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 [...]
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 [...]
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 [...]
Dispersion of an elevated release Often atmospheric dispersion models are needed to determine the potential for a gas release to impact workers or the public. This is typically encountered during Fire & Gas Mapping. There are quite a few decisions that go into a well-designed dispersion model, not the least of which are [...]
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) [...]
With the relatively new and growing interest in design of Fire & Gas systems using computer-aided mapping for detector placement, these software tools are rapidly evolving. Full disclosure here; Kenexis develops and licenses a very good software tool called Effigy™ for Fire & Gas Mapping, which is a component of the Kenexis Integrated Safeguard Suite. [...]
On June 8, 2015, OSHA issued a formal Letter of Interpretation regarding the application of Recognized and Generally Accepted Good Engineering Practices (RAGAGEP) to the Process Safety Management (PSM) Standard 29 CFR 1910.119. The requirements to comply with RAGAGEP are located in subpart (d) Process Safety Information and subpart (j) Mechanical Integrity. The new information [...]
Designers of fire and gas systems have long struggled with the question of how many detectors are required and where those detectors should be located. Historically, decisions about the number and location of detectors were made based on heuristics, expert judgement, or rule-of-thumb. The first step forward in gas detector placement came in 1992 with [...]
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, [...]
Quality has long been a priority for Kenexis. The recent implementation and accreditation of our ISO 9000 Quality Management System (QMS) has focused our attention both externally and internally, ultimately greatly improving the execution of our engineering consulting services. From an external point of view, the QMS compels us to actively pursue our customers for [...]
Recently, I was reminded by a customer of the importance of “Inspection” as part of maintenance program for Safety Instrumented System (SIS). When designing SIS, we are very concerned about the type and frequency of functional testing because this is a critical input to Safety Integrity Level (SIL) verification. However, a maintenance & testing program [...]
Many users of safety automation equipment employ a practice of using redundant field devices on safety-critical process measurements (e.g., level transmitters, flow transmitters, pressures transmitters, etc.). These users, who are often in the petroleum refining industry, typically use these measurements in a 2oo3 (two-out-of-three) vote to shutdown using triplicated field instruments, with this logic being [...]
I recently assisted a customer in testing a newly installed Safety Instrumented System (SIS) at a Natural Gas Liquids (NGL) processing facility. The activity was a Site Acceptance Test (SAT) in which Safety Instrumented Function (SIF) is thoroughly tested. The plan involved exercising each transmitter through its range of normal operation, alarm points, and trip [...]
I recently assisted a customer in conducting risk analysis to develop a Safety Instrumented System (SIS) design. The chemical process involved storage and handling of Methyl Isocyanate (MIC), and I was reminded that this coming December will be the 30th anniversary of the Bhopal tragedy, which involved the same chemical. Bhopal was one of the [...]
Kenexis is commonly asked to assist in specifying requirements for bypassing functions the Safety Instrumented System (SIS). Most SIS share a common Human Machine Interface (HMI) with the Basic Process Control System (BPCS). The HMI application software typically runs on a server and communicates with both the BPCS and the SIS using a digital protocol [...]
Recently Kenexis was asked to develop an SIS design for an NGL processing facility. The hazards were associated with operation of equipment beyond design temperature and pressure ratings of equipment including pressure vessels, distillation towers, condensers, reboilers, and pressurized liquid storage tanks. A third party conducted a hazard and risk analysis to establish target Safety [...]
