HEALTH & SAFETY “


As adoption grows, ANSI/ISA-84.91.03 is likely to become a recognised


reference point for good engineering practice


clear that these practices matter for low integrity protection layers too.”


”


Who is affected and how The standard applies broadly across the process industries, including oil and gas, refining, chemicals, pharmaceuticals, food and beverage, pulp and paper, and non-nuclear power generation. Any facility that credits instrumented protection layers outside of SIS during process hazard analysis will need to understand how those functions fit within the new framework. Facilities that historically pushed most


protective functions into SIS may see little change. Others that relied heavily on control- system-based interlocks or loosely managed safeguards may uncover gaps.


“The first place companies feel this is in how they move from hazard analysis into layer of protection analysis,” Summers explained. “Many organisations only ran scenarios through LOPA if they believed a SIS would be required. That left other credited functions outside a formal lifecycle.”


ANSI/ISA-84.91.03 effectively expands the scope of discipline by applying lifecycle expectations to a broader set of functions. More scenarios are likely to require structured evaluation, and more functions must be managed intentionally, not because they are high integrity, but because the organisation depends on them to reduce risk.


ANSI/ISA-84.91.03 is now published. While adoption timing remains up to individual companies, the expectations it reflects are now formally articulated.


“This is now the consensus view of what good practice looks like,” Bhojani said. “You don’t have to implement everything overnight, but you


do need to understand how what you’re doing compares to this standard.” Klein echoes that view, noting that the risk is not in the existence of gaps, but in ignoring them.


“If you’re depending on low integrity


protection layers and don’t have a clear program to manage them, a question worth asking is ‘What are my gaps and when should I close them,’” he said.


Regulators typically do not audit facilities


proactively for compliance with standards such as ANSI/ISA-84.91.03. The real impact comes after an incident.


“When something goes wrong, investigators look for benchmarks,” Klein said. “They ask what standards existed, what others in the industry were doing, and whether the company followed an equivalent approach.” As adoption grows, ANSI/ISA-84.91.03 is likely to become a recognised reference point for good engineering practice. At that point, companies may be expected to either follow the standard or


demonstrate how their internal programs achieve equivalent outcomes.


Summers points to incident history as a


reminder that low integrity does not mean low consequence.


“I’ve worked cases where the function that failed wasn’t SIS,” she said. “It was an interlock or instrumented function that had been bypassed or poorly managed. The failure wasn’t dramatic until it was and by then, the consequences were very real.”


One concern often raised with new standards


is overcorrection. “That’s not the intent,” Klein emphasises. “This standard is about rightsizing. A consensus standard helps normalise expectations.” For many organisations, assessing alignment with ANSI/ISA-84.91.03 will require a mix of internal review and external expertise. Engineering firms with deep process safety experience can help identify which functions truly serve a safety role and where lifecycle gaps exist. Summers noted that one of the most valuable first steps is simply making an honest inventory. “You can’t manage what you haven’t clearly identified,” she said. “Once you understand what you’re relying on, the path forward becomes much clearer.” Author: Greg Rankin, a freelance writer with more than 20 years experience writing about the oil and gas industry, petrochemicals, and refining


SIS-TECH www.sis-tech.com


APRIL 2026 | PROCESS & CONTROL ENGINEERING 31


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