Danger – keep out Written by: European Editors Contributed By DigiKey's European Editors
Rigorous attention to safety at work has become ingrained in the industrial culture of developed economies. Safety is viewed as important not only for workers but also for employers, who understand the financial and reputational benefits of a good safety record. Safety-oriented regulations cover numerous aspects from the working environment and practices to the design of equipment used in the workplace. Machinery must meet essential health and safety requirements (EHSRs), such as those listed in the European Machinery Directive 2006/42/EC, to ensure the health and safety of machine users and others who may be affected. Safety standards and the machinery directive Machine design is subject to a system of standards that extends to cover a wide range of risk reduction and safety-protection mechanisms. At the highest level, type A standards include ISO12100, which sets out basic concepts and design principles that are applicable to all types of machines and also makes reference to risk assessment and risk reduction. At a lower level, type B1 standards set out general requirements for safeguards and type B2 standards apply to particular safety devices. Among the type B standards, those set by the International Standards Organization (ISO) tend to focus
on machinery and management, while International Electrotechnical Commission (IEC) standards are concerned with electrical and electronic safety systems. ISO standards include ISO13849-1 covering safety-related parts of control systems. IEC standards, on the other hand, include IEC60204 concerning electrical equipment in general, IEC61496 for electro- sensitive protective equipment, and IEC62046 for equipment designed to detect the presence of persons. Equipment marketed in Europe must be shown to comply with the Machinery Directive 2006/42/EC, which aims to establish common minimum standards for the health and safety of new products. These common standards are expected to facilitate trade and the free movement of goods between member states. The Directive references ISO12100 and the ISO and IEC Type A and Type B standards, as well as Type C standards that cover particular types of equipment such as forming machinery or industrial sewing machines. Meeting the specifications of the ISO and IEC standards helps machine designers demonstrate compliance with the Machinery Directive. As far as design principles are concerned, the expected approach is to design out hazards where possible and implement protective systems where necessary to minimize risks. These protective systems may take the form of physical guards that prevent
personnel entering hazardous areas or placing fingers, hands or limbs in harm’s way. By preventing such intrusions, which can result in personal injury, physical guards can enable machinery to operate continuously for long periods without interruptions from emergency stop signals. This can help maximize productivity. On the other hand, sensor-based systems that detect intrusion and trigger an alarm or stop the machine can allow greater flexibility and permit easier access for replenishing consumables or carrying out routine maintenance. Some applications may call for a combination of physical guarding where frequent access is not required, and intrusion detection where easier access is desirable or a barrier is not practicable. Safety systems Physical barriers must incorporate safeguards that can either prevent any access doors or hatches from being opened while the machine is operating, or stop the machine in the event the door is opened. These safeguards can be implemented using limit switches that can detect when the door is opened or closed, or by using a safety-door switch such as the Omron D4BS . The D4BS switch has up to two normally closed (NC) contacts and incorporates a direct-acting mechanism that opens the contacts if the safety barrier is
we get technical
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