Safety Instrumented System

//Safety Instrumented System

Comparison of Voting Arrangements in SIS

By |2018-11-07T16:31:42+00:00November 7th, 2018|Edward M. Marszal, Safety Instrumented System|

While I'm certain that all of you have all of the strengths and limitations of the different voting arrangements tatooed in your memory, I know that you also have to explain these strengths and limitations to others.  For instance, a manager might be insisting that 2oo2 voting is superior to 2oo3 voting, because it has [...]

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Systematic Safety Integrity; what you need to know.

By |2018-07-06T12:24:59+00:00July 6th, 2018|Kevin Mitchell, News, Safety Instrumented System, Services, Vertigo|

There's a lot of confusion about Systematic Safety Integrity in new IEC61511.  We are starting to see devices certified for SIS applications to have a rated Systematic Capability (SC) of 2.  What does this mean?  Is this yet another hurdle I need to jump over to meet a SIL target?  Let's shine some light on Systematic [...]

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When all your eggs are in the BPCS and SIS protection layers

By |2018-01-26T12:22:25+00:00January 26th, 2018|Arbor, Kevin Mitchell, News, Safety Instrumented System, Vertigo|

During Layer of Protection Analysis (LOPA) of high hazard scenarios, we often rely on a diversity of protections including instrumented and non-instrumented safeguards.  Invariably, we run into situations where instrumented safeguards must bear the full weight of risk reduction.  Of course, we never want to design a Safety Instrumented Function to a SIL 4 or [...]

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Derivation of PFD Equations for SIL Verification

By |2018-01-26T11:42:41+00:00October 12th, 2017|Arbor, Author, Edward M. Marszal, News, Products, Safety Instrumented System, Services, Vertigo|

Have you ever wondered where the equations that are used to calculate probability of failure on demand for SIL verification came from?  In this video, Kenexis CEO Ed Marszal goes the white board to show you.  This video will demonstrate how all of the equations are based on the fundamental definitions of availability and reliability.  [...]

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SIS Testing Optimization

By |2018-01-26T11:43:35+00:00August 29th, 2017|Process Hazards Analysis, Reducing Turnaround Cost, Safety Instrumented System, Todd Longendelpher|

Testing of the safety instrumented system (SIS) is a critical lifecycle task that ensures the proper operation of functional safety devices, identifies component failures that can be repaired and tracked, allows tolerable risk goals of the organization to be achieved, and maintains compliance with functional safety standards and safety regulations.  While testing of functional devices [...]

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How do I decide on the need for toxic gas detection?

By |2018-01-26T11:43:48+00:00August 10th, 2017|Effigy, Fire and Gas Systems, Kevin Mitchell, Safety Instrumented System|

We were recently asked about placing Hydrogen Sulfide (H2S) gas detectors in an area of the process where no H2S gas is normally present. Does the possibility for process upset conditions to abnormally result in the presence of toxic gas give rise to a requirement for detection? There was no way to simply answer the [...]

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Reducing Turnaround Time and Cost

By |2018-01-26T11:44:12+00:00July 26th, 2017|Jim McGlone, Process Hazards Analysis, Reducing Turnaround Cost, Safety Instrumented System, Vertigo|

In todays oil and chemicals market, time and budgets are strained to remain operational with a slight profit. Many facilities are making difficult operational and turnaround decisions to survive while possibly putting their operation at risk at the same time. There might be a significant way to reduce time and cost during operations and [...]

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1947 Texas City industrial accident

By |2017-08-29T14:56:36+00:00April 17th, 2017|Jim McGlone, News, Process Hazards Analysis, Safety Instrumented System|

Today, we remember the 1947 Texas City industrial accident. The picture in our office, reminds us daily that Kenexis exist to prevent these. ‬ Learn more at https://en.wikipedia.org/wiki/Texas_City_disaster  

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Design of SIS Bypasses

By |2017-06-25T19:58:08+00:00December 6th, 2016|Author, Edward M. Marszal, Safety Instrumented System, Services|

The mechanism for the bypass needs to meet the requirements of the IEC 61511 (ISA 84) standard.  The relevant sections from the 2016 version of IEC 61511 are as follows: 11.7.2.1  Where the SIS operator interface is via the BPCS operator interface, account shall be taken of credible failures that may occur in the BPCS [...]

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Achilles JQS Registered

By |2017-06-25T19:58:08+00:00November 15th, 2016|Fire and Gas Systems, ICS Cybersecurity, Jim McGlone, News, Process Hazards Analysis, Safety Instrumented System|

Achilles JQS Registered Supplier Kenexis Consulting Corporation is pleased to announce that it is a registered, verified, and compliant supplier on Achilles Joint Qualification System (JQS) for the Oil and Gas Industry in Norway and Denmark. Achilles creates and manages a global network of collaborative industry communities, allowing trading partners to share high quality, structured, [...]

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Determining Shutoff Valve Leak Tightness Requirements

By |2017-08-30T14:22:23+00:00October 5th, 2016|Author, Edward M. Marszal, News, Reducing Turnaround Cost, Safety Instrumented System, Services|

A prior blog on the Kenexis web site related to the requirements for tight-shutoff (TSO) for valves that are part of a safety instrumented function generated a lot of interest in the engineering community.  A link to that blog is shown below. Tight Shutoff Requirements in SRS Blog After writing that blog, Kenexis routinely received [...]

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Another Limitation to Extending Test Intervals

By |2016-08-11T12:48:36+00:00August 11th, 2016|Author, Edward M. Marszal, News, Safety Instrumented System, Services|

A customer noted that some operating companies limit the extension of their test intervals so that the test interval is at least half of the expected demand rate.  For instance, if a safety instrumented function (SIF) is intended to prevent against a hazard whose initiating event rate is once in ten years, then the test interval [...]

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Low O2 / High Combustibles Heater Shutdown

By |2017-06-25T19:58:09+00:00August 5th, 2016|Author, Edward M. Marszal, News, Safety Instrumented System, Services|

I received this customer question that is common enough that I thought that I would publish the answer in a blog... >> Have you seen others in the petrochemical industry using analytical measurements (combustibles, CO, O2) of flue gas to shut down fired heaters? Yes >> Many of our PHAs are identifying unburned fuel in [...]

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Unavailability Simplified Equation Derivation

By |2017-06-25T19:58:09+00:00July 22nd, 2016|Author, Edward M. Marszal, Safety Instrumented System, Vertigo|

The process of safety integrity level (SIL) verification requires calculation of probability of failure on demand.  As per convention and the information contained in the IEC 61511 standard (ISA 84.00.01), ISA technical reports on the topic and ISA training, the calculation is typically done using simplified equations.  The terms of these equations are either based [...]

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Cybersecurity PHA Review

By |2017-06-25T19:58:09+00:00April 20th, 2016|Author, ICS Cybersecurity, Jim McGlone, Process Hazards Analysis, Safety Instrumented System|

Make sure to check out the cover article in ISA’s InTech publication. In the article, Ed Marszal explains: “Even though cyber-threats are not adequately addressed with existing process hazard analysis (PHA) methods, there is no reason to abandon everything that we know about process risk assessment and start from scratch. Instead, industry is extending tried-and-true [...]

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Analyzing for Cybersecurity Risks during HAZOP

By |2016-02-23T15:09:30+00:00February 10th, 2016|ICS Cybersecurity, Jim McGlone, Process Hazards Analysis, Safety Instrumented System|

Attached is a presentation on how to analyze hazardous process situations for cybersecurity risks during a HAZOP or an interim review. We would be pleased to assist you in facilitating this type of review with a HAZOP expert and an Industrial Control System Cybersecurity expert. https://youtu.be/DcOAycWNgIE  

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Comparing Safety Instrumented Systems and Machine Safeguarding

By |2017-06-25T19:58:09+00:00February 2nd, 2016|Author, Edward M. Marszal, Safety Instrumented System, Services|

Industry has applied instrumentation and control devices for the purpose of safeguarding people, equipment, and business for almost as long as instrumentation and control has been used - that is machine safeguarding and safety instrumented systems. In the “wet” process industries these devices and systems have been employed to detect out of control conditions in [...]

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Brittle Fracture Hazards in Carbon Steel AMSE-Rated Equipment

By |2017-08-07T10:49:47+00:00January 20th, 2016|Kevin Mitchell, Process Hazards Analysis, Safety Instrumented System|

Whenever a PHA or LOPA considers a low temperature hazard for carbon steel equipment, the team examines the P&IDs and possibly the mechanical data file to find the mechanical temperature rating.  The upper temperature limit is usually shown on P&Ds with the corresponding design pressure (MAWP).  Less frequently is the Minimum Design Metal Temperature (MDMT) [...]

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Tight Shutoff Requirements in SRS

By |2017-08-08T09:14:22+00:00November 24th, 2015|Edward M. Marszal, Safety Instrumented System|

The IEC 61511 standard requires that the need for tight shutoff be specified in the safety requirements specifications. Section 10.3 SIS safety requirements states, 10.3.1 These requirements shall be sufficient to design the SIS and include  the following: ... A description of the SIS process output actions and the criteria for successful operation, for example, tight [...]

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PHA/LOPA Study Findings for Separation of Basic Process Control and Safety Instrumented Systems

By |2017-06-25T19:58:12+00:00July 17th, 2015|Kevin Mitchell, Safety Instrumented System|

Recently I had a customer request Kenexis conduct SIL verification analysis on several safety functions implemented in a safety-configured, general purpose controller.  This was associated with a new capital project at the customer facility.  There was a modest SIL 1 required on each Safety Instrumented Function (SIF).  The client had previously determined the target SIL, [...]

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Documenting Environmental Extremes in Safety Requirements Specifications

By |2017-06-25T19:58:13+00:00April 24th, 2015|Edward M. Marszal, Safety Instrumented System, Vertigo|

The IEC 61511 standard requires that the user specify extremes of environmental conditions as part of the safety requirements specifications package. This requirement is actually not a safety requirement but a general requirement for operation of all instrumentation and control devices, but its inclusion in the list of safety requirements specifications implies that the associated [...]

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