“…there is a belief amongst many engineers and managers that human error is both inevitable and unpredictable.
However, human error is inevitable only if people are placed in situations that emphasize human weaknesses and that do not support human strengths”
Martin Anderson, IChemE Safety and Loss Prevention…
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…
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…
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…
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…
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…
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”…
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…
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…
It’s hard to believe that it’s been 10 years since the Deepwater Horizon incident on April 20th 2010. Even today, the Gulf Coast is still feeling the effects. In its latest estimates, BP is looking at a total loss of $65Bn USD, in settlements, fines and compensation. This latest estimate was published in…
The Greek symbol λD represents dangerous failure rates in functional safety, usually expressed in the unit of measurement of FITs, and can be determined through FMEDAs. (FITs (λ) are failures per billion hours, expressed by 10-9 hours).
λD is the number of dangerous failures per…
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:
Failures In Time 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…
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…
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…