New machining techniques and technologies are emerging amid increasing interest in the rehabilitation of aging hydropower projects. Hydro Review details some of the innovations being employed for hydropower.
By Russell W. Ray
Machining, a trade that specializes in cutting materials to achieve a specific geometry, is one of the most important aspects in the rehabilitation of hydropower projects.
It's an evolving industry, as new techniques and technologies to shape, bore, and drill metal are realized to improve the efficiency and lifespan of a project.
Hydro Review examined some of the modern machining techniques and technologies being used to rehabilitate North America's aging fleet of hydropower projects.
The following are a few examples of some of the machining challenges power producers and service providers are facing and the innovative solutions being used to overcome those obstacles.
Main Channel Dam gets a major machinery upgrade
The 1938 vintage Main Channel Dam at the Emsworth Locks and Dams on the Ohio River near Pittsburgh, Pa., recently underwent a major rehabilitation. Eaton Corp. was a key supplier for the project.
Working with the U.S. Army Corps of Engineers' primary contractor, the Heavy Civil Division of Joseph B. Fay Company of Tarentum, Pa., Eaton supplied hydraulic systems, including cylinders, power units, valve manifolds, and related installation services used in the replacement of gate operating machinery for the dam's eight lift gates.
"The Corps of Engineers had recently completed upgrading the Back Channel Dam at Emsworth using competitive hydraulic products," said Kevin DuPont, Eaton's product sales manager. "This was our first experience working with the folks at Fay Company. So, we had to make up a lot of ground to win this bid."
Eaton assembled a multi-functional team that worked closely with engineers and managers from Fay to put a proposal together. The proposal stressed that the specified products would be produced primarily by Eaton facilities in the U.S., resulting in a pricing advantage for the customer, and that Eaton would be able to meet Fay Company's tight delivery schedule, DuPont said.
Eaton's hydraulic cylinders met two important requirements: Anti-corrosion protection from Application-Based Coatings (ABC) that provide anti-corrosion and anti-wear protection in harsh environments; and precision position sensing with an integrated Hypos position sensor.
Eaton also provided the following products for the Emsworth project: Custom Hydrowa cylinders, cardan rings, suspension hook cylinders, dogging pin cylinders, dogging beam cylinders, custom brush systems, bellows and bellows covers, custom hydraulic power units, custom valve manifolds, and electrical controls.
Streamlining the machining process with better technology
In 2009, Ontario-based Canadian Hydro Components (CHC) acquired a Fortus FDM Maxum rapid prototyping machine. It gave the company the ability to produce 3-D thermoplastic turbine component prototypes, which have improved the design process by confirming dimensions and assembly sequence of components.
These scale models also have helped customers visualize equipment configurations and have proven to be a useful tool in advancing discussions with project financing parties and suppliers and contractors involved in various stages of hydro projects.
In addition, CHC said it recently acquired one of only three Toshiba BTU-14 universal machining centers found in North America - and the only one in Canada - to eliminate multiple setups previously required when machining complex shaped components such as turbine distributors and blades.
|Canadian Hydro Components said it recently acquired one of only three Toshiba BTU-14 universal machining centers in North America to eliminate multiple setups.|
"With this five-axis system, most multi-step machining operations can be completed in only one setup, thanks to a tilting spindle which provides a 150 degree range of motion, a fully programmable rotary table and a direct drive spindle motor which results in high speed machining of complex shapes and large size components," said Mike Dupuis, president and owner of Canadian Hydro Components.
By streamlining the machining process, the accuracy and integrity of the component's geometry are maintained and all machining operations are done in house, as the BTU-14 machines all sides, all angles, all shapes and, all sizes. The shorter tool lengths provide more stability with cutting tools and the spindle can get to hard-to-reach areas.
The addition of the Toshiba BTU-14 to CHC's existing line-up of machining and boring centers has paved the way for the company to work on larger scale hydro projects and CHC has now developed turbines with diameters exceeding 3.0 meters.
CHS has been manufacturing hydraulic turbines for over 20 years. Unlike other turbine manufacturers, CHC designs, engineers, and manufactures as many components as possible in-house to maintain maximum control over quality, cost, and delivery.
CHC utilizes the most technologically sophisticated pattern, casting and machining techniques in the manufacturing process and has successfully installed its equipment in hydro projects all over the world.
The benefits of laser tracker technology
Hydro Tech Inc. has developed machining techniques employing the accuracy and consistency of laser tracker technology. Such techniques streamline the manufacturing processes and result in a finished product with greater consistency.
Hydro Tech Inc. has developed several new machining techniques that use laser tracker technology.
"The greatest benefit occurs during the rehabilitation machining of hydro turbine components when years or decades of operation create deviations from the nominal stack up," said Hydro Tech's Sean Whelan Marcolini.
Subsequent to machine disassembly, a laser tracker is brought to the site and used to determine the independent embedded features that control the stack up.
With this data taken into consideration, effects such as concentricity and alignment may be accounted for during both the offsite and onsite machining.
|This long hydropower piston being machined at Eaton's cylinder plant in Decatur, Ala., was part of a major rehabilitation of the Main Channel Dam on the Ohio River.|
The laser tracker also is used to determine the wicket gate bore misalignment between the discharge ring and headcover. By capturing this feature, the bores may be machined offsite to compensate on a vertical boring mill rather than depending solely on costly line boring.
While on site with the tracker, it is also convenient to perform the stationary alignment.
Using the tracker, it is possible to return the stator circularity to within tolerance - and often close to the factory tolerance - quickly, without relying on the time-consuming practice of hanging wires.
Subsequent to machining, the laser tracker can be used to quickly perform quality assurance checks on critical components before shipment. It is also used during assembly to check alignments and provide the final machined stack up information.
By using the tracker to identify minor variations in the turbine components, the machining processes required for rehabilitation may be consolidated and simplified, resulting in reduced costs and lead times.
This is achieved without a loss of accuracy while automatically providing digital geometrical documentation of the results.
Overcoming machining challenges at Wells hydro plant
IPS Portland is working on an extended project with Toshiba, machining brake rings and hydro shafts for a 75-MW hydro generator at the Douglas County Public Utility District's Wells Hydroelectric Project on the Columbia River in Washington.
Dick Bloomquist, IPS Portland's machine shop manager, said the original equipment manufacturer (OEM) was looking for qualified, experienced machining services.
|A technician performs machining work on a hydro shaft for the Douglas County Public Utility District's Wells Hydroelectric Project on the Columbia River.|
"This is the kind of work we do every day," Bloomquist said. "The turbine shafts weigh 76,000 pounds and have an overall length of 167 inches with a 42-inch seal fit.
"The shafts have 71-inch flanges at both ends, so we had to include splitting the rings in our job scope."
IPS Portland technicians machined the old sleeves off the shafts, manufactured new sleeves, then split and welded them into place.
Tolerances, according to Dick, were less than two one-thousandths of an inch.
|Laser tracker technology can be used to determine the independent embedded features that control the stack up. With this, effects such as concentricity and alignment may be accounted for during offsite and onsite machining.|
"The gratifying part of the job, for us, was the way the responsibilities kept expanding. Once our customer visited the shop and saw our capabilities, we started adding to the to-do list," Bloomquist said.
IPS started with brake rings and shafts. In short order, it was machining the flange runners and removing old pins and bolts. Technicians built a blast booth in the shop, to sandblast the flange faces before painting. They also machined and polished bearing fits and cleaned, detailed, and re-cut flange faces.
"By the time we finished, we had restored the shafts and rings to OEM spec, with everything documented and validated," Bloomquist said.
Russell Ray is senior associate editor of Hydro Review