Q & A: Category 2 and Testing Intervals

This entry is part 1 of 2 in the series Q&A

Dur­ing the Free Safety Talks that we did with Schmersal Canada and Frank­lin Empire, we had a “hot ques­tion” come up regard­ing Cat­egory 2 archi­tec­ture and the test­ing inter­val require­ment. In the short video below, Doug answers that ques­tion.

If you have more ques­tions or felt some­thing wasn’t clear in the video, leave us a com­ment and we will get back to you!

If you are hav­ing prob­lems with devel­op­ing your safety func­tion, please get in touch with Doug dir­ectly.

Notes

Email Doug dir­ectly.

References

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

[2]     “The Bathtub Curve and Product Fail­ure Beha­vi­or (Part 2 of 2)”, Weibull.com, 2018. [Online]. Avail­able: http://www.weibull.com/hotwire/issue22/hottopics22.htm. [Accessed: 13- May- 2018].

[3]    Ger­man Social Acci­dent Insur­ance (DGUV) – Insti­tute for Occu­pa­tion­al Safety and Health (BGIA), “Func­tion­al safety of machine con­trols — Applic­a­tion of ISO 13849 – 1 — Report 2/2008e”, Insti­tute for Occu­pa­tion­al Safety and Health (BGIA), Sankt Augustin, DE, 2008.

[4]     “Safety Cir­cuit Examples of Safety Com­pon­ents | Tech­nic­al Guide | Aus­tralia | Omron IA”, Omron.com.au, 2018. [Online]. Avail­able: http://www.omron.com.au/service_support/technical_guide/safety_component/safety_circuit_example.asp. [Accessed: 14- May- 2018].

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Acknow­ledge­ments: ISO, OMRON, oth­ers as cited.
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Five reasons you should attend our Free Safety Talks

Reason #1 – Free Safety Talks

You can’t argue with Free Stuff! Last week we partnered with Schmersal Canada and Frank­lin Empire to put on three days of Free Safety Talks. We had full houses in all three loc­a­tions, Wind­sor, Lon­don and Cam­bridge, with nearly 60 people par­ti­cip­at­ing.

We had two great presenters who helped people under­stand Pre-Start Health and Safety Reviews (PSRs) [1], CSA Z432-2016 [2], Inter­lock­ing Devices [3] and Fault Mask­ing [4].

Mr Vashi at Franklin Empire Cambridge
Mr Vashi at Frank­lin Empire Cam­bridge

Frank­lin Empire provided us with some great facil­it­ies and break­fast to keep our minds work­ing. Thanks, Frank­lin Empire and Ben Reid who organ­ized all of the regis­tra­tions!

Mr Nix discussing injury rates in machine modes of operation
Mr Nix dis­cuss­ing injury rates in machine modes of oper­a­tion

Reason #2 – Understanding Interlocking Devices

A portrait of Mr Kartik Vashi
Mr Kartik Vashi, CFSE

Mr Kartik Vashi, CFSE, dis­cussed the ISO Inter­lock­ing Device stand­ard, ISO 14119. This stand­ard provides read­ers with guid­ance in the selec­tion and applic­a­tion of inter­lock­ing devices, includ­ing the four types of inter­lock­ing devices and the vari­ous cod­ing options for each type. Did you know that ISO 14119 is also dir­ectly ref­er­enced in CSA Z432-16 [2]? That means this stand­ard is applic­able to machinery built and used in Canada as of 2016. If you don’t know what I’m talk­ing about, you can con­tact Mr Vashi to get more inform­a­tion.

ISO 14119 Fig 2 showing some aspects of different types of interlocking devices.
ISO 14119 Fig 2 show­ing some aspects of dif­fer­ent types of inter­lock­ing devices [3]

Reason #3 – Understanding Fault Masking

Mr Vashi also talked about fault mask­ing, an import­ant and often mis­un­der­stood situ­ation that can occur when inter­lock­ing devices or oth­er elec­tromech­an­ic­al devices, like emer­gency stop but­tons, are daisy-chained into a single safety relay or safety input on a safety PLC. Mr Vashi drew from ISO/TR 24119 to help explain this phe­nomen­on. If you don’t under­stand the impact that daisy-chain­ing inter­lock­ing devices can have on the reli­ab­il­ity of your inter­lock­ing sys­tems, Mr Vashi can help you get a handle on this top­ic.

A part of ISO 24119 Fig 2 showing one method of daisy-chaining interlocking devices.
A part of ISO 24119 Fig 2 show­ing one com­mon meth­od of daisy-chain­ing inter­lock­ing devices [4]

Reason # 4 – Pre-Start Health and Safety Reviews

Portrait of Doug Nix, C.E.T.
Mr Doug Nix, C.E.T.

Mr Nix opened his present­a­tion with a dis­cus­sion of some com­monly asked ques­tions about Pre-Start Health and Safety Reviews (PSRs). There are many ways that people become con­fused about the WHY, WHAT, WHEN, WHERE, WHO and HOW of PSRs, and Mr Nix covered them all. This unique-to-Ontario pro­cess requires an employ­er to have machines, equip­ment, rack­ing and pro­cesses reviewed by a Pro­fes­sion­al Engin­eer or anoth­er Qual­i­fied Per­son when cer­tain cir­cum­stances exist (see O. Reg. 851, Sec­tion 7 Table). If you are con­fused by the PSR require­ments, con­tact Mr Nix for help with your ques­tions.

Reason #5 – Understanding the changes to CSA Z432

CSA Z432 [2] was updated in 2016 with many changes. This much-needed update came after 12 years exper­i­ence with the 2004 edi­tion and many changes in machinery safety tech­no­logy. Mr Nix briefly explored the many changes that were brought to Cana­dian machine build­ers in the new edi­tion, includ­ing the many new ref­er­ences to ISO and IEC stand­ards. These new ref­er­ences will help European machine build­ers get their products accep­ted in Cana­dian mar­kets. Both Mr Vashi and Mr Nix sit on the CSA Tech­nic­al Com­mit­tee respons­ible for CSA Z432.

Reason #6 – Hot Questions

We like to over-deliv­er, so here’s the bonus reas­on!

We had some great ques­tions posed by our attendees, two of which we are answer­ing in video posts this week. If you have ever con­sidered using a pro­gram­mable safety sys­tem for lock­out, our first video explains why this is not yet a pos­sib­il­ity. Mr Nix gets into some of the reli­ab­il­ity con­sid­er­a­tions behind the O.Reg. 851 Sec­tions 75 and 76 and CSA Z460 require­ments.

Mr Nix pos­ted a second video dis­cuss­ing ISO 13849 – 1 [5] Cat­egory 2 archi­tec­ture require­ments and par­tic­u­larly Test­ing Inter­vals. This video explains why it is not pos­sible to meet the test­ing require­ments using a purely elec­tromech­an­ic­al design solu­tion.

Edit: 16-May-18

A case in the UK illus­trates the dangers of bypassing inter­lock­ing sys­tems. A work­er was killed by a con­vey­or sys­tem in a pre-cast con­crete plant when he was work­ing in an area nor­mally pro­tec­ted by a key-exchange sys­tem. Here’s the link to the art­icle on OHSOnline.com. Allow­ing work­ers into the danger zone of a machine without oth­er effect­ive risk reduc­tion meas­ures may be a death sen­tence.

References

[1]     Ontario Reg­u­la­tion 851, Indus­tri­al Estab­lish­ments

[2]     Safe­guard­ing of Machinery. CSA Z432. 2016.

[3]     Safety of machinery – Inter­lock­ing devices asso­ci­ated with guards – Prin­ciples for design and selec­tion. ISO 14119. 2013.

[4]     Safety of machinery – Eval­u­ation of fault mask­ing seri­al con­nec­tion of inter­lock­ing devices asso­ci­ated with guards with poten­tial free con­tacts. ISO/TR 24119. 2015.

[5]     Con­trol of haz­ard­ous energy – Lock­out and oth­er meth­ods. CSA Z460. 2013.

[6]     Safety of machinery — Safety-related parts of con­trol sys­tems — Part 1: Gen­er­al prin­ciples for design. ISO 13849 – 1. 2015.

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Acknow­ledge­ments: Kartik Vashi, ISO, Frank­lin Empire, S more…
Some Rights Reserved

Q & A: Can Safety PLCs be used for Lockout?

This entry is part 2 of 2 in the series Q&A

The ques­tion of lock­out and the use of safety PLCs as a means to meet the lock­out require­ments comes up more and more fre­quently these days. Can Safety PLCs be used for lock­out? Safety pro­fes­sion­als don’t always agree on this con­tro­ver­sial top­ic!

Dur­ing the Free Safety Talks that we did with Schmersal Canada and Frank­lin Empire, this hot ques­tion came up, so I thought I’d cov­er it off in a video. If you need some spe­cif­ic help with an applic­a­tion like this, please get in touch with Doug dir­ectly.

There is a lot to say, and in this video I try to cov­er off the reas­ons why Safety PLCs and Lock­out don’t always mix well.

Notes

Ontario Reg­u­la­tion 851, Indus­tri­al Estab­lish­ments

CSA Z432, Safe­guard­ing of Machinery

CSA Z460, Con­trol of haz­ard­ous energy – Lock­out and oth­er meth­ods

ISO 13849 – 1, Safety of machinery — Safety-related parts of con­trol sys­tems — Part 1: Gen­er­al prin­ciples for design

ISO 13849 – 2, Safety of machinery — Safety-related parts of con­trol sys­tems — Part 2: Val­id­a­tion

IEC 62061, Safety of machinery – Func­tion­al safety of safety-related elec­tric­al, elec­tron­ic and pro­gram­mable elec­tron­ic con­trol sys­tems

IEC TR 62061 – 1:2010, Guid­ance on the applic­a­tion of ISO 13849 – 1 and IEC 62061 in the design of safety-related con­trol sys­tems for machinery

Ques­tions? Leave a com­ment below or email Doug.