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Understanding Safety-Critical Equipment: Definition, Importance, and Best Practices

Understanding Safety-Critical Equipment: Definition, Importance, and Best Practices

In industries where human safety, environmental protection, or high-value assets are at stake, Safety-Critical Equipment (SCE) plays a fundamental role in preventing incidents and controlling hazards. Whether in oil and gas, nuclear energy, aviation, or manufacturing, SCE is essential for maintaining safe operations. It ensures that processes either continue safely or are brought back to a safe state when abnormal conditions or deviations occur due to equipment failure, human error, or external factors.

Posted

23.10.2025

Written by

Nick Freer

This article explores what the safety-critical equipment concept is, why it matters, and how organisations can manage it effectively.

What are Safety-Critical Equipment?

Safety-Critical Equipment refers to any system, device, or component whose failure could lead to serious consequences such as injury, loss of life, major environmental harm, or significant damage to assets. These components are essential to maintaining safe operations and are often subject to strict regulatory standards. The equipment is designed to automatically activate in the event of a process upset, acting as a safeguard to prevent serious consequences such as injury, environmental harm, or asset loss. Its primary function is to detect abnormal conditions and initiate protective actions that mitigate risk before it escalates into a hazardous event.

To assess and manage the risks associated with such equipment, two key methodologies are commonly used:

  • Layers of Protection Analysis (LOPA): LOPA is a semi-quantitative risk assessment technique used to evaluate the effectiveness of multiple independent protection layers (such as alarms, shutdown systems, or physical barriers). It helps determine whether existing safeguards are sufficient or if additional layers are needed to reduce risk to acceptable levels.
  • Safety Integrity Level (SIL): This is a measure of the reliability and performance required of safety functions. SIL ratings range from 1 to 4, with SIL 4 representing the highest level of risk reduction. The higher the SIL, the more stringent the design, testing, and maintenance requirements for the equipment.

Together, SIL and LOPA form the backbone of a facility’s safety strategy, ensuring that Safety-Critical Equipment is properly evaluated and maintained to prevent hazardous events.

Why Safety-Critical Equipment Matters

Safety Critical Equipment matters for the following reasons:

  • Protection of Human Life: Many SCEs are designed to prevent accidents that could cause injury or death. For example, fire suppression systems in industrial facilities can stop a minor flame from becoming a major disaster.
  • Environmental Responsibility: Equipment like containment systems prevent toxic leaks or spills, helping companies comply with environmental regulations.
  • Asset and Infrastructure Protection: SCE helps avoid costly equipment damage and plant shutdowns by stopping failures before they escalate.
  • Regulatory Compliance: Various industries are subject to stringent health and safety regulations. Failure to maintain SCE can result in fines, shutdowns, or legal consequences.

Risk Assessment and Identification

Before SCE can be implemented, companies must perform hazard and risk assessments (e.g., HAZOP or FMEA) to:

  • Identify potential hazards
  • Determine the level of risk
  • Determine what safeguards are in place to prevent or mitigate the hazardous event
  • Designate specific equipment as safety-critical

This process ensures the right equipment is identified to protect against the most severe and likely risks. Once hazard and risk assessments have been performed the SCE can be determined by 6 key steps highlighted in Figure 1 below. It is a cyclical process, requiring periodic reviews to ensure that any new equipment additions or removals during project upgrades are reflected in the SCE list, maintaining compliance.

Define

Define the critical screening criteria for determining SCE – this can be looking at consequence of failure, does the equipment have a preventative or mitigative safety function, is it referenced in LOPA or part of a SIL requirement, does the equipment protect against credible worse case events.

Select

Select the process areas where the SCE needs to be identified – splitting the plant into nodes/areas can make identifying SCE in each of the areas easier and focus on areas with high-risk operations.

Acquire

Acquire the correct and critical data for the SCE identification – look at major accident hazard (MAH) events and which equipment needs to be present, so the MAH event does not occur and obtain key safety data for that equipment i.e. probability of failure data, SIL rating requirements, performance standards.

Conduct

Conduct the SCE identification process with the use of different hazard analysis techniques including HAZOP, LOPA and highlight the equipment that meets the SCE criteria and document findings in a clear and traceable format.

Determine

Determine the safety critical equipment maintenance/inspection criteria and include this on the sites Computerised Maintenance Management System (CMMS) system.  Establish performance standards and testing intervals.

Review

Implement a review process to reassess SCE during plant modifications, projects or operational changes. Add or remove equipment as needed based on the updated risk assessments.

Maintenance and Inspection of SCE

Safety-critical equipment must be maintained rigorously and tested regularly to ensure reliability. Best practices include:

  • Preventive Maintenance Schedules: Ensure routine checks based on manufacturer recommendations and risk levels.
  • Proof Testing: Demonstrates that equipment will perform its safety function when needed.
  • Condition Monitoring: Using sensors and data analytics to detect early signs of failure.
  • Documentation & Audit Trails: Maintaining logs of inspections, failures, and repairs for compliance and traceability.

Challenges in Managing SCE

The following aspects highlight the challenges in managing SCE:

  • Aging Equipment: Older equipment may not meet current standards and may be more prone to failure.
  • Human Error: Misuse or failure to follow procedures can negate even the best-designed and maintained safety equipment.
  • Budget Constraints: Safety-critical systems are often expensive to install and maintain which creates a significant barrier for smaller organisations with smaller budgets to implement SCE.
  • Complexity: Integration of SCE with digital systems (like SCADA) requires specialised knowledge and can introduce cybersecurity risks.

Best Practices for Effective Management

The below are some best practices to follow for effective management:

  • Robust Training: Ensure personnel understand the function and importance of SCE.
  • Lifecycle Approach: Consider safety from design through decommissioning.
  • Third-Party Audits: External reviews help ensure compliance and identify gaps.
  • Use of Standards: Follow international standards such as IEC 61508, IEC 61511 (for process industries).
  • Regular Review: Risk and equipment assessments should be updated periodically, especially after incidents or changes in operation.

Conclusion

Safety-critical equipment is not just a regulatory checkbox, it’s a vital part of protecting people, assets, and the environment. With proper identification, maintenance, and management, SCE ensures that high-risk operations can be conducted safely and responsibly. In a world where failures in safety can have far-reaching consequences, investing in safety-critical systems is not only a legal duty but a moral and operational imperative. Finch Consulting can help by providing expert guidance, risk assessments, and tailored solutions to ensure your safety-critical systems meet both regulatory standards and real-world operational demands.

For more information, please call 01530 412 777, or email [email protected].

Written by

Understanding Safety-Critical Equipment: Definition, Importance, and Best Practices

Nick Freer

Senior Consultant

View profile

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