By Cody Vandiver, Power & Industrial Sales, Hanson Pressure Pipe
The construction of two new reactors at the Vogtle Electric Generating Plant in Georgia represents a significant milestone in the energy industry: the first contract awarded for new nuclear builds in nearly 30 years. The facilities will employ the Westinghouse AP1000 pressurized water reactor technology, which uses natural air convective currents and simplicity of design to enhance plant safety and operations while reducing construction costs.
|Hanson’s pipes laid out end to end at the Vogtle 3 & 4 construction site with Vogtle 1 & 2 in the background.|
Like in other nuclear plants, water is an essential component to keeping the reactors cool. A network of 12,000 feet of Hanson 120-inch pre-stressed concrete cylinder pipe circulates water from the units’ power-generating turbines to a cooling tower and back again. Hanson engineers worked closely with Shaw and the rest of the project team to design the optimal layout for the dual supply and return lines, along with determining what custom and specialty components would be required.
Hanson’s testable joint enabled the installers to quickly assemble each joint and then test the joint to ensure it is water tight immediately after installation, a key detail since the pipelines could not be field pressure tested and will not be in service until the reactors are brought online in 2016 and 2017.
Among the other unique features are Wye connections following the cooling tower’s pump station: Four 78-inch pipes emerge from the pump station, then convert to two 120-inch pipes; those 120-inch pipes enter a 120×144 Wye, allowing the water to mix along a 10-foot stretch of 144-inch-diameter pipe before exiting another Wye into the dual 120-inch pipes returning to the turbine. Hanson also created cut-to-fit closures to accommodate staging that saw lines meeting in the middle rather than from one end to the other.
Though other materials were considered, Hanson PCCP was the ideal choice for this high-profile project because of its reliability and strength to support the required loads. Hanson pipes running under the turbines feature an 11.5-inch wall with a second wrapping of pre-stressing wire to accommodate the substantial loads without requiring additional support. PCCP’s sturdy cylinders also better manage the water’s 100 psi of force while the mechanical restrained joints eliminate the need for thrust blocks at elbows and other areas where thrust displacement will be present. For installers, the pipes’ rigidity allowed for open-trench construction while their modular nature eliminated on-site cutting.
Along with these product features, Hanson’s involvement early in the design stages and continuing through installation was essential to bringing clarity to its portion of the massive project.
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