INDUSTRIAL MACHINES built to comply with national or international standards require the use of approved components, adherence to electrical panel assembly and wiring rules, and, in some cases, the provision of proper panel inspection stickers.
Approved components in North America have UL/cUL certification. In Europe, the CE mark is needed. Various Asian countries have their own added requirements, but they often honor North American and European certifications.
In the U.S. and Canada, electrical components and panel assembly are governed by UL and cUL. If your company follows UL guidelines, then your panels should be accepted by local electrical inspectors.
But (theres always a but when standards are involved), jurisdictional rules and individual inspectors quirks vary, so the safest route to compliance is to make sure theres a UL sticker on your panels. UL-certified panel shops and suppliers affix a UL sticker to each of their assembled panels.
If your company assembles its own panels in significant quantities, then it might make sense to contact UL and find out what it takes to become a UL-certified panel shop. If you wish to outsource panel assembly, its generally easy to find a local UL-certified panel shop.
Machine builders selling outside of the U.S. and Canada must comply with the same general component usage, assembly, and panel sticker requirements. However, finding information and panel assembly services can be difficult.
In Europe, TÜV Rheinland can assist. Think of it as the German equivalent of UL. TÜV marking is widely accepted across Europe and in other countries as a sign of compliance. TÜV offers domestic and international testing and certification services for industrial machinery. It also offers CE Marking services to those manufacturers needing to export their machinery to the EU. Testing services are available to make sure machinery complies with requirements.
In the U.S., TÜV is a Nationally Recognized Testing Laboratory (NRTL), and can test to applicable UL standards. In the semiconductor industry, for example, TÜV provides SEMI/S2 guideline assessments for builders of semiconductor manufacturing equipment. As an NRTL, TÜV can list machinery to insure acceptance by local authorities. For unlisted equipment, TÜV can provide field evaluation services at the installation site.
For an independent worldwide view of machinery and panel compliance, third-party vendors also can assist. Pilz Automation Safety is one company that provides engineering services including formal tests, design calculations, and documentation for compliance with worldwide standards and legislation.
Pilz provides a CE marking service to the European Machinery Directive 98/37/EC, whereby Pilz CE marks machines, and assumes responsibility for these machines when they enter Europe, says Craig Torrance, safety services manager for Pilz in North America. Any machine that has electrical subsystems normally will have to comply with the European Low-Voltage Directive (89/366/EEC) and the Electro-Magnetic CompatibilityEMC Directive (73/23/EEC). Pilz engineers will carry out the required tests on the machine to determine compliance with the Low Voltage Directive and the EMC Directive.
Pilz also can complete the design calculations required to claim compliance with some of the probability-based standards gaining popularity. EN IEC 62061Safety of Machinery, functional safety of safety-related electrical, electronic and programmable electronic control systemsis a probability-based standard that machine builders now use for control system design, explains Torrance. EN IEC 62061 uses Safety Integrity Levels (SILs) to identify hierarchical levels of integrity for the electrical control system. To claim compliance with this standard, SIL verification must be performed. This involves calculating the reliability, failure-mode, and probability of dangerous failures per hour of the various components used in the control system.
These calculations are alien to many machine builders, and it can take some time for machine builders to get accustomed to the process and the large mathematical formula, adds Torrence. Pilz engineers can assign a SIL via a determination exercise, obtain the relevant component data, and then perform the SIL verification calculations to show that the machine does comply with the standard.
While UL and TÜV are primarily audit services, companies like Pilz can assist machine builders by acting as independent consultants or as outsourced engineering labor. The consulting services are not just audit services, but are practical sessions to establish long-term safety and compliance methodologies and processes, concludes Torrance.
This discussion centers around European and North American compliance, but Pilz and a growing number of other companies can provide compliance services for other parts of the world as well.