HOBAS CC-GRP Pipes Prove their Worth in Bulgarian Hydropower Plant Kalin

Hydropower plants in Bulgaria play an important role in covering peak consumption. Two particularly interesting ones have been realized with HOBAS Pipes – and they are doing an excellent job in providing the country with clean energy. , The name “Rila” means “well-watered mountain”, which is definitely a suitable name for the highest mountain range of Bulgaria and the Balkan Peninsula: It features more than 200 lakes and a great number of mineral springs. Rila is also the name of the first complete cascade of hydropower plants in the Bulgarian mountains. The highest one among them is Kalin which feeds the other plants from 2394 meters altitude and, with a flow rate of 650 l/sec., generates 4 MW. Kalin was built in the 1940s. At the time, the reservoir was connected to the powerhouse with a 2-km-long steel pipeline DN 600 leading through a tunnel in the mountain on concrete supports. Over the years the pipe corroded, weakened and could no longer withstand the water pressure. It became inevitable to replace at least 300 m of the pipeline in an altitude of approximately 2200 m. Drawing on very good experiences with HOBAS, the client BAD Granitoid AD decided to opt for HOBAS Products again for a variety of reasons – among them the pipe system’s reliable tightness, dimensional accuracy and low weight that facilitated the transportation via the narrow and steep way to the Kalin powerplant. The 3-m-long pipe sections were brought close to the construction site with trucks, then loaded onto trolleys and transported to the entrance of the tunnel on small rails, which lead all the way alongside the pipeline inside the tunnel. 375 m of steel pipes were dismantled and replaced by HOBAS GRP Pipes with the help of winches. In addition, some of the old concrete supports had to be removed and new ones built. Despite all challenges, the installation works could be completed within one week only and the client was more than satisfied.