Hydro Tech Bearing Booklet

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Transcript of Hydro Tech Bearing Booklet

Mike Dupuis, President mike.dupuis@hydrotech-inc.ca www.hydrotech-inc.ca +1 705 946 3182

Hydro Tech Inc. was founded in 2001 to provide innovative engineering, maintenance and construction solutions to the hydropower industry. Hydro Tech specializes in the design and supply of thrust bearings for medium to large hydroelectric generating companies. After extensive research and development, Hydro Tech designed a bearing suitable for retrofitting existing vertical Francis, Kaplan and Pelton turbines, and for installation into new generating stations in the >5MW power range. This innovative bearing has proven to be the best and most effective solution for conversion of flat-plate Babbitt bearings to modern tilting pad bearings. PolyTetraFluoro-Ethylene (PTFE) bearing pads can be incorporated into the thrust bearing support system providing better efficiency and load carrying capacity. Hydro Techs PTFE bearing conversions provide their customers with:

x x x

increased load capacity (unit plus hydraulic thrust) of at least 100% lowered operating temperatures increased durability and reliability

At Hydro Tech, we pride ourselves on developing sound working relationships with our clients. Thanks to their positive referrals we have rapidly gained global recognition in our industry. We are proud that our bearings speak for themselves and that our clients speak for us.

Experience the superior support and bearing expertise that Hydro Tech offers we look forward to meeting you.

Akosombo runner plate photos courtesy of Canadian Babbitt Bearings Ltd.

We provide innovative solutions to meet our clients technical and business challenges.

Akosombo GHANA, AFRICAFACTSLOCATION Akosombo Generating Station Volta River, Ghana Man-made Lake Six 170MW Francis Umbrella Generators Six Spring-Supported Thrust Bearings (PTFE) December 2009 Volta River Authority TYPE EQUIPMENT BEARINGS SUPPLIED

BEARING DELIVERY OWNER

THE PROJECTBackground

The six generating units were commissioned in 1965 with an original installed capacity of 912MW. Having operated successfully for 30 years since inception, a major overhaul was carried out to upgrade and modernize the plant for an additional 25 to 30 years of trouble-free operation. Generation capacity was increased from 912MW to 1020MW however, recurrent thrust bearing damages were occurring which required frequent repairs and, in some severe cases, caused bearing failure. These failures were attributed to the turbine runner upgrades which had increased loading on the thrust bearings. Several attempts were made to correct the problem by modifying various parts of the thrust bearing with only partial, temporary success followed by eventual bearing failure.Bearing Design

HIGHLIGHTSx x x xReduced operating temperature from 83 Celsius to 76 Celsius PTFE bearing has one fifth the coefficient of friction, preventing excess heating of the thrust oil. No additional cooling was required to lower thrust bearing temperature New thrust bearing supports 1132 imperial tons of thrust load

Hydro Tech was contracted to design a reliable and permanent solution. The designed solution featured new and modified split thrust bearing rotating rings and superior Polytetrafluoro-Ethylene (PTFE) thrust pads providing higher load carrying capacity than traditional babbitt bearings. The new bearings have eighteen spring-supported bearing pads consisting of a PTFE surface with a steel backing plate supported by a bed of precision manufactured springs. The segmented runner plate is supported by a thrust block and held in place with radial keys and vertical bolts securing the runner plate to the thrust block. The runner plate segments are tightly bolted and keyed together, then machined to provide a solid, smooth and polished running surface. The new bearing design has reduced the operating temperature (to ambient) by 25 to 30% and increased thrust load capacity by more than 70%.

Cataract SACO, MAINEFACTSLOCATION Cataract Generating Station Saco River, Maine Run-of-River 6.5 MW Kaplan Turbine One Low-Profile Thrust Bearing (PTFE) June 2006 Florida Power & Light (FPL) Energy Maine Hydro TYPE EQUIPMENT BEARINGS SUPPLIED BEARING DELIVERY OWNER

THE PROJECTBackground

Having commenced commercial operation in 1938, Cataract Generating station experienced recurrent thrust bearing failures. Particularly problematic were failures surrounding startups subsequent to a major overhaul in 2004. Contributing factors included a bearing design capacity that was marginal for the conditions, increased loads on the bearing due to misalignments caused by concrete growth associated with AAR, and decreased bearing capacity due to modifications implemented to a bearing design that was not fully understood. A review of maintenance history at Cataract indicated that the unit had experienced eight thrust bearing failures since 1959, with four of them occurring since 2003.Bearing Design

HIGHLIGHTSx x x xReduced bearing operating temperature by 33 Celsius Reduced bearing pot (oil approximately 25 Celsius bath) temperature by

Bearing and support system retrofitted within a profile height of 4 and 1/16th inches (10.31875 cm) New PTFE bearing supplies greater thrust load capacity and reduced torque load (5 times lower coefficient of friction) Completed in 7 weeks from purchase order to time of supply

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The station was retrofitted with a PTFE (PolytetraflourideEthylene) design using individual pads and springs in the existing bearing envelope. The goal behind this retrofit was to install a bearing design that could tolerate a wide variety of operating and induced loading without significantly impacting bearing design margin capacity. The advanced thrust bearing system incorporated individual PTFE-surfaced pads on a spring bed and a flat, one piece thrust runner plate with no grooves. At the request of the client, a new thrust block was designed and manufactured. Commissioned in early July 2006, the Cataract conversion was very successful. The previously recorded August 2004 thrust bearing temperature of 83 deg C (prior to shutdown) has been reduced to 50 deg C. The oil bath temperature has also been substantially reduced by 25 deg C. In addition, the newly designed PTFE thrust bearing is expected to require less maintenance due to its durability and higher load capacity. It is expected to also accommodate on-going misalignment from AAR more successfully.

DeCew Falls WELLAND CANAL, ONTARIOFACTSLOCATION DeCew Falls No. 2 (NF23) Welland Canal, Ontario, Canada River (Welland Canal) (2) 72 MW Vertical Francis Tilting pad conversion from flat plate February 2006, May 2007 Ontario Power Generation TYPE EQUIPMENT BEARINGS SUPPLIED BEARING DELIVERY OWNER

THE PROJECTBackground

Photo by Ontario Power Generation

HIGHLIGHTSx x xReduced bearing pot oil temperature by more than 50% to ambient Eliminated need for high pressure oil lift system Capacity increased by approximately 300%

The two generating units were put in service in 1943 and 1948 and originally generated power at 25 Hz. They were converted to 60 Hz in 1954. The Francis turbine runners in both units historically suffered from rubbing and wear damage. The original design was a flat plate thrust bearing with Babbitt pads bonded to a single base plate. The bearing pads were held parallel to the rotating runner plate limiting the bearing load capability by eliminating the capacity of the trailing edge of the bearing pad.

Bearing Design

Hydro Tech was contracted to design and supply a modern tilting pad thrust bearing and support system which included the design and supply of thrust bearing runner plates and spring plates. The new titling pad bearing design allows the thrust bearing pad to maintain load capacity over the entire length of the pad thus increasing the load carrying capability of the thrust bearing without increasing the bearing surface area. This innovative Hydro Tech design was installed with little effort and without modifying the bearing pot. Hydro Techs design is a durable, low-profile thrust bearing suitable for retrofitting existing vertical Francis, Kaplan, and Pelton turbines and is proven to be the best and most cost effective solution for bearing conversion from a flat-plate Babbitt to a modern tilting bearing.

Bearing ConversionFlat Plate Thrust BearingBackground

HIGHLIGHTSx x x xUp to 500% additional capacity when compared to flat plate Babbitt designs Inexpensive to convert single or half plate bearing to tilting pad Up to 30 degrees Celsius temperature reduction Zero failures to date

Flat plate babbitt pads are bonded to a single base plate. The bearing pads are held parallel to the rotating runner plate due to the babbitted pads being secured to the base plate. This arrangement limits the bearing load capabilities by eliminating the capacity of the trailing edge of the bearing pad. This flat plate design arrangement was abandoned completely during the 1940s in favour of the modern designs that can have 2 to 3 times the load capacity. A modern, individual, tilting pad bearing design allows the thrust bearing pad to maintain load capacity over the entire length of the pad. This increases the load carrying capability of the thrust bearing without increasing the bearing surface area.Design

Conversion of the flat plate bearing to a tilting pad arrangement presents obstacles that are inherently difficult to overcome. Such obstacles include: i i Finding a way to hold the individual pads in place Frequently, the thrust pad arrangement has a very low profile making it difficult to fit a tilting bearing in the height available Maintaining the ability to easily adjust the bearing pads for alignment and even pad load distribution

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