Stability

Damping for Increased Stability

Damping decreases vibrations by removing energy through resistance to motion. For rotating equipment, damping is necessary to control vibrations and prevent them from damaging the rotor, bearings or other components in the machine.

Using an engineered damper can increase stability, reduce rotor response, increase the separation margin between operating speed and critical speeds, reduce forces transmitted from rotor to ground, reduce pedestal vibrations, reduce bearing wear, and decrease sensitivity to changes to the rotor, such as material buildup on a rotating component.

To learn about the particular benefits of ISFD® technology – the integral squeeze film damper – read the article on engineerlive.com.

Advanced Bearing Technology Eliminates Subsynchronous Steam Turbine Vibrations

By Jong Kim, Waukesha Bearings
Published in POWER magazine, March 2015

For one of its power generation customers in Scandinavia, Doosan Škoda Power engineered a 46 MW steam turbine as part of a combined cycle system for generation of electricity as well as heat recovery. During the initial commissioning, the turbine experienced rotor instability that prevented the drive train from operating at full load. High subsynchronous vibrations forced a trip in turbine operation at just 27 MW versus the rated 46 MW.

Changes to the bearing clearances and configurations mitigated the vibrations but were not able to eliminate them completely. Doosan Škoda Power decided to contact Bearings Plus, a Waukesha Bearings business, for a damper solution.

Learn how ISFD technology maximized the damping ratio and eliminated the subsynchronous vibrations spikes in the March 2015 issue of POWER magazine or online at www.powermag.com.

Reducing Spiral Vibration on a Genset

By Richard Livermore-Hardy, Waukesha Bearings
Published in Turbomachinery International, July/August 2014

An Alstom 450MVA hydrogen-cooled generator operating at 3,600 rev/min and equipped with a brush gear unit showed spiral vibration with a forward rotating unbalance vector.

Spiral vibration, also known as the Newkirk effect, can be observed on various types of turbomachinery and is caused by a vibration-induced hot spot on the shaft surface generated by friction.

Potential modifications were studied by Alstom using hot spot stability analysis with a rotor dynamic model of the generator rotor, and bearing supports. Based on the calculated results, a modification of the generator shaft line was implemented using tilting pad radial bearings at the generator non-drive end and exciter end locations to shift the slip ring shaft critical speeds well above the rated speed.

Read the article in the July/August 2014 issue of Turbomachinery International.

ISFD Paper Presented at ASME Turbo Expo

Waukesha Bearings, a global leader in the design and manufacture of oil- and process-lubricated engineered bearings, is proud to offer the presentation of the integral squeeze film damper (ISFD) 8 – 10 a.m. June 19, at the American Society of Mechanical Engineers (ASME) Turbo Expo in Düsseldorf, Germany.

The presentation is based on a paper that presents experimental tests and analytical results focused on stabilizing a 46 MW 6,230kg utility steam turbine experiencing subsynchronous rotordynamic instability. The paper, coauthored by Dr. Jong Kim, Sr. Principal Engineer of Waukesha Bearings, and several other ASME colleagues, advances an integral squeeze film damper (ISFD) solution which was implemented to resolve the subsynchronous vibration and allow full-load and full-speed operation of the machine.

View more information about the ISFD bearing system 

Dr. Jong Kim is Senior Principal Engineer for Waukesha Bearings. Joining KMC/BPI in 2001, he possesses extensive experience in rotordynamic analyses and bearing failure analyses. A former mechanical engineering teacher at Korea Maritime University for 10 years, Dr. Jong Kim received a BS degree (Mechanical Engineering, 1985) from Busan National University, and an MS degree (Mechanical Engineering, 1987) and a PhD (Mechanical Engineering, 1991) from KAIST (Korea Advanced Institute of Science and Technology). He has authored and coauthored several technical papers and holds patents on bearings and dampers.

Bearings Reduce Spiral Vibration on Turbo-generators

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.

Read the full article on page 21 of International Power Engineeringmagazine, or download the article below.

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