Smarter, safer working

18 September 2023

Mark Breese discusses Control of Work risk management and the effect that this can have on functional safety.

Control of Work risk management plays a crucial role in ensuring the safety and integrity of process plants. Accidents resulting from an inability to control process conditions have led to significant consequences, including loss of containment, emissions, explosions, and harm to workers, nearby communities, and the environment. 

Modern plants are increasingly recognising the advantages of safe working practices, not only for safety but also for improved reliability, efficiency, reduced downtime, and enhanced visibility of plant activities. 

Among the critical aspects of safety is the evaluation, management, and monitoring of functional safety systems, which encompass alarm management, process control, and safety instrumented systems (SIS).

Functional safety revolves around ensuring that the design, installation, operation, maintenance and management of instrumented process safety systems are sufficient to ensure plant safety during upsets. This entails evaluating potential hazards that may impact people, the environment, and plant operations. 

Each hazard is assessed based on the likelihood of occurrence and the severity of consequences. Safety Instrumented Functions (SIFs) are implemented to reduce risks, with controls such as fire detection and mitigation, high integrity pressure protection, and emergency shutdown systems. These functions are assigned a Safety Integrity Level (SIL), representing the level of risk reduction they provide.

The impact of maintenance 
The maintenance of safety systems is essential to maintain their safety integrity levels. Proof test intervals are specified to verify system effectiveness periodically. Testing can be accomplished through full testing or diagnostic testing methods such as partial stroke testing. 

During maintenance or offline work, changes to the safety system can affect its effectiveness, and these changes must be evaluated from a risk perspective. It is essential to monitor the safety system during these activities, and to ensure proper reconstitution once the work is completed.

Implementing an effective Control of Work software system is vital for monitoring critical changes to safety systems. Such a system should restrict permit issuance until all required isolations are in place and monitor safety override requirements. It should also prevent de-isolation until all related permits are returned and monitor the reconstitution of any overrides before permits can be completed. 

Monitoring safety critical asset items and linking them to permitted activities will provide significant benefits to plants. It enables efficient management of the interactions between critical asset items, permitted work, and isolations of power, fluid, or motive sources in one centralized platform. This enhanced visibility enhances safety controls, including the management of simultaneous operations (SIMOPS) and exclusions, to ensure all workers' safety during tasks, including those related to safety instrumented systems.

Control of Work risk management is vital for ensuring the safety and integrity of process plants. Maintenance of safety systems is essential to retain their effectiveness and safety integrity levels. By implementing effective Control of Work software systems and monitoring safety critical asset items, plants can ensure a safer working environment, thus reducing the risk of accidents and enhancing overall operational efficiency.

Mark Breese is a Principal Consultant at Yokogawa RAP.

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