Repair of structural damage of the turbine area of ČHE Avče

Introduction

Despite its successful operation, the plant has faced certain technical challenges that necessitated repair and maintenance. This case study will examine the plant's efficiency, the challenges faced, and the solutions implemented to maintain operational integrity.

Key Features and Efficiency

• Height Differential: 105 meters to 625 meters
• Capacity: Reservoir holds 2 million cubic meters of water
• Generator Power: 185 megawatts (248,000 hp) during production, 180 megawatts (240,000 hp) during pumping
• Efficiency: 77%
• Discharge Rate: 40 cubic meters per second
• Operational Hours: 6 to 10 hours normally, with the reservoir usually filled at the end of the week.
• Construction Cost: €122 million

Technical Challenges

Structural Issues

The plant faced structural problems related to poor weld quality in the construction wall, made of structural steel. Operating pressures of about 55 bar led to a leak in the concrete structure, affecting the operational efficacy.

Equipment Damage

The turbines, manufactured by Mitsubishi Heavy, were showing signs of damage, posing a risk to the generator room located directly above the turbine. The leakage rate was measured at approximately 20.0 l/min, and it was increasing.

Remediation and Solutions

Diagnosis and Material Selection

Euras Gel typ B was selected as the material to address the leakage. This material was injected into the concrete-metal joint near the damaged areas, forming a homogeneous sealing layer.

Application

The gel penetrated through zones previously filled with water, significantly reducing seepage. The same material was used to supplement the pit liner zone, stopping the penetration of water into the generator area.

Results

After the application, the leakage was reduced to zero, and the structure was stabilized. This met the investors' requirements for operational integrity.

Contingency Plan

For future preventive measures, a specialized Euras gel type g has been developed. This gel has low-abrasive fillers based on rubber flour, which would protect against the abrasion of the turbine.

Conclusions

The Avče Pumped Storage Plant represents a significant investment in Slovenia’s energy infrastructure but faced challenges related to structural integrity and equipment damage. Prompt and effective remediation using specialized materials has returned the facility to optimal operational standards. This case underscores the importance of stringent quality control in the construction phase and the need for ongoing maintenance to ensure long-term operational efficiency.

Recommendations

1. Periodic inspections and maintenance should be conducted to ensure the structural integrity and efficiency of the plant.
2. Training programs should be implemented to improve weld quality and reduce the likelihood of future structural issues.
3. Further research and development into sealing and bonding materials should be conducted to prepare for any future challenges.

The Avče Pumped Storage Plant serves as an educational case for the deployment of pumped storage plants, particularly in the areas of construction quality and ongoing maintenance.