Category 3 safety circuit requirements 4

[steelerr]

Is a RESET pushbutton required for Cat. 3, or is that just a "recommendation"? I see lots of examples of the RESET pushbutton in mfg. literature, but no reference to a requirement.

I do have the required redundancy, feedback aux. contacts, safety-rated interlock switch and E-Stop pushbutton, etc., but I wonder about the RESET.

Also, is there a thread or forum group here dedicated to electrical safety (motor control, hazardous machinery, etc.)circuit design?

Are you aware of any good training course on safety circuit design, other than the Pilz training in England?

Thanks.

 

[dpc]

It would be really helpful if you told us whose "Category 3" you are referring to. We have members located all over the world.

 

[ScottyUK]

dpc,

This sounds like a European SIL rating. Category 3 is pretty high.

steelerr,

ABB Eutech have done a lot of presentations in the Teesside area and probably further afield on the subject of SIL. Siemens also have published a lot literature - the rep dropped it in a while ago and I simply haven't had the time to go through it. If you want to trace it, the reference is 6ZB5 000-0AA02-0BA1


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Sometimes I only open my mouth to swap feet...

 

[ozmosis]

Siemens do have a very extensive manual on Safety systems. You can download from here:

http://support.automation.siemens.com/WW/view/en/17711888

it is a big download (12.1MB) so use broadband or better still, somebody elses.

 

[steelerr]

Category 3 isn't necessarily a Euro thing. Lots of applications in the US use Category 3 or other level of protection. STI, A-B, Banner and a host of others sell safety monitoring relays and associated components to accomplish this. I was just wondering about the RESET pushbutton.
After a risk assessment is done, a manufacturer of industrial machinery determines whether Category B, 2, 3, or 4 (highest level) should be applied. Category 4 would be required if there were a possibility of death or very serious injury. Also into the consideration comes likelihood that the hazard would be present, how frequent the exposure (daily, constantly, for example).

Thanks for the feedback.

Bob Steele

http://www.gala-industries.com

 

[steelerr]

Wow, that Siemens document is huge. I'll download it and look it over. Thanks for the link.

 

[steelerr]

dpc, I see now that Category 3 is a Eurpoean standard, EN 954-1. I wonder if I have to buy a copy of the standard to answer my original question precisely.

 

[jraef]

The SIL catagory determinations are now incorporated into the latest version of NFPA79 and harmonized to the IEC standards anyway. They are only just now beginning to be enforced here in the US.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[jraef]

Damn, meant to hit the spell checker, hit the Submit button by accident...

<Category>

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[steelerr]

I have a copy of NFPA 79 2002 Edition. I assume it's now out of date, correct?
I'll hit their website - thanks.

 

[dpc]

There's a 2007 version just out. But NFPA 79 doesn't apply to all control systems in the US.

Thanks for the link, sed2. The Siemens US web pages are hard to navigate, or at least used to be - I gave up. Maybe they have improved

 

[ScottyUK]

dpc,

The European one hasn't.

Thanks for the link, sed2. I tried to find it and was defeated as normal. I have largely given up on the Siemens website because it is so difficult to find anything: the distributors know to send me a paper catalogue if they want any business. It's a shame because I actually like a lot of the Siemens products, but finding them is a nightmare!


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Sometimes I only open my mouth to swap feet...

 

[ozmosis]

Scotty
Maybe I'm biased or just used to it but I find the European website fairly easy to navigate:

http://support.automation.siemens.com/WW/view/en/4000024

The navigation tree on the left puts you into the right product group and then clicking on the "search documents for........" box will tend to home down on the right ones.
The North American internet does not have has much a range of info but I tend to find that they will have more detail that Europe tends to keep on intranet:

http://www2.sea.siemens.com/Support/

 

[ScottyUK]

I commend your loyalty to your employer!

 

[HCBFlash]

Thanks for the link and info sed2!

I'm glad to stumble across this thread here where I usually lurk, but I wish similarly useful discussion would be common on the "Codes, Standards, and Certifications" area of eng-tips. Without doing a cross post, I'll say that I have some interest in safety as a dominant part of machinery and motor control systems, yet I feel like I'm missing something.

I come from a background of the "NEC" where the distance between convenience receptacles is stipulated, but have yet to find a similarly specific and binding standard for the placement of E-Stops on machinery that can readily injure or kill it's users or operators. This strikes me as somewhat counterintuitive.

OSHA certainly doesn't handle such specifications or recommended engineering practices very well. I'm going to attempt to pore over the .pdf I got from the siemens link, but I'm skeptical about it's usefulness for prompting or enforcing better practices in dangerous applications. Are there any (other?) good forums or links dealing with this stuff?

 

[Blackcountryman]

One point of warning SIL or Safety integrity levels and the reliability categorys B, 2, 3 & 4 and not the same things.

SILs come from IEC61508 family (61511 62061) of standards and the category's from EN 954-1. which I think has since been superseded but I can't remeber the new reference.

They both have similar uses but they are NOT interchangeable. SIL3 and Category 3 not the same.

The reliability category deals with the design of e-stop circuits etc. While the SIL is about the whole life cycle.

I think a forum on machine safety and standards would be a good idea.

 

[steelerr]

Fellow group members, I believe I've found the reference I was looking for. The attacked link to Allen-Bradley's Safety Products catalog refers to EN 292-2: 3.7.2

http://www.ab.com/en/epub/catalogs/3377539/5866177/3378082/3384394/

Without actually purchasing the Standard, the second sentence under Note 3 of the A-B catalog refers to the RESET pushbutton I was asking about.

If the risk is rated high enough, you want to make sure that the system / machine doesn't suddenly restart as soon as you close the guard or reset the E-Stop or clear the error. Pressing the RESET pushbutton is a voluntary, intentional action, so no surprises occur if the controls are designed properly.

Many thanks to all who responded. I hope some sort of machine safety controls group eventually evolves in this forum. I'd be happy to participate.

Peace, Bob Steele
Eagle Rock, Virginia, USA

 

[HCBFlash]

steelerr, another note, see thread249-163625,

Also the "Engineering Codes, Standards, and certifications section of eng-tips, has pretty low activity (at least compared to this forum), but a few items have been a bit informative to me.

I picked up the latest NFPA79, and am discouraged to find that it seems to be becoming the standard code for machinery controls/safety. I guess the other groups with published standards decided to just let the NFPA handle all that kind of stuff. I have some old IEEE published standards which were great at their time and as far as they went.

I have a LOT more regard for IEEE than the NFPA. IEEE has never had any publication which would be seen as the "National Exception Catalog" (N.E.C).