exida explains Blog

Bow Ties Part II: Do Bow Ties have a place in Alarm Management?

Bow Ties Part II: Do Bow Ties have a place in Alarm Management?

As discussed in Part I, bow tie diagrams provide an easy-to-understand visual representation of risk management information (hazards, potential consequences, barriers, degradation factors and controls). In this article we examine the applicability of bow ties to alarm management.

According to the CCPS book “Bow Ties in Risk Management”,…

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Back to Basics: Failure Rates - λ

Back to Basics: Failure Rates - λ

The Greek symbol lambda, λ, represents failure rates in functional safety, usually expressed in the unit of measurement of FITS.

λ can be expressed as a total failure rate for a device (λT), or it can be broken down into more specific groupings:

  • Safe detected (λSD)
  • Safe undetected (λSU)
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The CFSE Exam is Now Offered Online!
  • by Ted Stewart, CFSP, exidaCSP
  • Tuesday, March 17, 2020
  • Certification

The CFSE Exam is Now Offered Online!

Alarm Philosophy Development – Going to Great Lengths

Alarm Philosophy Development – Going to Great Lengths

Creating an alarm philosophy document is often the entry point into the ISA-18.2/IEC 62682 alarm management lifecycle. Many tasked with developing one are discouraged by its length and the barriers it creates. When it comes to using the philosophy document, a common concern is that if the…

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Back to Basics: Failure Rates - FITS

Back to Basics: Failure Rates - FITS

Failures ITime or Failure UnIT

FITs is the number of failures per billion hours for a piece of equipment. 

It is mentioned in both IEC 61508 and IEC 61511 standards as a preferred unit of measurement expressed by 10-9 hours.

Example: 5 FITs is expressed as 5 failures every 10-9 hours (5x10-9). 

When you…

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I Failed the CFSE Exam, HELP!
  • by Dr. William Goble, CFSE
  • Thursday, February 27, 2020
  • Certification

I Failed the CFSE Exam, HELP!

It is tough to receive an email with this message from a prospective CFSE candidate.  I know that when I have failed exams, I want to understand what was wrong so I can study those areas of knowledge more deeply and try again. Given the recognition and prestige…

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Back to Basics: Failure Rates

Back to Basics: Failure Rates

Failure rates are the number of failures per unit time for a piece of equipment which are usually assumed to be a constant value. They can be broken down into several categories, such as safe and dangerous, detected and undetected, and independent/normal and common cause. Failure rates are often…

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Bow Ties Part I: Great for Formal Occasions and for Risk Management

Bow Ties Part I: Great for Formal Occasions and for Risk Management

The bow tie methodology, originally developed by ICI in the late 1970’s, has seen increasing industry adoption over the last 20 years. Bow tie diagrams build on the “Swiss Cheese Model” of hazard escalation and causation popularized by James Reason. They provide a powerful means for visualizing how a…

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Psychometrics – Another reason CFSE remains the Gold Standard
  • by Ted Stewart, CFSP, exidaCSP
  • Thursday, February 13, 2020
  • Certification

Psychometrics – Another reason CFSE remains the Gold Standard

In today’s day and age, functional safety certificate and certification programs are becoming common. There are many to choose from with their own set of requirements and expectations.  

So how do we know which one to choose?

The…

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Back to Basics 23 – Stiction

Back to Basics 23 – Stiction

What is Stiction? 

stiction

Stiction is the resistance to the start of motion usually measured as the difference between the external force being applied in order to overcome the static friction and the force to maintain movement between the two contacting or working surfaces.

It can…

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Why Bother With Systematic Issues?

Why Bother With Systematic Issues?

You may be wondering why this question is being asked?  Isn’t it obvious that systematic issues are important and need to be considered?  It may be that some of you reading this blog may not even understand what is meant by systematic issues.  In which case, it may surprise you to know…

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Back to Basics 22 – Cycle Testing

Back to Basics 22 – Cycle Testing

A cycle test is done on a set of products (>20) until 10% of the units under test fail. 

The number of cycles is converted to a time period by knowing the cycles per hour in any particular application. 

A failure rate is calculated by dividing the 10% failure…

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ISO 26262 Independence and Related Terms

ISO 26262 Independence and Related Terms

The “ISO 26262 Road vehicles – Functional safety” specification defines the concepts of “Independence”, “Interference” and other terms which can be a little confusing. This discussion will try to make the concepts clearer.

Independence

Let’s talk about “Independence” and associated concepts first.  “Independence” is a concept used within Dependent…

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Back to Basics 21 – The B10 Method

Back to Basics 21 – The B10 Method

The B10 method uses cycle test data to predict failure rates. 

A cycle test is done on a set of products (>20) until 10% of the units under test fail. The number of cycles until failure is called the B10 point.

The B10 number of cycles is converted to a…

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Alarm Response Procedures: More than Just a Good Idea

Alarm Response Procedures: More than Just a Good Idea

From an operations point of view, one of the significant parts of the ISA-18.2 and IEC 62682 alarm management standards is the endorsement of alarm response procedures. An alarm response procedure, otherwise known as “Alarm Help” or “Alarm Response Manual”, is defined as guidance for response to an alarm (e.g., operator…

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