In the field of hydroelectric maintenance, guaranteeing the hydraulic isolation of a plant is the absolute prerequisite for any major refurbishment work. Building on the successful sealing of the Bargi Power Plant intakes, Drafinsub was once again commissioned by Enel Green Power to execute a critical operation at the nearby Suviana Dam complex: the closing and watertight sealing of the Power Plant Intakes Guard Gates.
This operation was essential to create a “dry environment” downstream, allowing technicians to work safely on the penstocks and turbine valves.
The Technical Challenge of High Head and Freezing Deep Waters
Operating on the bottom intakes of a large dam presents specific engineering challenges. The Guard Gates are located at significant depth, subjected to high hydrostatic pressure and freezing waters. This harsh environment, combined with sediment accumulation and wear on the sealing surfaces, can compromise the gate’s ability to provide a perfect seal.
The objective was clear: achieve Zero-Leakage integrity to ensure the safety of the dry-works occurring inside the plant tunnels.
Operational Methodology
Drafinsub deployed a specialized commercial diving team and advanced equipment to execute the project in three distinct phases:
1. Inspection and Clearance
Before the gate closure, an initial survey was conducted using ROVs and divers to inspect the intake trash racks and the gate guides. Key activities included:
Removal of sediment and debris interfering with the gate’s travel.
High-pressure hydro-blasting of the sealing surfaces (steel and concrete) to ensure a clean contact area.
2. Guard Gate Closure and Sealing
Once the mechanical closure of the Guard Gate was performed, Drafinsub divers tackled the Watertight Sealing phase. Because mechanical closure alone rarely guarantees a 100% seal in aging infrastructure, our team intervened to seal the perimeter. Depending on the specific gap analysis, this involved:
The application of specific underwater sealing compounds or temporary gaskets along the gate’s perimeter.
The installation of mechanical wedges to force the gate against the pressure side, optimizing the seal.
The use of temporary blanking devices where necessary to manage differential pressure leaks.
3. Verification and Monitoring
Safety in hydroelectric projects relies on certainty. We did not rely on assumptions.
Differential Pressure Tests: We monitored the water levels downstream to verify the effectiveness of the seal.
24/7 Stand-by: During the critical dewatering phase, a Drafinsub team remained on standby to intervene immediately in case of pressure anomalies or seal failure.
Safety Protocols for Managing Delta-P
Working near active intakes or drains involves the risk of Delta-P (Differential Pressure), one of the most lethal hazards in commercial diving. Drafinsub implemented strict Lock-Out / Tag-Out (LOTO) procedures with the dam management entity (Enel Green Power). No diver approached the critical zone until positive confirmation of hydraulic stasis was achieved and verified, adhering to the highest safety guidelines for diving in differential pressure environments.
Conclusion
The successful sealing of the Suviana Dam bottom intakes demonstrates Drafinsub’s capability to blend underwater operations with civil engineering. By ensuring a completely dry environment downstream, we enabled the client to proceed with essential maintenance works, minimizing downtime and maximizing safety.