Progressing from design to operation with a SIL rated system

Many companies operating industrial production systems have learned how to use risk assessments and safety integrity levels during design and process development. Many have however asked how do we actually work with this in operations to make sure the safety functions actually provide the level of safety we need. Maintaining the safety ingrity level throughout the operational part of the asset’s lifecycle can actually be very demanding, and it requires a holistic view of asset management considering many aspects. A good asset management program needs to make sure design requirements are fulfilled; it needs to have provisions for monitoring the state of the asset for damage or degradation such as corrosion, instrument drift or material defects. It must also prioritize such that maintenance is effective and does not drive costs in unhealthy ways. Asset management and barrier integrity management is thus no easy task.

When taking a system from design to operation we are equipped with theoretical foundations and plans for how to use the asset. We do not have operational experience, and we do not know how the asset actually will perform in practice. We need to take what we have learned during engineering and transform this into a system for managing our assets in a way that includes barrier integrity, and that takes the requirements and limitations of SIL rated systems into practice. Necessary functions and considerations for establishing a good barrier management system are shown in the figure below. You should include planning for operations already when establishing the functional safety management plan in the design phase.

We need to take with us the safety requirements from engineering into the barrier management system. For your safety instrumented system this would consist of information found in the Safety Requirement Specification (SRS) and the risk assessments used to establish the SRS. The reason for the latter is that we need to make sure that the assumptions about other independent protection layers are not violated, or that protection layers do not disappear. Further, your company needs to have performance standards for different systems – these should also be integrated into your barrier management system. Finally, from a practical and economical point of view, you need to take your maintenance and spare parts philosophy to the next level by implementing the necessary maintenance activities for barrier elements in your barrier management system.

Monitoring for safety is very important if you want your risk management system to work. For SIL rated systems there are many sources of performance data. These should at least include results from proof testing, from diagnostics and automated monitoring systems, and from maintenance focused inspections. All of these data should be analyzed using suitable tools, and the results of this analysis should be taken into your overall barrier management data storage or data warehouse. Based on the data gathered and the state of the barrier system, you need to device actions and make sure they are done in due time to avoid deterioration of the system.

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