Issue link: http://palletcentral.uberflip.com/i/1141207
palletcentral.com PalletCentral • May-June 2019 37 … a circuit that meets the control reliability and control- component-failure-protection requirements of the American National Standards for machine tools (ANSI B11.19-1990) would provide alternative safeguarding measures with respect to the minor servicing exception contained in 1910.147(a)(2)(ii). In other words, a circuit meeting the above referenced control reliability standards may be used in cases in which minor tool changes and adjustment, and other minor servicing activities, are performed during normal production operations, and are routine, repetitive, and integral to the use of equipment for production. Thus, employers may legally use circuit control devices to stop equipment in order to perform routine adjustments, clearing jams, changing tools, etc., but may not use circuit control devices as "energy isolation devices" when maintaining and repairing equipment. It is important to note that National Fire Protection Association (NFPA) publication 70E, Standard for Electrical Safety in the Workplace (2018), also prohibits the use of circuit control devices as "energy isolation devices." More specifically, NFPA 70E, Art. 120.2.(F) states: "Locks/tags shall be installed only on circuit disconnecting means. Control devices, such as push-buttons or selector switches shall not be used as the primary isolating device." OSHA & Consensus Standards OSHA is now evaluating criteria used by consensus standards to determine the safety effectiveness of control circuits. For example, the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) both have standards with detailed requirements for control circuit devices used for protection from machine hazards. The ISO and IEC standards evaluate the safety of a control system by considering its design and function. The IEC standards evaluate whether a system can achieve a certain "safety integrity level," while the ISO 13849-1 consensus standard evaluates "performance levels" for each safety function. The ISO 13849-2 consensus standard also has safety categories that describe both the performance level required for that category and the characteristics of the error-checking of a system in that category. The highest safety category requires both the highest