Conformity Magazine- May 2008 - (Page 26) What this means is that a product is “listed” if a NRTL tests and approves a product as meeting published safety standards, performs periodic reviews of the compliance of continuing production, and then lists that approval in a publication by the NRTL. In actual practice, the NRTL performs at least two follow-up inspections per year to verify continued compliance with the safety requirements, and the publication of listed products is commonly performed via the Internet. The NEC also defines a method for labeling approved equipment. The NEC, in article 100, defines labeling as: “Equipment or materials to which has been attached a label, symbol, or other identifying mark of an organization that is acceptable to the authority having jurisdiction and concerned with product evaluation, that maintains periodic inspection of production of labeled equipment or materials, and by whose labeling the manufacturer indicates compliance with appropriate standards or performance in a specified manner.” This means that a product is “labeled” if a NRTL tests and approves a product as meeting published safety standards, performs periodic reviews of the compliance of continuing production, and then affixes on each approved product a mark indicating compliance. Again, in actual practice, the NRTL performs at least two follow-up inspections per year, and each product manufactured is marked with the NRTL’s trademarked listing symbol indicating compliance. Often a product is both listed and labeled, that is, it is both listed in a publication (or online directory) and bears the NRTL listing mark. The AHJ requires that products which connect to the electrical system or which have electrical power within them be listed or labeled. This requirement fulfills the requirements of the National Electrical Code, which most jurisdictions have adopted as a legal requirement in the jurisdiction. It also fulfills the requirements of OSHA for usage of machinery in the workplace. Technical Standards for Machinery Approval Machines that undergo a field evaluation process are assessed according to published technical standards. The definition of applicable standards follows a hierarchy. First, the standards defined by OSHA as applicable standards under the NRTL program should be applied. Since these standards are legally required by OSHA under U.S. statutory authority, they take precedent over all other technical standards. The list of standards required by OSHA for use by NRTLs in approving products is publicly accessible at www.conformity.com/1741. After the OSHA required standards, the second most important source of defining applicable standards for equipment is the National Electrical Code. The NEC itself is always applicable. In addition, where specific requirements 2 Conformity mAy 2008 for products exist, the NEC defines product safety standards in Annex A, Product Safety Standards. This list of standards is informational, but it should be followed wherever possible. Third, standards that are published by standards development organizations in the United States (such as the National Fire Protection Association (NFPA) or the American Society of Mechanical Engineers (ASME)), or standards which have been recognized by the American National Standards Institute (ANSI) should be followed if there is no directly applicable OSHA-recognized standard or no direct requirements in the NEC. Compendium of Common Standards for Machinery Generically, all machines in the United States are assessed to two technical standards: ANSI/UL 508A, Industrial Control Panels, and ANSI/NFPA 79, Electrical Standard for Industrial Machinery. UL 508A, being an OSHA recognized standard, is the primary standard, and applies to all industrial control enclosures on the machine. The overall machine is assessed per ANSI/NFPA 79, which addresses wiring outside the machine enclosures, as well as machinery-related requirements such as interlocking devices, guarding, and so forth. In addition, special requirements exist for special types of machines. These requirements are applied over and above the basic requirement for ANSI/UL 508A and NFPA 79 compliance. Examples of these requirements are the ANSI B11 series of standards for metal working machines, the ANSI B151 series of standards for injection molding machines, the ASME B20.1 and B30.13 standards for factory automation machinery, and the ANSI RIA R15.06 standard for industrial robots. When in doubt about the required standards for a particular machine, an NRTL should be consulted to help define the applicable standards and requirements. Panel Shop Approval Programs A panel shop program is a program whereby a machinery manufacturer can produce industrial control panels and place an NRTL panel shop approval mark on the completed control panel. These industrial control panels are approved per the technical standard UL 508A, Industrial Control Panels. A panel shop approval is not the same as listing of the panel. During a listing examination, the NRTL directly examines the panel and approves the construction of the specific panel under consideration. That exact panel may then be produced by the manufacturer, with quarterly follow-up inspection of the panel manufacturing process to assure continued compliance with the standard. Under a panel shop approval program, however, the NRTL may never directly inspect the approved panel. Instead, the panel shop performs a self-assessment of the panel and records basic information regarding the panel construction. On a quarterly basis, the NRTL inspects the panel shop, verifying http://www.conformity.com/1741
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