SF₆ Gas Handling Services in a GIS Room on an Offshore Substation

Operational Execution

Upon mobilization, the SF₆ service unit was connected to the GIS compartment using self‑sealing, leak‑tight hose connections, preventing any release of gas during connection or disconnection. Approximately 30 kg of SF₆ was recovered from the compartment into the service unit using a closed recovery cycle. This recovery phase typically takes several hours (around six hours in this case) and runs largely automatically once configured, with the team supervising process parameters and system integrity.

After recovery, the compartment was evacuated and conditioned to prepare it for opening. Clean air was introduced to render the space accessible for internal work. Where required, nitrogen purging was applied to lower the moisture content and ensure a sufficiently dry internal environment, reducing the risk of condensation or contamination prior to recommissioning.

Gas Quality Control and Reporting

Before re‑filling, SF₆ gas quality checks were carried out in line with established industry practice and manufacturer guidance. These checks typically include verification of SF₆ purity, moisture content and the presence of decomposition products, ensuring that only gas meeting the required quality criteria is re‑introduced into the GIS compartment. The results of these gas quality checks were documented and reported as part of the scope, providing transparency and traceability for the client.

Following completion of the internal works, the GIS compartment was re‑evacuated and then refilled with SF₆ gas to the specified pressure using the same closed‑loop system. All filling operations were monitored and controlled via the service unit to prevent overfilling and emissions.

Safety and Environmental Considerations

Although SF₆ is hazardous if released into confined spaces and environmentally harmful if emitted, no breathing protection was required for the OIS team due to the use of sealed systems, controlled procedures and continuous supervision. The combination of certified equipment from WIKA‑class and DILO‑class suppliers, trained personnel and closed handling processes ensured safe execution and strict environmental protection throughout the offshore operation.

Client Relevance

This project demonstrates OIS’s capability to support specialized SF₆ gas handling activities in offshore GIS environments, integrating seamlessly into complex outage campaigns. By using industry‑standard equipment platforms and applying disciplined operational procedures, OIS enables clients to carry out essential maintenance on offshore substations while maintaining compliance with safety and environmental requirements.

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