Turbine shutoff valve upgrade completed at 129-MW Horse Mesa Dam hydro project

Dam

This week, Salt River Project (SRP) announced that its engineers have finished a project to replace the original turbine shutoff valves at the 129-MW Horse Mesa Dam project at Apache Lake, Ariz. The original valves, which were 10.5 feet tall and weighed about 27,000 pounds each, were installed in 1927 and had reached the end of their life for the three hydro generating units.

The 1920s dam serves SRP in a series of dams storing water on the Salt River, releasing the water downstream and providing electricity to the valley with its hydro generating units.

Turbine shutoff valves control and stop the water flow from the lake to the turbines. This occurs each time the unit is started, often several times a day. The valves also act as protective devices that prevent damage to the turbines in the event of a malfunction.

“Replacing the turbine shutoff valves restores a safe and reliable means to maintain our units,” said Matt Pendergraft, manager of O&M baseload and gas generation.

One of the project’s challenges was removing the old valves. Because the original control house was built around the valves, crews had to cut through the powerhouse walls to reach them.

“The original construction crew didn’t anticipate having to eventually replace them. Luckily for us, they built things that lasted, so we didn’t have to do this for nearly 100 years,” said Pendergraft.

The new valves, which are 8 feet tall and weigh about 47,000 pounds each, were brought in from Germany and transported upriver.

When a major rainstorm hit Salt River in September, it set the project back weeks. The barge, which was holding the new valves and trying to access the dam, could not move past a large amount of debris. Crews had to use an excavator to remove the debris from the reservoir. Overall, they removed about 100 dump trucks full of logs and debris to get to the dam.

“The most challenging part of the project was dealing with Mother Nature,” Pendergraft added.

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