Safety Programmable Logic Controller
Brief Summary:
PLCs have been used to reduce costs and increase productivity. They are now being incorporated for safety aspects. Safety PLCs are easier to repair and use while also reducing false alarms.
- When the name is Safety programmable logic controller (PLC), the meaning seems obvious—a special class of PLC designed for use in safety critical applications.
- Namely, that Safety PLCs and associated safety networks can help save money and boost productivity.
- One reason for the optimism is the growing influence of international safety standards such as the IEC 61508—the International Electrotechnical Commission standard that governs functional safety in programmable electronic systems.
- Moreover, Safety PLC-based systems are less prone than hardwired safety systems to "nuisance trips" that can unnecessarily shut down a factory operation. And they are much easier and faster to troubleshoot, resulting in less machine or process downtime.
- Configured on Ethernet safety networks, the Guard units will provide safety monitoring and "control-reliable" access for plant personnel to robotic work cells that build vehicle doors, hoods and trunk lids.
- That approach enables a safe and orderly equipment shutdown by the redundant PLC unit if the primary unit fails. But it is also expensive, requiring a great deal of engineering, hardware and custom software to support the safety function.
- Fail-safe systems are used primarily in manufacturing, and are typically programmed to protect worker safety by safely shutting down machinery when faults or problems occur. Fault-tolerant systems, by contrast, are generally set up to keep processes running when faults are detected. This approach is favored for many continuous process applications in which a shutdown might actually be dangerous to workers or the environment, and could also produce economic damage in lost product or equipment.
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