Maintenance Technology October 2015 - (Page 30)

MACHINE SAFETY Select The Right Safety Logic System Understanding the complete spectrum of safety logic systems can help users specify the correct ones for particular applications. Edited by Jane Alexander Managing Editor MACHINE SAFETY SYSTEMS have evolved over decades from strictly hardwired systems, where safety and standard logic were always separate, to the multifaceted spectrum of newer programmable systems with varying levels of cost, complexity, and wiring methods. When designing safety into machinery, engineers need to ensure compliance with today's more-stringent standards, while also factoring in how safety will interplay with productivity to keep downtime to a minimum. They also should consider how flexible and scalable a safety system will be with expanding or evolving operations. Maintenance personnel-often armed with experience working on legacy equipment-need to help ensure that a new or upgraded safety system is designed to properly mitigate safety risks. Working together, engineering and maintenance departments face the challenge of determining which safety logic system is right for each application. Their goal is to select the best, most costeffective option that can ensure compliance, while maintaining optimal production capability and flexibility. Pivotal changes A combination of contemporary safety standards and advances in technologies has brought machinery safety to the connected, information-enabled state in which it now exists. The implementation of ISO 13849 and IEC 62061, and the withdrawal of EN 954-1 in 2011, ushered in a new era of safety 30 | MAINTENANCE TECHNOLOGY standards. EN 954-1 specified safetyfunction characteristics and performance categories, but it didn't require risk to be measured using quantitative calculation. Today's more rigorous standards require engineers to assess and document the reliability of a safety system by adding quantitative calculations to the design. This includes factors such as proving component reliability (mean time to dangerous failure) and common-cause failure fractions (design, wiring, and assembly issues that could cause system failure). As a result, these new standards allow a more methodical riskassessment process. When combined with the latest programmable safety technologies, machinery can achieve more predictable performance, greater reliability, and better return on investment. This is helping manufacturers improve the bottom line without losing sight of safety. Out with the old Compare a legacy safety system to the more advanced safety systems entering the market. The differences are night and day. Legacy safety systems consist of standard programmable logic controllers (PLC), with each input, logic, and output safety device hardwired. The significant amount of wiring involved in these systems makes installation more complex, resulting in longer startup times and more difficult system upgrades. Legacy systems also lack diagnostics. Consequently, troubleshooting takes more time OCTOBER 2015

Table of Contents for the Digital Edition of Maintenance Technology October 2015

My Take
Uptime
For on the Floor
Industry News
Crushing Limestone with Reliability
Choose Reliability or Cost Control
Get To The Root of the Cause
Select the Right Safety Logic System
Simple Purchasing Practices Incite Lubrication Failure
CMMS Upgrade Tips
Pump-Bearing Alignment
Lockout/Tagout Advice
Advancing Ergonomics
Products
Showcase
Ad Index

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