Introduction | When Safety Meets Operational Reality January 2026 — by Emily Henry, PE (SC) , CFSE, Functional Safety Group Manager — This is the third installment in The PHA Recommendation Playbook, a series intended to help process safety managers, EHS leaders, and facility managers navigate the practical challenges of resolving PHA recommendations. In Part 1, we examined how resource constraints can stall progress . In Part 2, we explored how technical complexity  can turn seemingly simple recommendations into multi-layered engineering efforts. In this article, we focus on a challenge that often emerges after solutions are identified and budgets are approved: scheduling and operational disruptions. Many PHA recommendations are fairly straightforward and are not technically difficult to implement. The challenge for implementation is typically timing. Commissioning equipment related to Safety recommendations often can require plant outages, temporary process changes, or reduced throughput. Production schedules, however, are rarely flexible. When commissioning equipment related to safety recommendations conflicts with operational demands, recommendations can remain open far longer than intended. This tension is not a sign of poor management. It is a structural reality in many regulated facilities. How organizations navigate it determines whether PHA recommendations become a source of frustration or a driver of long-term resilience.   Scheduling and Operational Disruptions in PHA Recommendations | Why Timing Becomes the Constraint Scheduling and operational disruptions refer to the practical limitations that prevent PHA recommendations from being implemented without affecting production. Unlike administrative actions or procedural updates, many recommendations require physical changes to equipment, controls, or processes. These changes often cannot be completed while a unit is running. Implementation may require planned outages or partial shutdowns, temporary workarounds to maintain production, or coordination with existing maintenance and turnaround schedules. In facilities with continuous operations, even short interruptions can have downstream effects on supply commitments, staffing, and revenue. These challenges are especially common in environments where production peaks are seasonal or where outage windows are limited and planned years in advance. Safety recommendation implementation due dates may conflict with commercial commitments, customer demand, or contractual obligations. As a result, recommendation implementations are often deferred not because they are unimportant, but because there is no scheduled outage during which to complete the work. It is important to recognize that these challenges are structural. They cannot be resolved with documentation alone. A justification memo does not create an outage window. A tracking spreadsheet does not reduce production pressure. Addressing scheduling conflicts requires coordination, planning, and leadership alignment.   The Cost of Deferral | When PHA Recommendations Stay Open Too Long When PHA recommendations are repeatedly deferred due to scheduling conflicts, risk compounds over time. OSHA expects recommendations to be resolved in a timely manner or to have clear documentation explaining why they remain open. While operational constraints may be valid, they are rarely sufficient on their own if delays persist without a plan for resolution. During audits, an insufficient deferral explanation for an incomplete recommendation action such as “open due to operations” would likely invite follow-up questions. Auditors want to understand what interim safeguards are in place to mitigate unresolved risk, whether the issue is being actively managed, and when resolution is expected. Without evidence of intent and resolution planning, deferrals can be interpreted as avoidance of addressing risk. From a safety perspective, prolonged deferral means operating with known unmitigated risks for extended periods. Over time, deferred recommendations can normalize the presence of known risk, particularly when scheduling constraints repeatedly delay implementation. Thus, the urgency of the recommendation basis fades due to stopgap measures seemingly serving a mitigative purpose even though the underlying risk remains. Operationally, deferring action items can create larger problems later. Work that could have been completed during a short outage may require a longer shutdown once conditions change. Deferred recommendations also increase maintenance burden and can contribute to fragile operations where unplanned events have outsized consequences. Avoiding disruption today often leads to greater disruption later.   Balancing Production Demands and PHA Resolution Internally Facilities that manage scheduling challenges effectively tend to be more successful at integrating safety recommendation work into their process. Facilities that practice intentional schedule management often treat safety as part of their operational planning rather than a separate obligation. This starts with early coordination. When PHA recommendations are identified, they should be reviewed alongside maintenance plans and turnaround schedules as soon as possible. Understanding which recommendations require equipment during the downtime allows teams to align resolution efforts with existing outage windows rather than waiting until conflicts arise. Phased implementation can also reduce impact. In some cases, recommendations can be partially implemented during normal operations, with final steps completed during an outage. While it is not always possible, this approach can reduce downtime and spread work more evenly. Leadership alignment around closing PHA recommendations plays a critical role. Safety, operations, and production teams must share ownership of outcomes. Communication around PHA Risk gap closure requirements should focus on operational consequences, not just regulatory language. Framing recommendations in terms of reliability, uptime, and asset protection often resonates more effectively than compliance alone. Resolving PHA recommendations should not be treated as extra work layered on top of production. It serves as a pathway to resilience in operations in the long run.   When Scheduling Conflicts Signal the Need for External Support Not every scheduling challenge requires outside help, but some situations benefit from additional perspective. Many PHA providers conclude their involvement once recommendations are issued. Internal teams are then left to reconcile safety needs with operational realities on their own. An experienced external partner  can help when scheduling complexity escalates. They can assist with developing implementation plans that minimize downtime, sequencing work to align with production constraints, and identifying opportunities where a single outage can address multiple recommendations. Partners that offer project management oversight add another layer of value. Coordinated scheduling, clear milestones, and defined accountability help keep resolution efforts moving, even when timelines extend across months or years. This structure reduces the risk of recommendations being forgotten or deprioritized as operational pressures shift. The right partner does not add friction. They provide clarity. They help establish a clear path from identified risk to operational resilience, even when timing is constrained.   Proactive Planning to Reduce Scheduling and Operational Disruption Many scheduling challenges can be reduced through proactive planning. During PHA sessions or revalidations, recommendations likely to require outages should be flagged early. This allows teams to assess feasibility and begin planning before production schedules are finalized. Including operations leadership in early discussions is essential. Their insight into outage availability and process constraints can shape more realistic implementation plans. Building safety-driven work into long-range maintenance planning also reduces the likelihood of last-minute conflicts. Documentation is equally important. Clearly recording why actions are deferred, what interim safeguards are in place, and how resolution will occur demonstrates intent and control. This documentation supports audit defensibility and helps maintain internal alignment. Scheduling challenges are not excuses for inaction. They are planning problems that can be addressed with foresight and coordination. From Risk to Resilience | When Smart Scheduling Strengthens Operations Facilities that address scheduling challenges deliberately often see benefits beyond compliance. Emergency shutdowns become less frequent. Outage scope and duration are better controlled. Confidence in the compliance posture improves because risks are actively managed rather than deferred indefinitely. Trust also improves across the organization. Operations teams trust that safety decisions consider production realities. Safety teams trust that execution timelines are realistic. Leadership trusts the results because progress is visible and defensible. Well-planned PHA recommendation resolution does not disrupt operations. It stabilizes them.   The Takeaway | Safety Shouldn’t Be an Operational Surprise Scheduling and operational disruptions are among the most common and underestimated barriers to closing PHA recommendations. They sit at the intersection of safety and production, where priorities often compete. Treating safety work as an interruption makes resolution harder. Treating it as a planned investment in uptime and reliability changes the conversation. When scheduling is addressed strategically, PHA recommendations stop feeling like a cost of doing business and start delivering measurable value. Whether handled internally or with trusted external support, the objective remains the same: defensible improvements, reduced risk, and a facility that emerges stronger, not just compliant.

Introduction | What is UL 508A? November 2025 - Erich Zende —  Industrial control panels are the backbone of modern plants. When those panels are built and labeled to UL 508A, inspectors and insurers have a clear basis for acceptance, and your maintenance team gains documentation that simplifies future changes. This article explains what UL 508A covers, where it fits with NEC and OSHA rules, how Short-Circuit Current Rating (SCCR) is established, what regulations changed in 2025, and what to ask a UL 508A control panel fabrication shop before you place an order. UL 508A  is the North American product safety standard for industrial control panels used in ordinary (non-hazardous) locations, operating at 1000 volts or less. The standard defines construction methods, component suitability, spacings, markings, and required documentation so a panel can be evaluated as “suitable” by Authorities Having Jurisdiction (AHJ). In practice, UL 508A sits alongside the National Electrical Code and OSHA rules. NEC Article 409  requires industrial control panels to be marked, including a Short-Circuit Current Rating (SCCR), and be installed so that the available fault current does not exceed the marked value. OSHA 1910.303  requires electrical equipment to be “approved,” which is shown through listing, labeling, or a field evaluation by a Nationally Recognized Testing Laboratory.   What Does UL 508A Cover? Construction and wiring UL 508A prescribes wiring methods, spacings, and clearances that prevent shock and arcing. It defines when and how to use overcurrent protection, disconnecting means, and the enclosure types required for the environment. It also mandates that markings must be present on the nameplate and drawings. Component suitability Components inside the panel must themselves be suitable. UL 508A references a companion document, commonly called Supplement SA  (now published as a separate UL document), that lists acceptable component standards and conditions of acceptability. For example, UL 489  molded-case circuit breakers are permitted for branch protection, while UL 1077  supplementary protectors are not a substitute for branch circuit protection. Marking and documentation A UL 508A panel must include required markings  such as voltage, full-load current, and SCCR, and deliver drawings and a field wiring diagram the installer can follow. What UL 508A does not cover Some electrical assemblies look similar to control panels but fall under different standards. Examples include UL 891 switchboards, UL 845 motor control centers, and fire alarm control units covered by UL 864. Additionally, panels with intrinsically safe circuit extensions into hazardous locations will refer to UL 698A.   UL 508A in the Code Landscape NEC Article 409 Panels must be marked and installed per 409.110 and related sections . The installer must verify that the available fault current at the point of installation does not exceed the marked SCCR. Failure to match these values is a common reason for red tags. OSHA “approved” equipment OSHA 1910.303 requires equipment to be acceptable only if “approved,” which means listed, labeled, certified, or otherwise determined to be safe by a recognized body. AHJs and insurers often expect a listed panel or a field evaluation report.   SCCR: What It Is and How It Is Established Short-Circuit Current Rating (SCCR )  is the maximum fault current a panel can safely withstand. NEC 409 requires it to be marked on the panel. It is established by UL 508A Supplement SB, which provides the methodology. This typically involves: Identifying the weakest link among power circuit components. Applying tables and tested combinations to determine each component’s rating. Considering current-limiting devices that can raise the overall SCCR. Marking the resulting SCCR on the nameplate and drawings. Design strategies to Raise SCCR Common approaches include using current-limiting fuses, tested combination motor controllers, and terminal blocks meeting the appropriate use groups and spacing.   Component Selection Under UL 508A A compliant panel uses components that are UL Listed or UL Recognized, following the conditions given in the component’s file. Supplement SA explains which standards apply, such as UL 489 circuit breakers, UL 98 disconnects, UL 1059 terminal blocks, and the UL 60947 family for many motor controllers. Underwriter’s Laboratory’s Product iQ tool  can help you verify the status of parts and to capture the specific conditions of acceptability in your bill of materials.   What Changed in 2025: Key UL 508A Revisions On June 26, 2025, UL published a revision to UL 508A that introduces several notable updates: Control circuit voltage limits are now defined at 120 Vac and 250 Vdc, aligning with NFPA 79 practices. Emergency stop requirements were adjusted, making E-Stop a function that may be required depending on the control scheme. Disconnecting means requirements for industrial machinery sections were clarified. Table SB4.1 received a correction for controllers rated 601 to 1000 V. UL 1059 terminal block requirements and overload protection for group motor applications were updated. UL maintains a “ future effective dates ” page so designers can see when new provisions take effect relative to publication. How UL 508A Certified Panels Add Business Value Smoother inspections Panels built and labeled to UL 508A provide a recognized basis for acceptance by AHJs and insurers, which reduces project risk and rework. Risk reduction A correctly established SCCR and appropriate protective devices add resiliency to an operation and reduce the likelihood of catastrophic faults and extended downtime. Simpler maintenance Standardized markings and documentation help technicians troubleshoot and make changes with confidence.   UL 508A in Fire and Gas Applications Panels that host Fire and Gas instrumentation , shutdown logic, and alarm interfaces are often constructed to UL 508A when they are installed in ordinary locations. If your design extends intrinsically safe circuits into hazardous areas, evaluate UL 698A for the related panel requirements. For dedicated fire alarm control units and accessories, reference UL 864. It is important to remember that functional safety for Safety Instrumented Systems is addressed by standards like IEC 61511; UL 508A covers panel construction and does not confer a SIL.   Understanding UL 508A Specification Language A typical clause example for a UL 508A specification will often read similar to this example: “Industrial control panels shall be UL 508A Listed. Provide nameplate marking with SCCR ≥ 65 kA at the service entrance. Enclosures shall meet NEMA 4X. Use UL 489 for branch protection and a UL 98 main disconnect. Use UL 1059 terminal blocks rated for field wiring. Provide documentation and labeling per NEC 409.110.”     Common Pitfalls to Avoid Treating UL 1077 supplementary protectors as branch circuit protection. Leaving the SCCR blank or below the available fault current at the installation point. Using terminal blocks that do not meet the correct use group for field wiring or spacing.   UL 508A Control Panel Deliverables Checklist Example Nameplate with SCCR and required electrical data Field wiring diagram and complete schematics Torque charts, conductor sizes, and protective device settings Bill of materials with component standards and conditions of acceptability   What to Ask a UL 508A Certified Panel Fabrication Shop Before Purchase When you engage a UL 508A panel fabricator , confirm both certification and methodology. Additional questions that are worth asking could include: What is your UL 508A shop file number and audit cadence under the Industrial Control Panel Shop Program? Do you have experience with NFPA 79 panels and, when relevant, UL 698A work for hazardous interfaces? How do you establish and document SCCR and what strategies do you use to reach higher ratings when the site’s available fault current is high? How do you track component suitability and conditions of acceptability, and how are those captured in the BOM and drawings? Can you support AHJ field evaluations when a listed panel needs on-site verification?   Designing for High SCCR and Maintainability Designing for high SCCR and maintainability begins with using current-limiting fuses and tested combination motor controllers to raise the panel’s SCCR without oversizing the assembly. Specify UL 1059 terminal blocks with the correct use groups and spacing and lay out the enclosure so power and control sections are separated, heat is managed, and service access is clear. These practices help reduce downtime throughout the panel’s life. Common Mistakes That Lead to Red Tags, Rework, or Downtime Marking an SCCR that is lower than the available fault current at the installation point. Misapplying supplementary protectors in place of branch protection. Using components without verifying their conditions of acceptability in Product iQ. Relying on outdated tables or assuming IEC ratings are equivalent to UL requirements in North America.   UL 508A vs Related Standards Topic Primary UL or IEC Standard When It Applies Industrial control panels in ordinary locations UL 508A General ICP product standard in North America Switchboards UL 891 Power distribution switchboards Motor control centers UL 845 MCC lineups Fire alarm control units UL 864 Life safety fire alarm equipment Panels with intrinsically safe circuit extensions into hazardous locations UL 698A ICPs related to hazardous locations Assemblies in IEC markets IEC 61439 Low-voltage switchgear and control gear assemblies Industrial machinery installation NFPA 79 / IEC 60204-1 Electrical equipment of machines   Frequently Asked Questions about UL 508A What does UL 508A mean? It is the safety standard used to evaluate industrial control panels for ordinary locations at 1000 V or less, including construction, components, markings, and documentation. Is UL 508A mandatory in industrial settings? There is no blanket federal law that makes it mandatory. In practice, AHJs and insurers often require listed equipment or a field evaluation. NEC 409 requires SCCR marking, and OSHA 1910.303 requires equipment to be “approved.” What is a UL 508A control panel? An assembly containing power and control components evaluated to UL 508A, installed in ordinary locations. It is not the same as a switchboard or Motor Control Center (MCC). What are the requirements for UL 508A certification? Use suitable components per Supplement SA, meet construction and spacing rules, establish SCCR per Supplement SB, apply required markings, and maintain documentation. Shops that participate in the Industrial Control Panel Shop Program  are audited and trained to apply the standard. What components are permitted in a UL 508A listed panel? Components must be UL Listed or UL Recognized for the intended use with appropriate conditions. Examples include UL 489 circuit breakers, UL 98 disconnects, UL 1059 terminal blocks, and UL 60947 motor controllers. What is SCCR and how is it established? SCCR is the panel’s withstand rating for short-circuit events. It is established using UL 508A Supplement SB tables and tested combinations, then marked per NEC 409. What are the benefits of using UL 508A listed panels? They streamline inspections, reduce risk through appropriate protective coordination and SCCR, and provide clear documentation for maintenance. What are the benefits of working with a UL 508A certified panel fabricator? Panel shops in the UL program have been audited and trained to apply the standard and can apply the UL certification mark under general coverage. What recent changes have happened in UL 508A? The June 26, 2025 revision adds control circuit voltage limits at 120 Vac and 250 Vdc, adjusts E-Stop expectations, clarifies disconnecting means for industrial machinery, corrects Table SB4.1, and updates terminal block and group motor overload provisions. What is the difference between UL and ISO? UL publishes and administers product safety standards and certifications for equipment. ISO publishes management system and other international standards that focus on how organizations operate. Ultimately, they address different scopes. What is the difference between IEC and UL 508A? IEC 61439 covers assemblies in IEC markets and IEC 60204-1 covers machinery. UL 508A is the North American product standard for ICPs. There is no one-to-one equivalency, so designs often need adaptation for each regime. What is the difference between UL 589 and UL 508A? UL 589, in its current joint form with ULC as CAN/ULC 589, covers single and multiple station heat alarms. It is unrelated to industrial control panel construction, which is covered by UL 508A. How do UL 508A and NFPA 79 interact? UL 508A governs panel construction and evaluation. NFPA 79 governs the electrical equipment of industrial machinery as installed and operated. Both are commonly applied . How do I verify a shop’s UL 508A capability or a component’s status? Ask for the shop’s UL file number and check UL Product iQ , which is the certification database used by engineers and AHJs.   What to Prepare Before You Talk to a UL 508A Control Panel Fabrication Partner Having the following items on hand before reaching out to a UL 508A certified control panel fabricator  can make the process both smoother and less time consuming.   Available fault current at the planned installation point and any utility short-circuit study excerpts. Target SCCR for the panel and any upstream device limitations. Environmental rating needs such as NEMA 4X, corrosion resistance, or temperature requirements. One-line diagram or power distribution sketch. Motor and heater loads, starting methods, and protective device preferences. Control circuit voltages and any safety relays or networked I/O. Interfaces to Fire and Gas, building fire alarm, or intrinsically safe circuits. Preferred vendor lists for breakers, disconnects, terminals, and PLC hardware.   The Takeaway If your industrial facility needs to procure or specify industrial control panels in North America, UL 508A is the product standard that aligns your design with the NEC and gives AHJs a clear basis for acceptance. Getting SCCR right, selecting suitable components, and understanding the 2025 updates reduces risk and smooths inspections. If you need a UL 508A-certified panel fabrication shop, aeSolutions maintains that capability and can integrate panels with Fire and Gas systems and other safety-critical applications, while keeping the focus on code compliance, maintainability, and operational resilience.

aeSolutions Erich Zende helps his FIRST Robotics Team with their robot. Nice pants Erich! Pictures courtesy of FRC Flash 1319 As insightful as conventional high school career aptitude surveys with pen and paper can be — hands-on, real world experience is instrumental in shaping capable young minds. Add high stakes adrenaline and stiff competition to the equation, and FRC Flash 1319 Robotics Team emerges as a fusion between the three. This FIRST (For Inspiration and Recognition of Science and Technology) Robotics team hails from Greenville, SC and competes in state and national level field games under the adept guidance of mentor and aeSolutions SIS FEL Specialist, Erich Zende. We conducted an informal interview with Erich at the close of the team’s regular season to discern a better understanding of the year-round volunteer effort he lends so much of himself to . aeSolutions: What is your role on the FRC Flash 1319 team? Erich Zende: I am the Lead Mechanical Design Mentor and Drive Team Coach for the robotics team. I lead the students through the design, prototype, and build phases during a six-week build season, and I also advise students on the safe use of tools and other safety procedures. Pictures courtesy of FRC Flash 1319 aeSolutions: The advisory role concerning proper tool usage and safety procedures makes sense, given that safety is one of the fundamentals that embodies the spirit of aeSolutions. How much of your personal resources (time, money, energy) do you invest per season? Erich Zende: During the build season I meet with the students for roughly 30 hours a week, for six weeks, and during the weeks leading up to the competitions I meet with students somewhere between 20-30 hours. The majority of this time is spent practicing with a prototype robot along with packing spares and tools for the competition, as well as going over the presentations prepared by students for the judged technical awards at completion. Typically, FRC Flash 1319 competes at 2 or 3 select events. In total, I contribute an overall average of 250 hours give or take. In order to mentor to my fullest ability, I contribute 8-10 days of my time- off-with-pay, my hotel rooms expenses, occasional robot parts, and a trailer to transport the team’s robot. Pictures courtesy of FRC Flash 1319 aeSolutions: It goes without saying that you volunteer in multiple capacities. In regards to the season ending though, what does the “off-season” look like when the team isn’t gearing up for the building phase and qualifier competitions? Erich Zende: In the time period that we refer to as the “off-season,” I focus my time on recruiting and training new members. In regards to a combined effort, the team attends outreach events in addition to hosting several Lego League tournaments for the younger students interested in S.T.E.M. activities. Recently we hosted an event with one of our sponsors, the Synnex Corporation, to put on a STEAM (Science, Technology, Engineering, Arts and Math) Girls Night Out. This was a Makerspace event created to inspire, empower and engage girls in grades 3rd to 8th in Greenville County. The goal was to help foster young girls’ appreciation for STEAM and raise STEAM awareness among parents. The event boasted an overall attendance exceeding 350 students. Aside from requested team demonstrations at Roper Mountain Science Center, we also take part in the IMAGINE Upstate Annual Festival; which showcases pre-K through 12th grade education and STEAM career pathways centered on having fun and hands-on learning. Pictures courtesy of FRC Flash 1319 aeSolutions: Given what you’ve told me, the season isn’t necessarily limited to building and competing for a span of a few months but rather it’s a year-round effort of recruiting, team building and spreading awareness. It’s clear what you give to the program and the impact you have on the malleable futures of these students, but what do you get out of this exactly? What keeps you coming back year after year? Erich Zende: There are many reasons why I continue to mentor. Although challenging for a variety of reasons, the rewards generally make it all a worthwhile endeavor each and every year. Speaking of years, this will be my 16th year as a mentor and 20th year participating in FIRST Robotics. To be more specific: I mentor because others mentored me. I mentor to hopefully aid and impact future generations of students who will be contributing members of our society. I learn something new every year, and I enjoy the competitive experience. I mentor because the robotics team is a creative outlet outside of my day job. And truly, I mentor because I yearn for my daughter to have a long-standing and well-developed STEM program to be a part of when she is older. Pictures courtesy of FRC Flash 1319 aeSolutions: Well said. Special thanks to Erich Zende for the continued efforts and contributions to this FIRST Robotics team. You have not only gone above and beyond for the robotics team, but you have also created a praiseworthy legacy that speaks to the very core of this company. More information on FIRST Robotics Click here to keep up with Erich Zende and the FRC Flash 1319, visit the team website Or follow them on social media: https://www.facebook.com/pg/FRCFlash1319 https://twitter.com/FRCFlash1319 https://www.instagram.com/frcflash1319/ https://www.youtube.com/channel/UCG40LSBnquEsIMQ2hyiyv8w #aesolutions

There are many devices (sensors, logic solvers and final elements) used in safety instrumented systems  that are independently certified for use in safety applications to different safety integrity levels (SIL). There is considerable debate however whether fire and gas system hardware should have SIL ratings at all. Vendors are naturally interested in promoting independently certified hardware in order to differentiate their products. Considering the differences between safety instrumented systems and fire and gas systems, focusing on the SIL rating or performance of the actual fire and gas hardware  alone is considered by some to be a misleading and questionable practice. This paper reviews a) the differences between safety instrumented systems and fire and gas systems, b) how typical voting of fire and gas sensors not only reduces nuisance trips (which is desirable) but also reduces the likelihood of the system actually responding to a true demand (which is not desirable), and c) why concepts and standards that apply to safety instrumented systems (e.g., SIL ratings) may not be appropriate for fire and gas systems . Click here for the complete whitepaper ​

STAMP ( Systems Theoretic Accident Model and Processes ) is a relatively new accident causality model based on systems theory. It draws its main tenets from systems thinking that (1) accidents can happen even when there has been no failure, (2) that interactions between components of the system create emergent properties that can lead to failure, and (3) it treats accidents as a control problem rather than a failure problem. STPA (Systems Theoretic Process Analysis) or colloquially “Stuff That Prevents Accidents” is a powerful hazard analysis technique based on STAMP. The STPA technique is based on a control structure rather than a traditional hardware-based structure as typically shown on a P&ID (Piping & Instrumentation Diagram). STPA is not so concerned with identifying component failures, but rather how those components interact and what controls or constraints are placed on the interactions that can lead to hazards. The STPA technique is a good fit for identifying the ways hazards can arise during transient operating states such as maintenance, start-up, or response to abnormal situation. It identifies unsafe or missing controls related to the transient mode needed to prevent an accident. It works off of a control structure of the transient mode versus procedures or P&IDs. A typical control structure can include components, humans, software, requirements, expectations (written and unwritten). Traditional PHA (Process Hazards Analysis) methods such as HAZOP or What-if will not provide the same perspective. This paper will provide two examples of transient mode control structures, one for maintenance and one for response to abnormal situation, and show how to perform the STPA hazard analysis on those control structures to ensure the proper controls and constraints are identified to prevent an unwanted event. This paper was originally presented at the 2022 AIChE Spring Meeting & 18th Global Congress on Process Safety. Click here to view the complete whitepaper CHAZOP : Controls Hazard Operability Study

The case for incorporating site specific process safety data into our calculations, and how to do it. Originally presented at the AIChE 2023 Spring Meeting and 19th Global Congress on Process Safety If we’re honest with ourselves, Process Safety has a lack of data problem. Nowhere does this show up more than in the types of calculations we perform for Layer of Protection Analysis (LOPA) and Safety Integrity Level (SIL) calculations, for example. Sure, we have generic failure data. But do we have the confidence that this generic data is right for our specific application? In addition, many LOPA scenarios contain “one-off” equipment parameters (either initiating event frequency or probability of failure) for which there is no generic data, leaving teams guessing at what value to use. Worse, LOPA targets are getting smaller (i.e., 1e-5 or 1e-6 per yr) which often leaves gaps, requiring decisions to be made regarding capital spending. Sticking with generic data in these cases can leave us feeling that we are being too conservative. On the Operations and Maintenance side of the LOPA equation, we face similar problems when attempting to verify the installed performance of an IPL (Independent Protection Layer). A multitude of assumed parameters (e.g., failure rates, test and inspection intervals, time in bypass, etc.) for which we would like a method to incorporate actual site data into the values used during design. And ideally this method could optimize these parameters for potential cost savings (for example, extending maintenance intervals). This paper will present a straightforward and easy to use method for feeding operational data back into process safety calculations, using commercial software that is already running on your computer. The paper will explore how much data is needed to confidently claim a parameter value, starting with an assumed or generic value, and periodically updating that value with small data, as evidence (from testing, maintenance, actual demands, etc.) is collected over time. The authors have been using these methods successfully on real process safety applications for several years now, that were all triggered by difficulties and shortcomings in LOPA. These application case studies will be discussed as well. Click here to view the complete whitepaper

by Ron Nichols Introduction to Using RAGAGEP for Overpressure Risk Mitigation : Process Hazard Analysis (PHA) is a key tool used by the chemical, oil, and gas industries to assist companies in identifying, implementing and managing the critical safeguards needed to achieve their risk tolerance criteria. The Process Hazard analysis for some sites may be regulatory driven (e.g., Occupational, Health and Safety Administration’s (OSHA’s) 29 CFR 1910.119 Process Safety Management of Highly Hazardous Chemicals (PSM), or the United States Environmental Protection Agency’s (USEPA’s) 40 CFR 68 Chemical Accident Prevention Provisions (RMP)). During the PHA the team identifies consequences of concern arising from potential process deviations, identifies existing safeguards, or if LOPA (Layer of Protection Analysis) is required, the Independent Protection Layers (IPLs) available to reduce the likelihood of the consequence to a tolerable risk level. If the team identifies a gap between the potential event likelihood, severity and the minimum target set by the company, the team will propose recommendations to close the gap. An overpressure scenario can be a significant contributor to the risk of a facility. Overpressure of pressure vessels, piping, and other equipment can result in loss of containment of flammable or toxic materials. This paper will develop guidance including related RAGAGEP (Recognized and Generally Accepted Good Engineering Practice) to help engineers and designers participate in the safety lifecycle for managing the risk of overpressure. Click here for the complete whitepaper

While there is extensive testing and validation of hazards from flammable vapors, less information is available regarding flammable liquid mists. A method is suggested for reasonably estimating the nature and severity of flammable liquid mist hazards by applying published mist property correlations to model inputs and outputs in dispersion modeling software. Better estimating these hazards is important to properly evaluate what mitigations will be needed. One common high flash point liquid that can pose a flammable mist hazard is heating oil. Published literature has documented that the lower explosion point (LEP) temperature of a flammable mist can be much lower than the flash point of the vapor-phase material, and the lower flammability limit (LFL) concentration of a flammable mist can be as low as 10% of the material’s vapor-phase LFL. The actual LFL of a flammable mist has been experimentally observed to be a function of the droplet size. Since many oils consist of a blend of hydrocarbons with various carbon chain lengths, only a few compounds may be chosen to represent the material in commercially available consequence modeling software. This paper will propose: 1) further guidance on an approach that will reasonably approximate the mist properties in the model; and 2) a practical example of modeling the consequences of a mist release. Finally, a case study will be provided where a range of known real world preventative and mitigative measures were tabulated, the existing measures were evaluated against these measures, and then upgrades were proposed based on the model observations. Click here to view the complete whitepaper

Functional safety engineers follow the ISA/IEC 61511 standard and perform calculations based on random hardware failures. These result in very low failure probabilities, which are then combined with similarly low failure probabilities for other safety layers, to show that the overall probability of an accident is extremely low (e.g., 1E-5/yr). Unfortunately, such numbers are based on frequentist assumptions and cannot be proven. Looking at actual accidents caused by control and safety system failures shows that accidents are not caused by random hardware failures. Accidents are typically the result of steady and slow normalization of deviation (a.k.a. drift). It’s up to management to control these factors. However, Bayes theorem can be used to update our prior belief (the initial calculated failure probability) based on observing other evidence (e.g., the effectiveness of the facility’s process safety management process). The results can be dramatic. Click here to view the complete whitepaper

by Lauren J. Caldwell, PE(SC), CFSP, CMSE When performing risk assessments on process equipment, are you reviewing machinery as well? Bag dump stations, conveyors, and various vendor-packaged machinery provided with E-Stops are sometimes evaluated in a Process Hazards Analysis (PHA), but they tend to be reviewed at a high level. Because they do not have process flow, they may not be viewed as having traditional process safety hazards. Machines still have hazards, and there is a need for a deeper dive with respect to machinery-related hazards. Did you know that machinery E-Stops fall under OSHA’s General Duty Clause? In an interpretation letter from April 28, 1999, OSHA noted, “If a serious injury could result from an improperly-designed or installed emergency stop device, a citation under the OSH Act’s General Duty Clause could be issued.” This brings the question – how should machinery without process flow be addressed? There are separate standards available for evaluating machinery hazards and designing their safeguards appropriately: ISO 12100, IEC 62061, and ISO 13849. Fortunately, functional safety of machinery follows a similar workflow to the process safety lifecycle. Similar to identifying risk gaps in a Process Hazards Analysis (PHA), we can identify risk gaps for machinery. We can define risk targets, determine how to best close the risk gaps, specify a design, and verify the risk has been adequately addressed. This paper will present a practical example application to demonstrate machinery safety risk reduction in accordance with machinery safety standards for machinery common to chemical process plants. Click here to view the complete whitepaper

The Process Industry has an established practice of crediting IPLs (Independent Protection Layers) to meet risk reduction targets as part of LOPA (Layer of Protection Analysis) studies. Often the risk targets are calculated to be on the order of 1E-4 per year or lower. Achieving the risk target on paper is one thing, but what is missing from the LOPA calculation is a statement of the confidence in the result. LOPA is an order-of-magnitude method, however, this only reflects the tolerance of error, not the tolerance of uncertainty. It is often stated that LOPA uses generic credits that are conservative, thereby implying the LOPA result should be conservative. By itself this statement is dubious because the generic data used in LOPA did not originate from the facility for which the statistical inferences are being made (which for frequentist-based statistics makes the inference invalid). Worse, when conservative credits are multiplied together to produce a rare-event number, does the conservative property emerge from the combination? There is no way to answer this question without performing IPL Validation (i.e., ensuring the IPL will function when needed). However, IPL Validation and related Safety Life-cycle methods (e.g. functional safety assessments and cyber-security audits related to barrier integrity) are purely qualitative and have no apparent relation to the quantitative risk target. There is a need therefore, to bridge the qualitative results of IPL validation with the quantitative result of the associated LOPA calculation, as a way to establish a site-specific confidence level in the risk target we are trying to achieve. This is where Bayes’ Theorem comes in. Bayes’ Theorem is an epistemological statement of knowledge, versus a statement of proportions and relative frequencies. It is therefore a method that can bridge qualitative knowledge with the rare-event numbers that are intended to represent that knowledge. Bayes’ Theorem is sorely missing from the toolbox of Process Safety practitioners. This paper will introduce Bayes’ Theorem to the reader and discuss the reasons and applications for using Bayes in Process Safety related to IPLs and LOPA. While intended to be introductory (to not discourage potential users), this paper will describe simple Excel based Bayesian calculations that the practitioner can begin to use immediately to address issues such as uncertainty, establishing confidence intervals, properly evaluating LOPA gaps, and incorporating site specific data, all related to IPLs and barriers used to meet LOPA targets. Click here to view the complete whitepaper

by Richard E. Hanner & aeSolutions Technical Team There are many critical activities and decisions that take place prior to and during the Safety Integrity Level (SIL) Verification and other Conceptual Design phases of projects conforming to ISA84 & ISA/IEC 61511. These activities and decisions introduce either opportunities to optimize, or obstacles that impede project flow, depending when and how these decisions are managed. Implementing Safety Instrumented System (SIS) projects that support the long‐term viability of the Process Safety Lifecycle requires that SIS Engineering is in itself an engineering discipline that receives from, and feeds to, other engineering disciplines. This paper will examine lessons learned within the SIS Engineering discipline and between engineering disciplines that help or hinder SIS project execution in achieving the long‐term viability of the Safety Lifecycle. Avoiding these pitfalls can allow your projects to achieve the intended risk reduction and conformance to the ISA/IEC 61511 Safety Lifecycle, while avoiding the costs and delays of late‐stage design changes. Alternate execution strategies will be explored, as well as the risks of moving forward when limited information is available. Click here to view the complete whitepaper Topics Include: IEC 61511, ISA/IEC 61511 , Safety Instrumented Systems (SIS) , Independent Protection Layers (IPL) , Functional Safety Assessment (FSA) , Safety Requirement Specification (SRS) , Safety Lifecycle , Functional Safety Management Plan (FSMP ), Project Execution Plan (PEP), SIS Front‐End Loading (SIS FEL), Layer of Protection Analysis (LOPA ), SIL Verification ​