Yes I suppose it was vague, but you sometimes get a broader response, different documents reference class, some catagory, just looking for a breakdown if one exists, that can itemize when each is required, I believe it is 13849 but wanted to make sure, RA can always be done a little subjectively
Perhaps you can look at vendor catalogs & engineering manuals for safety components like safety relays and interlock switches targeted at the "machine safety" business. Those documents usually have very good overall information summarizing the safety standard requirements, applications examples, and so forth. In addition to referencing all the pertinent standards. You may try that approach. Go see what you can find at SICK, Euchner, Schmersal, Banner Engineering. I'd point you to the Allen-Bradley site, but finding anything useful on that labyrinthine site is almost impossible.
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
There is no "itemizing" when each category is required. You go through the risk assessment procedure as prescribed in the relevant standard, and identify the various tasks that people have to do and the risks that they are exposed to when doing those tasks, and assign "severity", "exposure", "avoidance" factors as prescribed in the standard, and *that* tells you what circuit category is required.
But, having been through this many hundreds if not thousands of times, you are likely going to find that all but the most trivial risks are going to require dual channel circuits with safety relays, etc. You may have some risk combinations that allow a lower risk category, but all it takes is one combination that's guarded by the same guarding to require "control reliable" or "category 3" or "performance level d" to govern that the whole thing needs to meet that category or performance level or whatever you want to call it.
The low and decreasing cost of safety-related hardware these days usually isn't worth the aggravation and risk associated with trying to save a few pennies by cheaping out by using a lower risk category.
As a rule I do almost every thing as control reliable(dual reduntant),Just to avoid the hassle of doing a RA on everything. I am trying to put something together for senior managment to explain my actions. ( because we still do not do RA and keep them on file)
The "prescribed method" in ANSI/RIA R15.06-1999 (for when you don't want to do a risk assessment) specifies using "control reliable" for every safety device. Unfortunately, it also prescribes a couple of other things that are a real bugger to deal with in practice - like 500mm clearance to the fence from the robot restricted space as defined by the hard-stops, which almost never happens ...
In Europe they commonly use OHSAS 18001,2007 for safety. You will have to do risk assesments rating the risks in your work place and have plans to reduce risks. At my plant powered industrial vehicle (PIV) is one of our highest risks.
Plant safety must be approached in the broadest sense and then broken down to all the various activities where there is risk. You will need to understand what your hazards are, have mitigation plans to reduce the risks. You will then have to communicate the risks and train the people on how to properly do a function safely. You will also have to monitor and audit your safety program to know it is being used.
You can find a breakdown of the different classes of safety in NFPA 79. I don't have my copy in front of me, so I can't quote chapter and verse, but it is in there.
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