Waukesha Bearings, a global leader in the design and manufacture of oil- and process-lubricated engineered bearings, is proud to announce the availability of its Multi-Lobe Semi-Floating (MLSF®) bearings. The unique MLSF technology, which improves stability and reliability compared to conventional floating ring bearings, can extend the life of host equipment and surrounding parts.
“Our MLSF design is specifically engineered to minimize vibrations, which promotes longer-lasting equipment and lessens the likelihood of early failures in the turbocharger or downstream equipment,” said Ken Bischof, Senior Development Engineer at Waukesha Bearings. “A failed bearing can lead to downtime for a replacement bearing, or worse, replacement of related equipment. A bearing system operating at an optimized temperature, which is cool enough to prevent coking yet hot enough to maintain optimum viscosity, can minimize both downtime and power loss.”
By designing the MLSF bearing system to operate at optimized temperatures with minimal vibrations, the life of the equipment and surrounding parts is extended. In addition to global customer service and Waukesha Bearings’ proven results, the MLSF bearings offer an ideal solution for smaller, high-speed turbomachinery, as well as for turbochargers in large diesel or natural gas engines.
Waukesha Bearings’ MLSF bearings, available for use with shafts as small as 0.5 inches in a single bearing or cartridge, can handle a static unit load as light as 10 psi (.07MPa) to a dynamic unit load exceeding 700 psi (4.8 MPa). The MLSF, which can handle multi-viscosity oils, is engineered to accommodate temperature ranges up to 300ºF (149ºC) with even higher temperatures available. The first Waukesha Bearings MLSF bearing, which has been in field operation for more than 30,000 hours, continues to surpass competitive bearing performance of only 500 hours in the same application.
With the industry trending toward improved efficiency, in both new and existing equipment, higher demands are placed on the equipment and the bearings.
When Alstom Power identified a phenomenon of spiral vibration close to the trip level on one of their 450MVa hydrogen-cooled generators, our proprietary predictive tools and extensive industry experience on equipment of this size made Waukesha Bearings the clear choice to design and manufacture a drop-in bearing replacement.
More than 13 generator sets have been commissioned since the initial phenomenon was detected in 2003. In total, the Maxalign bearings have seen 600,000 cumulative operating hours with these particular Alstom generators.
In the May 2010 issue of International Power Engineer, Jessica Whelan and Richard Livermore-Hardy look at new large tilting pad radial bearings designed to further improve safety margins.
It is difficult to pick up an industry publication without seeing an article or viewpoint covering the trend away from coal toward natural gas as part of the global power generation mix.
Whether climate-change legislation happens this year, in 2011 or in 2020, project owners and financiers at the very least are ‘cautious on coal.’ This shift toward cleaner energy is creating increased focus on alternative fuel sources; nuclear energy and the many forms of renewable energy are the targets of technology development, investment and new business ventures.
However, in the short to mid-term, natural gas-driven power generation is the obvious substitute for coal as the economy recovers…as GDP grows, so does the demand for energy.
This move toward natural gas as a primary source of energy has placed new demands on the makers of gas-fired combustion turbines. Larger, lower emission, and more reliable and efficient machines are required if turbines are to play a more vital role in the global power mix.
In anticipation of these market demands, Waukesha Bearings, a leader in hydrodynamic bearings and magnetic bearing systems, has developed the next generation of large tilting pad radial bearing designs to further improve safety margins and provide superior performance to address the challenges associated with these machines.
The next generation technology was applied to Waukesha’s existing ball and socket tilting pad radial bearing with Directed Lubrication, which has been used successfully over the past 25 years in large frame gas turbines, steam turbines and turbo-generators. Throughout the development cycle, Waukesha engineers worked closely with leading original equipment manufacturers to translate turbine performance requirements into improved bearing designs using a combination of field experience, testing and advanced analysis techniques.
In order to directly address requirements for improved machine efficiency, Waukesha’s latest design uses an efficient 4-pad arrangement to minimise power loss and reduce the number of components.
As a result of the trend towards larger machines, higher bearing loads and surface speeds, the design also includes an optimised pad and hydrostatic jacking groove design to further reduce pad temperatures, leading to increased safety margins and machine reliability.
The latest technology compliments Waukesha’s proven ball and socket pivot design, which, due to the proprietary design and materials, has excellent dynamic alignment capability typically required on ‘hot’ machines during the transition from cold to hot conditions plus high stiffness for assured bearing dynamic characteristics.
Waukesha engineers used proprietary predictive tools and testing to design and verify the performance of the next generation of large tilting pad radial bearing designs, which have now been in service for several years on numerous gas-fired combined cycle turbo-generator applications.
The knowledge gained during this process will allow Waukesha to further adapt their technology for the ever increasing requirements for improved performance and reliability in the gas-fired power generation market.
Tight-tolerance tilt pad journal bearings provide increased stability in high speed turbomachinery equipment.
By Dr. Kenneth R. Bischof
Published in International Oil & Gas Engineer, 2009
As machinery builders strive for improved efficiency, higher pressure ratios or increased operational flexibility, static performance and rotordynamic challenges become even greater for rotor-bearing system engineers. Often these challenges are a direct result of a more flexible rotating system and increased rotor length, leading to increased bearing spans.
To combat these challenges, fluid film bearing engineers have traditionally relied on a variety of features within a tilt pad journal bearing, such as assembled clearance, pad-angle, pre-load and pivot offset. When traditional feature variations are not sufficient for more challenging systems, bearing structural stiffness and damping have also been improved through the use of higher performing ball-and-socket pivot designs as well as employing squeeze-film dampers, respectively.
System rotordynamic challenges have placed an increased emphasis on reliably maintaining tight tolerances within bearing manufacturing processes. Even the slightest tolerance variations can have dramatic impact on bearing stiffness and damping characteristics, ultimately leading to differences between predicted and actual performance of the machine.
Early in 2008 Waukesha Bearings completed development of a new bearing design aimed at solving many of the technical issues surrounding the dynamic performance of the rotor-bearing system. This new design utilises a patent-pending, single-piece frame construction with the tilt pads integral to the shell and without sacrificing pivot stiffness, creating a potential fatigue-failure point or restricting free-tilt of the journal pads. This is accomplished through the use of an EDM manufacturing process used in combination with a hardened steel pivot, offering a solution with reduced pad flutter, particularly in unloaded pads, and less vibration, fatigue and wear. The bearing is also designed with a secondary integral pad stop that prevents over-rotation as well as improved oil distribution across the pads.
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