INNOVATION May-June 2019

F E A T U R E

potentially incorrect manual settings. When hazards can’t be engineered out, clear instructions and visible caution signs should be included as part of the engineered design to mitigate the associated risks.” Designs also need to consider future safety risks. While new equipment and technical systems are more reliable, designs still need to consider the conditions that might lead to incorrect operations and maintenance decisions, as was the case in Langley, Ng notes. It’s also important to ensure that professional engineers remain available to system operators and managers throughout the life cycle of systems and equipment. In Fernie, for example, the managers and maintenance contractor discussed

The uncontrolled ammonia leak in Langley on October 24, 2018, forced road closures, and worker and business evacuations. No one was injured. P hoto CoUrteSy oF l anGley a DVanCe t imeS /B laCk P reSS m eDia .

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and operating issues that contributed. In this case, they included: • a failure to effectively mitigate oil migration, respond to changes, and remove migrated oil from the refrigeration system; • incorrect configuration of the ammonia supply valve after valve settings that were designed to remain unchanged during operation were altered, with unintended consequences; • closure of the suction valve with the system flooded; and • inadequate methods to promote awareness of hydrostatic expansion risks. The incident in Langley is noteworthy in part because the refrigeration plant is relatively new—only three years old. In Fernie, aging equipment was used past its effective lifespan and run to failure. In Langley, the plant equipment, while relatively new, had some process safety design characteristics that contributed to the incident. USING PROCESS SAFETY DESIGN FOR PREVENTION “The system was capable of being manually configured in such a way that, during low- load conditions, there was a significant risk of hydrostatic expansion failure if the suction valve was closed,“ explains Technical Safety BC’s Eric Lalli, P. Eng., Leader of Incident Investigations. “While

that risk was documented in a standard operating procedure, those working on the system that night weren’t aware of the procedure or the risk.” The incident highlights a potential “blind spot” around process safety engineering, Lalli says. “Ideally, this hazard would have been engineered out of the design. However, failing that, the addition of clear signage warning of the risk of hydrostatic expansion might have helped prevent this failure.” Technical Safety BC is working to improve awareness of hazards through an increased focus on process safety management as part of the engineered design. However, while Technical Safety BC can, in some cases, review, assess, recommend, and require changes as part of the design registration process, there are limits to what the organization alone can achieve. As such, the important role professional engineers play in this process can’t be overstated. “Those involved with engineering and system design should not just be concerned with meeting the minimal regulatory or engineering code requirements,” says Technical Safety BC’s Leader of Engineering Tom Ng, P.Eng. “Engineers who design these plants have a tremendous opportunity and role to play around prevention. Engineered systems should be assessed to determine the impact of

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