our recruit­ing page and join us!

Committee Membership Matrix

Matrix Category Min Max Current
Total  15  25  6
Producer Interest (PI) 3 5 3
User Interest, Management (UM) 3 5 1
User Interest, Labour (UL) 3 5 0
Regulatory Authority (RA) 3 5 1
General Interest (GI) 3 5 1

As you can see from the table, we need mem­bers in every group except the pro­du­cers to meet our inten­ded balance.

Definitions of the Categories

Producer Interest (PI) — Machine build­ers, Auxiliary Equipment Manufacturers, Consultants, and Engineering Companies provid­ing for-​profit ser­vices related to plastics and rub­ber machinery.

User Interest, Labour (UL) — Canadian labour uni­ons, labour organ­iz­a­tions, and indi­vidu­al work­ers loc­ated at Canadian workplaces.

User Interest, Management (UM) — Trade asso­ci­ations, com­pan­ies, con­tract­ors, and organ­iz­a­tions rep­res­ent­ing com­pan­ies engaged in work per­formed in Canada.

Regulatory Authorities (RA) — OHS pro­vin­cial and fed­er­al reg­u­lat­ory bod­ies (labour and electrical).

General Interest (GI) — Safety asso­ci­ations, research organ­iz­a­tions, insti­tu­tions, and non-​commercial con­sult­ants who have expert­ise in the sub­ject area.

We need your help!

CAC ISO TC 270 needs your help!

Can you volun­teer some time? Sign up!

Can you help dir­ect us? Answer our questionnaire!

Need more inform­a­tion? Contact Doug Nix!