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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