PT Notes
Addressing Safety Critical Actions In Process Safety Management
PT Notes is a series of topical technical notes on process safety provided periodically by Primatech for your benefit. Please feel free to provide feedback.
A safety critical action (SCA) refers to any human operation, task, or intervention that, if performed incorrectly or not performed at all, could directly lead to or significantly contribute to the occurrence of a hazardous event, potentially resulting in harm to people, damage to property or the environment, or loss of process control. These actions are deemed safety critical because they play a fundamental role in maintaining the safety of a system, process, or operation, often acting as the last line of defense against the realization of a hazard. Examples of SCAs are installing or verifying the functionality of an emergency shutdown valve, updating a critical interlock, and ensuring correct operator response to a critical alarm.
Characteristics of safety critical actions include:
Direct Impact on Safety: SCAs have a direct influence on the operational integrity and safety of a system. Their proper execution is essential to prevent accidents or mitigate their consequences.
Defined in Procedures: SCAs are usually clearly identified and documented within operational procedures, safety protocols, or emergency response procedures to ensure that they are understood and executed correctly by personnel.
Training and Competence: Individuals responsible for performing SCAs typically require specialized training and must demonstrate competence to ensure these actions are carried out effectively and safely.
Monitoring and Oversight: Owing to their importance, SCAs often have enhanced monitoring, oversight, and verification processes to ensure compliance and effectiveness. This may include audits, checks, and regular reviews.
Failure Consequences: The failure to perform an SCA correctly can have severe consequences, including the potential for significant process safety incidents. As such, understanding and managing the risks associated with these actions are a priority for process safety management systems.
Addressing SCAs involves first identifying them through risk assessments and hazard analyses.
Process Hazard Analysis (PHA) (e.g. HAZOP, What-If, FMEA, LOPA) is used to identify SCAs. Actions that must be taken by personnel to prevent or respond to a significant consequence are flagged as safety critical. For example: If a scenario is “reactor temperature runaway,” and the control is “Operator responds within 10 minutes to high-temperature alarm by initiating emergency cooling,” that operator response is typically labeled safety critical.
In LOPA, each protective layer’s integrity is assessed. If a layer is operator-dependent (e.g., manual intervention), it is often scrutinized to confirm whether it meets the reliability and response time needed to maintain overall risk within acceptable levels.
Some companies perform Task Analysis or Human Factors Analysis to examine how human actions interface with equipment. This can uncover the specific steps that, if performed incorrectly, lead to major hazards.
Once identified, SCAs must be managed, which involves addressing documentation, procedures, competency, training, performance standards, ownership, maintenance, testing, emergency response drills, management of change (MOC), audits, reviews, and continuous improvement.
SCAs should be unambiguously described in operating and emergency procedures. Some companies color-code these actions or otherwise mark them as “critical” within procedures, so they stand out.
Operators, maintenance, and support staff must be trained specifically on SCAs to ensure they can execute them reliably. Beyond one-time training, organizations often provide refresher training, and test or evaluate personnel regularly to confirm their continuing proficiency.
Each SCA should have a performance criterion (e.g., response time, frequency of checks, sequence of actions). For alarms requiring operator response, the required action time (e.g., within 10 minutes) is a key performance metric. Verification can include operator drills, scenario simulations, or routine audits to ensure people can perform SCAs reliably.
A single point of accountability (e.g., specific role, supervisor, or engineer) should be designated for each SCA. This accountability ensures clarity about who is responsible for implementing, monitoring, and verifying the action.
If an SCA relates to equipment (e.g., testing a relief valve, or calibrating a gas detector), scheduled maintenance and integrity checks are crucial. Records of completion and test results should be kept to show ongoing compliance with safety requirements.
Periodic exercises or drills should be conducted to determine how well operators and other personnel perform SCAs during emergency scenarios, which helps to identify gaps and drive improvements in procedures and training.
Any change in process conditions, control systems, or equipment may alter or create new SCAs. MOC reviews should revisit the studies used to identify SCAs, and procedures or training should be updated, as needed.
Regular process safety audits confirm that SCAs remain relevant, are clearly documented, and are carried out as intended. Organizations often have Key Performance Indicators (KPIs) or metrics (e.g., overdue tasks, missed checks, training completion rates) to track compliance.
Incident investigations and lessons learned can reveal shortcomings in how SCAs are defined or executed. Corrective actions might include retraining, rewriting procedures for clarity, or adding automation to reduce human reliance where feasible.
Some common challenges in managing SCAs are:
Operator Workload: If operators are overloaded with too many duties or alarms, SCAs may not receive the necessary priority or attention. Best practices ensure a manageable balance of tasks and implementation of alarm rationalization.
Vague Procedures: Poorly written or overly generic instructions can lead to confusion in critical moments. Best practices ensure procedures are user-friendly, concise, and specific to the actual task conditions.
Human Factors Considerations: Human error is often a result of system design rather than individual failures. Best practices include designing tasks and interfaces (e.g., HMI, control panels) to be intuitive, and incorporate ergonomics and clarity in labeling and control layout.
Culture and Accountability: Even if SCAs are well-defined, a weak safety culture can undermine their effectiveness. Best practices foster a culture where reporting near-misses, asking questions, and clarifying procedures are encouraged and supported by management.
Regular Validation: Processes evolve over time and so do hazards. Best practice is to revalidate PHAs and confirm if existing SCAs still apply or require updates.
Safety Critical Actions form an essential layer of protection against catastrophic incidents, focusing on the human element in process safety. By systematically identifying SCAs, documenting them in clear procedures, training and assessing personnel, and continuously auditing and improving their execution, organizations ensure these vital actions are performed correctly and consistently. Proper management of SCAs helps maintain robust process safety, safeguarding people, the environment, and assets..
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