The difficulty of the task was significantly increased due to the requirement for the plant to remain operational during this transfer process. This process has to be carefully managed and the implications of the added complexity fully understood. To mitigate the risk in the transfer between the two SCADA systems, Tenet was contracted by AXIOM (Design Services Alliances (DSA)) to evaluate the potential impact of removing the analogue / digital signals when each SCADA fan-card was swapped out as part of the changeover strategy. Through a great deal of collaborative working at the front end of the project, our team was responsible for identifying the potential problems from the outset and creating a risk reduction strategy for implementation.
Scada replacement project
Introduction
As part of a Supervisory Control And Data Acquisition (SCADA) replacement project it was recognised that the physical migration from the existing control system to the new system would require significant care and management.
Scope of work
The existing SCADA system consisted of 8 outstations, with each outstation containing a varying number of associated analogue and digital input fan-cards in an A&B arrangement. Tenet was tasked with evaluating the impact on plant and process on the removal of each fan-card. This was achieved through inspection of each digital and analogue signal path to identify any associated Safety Mechanisms (SM) and Safety Related Equipment (SRE). The purpose of this being to assess any inherent effect on the performance of each Safety Function. This information was captured in the form of Operator Worksheets. As part of this assessment, recommendations were made on how any impact on the safety case could be minimised by identifying substitution systems and allowable outage times for each Safety Mechanism and detailing what actions would be required prior to each outage. Additional to this, any instances where it was found that the SCADA system was responsible for delivering a safety function, a shortfall was raised and captured on the Operator Worksheets.
To aid the strip out and installation process, an Installation Worksheet for each fan-card was produced to collate the existing signal and termination detail against the “proposed modification” detail for the replacement system. The Installation Worksheets was then be used to form part of the Commissioning Test Documentation.
A red line mark-up of each plant record Hook-Up was also produced to reflect the input signal connections to the new SCADA system, including new signal isolator or fuse and link details where required.
Collaborative integrated project solution
As some work had already been completed by the client, the successful collation of existing plant information was reliant on the collaboration between Tenet and the client design team. A close and open working relationship was established as early as possible by relocating our team to the client’s premises during the primary stages of the project. This time was used to develop a good understanding of the source documentation available and to evolve and standardise on the format of the deliverables. Working in this integrated manor ensued confidence in the client that our team of engineers fully understand all project requirements. This flexibility in our working practices ensured that the project started positively.
Successful channels of communication between Tenet and client’s site based engineers were established early on in the project lifecycle. These were used to good effect in clarifying inconsistencies found between plant design records. This proactive approach adopted by Tenet has allowed a mechanism to capture all inconsistencies found between plant design records within the Installation Worksheets.
Cost saving
Tenet was initially contracted to carry out the assessment on a single SCADA outstation. Successful delivery of first package demonstrated to the client, our effective utilisation of the available resources and potential cost savings to the project. This resulted in the scope being increased to include all of the associated SCADA outstations, including the checking and subsequent reworking of the work previously completed by the client.
Conclusion
Successful delivery of the SCADA replacement project was reliant on effective client engagement and collaboration, allowing the accurate collation and validation of plant record information that existed in various formats and across multiple locations.
Tenet implemented sound communication channels with both the client design team and the site-based engineers to allow the sharing of information. By utilising the client database environment this process was ensured to be both transparent and controlled. Early preparation from Tenet in the standardisation in the format of the deliverable documentation ensured effective continuity between multiple work streams and allowed for sufficient savings in project delivery timescales.
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