Machine Safety Blog

09.03.2008

Check this out! Do you wire your e-stops to a standard (non Safety) PLC or controller in order to comply with the mandatory category 0 or 1 stop? Think twice is my advice! Yes, the safety standards such as NFPA 79, 9.2.5.4.1.3 require that an e-stop "shall function as either Category 0 or a Category 1 stop". These are stopping categories. Furthermore, your required risk analysis may require mitigation of a risk or hazard identified as Cat. 3 or 4. These are categories of risk. If you're wiring direct to a standard PLC your e-stop may only be at best achieving Cat. 2 or less so my advice is to check your risk analysis thoroughly.

Has anyone ever encountered this problem?

07.10.2008

Great News!   My machine safety blog is now part of an innovative new educational-based safety website that’s sole purpose is to serve the safety needs of general industry.  I’m excited to be a part of a group of industry experts who’ve come together to provide up-to-date, comprehensive information, ideas, forums, and solutions for the dynaically-changing landscape of machine safety.

06.04.2008

How many hands can I see for “safety device”? Now, how many of you say – no, an e-stopping device is not a safety device? I see! So the room is practically divided into two camps. One of the camps has several individuals that sit on safety standards committees and others who are suppliers of e-stopping devices. You guys have voted that it’s not a safety device. The other camp, ahhh, has voted yes and, most of you guys are end users, OEM’s and systems designers. Why have you guys voted yes?

06.04.2008

Tolerable risk is the term used for the past several years referring to a level of residual risk for a given hazard after applying risk reduction measures. ANSI B11.TR3; 2000 further defines tolerable risk as: Risk that is accepted for a given task and hazard combination [hazardous situation]. However, as more focus continues to be directed at integrating the safety mindset into all phases from womb to tomb of a machine life cycle, a more current term has come to life replacing tolerable risk.

01.23.2008

I often hear discussions about NFPA 79 (Electrical Standard for Industrial Machinery) having more importance than the ANSI B11 series of machine tool standards. Conversely, there’s an equal if not larger camp of user’s that profess the ANSI B11 series as “the rule of the land” inferring that NFPA 79 takes a back seat to ANSI.

09.12.2007

Yes it’s true, Europe has started a two year phase out of the risk categories; B, 1, 2, 3, & 4 as established by EN 954:1996 and hence referenced in numerous US based standards such as NFPA 79, ANSI B11, S2, ANSI B155.1, etc. to name a few. A  European standard, EN ISO 13849-1:2006, has recently been approved announcing a new system called Performance Level (PLa, b, c, d, & e) for determining risk levels on a machine replacing the Category system by 2009.