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…
exida explains Blog
- by Loren Stewart, CFSE
- Tuesday, February 25, 2020
- Functional Safety
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…
- by Todd Stauffer
- Thursday, February 20, 2020
- Functional Safety
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…
- by Loren Stewart, CFSE
- Tuesday, February 11, 2020
- Functional Safety
Back to Basics 23 – Stiction
What is 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…
- by Steve Gandy, CFSP
- Thursday, February 06, 2020
- Functional Safety
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…
- by Loren Stewart, CFSE
- Tuesday, February 04, 2020
- Functional Safety
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…
- by Jeff Davis
- Thursday, January 30, 2020
- Functional Safety
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…
- by Loren Stewart, CFSE
- Tuesday, January 28, 2020
- Functional Safety
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…
- by Todd Stauffer
- Tuesday, January 21, 2020
- Alarm Management
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…
- by Loren Stewart, CFSE
- Tuesday, January 14, 2020
- Functional Safety
Back to Basics 20 – Safe Failure Fraction, SFF
Safe Failure Fraction (SFF) is defined as the ratio of the average rate of safe failures plus dangerous detected failures of the subsystem to the total average failure rate of the subsystem. It is defined for a single channel (no redundancy, 1oo1).
It is a measurement of the likelihood of…
- by Dr. William Goble, CFSE
- Thursday, January 09, 2020
- Certification
Getting the Best IEC 62443 Cybersecurity Certification?
After careful planning and development of your system, the last thing you want to worry about is the credibility of your certification. Although it may seem like a given for your certification to be well accepted by your customers, it is never a bad idea to dig a little…
- by Loren Stewart, CFSE
- Thursday, January 02, 2020
- Functional Safety
Back to Basics 19 – Route 2H
Route 2H is one of two Architectural constraints options made available in the standards IEC 61508-2 and IEC 61511. Route 1H . Both Route 1H and Route 2H are limitations that impose the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem.
What exactly is Route 2H…
- by Todd Stauffer
- Thursday, December 19, 2019
- Alarm Management
CSB Cites Lack of Alarm Management as Contributing Factors to Blowout in Oklahoma
US Chemical Safety Board cites lack of Alarm Philosophy, Alarm Rationalization, and State-Based Alarming as Contributing Factors to Blowout in Oklahoma
On January 22, 2018, a blowout and rig fire at the Pryor Trust gas well killed five workers, who were inside the…
- by Loren Stewart, CFSE
- Tuesday, December 10, 2019
- Functional Safety
Back to Basics 18 – Route 1H
Route 1H is one of two Architectural constraints options made available in the standards IEC 61508-2 and IEC 61511. Route 1H . Both Route 1H and Route 2H are limitations that impose the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem.
Route 1H is…
- by Loren Stewart, CFSE
- Thursday, December 05, 2019
- Functional Safety
exida’s Safety Reliability Analysis (SRA) and How It May Help You
We all know that an FMEDA is only as good as the assumptions made regarding typical design engineering practices and the database used for the failure rates. Here is the catch, not all products are designed and manufactured per the same rules! Many manufacturers boast that their…