CASE STUDY

Rex® PlanetgearTM Speed ReducersAre on a Roll at Nucor-Yamato Steel

By standardizing on a single family ofPlanetgear speed reducers, Nucor-Yamato Steel can replace any one ofthe hundreds of roll drives in its millquickly with the exact ratio it needs.Using a few sizes of the same configu-ration, the company can make fastreplacements without the need forextensive alignment, yet the drives lastseveral times longer than the units theyreplaced.

Nucor-Yamato Steel Companyproduces hot rolled wide flange struc-tural steel shapes, standard channeland miscellaneous channel shapes, carbuilding shapes, H-piling and hot rolledsteel sheet pil ing sections. Thecompany has produced structural steelin Blytheville, Arkansas since its firstmill opened in 1988. It melts scrapsteel and casts blanks in nearly the net

shape of the finished product, then hotrolls them into the final shape. In 1993,Nucor-Yamato Steel added a secondmill to produce the wide flange beamsand H-pilings.

The steel shapes are transpor tedthrough the mill on a series of poweredrollers as they move from one produc-tion process to another. The rollers andtheir drive systems are subjected toheat, impact loads mill scale and water.Under these conditions, maintenanceplanners look for simple yet ruggedmechanical components that are easyto install and maintain.

To power the many roll applications inthe Blytheville mill, Nucor-Yamato usesliterally hundreds of Rex Planetgearreducers. Maintenance Planner StacyBullard says, "We've been using thePlanetgear drives for as long as seven

Industry: Structural SteelApplication: Steel Mill

Product: Rex Planetgear Reducers

PHOTO:Several Rex Planetgear drives, during amaintenance shutdown, power rollers usedto move steel through the Nucor-Yamatomill.

CASE STUDY

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years in some applications. With them,we don't have alignment problems,because they couple up directlybetween the motor and the driveshaft."She says the drives are used through-out the mill on caster rolls, both sidesof the reheat, the descaler, finishingand many other areas.

Bullard notes that it is easier and fasterto change ratios so they can get theratios they need with the Planetgeardesign than with conventional gearbox-es. With a basic stock, local distributorBearing Headquar ters can simplychange ratios and have the r ightgearbox there very quickly. "We usemainly the Venus, Ear th and Marsseries and a few of the Atlas size," shesays.

To extend drive component life underextreme operating conditions, thecompany has added driveshaftsbetween some of the rolls and thedrives. Bullard explains, "We moved alot of the drives back so they aren'tright on the ends of the rolls. They areabout 10 feet away now, because weput driveshafts on them so the drive-shafts would take the beating."

She estimates that the drives typicallylast two to three times as long as theunits they replaced, which were not asrugged a design. This saves on laboras well as downtime. "I think thereversing action of the mills is whatdestroyed some of the old drives, butthe Planetgears hold up to the revers-ing," she notes.

For some applications, Nucor-Yamatochanges the Planetgear drives to a C-face mounting. Bullard says, "In a fewareas where there is a lot of shock, it ishard to keep the motor tight on ascoop-base mount, so we use a C-faceconversion kit to mount the drive rightto the motor. This eliminates problemswith the motor mount loosening up.

FOOTNOTE:This application also has been featuredin the April, 2000 issue of 33 MetalProducing magazine

Rexnord, Rex and Planetgear are trademarksof Rexnord Industries, Inc. All rightsreserved.

PHOTO:Typical Rex Planetgear roll drive with C-face mounting to motor.