Congratulations! You’ve completed the Analysis and Realization phases of the Safety Lifecycle, and are about to begin the Operation phase, but what’s next? Well obviously you need to do proof testing, but is there anything else? You may be familiar with the figure below:
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Entries tagged with: SIF
- by Iwan van Beurden, CFSE
- Monday, July 23, 2012
- Software
Analysis and Realization: Done. Let’s Start Operation… What’s Next?
- by Dr. Eric Scharpf, CFSE
- Thursday, February 16, 2012
- Functional Safety
Babies, Bathwater, and Australian Safety Laws
The old saying goes, “Don’t throw the baby out with the bathwater.” But it looks like a number of people in Australia may be in danger of doing just that with their response to the country’s newly harmonized health and safety laws.
Australia’s new Read More...
- by Loren Stewart, CFSE
- Sunday, April 21, 2019
- Functional Safety
Back to Basics 04 - Safety Instrumented System (SIS)
In the following series of blogs, we'll go back to basics and run down everything you need to know to get started in functional safety. We'll start with some more general terms and descriptions and make our way to more advanced material.
4. SIS
A SIS – Safety Instrumented…
- by Loren Stewart, CFSE
- Monday, April 29, 2019
- Functional Safety
Back to Basics 05 – What is a Safety Function?
A Safety Function is the action of a collection of equipment to implement automatic mitigation of a particular hazard. It is the job of the Safety Instrumented Function (SIF).
Some examples of common Safety Functions:
- Car brake stop
- ESD valve – Shutdown process
- Sprinkler system
- High…
- 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 Denise Chastain Knight, P.E., CFSE, CCPSC
- Wednesday, May 27, 2015
- Functional Safety
Close Enough? Not so Much
Performing a SIL Verification calculation on preliminary design information can be a very useful tool to dial in the Safety Instrumented Function (SIF), Safety Requirements Specification (SRS) content , and define critical elements for the field component purchase specifications. Conceptual verification is typically performed quickly with general design information.…
- by Dr. William Goble, CFSE
- Thursday, May 31, 2012
- Certification
DANGER, DANGER, DANGER!
Assumed 10 Demands Per Year
During a SIF verification calculation review this week, the engineer pulled out a safety certificate with very low failure rates for a solenoid valve. Certificate No. V139 2009 C4-4 [1] states that a solenoid valve has a dangerous failure rate of 4.57…
- by Iwan van Beurden, CFSE
- Thursday, March 15, 2018
- Functional Safety
Fake Fact: Final Elements should not be included in SIF evaluation
Ehh… If your safety action is stopping flow/closing a valve, how are you going to accomplish this if you consider that the remote actuated valve is not part of your SIF ?
So, what is this myth based on? The title of IEC 61508 reads “Functional safety of electrical/electronic/programmable…
- by Iwan van Beurden, CFSE
- Friday, April 15, 2011
- Certification
Functional Safety and Taxes: Are you an expert?
Today, April 15th, is tax-day in the US. Ok, the Internal Revenue Service (IRS) has given us a few extra days this year (the tax filing deadline is not until April 18th).
There are a lot of similarities between how you do your taxes and how you handle…
- by Chris O'Brien, CFSE
- Tuesday, February 05, 2013
- Software
How Do You Handle Interposing Relays?
Many times in the design of a safety instrumented system it is necessary to utilize an interposing relay. Typically there is not a certified relay available. Since no certified product is being used it is important to follow the requirements to justify prior use and also to design…
- by Dr. William Goble, CFSE
- Thursday, October 16, 2014
- Certification
How to Calculate Proof Test Coverage
Most engineers who design and verify safety instrumented functions (SIFs) understand how hard it is to design a manual proof test with high effectiveness (also called high proof test coverage). Those folks who understand that a proof test is not likely to detect all failures never use simplified equations…
- by Dr. William Goble, CFSE
- Friday, May 04, 2012
- Functional Safety
I Don’t Want No D*** Diagnostics!
After a false trip incident, I heard a control engineer express his displeasure with the automatic diagnostics in a new safety rated transmitter. The transmitter diagnostics were annunciated by sending the analog current out of range. In this case, the current went to 3.6 milliamps. The problem was that…
- by Steve Gandy, CFSP
- Thursday, September 13, 2018
- Functional Safety
Is It Possible to Extend Proof Test Intervals?
I am often asked whether extending proof test intervals will be a problem.
This is a tricky question. The design and engineering SIL calculations for the Safety Instrumented Functions (SIFs) are taking credit for a specific proof test interval with a defined level of coverage, as defined within the…
- by Dr. Eric Scharpf, CFSE
- Monday, April 18, 2011
- Functional Safety
Lifecycle Analysis: It’s Worth the Effort
Performing a risk analysis as part of an IEC61508 / 61511 / ISA 84.01 safety lifecycle process can be quite challenging. How can you be sure you get what you need within budget and how can your team provide the best value for money?…
- by Hal Thomas, CFSE
- Thursday, August 25, 2011
- Functional Safety
PHA to LOPA: Part I
Parts I and II of this article provide a framework for when it is appropriate to make the transition from qualitative analysis to more quantitative during the hazard review work process. It further illustrates that LOPA can be used as part of what is considered more qualitative analysis…
- by Hal Thomas, CFSE
- Tuesday, August 30, 2011
- Functional Safety
PHA to LOPA: Part II
In some cases the screening methods will indicate that a SIF is needed. These screening methods can be designed to determine how many orders of magnitude risk reduction is needed, allowing a required SIL to be documented for a particular SIF. The screening…
- by Steve Gandy, CFSP
- Thursday, October 19, 2017
- Functional Safety
Random versus Systematic Faults: What’s the difference?
I saw and responded to a LinkedIn discussion on this very issue, where someone had asked “if I have a misaligned limit switch that fails dangerously, then is it random or systematic? “. This is an intriguing question because many view human error as being systematic and, whereas, this…
- by Steve Gandy, CFSP
- Wednesday, February 19, 2014
- Certification
Ten Years Later
It’s hard to believe that the IEC61511 standard has been in existence since 2003, and most companies operating in the process, chemical, and refining industries (or any other hazardous process manufacturer) have adopted its practices. It’s also significant that any plants that were built back then with a…
- by Denise Chastain Knight, P.E., CFSE, CCPSC
- Thursday, August 27, 2015
- Certification
The Architectural Constraint Blind Side
I did my homework, purchased certified devices, and specified physical redundancy. I expected an uneventful SIL Verification but the assessor is telling me that I have functions failing Architectural Constraints in the sensor and final element groups. How can that be?
Low demand mode Safety Instrumented Function (SIF)…
- by Iwan van Beurden, CFSE
- Tuesday, June 14, 2016
- Software
The Meaning of Tool Integration
What does tool integration mean? One can argue it is the ability for different tools to talk to each other and exchange data. Though this may be true from a typical software tool integration, a common definition of integrate, i.e. to bring together or incorporate (parts) into a whole…