Dec 13, 2017

iWWD - Power Plant Contends With Terrain Challenges

Zhijin, China power plant constructed on mountainous terrain

For some facilities, working with the terrain is necessary. In the Guizhou province of China, the new Zhijin Power Plant is one such example. Constructed in mountainous terrain, the facility has different elevations to work with, but still requires water for cooling. This water is transported over 8.1 km from the Hongiiadu reservoir at an elevation of approximately 1,150 meters. Using this water, the facility produces power for the city of Guiyang and its surrounding communities.

According to William Su, technical manager for Singer Valve China, the water travels across this terrain up to the water treatment plant and water tank, then it travels down to the power plant. The water tank, in particular, is 180 meters higher than the power plant, making the final transportation gravity-fed over 6.3 km.

“The high lift and long distance of this water distribution system make it vulnerable to surges and pipe breaks,” Su said. The system required a more stable flow.

To achieve stability, Singer Valve designed manageable intervals for water control and protection in the event of surging. First, on the floating dock that pumps water, two surge-anticipating relief valves help relieve pressure from the pipe. In addition, Singer Valve installed air valves on the pipeline to release air trapped in the pipe.

“These two valves can be opened before the surge comes and relieve the pressure from the pipe. This is especially important if there is a power failure and water rushes back down to the pump station,” Su said.

To anticipate surges and avoid severe water hammer associated with power failure surges, Singer Valve also installed a control valve with a surge-anticipating relief valve mounted in a tee downstream of the pump check valve. Then, a pump control valve protects the pump that also can be used as a check valve when the flow returns. In addition, to prevent cavitation damage (the rapid vaporization and condensation within a liquid), Singer Valve installed anti-cavitation technology.

Finally, the project required one final step. “After the pressure reducing station, the water flows into the power plant with one last flow-regulating valve installed at the entrance gate to ensure stable flow and pressure,” Su said.

Because of the different elevations and the terrain, which provided challenges to overcome, Singer Valve needed to work with the surroundings to protect the facility.

“We knew it was going to be very challenging to transport the water to the power plant safely with [the] elevations and distance that it needed to travel,” said Liu Zhizhao, manager of Zhijin Power Plant. “Singer’s surge-anticipating plan and quality valves gave us the confidence to complete this project.”

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