Process Control and Monitoring System
Physical Infrastructure Preparation for Network Migration
Our customer is in the nuclear supply chain, there is a considerable responsibility for them to maintain a level of production that will continue to service the industry. It is therefore critical that they limit vulnerabilities in their processes at the plant to ensure steady production within a protected environment. Like all manufacturing businesses with such a long, successful history, they need to replace and update elements of their infrastructure to keep their operations running smoothly.
The problem that was outlined by their engineer, was that the network infrastructure supporting their manufacturing process was starting to have reliability issues. With failures on the increase it was clear that the obsolete network now had to be brought up to date.
This paper considers the challenges that relate, primarily, to the passive infrastructure where technology obsolescence, combined with 30+ years of organic changes in building usage, have resulted in a cluttered and hard to manage installation. The active network challenges are discussed in a second case story that describes the active network design and live migration.
An initial ‘restricted access’ survey identified a number of physical issues that would challenge any new network installation or upgrade, these included:
- Space and restricted access around operational plant
- Cable routing, labelling and certification records
- Operational status of backup paths.
Before full consideration of the active network topology and feature / product selection could be accomplished, it was clear major decisions on how the physical infrastructure would need to evolve had to be made. A meeting of minds between IT4A’s Consultant and the site Project team came up with a solution that would ultimately simplify the entire installation. A disused storage, area no more than 20m from the existing plant cabinets, would become the new network hub. Plant fibre optic cables would be extended from legacy panels to three new purpose built racks. Once migration was complete the legacy racks would then become passive patch panels able to be secured.
With the physical elements of the design in place, additional surveys were performed first to identify then validate the plant-wide fibre cabling. The identification process required all existing cables to be manually traced through the plant where they were clearly tagged, documented and numbered. Knowing where the ends were presented made the re-certification to a reference standard (EN-50173) far easier.
Re-certification was necessary as, while primary and backup paths were both physically connected, there was no evidence that a backup path worked. With live migration planned there was no space for error – all paths had to be proven and this proof was gathered through a formal fibre certification process.
IT4A’s fibre clean and certification service identified the cores that simply needed a clean to achieve certification and the ones that required repair and re-testing. This process identified multiple backup paths where the fibre’s poor condition gave operations a false sense of security and would have impacted the live migration process. Today all fibres are certified and, during the migration, carried live data.
While the network core was to be upgraded the decision was made not to change the transceiver equipment at the perimeter. The approach was reasonable; spares of the legacy Ethernet Attachment User Interface (AUI) to Dual Fibre Transceiver, albeit dated and end of life, had proven to be reliable over the years and spares were still available. With controllers AUI providing power to the Transceiver, beyond testing, no perimeter work was necessary.
The above approach made one major assumption that needed testing – would the legacy device interoperate seamlessly with the new network hardware? A thorough IT4A proof of concept determined the functional compatibility of the legacy interconnection but also identified a deficiency relating to limited link status information. This was seen as an acceptable compromise as plans were afoot to upgrade PLCs within the foreseeable future and any limitations would be overcome at this stage.
This phase of works resulted in a fully EN-50173 certified, labelled and documented fibre installation. Legacy plant-wide fibre has been extended to a new communication room that has become the network hub for the respective process areas, ready for the active Ethernet network replacement. The works were completed without introducing any risk to production. Higher risk activities that were carried out in the proximity of live plant were passive only – no disruption, planned or otherwise, was seen by the plant.