Haiyang and Sanmen order Hydratight RPV tensioner

6 June 2011

Hydratight is preparing to deliver its next-generation nuclear RPV tensioner system to two Westinghouse AP1000 nuclear power plants in China.

Westinghouse ordered two SCT systems — each of four tensioners — for AP- 1000 PWR generating plants at Haiyang, on the northern Chinese coast in Shandong province, and at Sanmen, on the coast of the eastern province of Zhejiang. Delivery is expected in July.

The Biach Self Contained Tensioner (SCT) system consists of four “smart” tensioning units, any one of which can control all four, and the EMS (elongation monitoring system) helps eliminate trim passes by showing actual stud elongation during the tensioning process.

Hydraulic units and controls are onboard each unit, and the only connections are to a 480V power line and standard inter-unit ethernet. Only one operator is required per unit, with no central supervisor.

Other tensioning systems have a central pumping/supervisory station linked by heavy hydraulic hoses and manifolds, and require several personnel to set up and use. Typical tensioning sequences can last several shifts of a scheduled outage.

During live tests in the US, closure time on a 92-stud boiling water reactor RPV fell from more than four hours with older systems to around 90 minutes with the SCT.

Hydratight has supplied Biach tensioning systems to more than eight out of 10 US generating plants and many overseas plants. The company also provides training programmes, on-site maintenance and outage support services.

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