What’s on your Christmas list? Instead of relying on Santa, here are some gifts you can expect from a SIL 3 compliant process:
- 12 safety requirements improved through review by test engineers
- 11 validation tests that uncovered problems before they reached the field
- 10…
- by Loren Stewart, CFSE
- Thursday, October 03, 2019
- Functional Safety
Back to Basics 15 - Architectural Constraints
Architectural constraints are limitations that are imposed on the hardware selected to implement a safety-instrumented function, regardless of the performance calculated for a subsystem. Architectural constraints are specified (in) according to the required of the subsystem, type of components used, and of the subsystem’s components. (Type A components are simple devices…
- by Loren Stewart, CFSE
- Thursday, March 05, 2020
- Functional Safety
Back to Basics: Failure Rates - FIT
Failures In Time or Failure UnIT
FIT 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 109 hours.
Example: 5 FIT is expressed as 5 failures within 109 hours .
When you…
- 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 Rick Smith
- Wednesday, January 04, 2017
- Functional Safety
Conceptual Design and SIL Verification’s Ultimate Resource
I was talking to a customer the other day regarding failure rate data and I brought up our Safety Equipment Reliability Handbook (SERH): 4th Edition. Through the years, along with our comprehensive safety lifecycle tool exSILentia, the book set has become one of exida's flagship products. If you…
- by Loren Stewart, CFSE
- Wednesday, March 12, 2014
- Certification
Cycle Testing for Static Applications? NO!
The failure rates of certain mechanical components used in solenoid valves, actuators, and valves vary substantially depending on operation. Seals such as O-rings, for example have fundamentally different failure modes when used in applications with frequent movement (dynamic) versus applications with infrequent movement (static).
Static is generally…
- by Loren Stewart, CFSE
- Monday, January 27, 2014
- Certification
Dare to Be Different
exida is often posed questions regarding our failure rates used in Failure Modes, Effects and Diagnostic Analysis (FMEDA) for products used in safety-related systems.
Today I would like to focus on a question that was recently asked: “What if my products are unique or different than products…
- by Dr. William Goble, CFSE
- Thursday, May 17, 2018
- Functional Safety
Does Everyone Really Ignore Failure Rates?
While discussing functional safety certification of an integrated valve assembly with a manufacturer, exida stated that all devices (actuator, pneumatic parts, valve, etc.) must be IEC 61508 certified. The manufacturer said this was no problem, and provided a set of exida and TÜV certificates.
Of…
- by Dr. Eric Scharpf, CFSE
- Tuesday, May 28, 2019
- Functional Safety
Duty of Care (Too Good to Be True Failure Rate Data)
I have received several calls lately to our Australia / New Zealand office about whether it is acceptable to use published failure rates that seem too good to be true.
The person calling is usually doing a SIL verification calculation for an operating plant or for an…
- by Valerie Motto
- Monday, August 05, 2024
- Software
Environmental Impact on Failure Rates
Good component failure rate data is a cornerstone of good quality reliability metric analysis. As mentioned in a previous exida whitepaper, one of the shortcomings of reliability databases has been the inability to handle variations in the operating environment. A sensor monitoring a flame and the processor interpreting the signal…
- 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…
- by Dr. William Goble, CFSE
- Wednesday, January 21, 2015
- Functional Safety
Field Data Validation with Predictive Analytics
Who cares about field failure data? Why are we even here?
IEC 61511 – Fundamental Concepts
The fundamental concepts from our functional safety standards are the probabilistic performance based design. Many of you know that this was terribly controversial when this was first proposed. Even to this day, there…
- by Loren Stewart, CFSE
- Thursday, September 01, 2016
- Certification
FMEDA Predictions
The FMEDA technique is performed on a specific device (e.g., ball valve, pressure transmitter, temperature sensor, electronic module, etc.) specified down to the manufacturer and series/model. Based on the specifics of the design, the parts used to execute the design, the design margins, any automatic diagnostics, the…
- by Valerie Motto
- Thursday, July 14, 2022
- Functional Safety
Getting Failure Rate Data on a New Component
Realistic component failure rate data is critical to an effective Failure Modes, Effects, and Diagnostic Analysis (FMEDA). This failure rate data can eventually be obtained from component parts manufacturers, research and field failure data analysis. For example, exida’s Component Reliability Database (CRD) has been built from internet research, technical…
- by Dr. William Goble, CFSE
- Thursday, July 09, 2015
- Functional Safety
Getting Realistic Failure Rate Data - Part 4
Over the course of several blogs , I will talk about getting realistic failure rate data, where this failure data comes from, and how different methods of failure data analysis compare. I think if you understand this, you will begin to get a very good feel of what it…
- by Dr. William Goble, CFSE
- Monday, July 20, 2015
- Certification
Getting Realistic Failure Rate Data - Part 5
Over the course of several blogs , I will talk about getting realistic failure rate data, where this failure data comes from, and how different methods of failure data analysis compare. I think if you understand this, you will begin to get a very good feel of what it…