Paul Cyr, James Price and Andrew Feimster
November 14, 2012 | 2 Comments
The lifting system has operated more smoothly than expected. The module has been raised and lowered more than 20 times, equivalent to four years of operation. It takes one person 60 minutes to raise the module 46 feet and 40 minutes to lower the module the same distance. Unit output when operating while discharging flow through one or both spillgates is not affected, rather it is improved due to increased submergence on the draft tube. Since put into operation, Unit 1 has had a down time of about 15 days due to various start-up commissioning and troubleshooting activities.
Two turbine-generator equipment-related design problems were encountered during start-up. An over-vibration occurred after 19 days of operation, and inspection showed five of 10 bolts had broken in coupling located just below the lowest grease-lubricated bearing. Early design work on the modules indicated that accurate alignment of the turbine, shaft, bearings and generator was impossible. Every time the module is raised and lowered, the entire shaft/bearing assembly shifts out of alignment.
Operation and analysis by Diehl Engineering showed that the long, relatively slender shaft will bend and deflect without overstressing the shaft steel or creating excessive guide bearing reactions.
One oversight was the strength of the coupling bolts supplied by the turbine manufacture. The shafts have typical one-piece forged ridged couplings supplied with ten 43 mm ASTM A668 Class J bolts. These bolts would have been adequate in a traditional hydro installation with a perfectly aligned, stationary shaft. At Jordan, bending and flexing of the shaft during operation caused cyclical loading and unloading of the coupling bolts at each revolution that resulted in the premature failure. The solution was to replace all the coupling bolts with 12.9 class socket-head bolts and applying a preload torque equal to 70% of yield.
The second equipment problem was with wicket gate operation, with the gates moving hesitantly in increments of 20% gate opening. Torsional backlash in the 63-foot-long wicket gate operating shaft caused a problem due to insufficient rigidity. The solution was to remove the 7.625-inch-diameter shaft and operating cylinder and replace them with an underwater hydraulic cylinder attached to the wicket gate operator ring.
Key development factors
The following key factors were identified in the design and construction of the Jordan Hydroelectric Project as being critical to the ability and success of installing a similar hydroelectric project at other discharge towers:
Factors of success
Relations with the Corps have been outstanding. Their review personnel and oversight teams have been cooperative and supportive of the project. Throughout the design and construction process, the development team made Corps personnel welcome in the design review, at the fabrication shops, and on site. The design and construction teams have been upfront with Corps personnel, taking the philosophy that the discharge tower and dam is their house. Project field personnel freely submitted diver plans and critical lift plans to the Corps and worked closely with Corps operating personnel in communicating and coordinating the timing and control of flows released from the dam. The Corps personnel who operate and manage the dam along with the district commanders have all been impressed and pleased with the level of communication and project personnel doing what they said was going to be done.
The Jordan Hydroelectric Project did not utilize any proprietary or patented design, equipment or operating systems. However, the concept and many of the operating systems were custom-designed to fit the site, accessibility and operating requirements. Many of the turbine-generator and associated components can be adapted or installed at other dams that contain a discharge tower.
The owner of the Jordan Hydroelectric Project is proceeding with a second hydroelectric development at a Corps dam, the 3.7-MW Gathright Project in Virginia, which will contain a single vertical Francis turbine. The unit will be installed in a 175-foot-tall, 250-ton module that will be placed on the upstream face of the discharge tower, against the 15-foot-wide by 70-foot-high intake opening. This project will be "a turbine strapped to the back of a floating bulkhead." Stay tuned.
Paul Cyr, P.E., is senior engineering consultant with Kleinschmidt Associates. James Price, PhD, is president of W.V. Hydro and Noah Corporation. Andrew Feimster is president of North Fork Electric Inc.
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