Background: the CATS asset and the permit to work challenge
The Central Area Transmission System — CATS — is one of the UK North Sea's most strategically important pieces of gas infrastructure. The pipeline and riser system transports processed gas from Central North Sea fields to the Teesside gas terminal at Seal Sands, handling volumes from multiple third-party producers across a complex, interconnected network.
Wood, as the operator of CATS on behalf of the asset owners, is responsible for ensuring that all maintenance, inspection, and modification activities on the pipeline and associated onshore terminal are carried out safely, under control, and in full compliance with the asset's safety case.
When Wood began a review of their permit to work arrangements across the CATS asset, the driver was not the absence of a digital system — one was already in place. The issue was that the existing platform had not kept pace with the complexity and pace of work the asset required. Isolation management was handled separately from the permit workflow, visibility across simultaneous work fronts was limited, and the system offered little support for the structured handover and conflict-checking that a transmission asset demands.
What a good permit to work system looks like on a transmission asset
Permit to work on a transmission pipeline and terminal environment has specific challenges that differ from a producing platform or a refinery. Work is spread across a large geographic footprint — from subsea tie-ins through to onshore terminal equipment — and the asset operates continuously, meaning there is rarely an opportunity to shut down sections of the system for planned work without careful coordination across multiple producers and shippers.
Any replacement system for this environment needed to handle:
- Simultaneous work across geographically dispersed locations, with clear visibility of all open permits at once
- Complex isolation schemes — including line breaks, depressurisation, and purging — linked directly to the permits they supported, with the integrity of that link enforced by the system
- Third-party contractors working alongside Wood personnel, with consistent application of the permit process regardless of who was doing the work
- Structured handover between shifts and control room teams without loss of situational awareness
- An unbroken audit trail for safety case assurance and regulatory inspection
The existing system was not delivering these consistently. Isolation certificates and permits existed in separate workflows without a systematic enforced link between them, and the control room had no consolidated live view of the full work picture across the asset at any given time.
Deploying Elisian's permit to work module
Wood selected Elisian's Permit to Work module as the replacement platform for CATS. The deployment covered the full permit lifecycle — from permit request and planning through to execution control, suspension, reinstatement, and close-out — with the isolation certificate register integrated directly into the permit workflow as a single unified system.
The implementation was structured in phases to manage the transition carefully across an operating asset:
Phase one: system configuration and procedure alignment. Elisian worked with Wood's operations and safety teams to configure the platform to reflect the CATS safety management system exactly. Permit types, isolation authorities, area authorities, and competency requirements were mapped in before go-live. The priority was a like-for-like transition that the operations team could recognise immediately, with improvements introduced incrementally once confidence in the platform was established.
Phase two: isolation register migration and build-out. All isolation points across the CATS system — valves, spectacle blinds, spades, and electrical isolations — were migrated into the Permit to Work isolation register, with existing data validated and gaps closed during the transition. The register gave controllers a single searchable view of every isolation point on the asset and its current status, directly linked to the permits depending on each isolation.
Phase three: go-live and training. The platform was rolled out to operations staff, control room teams, and the key contractor organisations working on CATS. Familiarity with the permit process meant training focused on the platform rather than the procedure, shortening the transition period significantly.
The shift in control room visibility
The most significant change following go-live was in the quality of control room visibility. Where the previous system required controllers to navigate between separate permit and isolation records to build a picture of the current work situation, Permit to Work presented a single consolidated view — every open permit on the asset, the isolation scheme each permit depended on, and the current status of work at each location, in real time.
For handover between shifts, the improvement was immediate. The incoming team could be walked through a structured, consistent dashboard rather than relying on a combination of system exports and verbal brief to establish situational awareness. Every permit suspension, reinstatement, and extension was logged automatically with a timestamp and authorising person, without additional data entry effort from the control room team.
Controllers could also see, before a new permit was raised, whether proposed work might conflict with existing permits — overlapping isolations, concurrent work in the same area, or activities that needed to be sequenced. Conflicts that had previously surfaced at the point of permit presentation could now be identified and resolved during planning.
Isolation management: enforcing the link
One of the most valued outcomes of the deployment was the enforced integration between isolation certificates and permits. In the previous system, the relationship between an isolation and the permits depending on it was tracked but not systematically enforced — a gap that, on a high-pressure gas transmission asset, represented a residual risk that was difficult to eliminate through process alone.
In Elisian's Permit to Work module, a permit cannot be closed out until all associated isolation certificates have been formally reinstated and signed off. An isolation cannot be lifted while any permit depending on it remains active. The system enforces the integrity of the isolation boundary as a hard control rather than a procedural requirement, eliminating a category of risk that no amount of individual diligence could fully close.
Outcomes
Following full deployment across the CATS asset, the key outcomes included:
- A single consolidated real-time view of all open permits and active isolations across the asset, accessible simultaneously by the control room and operations management
- Shift handover quality and consistency significantly improved, with structured dashboard-based handovers replacing reliance on system exports and verbal brief
- Isolation-permit integrity enforced systematically for the first time, eliminating a residual risk category that the previous system could not close
- Consistent permit process application across Wood personnel and third-party contractors
- Audit and safety case evidence preparation time significantly reduced
A platform for ongoing improvement
The transition to Elisian's Permit to Work on CATS was the starting point for a broader operational assurance programme. With a trusted, capable platform in place, Wood and Elisian have been able to introduce incremental improvements — enhanced reporting, additional permit types for specialist activities, and integration with the maintenance management system — without disrupting the base process that the operations team relies on daily.
The CATS deployment demonstrates what is achievable when an operator is willing to replace a system that works adequately with one that works properly — and when the replacement is configured to reflect the real operational complexity of the asset rather than a generic template.
To find out more about how Elisian's Permit to Work module can be deployed on your asset, speak to the Elisian team.