Upgrading Safety Systems in the Petrochemical Industry: Basic Guidelines

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Upgrade Strategies

Establish a baseline – The first step in a safety system upgrade is to establish a clear understanding of the existing design, including the specific nature of the system’s core architecture and the functional operation. The ‘as-built’ documentation status of many mature systems is poor, conflicting or non-existent. As a result, engineers often need to ‘reverse engineer’ the installed system to either confirm that the existing documentation is correct or mark it up to determine how to proceed.

During this phase of the project, the safety integrity level requirements may need to be established or re-affirmed. In some instances, this may necessitate revisiting the original system design approach. Carrying out this assessment not only means the design of the upgraded system can be compared to current SIS standards, but also may significantly reduce the complexity of the system needed.

Once this baseline is firmly defined, you can determine which system upgrades, enhancements and improvements may be needed. While this preparatory work can take a considerable amount of effort, it is absolutely essential in helping ensure the functionality is correct and the design is traceable.

Evaluate the system architecture – In order to execute a ‘live’ migration from the legacy system to the new system, designers need to exploit the inherent redundancy built into the legacy safety system. Given that most legacy systems have an ‘A’ and ‘B’ side (see figure 1), each executing the same logic, one ‘side’ can be switched off and removed without shutting down the system. It should be noted that while the system is in this degraded state, it is fully operational and, if designed that way, fail-safe.

How To Upgrade your Safety System

However, by switching off one ‘side,’ the system redundancy and fault-tolerant capabilities will no longer be available, the implications of which need to be understood through an appropriate risk review. This configuration will allow the new system to be installed and run in parallel to the legacy system, allowing a safer, quick and effective migration between the systems during live plant operations.

Build, test and document – Once the new system is built, it is essential that it is fully tested against the defined and agreed upon baseline before it is installed in the field. By testing the system before the live change out in the field occurs, you can be confident that the functionality will meet the operational requirements.

Any functional enhancements can only be implemented and tested after these tests are completed. During this phase, it also is critical to get the buy-in from all interested parties, particularly the oil and gas company’s operators and the relevant certifying authority. Oil and gas producers will focus on safety concerns, the functionality of the new system, how it will be migrated and any operational constraints that will

need to be addressed. The certifying authority will need to be assured that you have clear and demonstrable processes in place to show that the system build, test and – later on – commissioning and operation is safe and complies with legislative requirements, as well as local and international standards.

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