Rebuilding a Failing Pipeline
A STRAUB solution for the Gösgen Nuclear Power Station
The Gösgen Nuclear Power Station in Switzerland provides 13% of the country’s total electricity consumption, generating 8 million kilowatt hours annually. The Gösgen facility has an unrestricted approval to operate as long as safety is guaranteed. When a pipeline servicing the cooling tower needed replacing to keep the power station running safely, the operators turned to STRAUB to provide the solution and manage the project.
The excess heat generated by the power station is discharged into the atmosphere through a natural-draught wet cooling tower. The reinforced concrete cooling tower is 492 feet (150m) high and has a diameter at the base of 387 feet (118m). The cooling air enters the tower horizontally through 50 pipes that absorb the heat of the water, and the excess heat exits the cooling tower vertically as steam. During cold weather, a winter loop pipeline allows the air to be preheated before entering the cooling tower, preventing the interior of the tower from freezing in low ambient temperatures.
The Challenge
The existing winter loop pipeline proved to be damaged beyond repair, so the challenge was to remove the entire 1,079 feet (326m) of pipeline, design and manufacture an improved pipe support system and install a new pipeline with couplings that would handle thermal expansion and stand the test of time.
Inspection of the original pipeline revealed that the fittings were corroded, causing the pipes to slip. In addition, the pipes were deformed because the original concrete supports, combined with the weight of the water-filled pipes, resulted in great tensions. Over the years, cracks and dents developed at the pipe ends.
In addition, the winter loop pipeline was 42 feet (13m) above ground in confined space, which added concerns, since safety was the highest priority.
The Solution
In close cooperation with the team at the Gösgen Nuclear Power Plant, STRAUB developed a complete solution that fully met the project specifications. STRAUB managed the planning, engineering, design, manufacture, delivery and construction of the new winter loop pipeline.
The design of the new supports eliminated the fundamental defect, ensuring proper support for the pipes and absorption of the thermal expansion of the pipeline. The pipe bracket developed for the project allowed for fast and simple installation, a critical feature when installing pipes high above ground in tight spaces. After bolting the pipe brackets to the concrete support, the pipes were placed into the pipe support clamps, aligned, and tightened. Then the STRAUB-Flex 3LS was moved over the gap between the pipe ends and tightened to the specified torque.
Each coupling included a stainless steel strip insert to prevent the sealing sleeve from being damaged by the gap between the pipe ends, caused by the angular deflection of about 4°. The STRAUB design allowed the pipes to be laid with no inbuilt tension. This design also compensates for building tolerances and is unaffected by changes in temperature.
With the new winter loop pipeline in place, the operators intend to run the Gösgen Nuclear Power Plant for another 30 years. By designing and constructing the winter loop pipeline replacement, the STRAUB team made a substantial contribution to helping the operators achieve their goals.