exida explains Blog

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?

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:

Read More...

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...

Close Enough? Not so Much

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.…

Read More...

  • 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…

Read More...

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…

Read More...

  • 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…

Read More...

How to Calculate Proof Test Coverage
  • 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…

Read More...

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…

Read More...

Lifecycle Analysis: It’s Worth the Effort

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…

Read More...

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…

Read More...

Ten Years Later
  • 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…

Read More...

The Architectural Constraint Blind Side
  • by Denise Chastain Knight, P.E., CFSE
  • 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)…

Read More...

The Meaning of Tool Integration
  • 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…

Read More...

Too Good to be True

A.K.A You’re About to Severely Under-Design your SIF and Put your People at Risk. Twice this week alone, and much more often than I like to remember, I’ve had safety system designers blindly follow certificates that contain data that simply cannot be true. They get a certificate from…

Read More...

What is Systematic vs. Random Capability?
  • by Loren Stewart, CFSP
  • Tuesday, September 01, 2015
  • Certification

What is Systematic vs. Random Capability?

There seems to be a bunch of confusion surrounding systematic capability and random capability.  I will try to clear up the confusion by explaining what is all considered and what the IEC standard says about both. 

Systematic Capability

  • Development process/quality system requirements depend on certification SIL level, higher…

    Read More...

What’s Your Biggest Fear?
  • by John Yozallinas, CFSE
  • Friday, September 11, 2015
  • Certification

What’s Your Biggest Fear?

Plane crash?

Earthquake?

Ebola outbreak?

Shark attack?

There are probably lots more things to add to that list.  What could we do to prevent them?  Not too much for some… a little more for others.  But would those mitigations be practical?  What tolerable risk can we accept for these…

Read More...

Why should I get my mechanical device certified per IEC 61508?

I was recently approached with a question regarding why it would be necessary to certify mechanical devices, such as valves, per IEC 61508 when it is not clearly stated in the standard that the standard is applicable to such devices.  After looking through IEC 61511 and Read More...

World Cup Fever & Failure Rates

World Cup Fever & Failure Rates

Do you have World Cup Fever? Well I do. Especially after the Netherlands (Holland) beat Spain 5-1 on Friday. I wished that was the score last time they played. So what does this have to do with failure rates? Sometimes my mind works in odd ways. While driving home…

Read More...