Rexnord® Omega™ Couplings Solve Application Problems at Madison Paper
CASE STUDY
One of the challenges when Madison Paper Industries, Inc., North America constructed its first facility to produce uncoated supercalendered (SC) paper from pressurized groundwood pulp was to “marry” an assortment of equipment and components from Finland, Sweden, Germany, Canada, and the United States. Rexnord Omega couplings helped overcome a potential conflict with the mill’s unusual spacing requirements between its standardized English-measurement-based motors and metric-based process and water pumps.
The world’s largest producer of SC paper, Myllykoski Oy, of Finland, purchased the mill complex on the Kennebec River in Madison, Maine to compete better in the U.S. market. Demand grew so rapidly that the New York Times Co. agreed on a joint venture with Myllykoski Oy to build a new mill that would boost Madison’s total SC paper capacity to 200,000 tpy. It was completed in 20 months and included a new pressurized 280 tpd groundwood pulp mill and 600 tpd, 305-in. paper machine.
Process stock pumps, water pumps and motor couplings presented English/metric compatibility challenges. Madison previously had standardized on Ahlstrom Pumps and Westinghouse motors for the application, so it needed highly adaptive couplings that could span unusually wide non-U.S. standard separations and connect ISO metric standard pump shafts with ANSI standard motor shafts. The couplings also would have to have minimum requirements for extra maintenance or parts. Finally, they had to operate efficiently, reduce vibration transmission, and work within Madison’s alignment tolerances of ±0.001-in. between motor and pump shaft assemblies.
Rexnord Omega couplings were selected to meet these challenges. They have a urethane flex element and are split longitudinally. Their design provides a clear space between the hubs, without additional interfering parts. Their hubs have a bolt arrangement that can span any ANSI and most ISO or DIN shaft separations, using up to 33 possible connection combinations.
William S. Bridges, Madison’s plant manager, says the company benefited because the Rexnord Omega couplings need no lubrication. Previously, maintenance had to strip the mill’s metal-to-metal type couplings down periodically, check internal parts for wear, relubricate and reassemble them. The urethane flex-element couplings also reduce loads on bearings by reducing inertia and vibration transmission. After more than two years of operation, none of the 90 new couplings on process and water pumps had failed.
Madison’s stringent alignment requirements have helped reduce the number of problems associated with shaft alignment. The coupling’s flexible urethane element is capable of up to four degrees of angular and 1/8-in. of parallel misalignment without transmitting excessive shock overloads.
 ISO
standard pump shafts
and ANSI standard motor
shafts at Madison Paper’s
Madison, Maine SC paper
mill are connected with
Rexnord Omega couplings like
this one, visible beneath
the protective housing
behind the motor.
To link shaft ends, Madison’s maintenance crews mount one coupling hub to a shaft, leaving the other hub loose for spacing adjustment. One-half of the urethane flex element is then placed around the hubs and secured, using coarse-thread cap screws with self-locking patches. The loose hub is then secured, the. other half of the element is installed, and all cap screws are tightened in their pre-aligned holes.
Bridges says, “We have improved our coupling versatility and adaptability and have made it easier to replace parts because all units are easy to adjust to either a metric or English spacing.”
NOTE: This application has been featured in an article that appeared in Paper Trade Journal.
4-154-MadisonpaperCS/12-10-03
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