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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Entries tagged with: FITS
- by Loren Stewart, CFSE
- Thursday, March 19, 2020
- Functional Safety
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) …
- by Loren Stewart, CFSE
- Thursday, April 02, 2020
- Functional Safety
Back to Basics: Failure Rates - λD
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…
- 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…
- 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…
- 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…
- 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…
- by Chris O'Brien, CFSE
- Friday, January 17, 2014
- Certification
Product Stewardship and Engineering Ethics
Recently I witnessed something I never thought I would in the engineering profession: I was told by a system designer that even though they knew the safety reliability data for one device was too optimistic, they were going to use it because it meant they didn’t need to…