Making Use Of Leading And Lagging Indicators – Are You Using These For Functional Safety?

May 31, 2017

[:en][vc_row][vc_column][vc_column_text]Some of you reading this may not be aware or familiar with the terms “leading” and “lagging” indicators, when applied to Functional Safety.  The concept isn’t new but does provide significant benefit when applying this to Functional Safety because, if used correctly, these indicators can help significantly improve performance.  Let’s not forget that the IEC61511 standard is a “performance-based” standard and not prescriptive (i.e. tells you what you need to do but not how to do it).

In simple terms, “leading” indicators are an indication of the likelihood of having (or preventing) incidents from occurring that could have catastrophic consequences.  For example, by simply looking at how mechanical integrity is implemented, in terms of when and how proof testing is conducted, including timely repairs and maintenance, which will have an impact on the Safety Instrumented Systems overall integrity.  “Lagging” indicators, on the other hand, involve documenting incidents, failures, near misses, etc.  The fact that a relief valve (for example) goes off is an indication that all is not well with the process; an event which should be captured.

There are prime examples of where not paying attention to leading and lagging indicators has resulted in catastrophic events, such as the Texas City Isomerization Unit explosion in 2005.  The plant had experienced many years of incidents: releases, fires and fatalities that had largely gone ignored, resulting in a decline in infrastructure and poor maintenance.  Had leading and lagging indicators been used then things may have been different.

If this article has peaked your interest, then watch out for a webinar on the use of leading and lagging indicators to help improve process safety.[/vc_column_text][/vc_column][/vc_row][:zh][vc_row][vc_column][vc_column_text]No! They are not Inherently Safe!

A collaborative robot is intended to work “collaboratively” with a person. i.e. share a common workspace. It is force and speed limited by design to minimize any potential hazard. Collaborative robots fit the application where the task cannot be easily or cost effectively automated. They are easy to deploy, program and repurpose. Collaborative robots are new to everyone including the standards agencies.

A hazard and risk assessment is required that assesses the robot and the environment that it is deployed in. Just as any other robot, things such as collisions, speed, type of end effector and worksite need to be evaluated. Collaborative robots have their own sorts of collisions and hazards. They may not be as severe, but they still exist.

This all comes down to risk and the amount of risk that you are willing to accept! The diagram below shows the high-level steps for doing a Hazard and Risk Assessment. When following the steps, if you assess the risk and find it to be acceptable (your companies acceptable risk norms) then you are done. No need to add any risk reduction.

The next best approach is to determine if protective measures other than a Safety Function can reduce the risk to an acceptable level. If not, then you must assign a SIL and implement a safety function that will provide the required risk reduction.

exida can effectively train your team to perform machine hazard and risk assessments to identify all possible hazards and estimate the risk for each hazard. Specifically, exida coaches you through the process of evaluating the risk, developing and implementing risk reduction options. exida can also educate your team in multiple approaches to SIL target selection. These are just some of the things exida does to ensure you are on the right path![/vc_column_text][/vc_column][/vc_row] [:]

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