- by Steve Gandy, CFSP
- Thursday, November 19, 2020
- Functional Safety
The Dos and Don’t of SIS Application Programming
It’s interesting that the majority of the time when people talk about functional safety, they are usually thinking about hardware: what sensors to use, which logic solver, what actuator, solenoid or valve to select; what voting architecture, etc. What often gets overlooked, initially, is the application program.
Essentially, when…
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- by Paul Chan, CFSP
- Tuesday, October 13, 2020
- Functional Safety
How the PHA and LOPA are going to affect your SIS

Both Process Safety Analysis (PHA) and Layer of Protection Analysis (LOPA) occur in the early stage of the Functional Safety Lifecycle, detailed in both IEC 61511 and IEC 61508. They both serve significant roles in the whole process safety management. Yet, as a facilitator…
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- by John Yozallinas, CFSE
- Thursday, September 24, 2020
- Functional Safety
Share the Wealth (of Functional Safety Knowledge)
Experience is a good teacher. But how do you get the experience?
Formal classroom or online training is often available for more general skills, but on-the-job training usually provides a more in-depth path to gain such experience. After doing a job for a while, working through difficulties with colleagues,…
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- by Mark Kozub
- Thursday, August 20, 2020
- Functional Safety
IEC 62061 Machine Safety: “It’s simply the right thing to do”
I can't begin to tell you how many of our customers share with us how lucky they have been to be incident-free at their plant.
Or, because they have not had an incident in over 10 years, it is hard to justify the cost of a Machine Hazard…
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- by Loren Stewart, CFSE
- Tuesday, August 18, 2020
- Functional Safety
Back to Basics: Failure Rates - λS
The Greek symbol λS represents safe or spurious failure rates in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λS is the number of safe…
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- by Steve Gandy, CFSP
- Thursday, August 13, 2020
- Functional Safety
IEC61511 and Failure Rates
Most end users I teach in our FSE100 class are not really aware of or fully, understand when we talk about failure rates. For example, what’s a FIT mean? For those end users more versed in this, they understand what is meant by a FIT. Essentially a device can have…
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- by Steve Gandy, CFSP
- Tuesday, July 14, 2020
- Functional Safety
Functional Safety Management Systems & Engineering Companies
In recent discussions with several engineering and integrators of Safety Instrumented Systems (SIS), it’s become very clear to me that the majority I have spoken to, don’t have any form of Functional Safety Management System (FSMS) in place. This is interesting because one of the changes in the…
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- by Dr. William Goble, CFSE
- Tuesday, July 07, 2020
- Functional Safety
OLD component data = Bad FMEDAs
When we first invented the FMEDA technique in the late 1980s the biggest problem was the component failure rate and failure mode data. Still is. I picked up a well-known standard for component failure rates and saw a date of 2010. The technology world has gone through an order of…
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- by Loren Stewart, CFSE
- Tuesday, June 30, 2020
- Functional Safety
Back to Basics: Failure Rates - λDD
The Greek symbol λDD is the detectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λDD is the number of…
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- by Dr. William Goble, CFSE
- Tuesday, June 23, 2020
- Functional Safety
Risk Management in the News
I just read a great article in the May issue of IEEE Spectrum magazine called “Managing Risk and Responsibility During a Crisis.” The author Robert N. Charette says “If the American people desire the federal government to be their risk manager of first resort, then an open and…
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- by Steve Gandy, CFSP
- Tuesday, June 16, 2020
- Functional Safety
What is Prior Use Justification?
When it comes to IEC61511 and the selection of equipment for use within Safety Instrumented Systems (SIS) and Safety Instrumented Functions (SIF), there are only two methods that can be used to justify selection: IEC61508 Certified devices for the required SIL or Prior Use Justification. Just…
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- by Todd Stauffer
- Thursday, June 11, 2020
- Functional Safety
Know Your Human Error (Part I)
Increases in levels of automation and system complexity impact human error. Medical errors in hospitals and clinics result in approximately 100,000 people dying each year and cost the healthcare industry between $4B – $20B each year. In the petrochemical industries, operational error can cost upwards of $80M per incident. “Operator error”…
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- by Loren Stewart, CFSE
- Thursday, June 04, 2020
- Functional Safety
Back to Basics: Failure Rates - λDU
The Greek symbol λDU is the undetectable dangerous failure rate in functional safety expressed in the unit of measurement of FITs which can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).

λDU is the number of dangerous undetected failures…
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- by Dr. William Goble, CFSE
- Tuesday, May 12, 2020
- Functional Safety
What’s inside a COVID-19 Ventilator?
At exida, we just finished a Failure Modes and Effects Analysis (FMEA) on a medical ventilator. This was done for a new manufacturer who needed independent design verification. It was a fascinating job. We found lots of pneumatic devices very similar if not identical to the kind used in…
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