Rexnord® Planetgear™ Reducers Keep Operations in Orbit at Phoenix Cement
CASE STUDY
By replacing conventional right-angle gear drives with Planetgear drives on everything from screw conveyors to bucket elevators, the Phoenix Cement Company has simplified maintenance, reduced downtime, and lowered drive replacement costs. In the 10 years after the first unit was installed, the plant's assistant manager replaced approximately 20 different reducers with the new drives.
Cooler grate drive is powered by a 20 hp motor, driving through an Atlas Series
Rexnord
Planetgear reducer. A Rexnord Omega coupling (under guard) connects motor and reducer.
The 650,000 tpy Phoenix Cement plant in Clarkdale, Arizona, a few hours north of Phoenix, is a wholly owned subsidiary of the Salt River Pima-Maricopa Indian Community and serves markets throughout Arizona, as well as Southern California, Nevada, and New Mexico. A fleet of 100-ton haul trucks feeds the plant's primary crusher from an open-pit quarry. After size reduction in a secondary crusher, the product is ground in the raw mill and blended before being processed through one of three kilns and finish mills.
When some of the original gear reducers in the plant needed replacement, Assistant Plant Manager-Maintenance Joe D'Avignon recalls,
"I put one of the Rexnord Planetgear drives on a screw conveyor and found it was rugged and easy to work on. Over time, I added more and more, on other screw conveyors, belt conveyors and elevators, so they're
our standard now." D'Avignon explains that much of the equipment previously was equipped with conventional right-angle gear boxes. When it became necessary to replace gears in some of the reducers, he found he would have had to replace the entire gear train at a cost greater than the reducer’s original cost. Replacing the entire unit with the same kind of reducer also was impractical, since many of the configurations had changed and would have required extensive modification of the base and time-consuming realignment.
Drives for drag chain conveyors move material from the cooler areas of two kilns to a
belt conveyor below, which transports it to storage. Saturn Series Planetgear reducers with
295:1 ratio reduce speed of 15 hp motors to about 6 rpm.
By contrast, the Planetgear reducers were easy to install with a coupling. They also required less room and fewer modifications to the base because of their in-line, planetary configuration. According to D'Avignon, replacing right-angle reducers with Planetgear reducers has resulted in considerable cost savings in downtime, in addition to the lower cost of the components.
When required, maintenance and repairs are easier and faster. "The previous gear reducers could have as many as three or four different gearsets to reduce the speed," says D'Avignon.
"In the Planetgear, everything is in a straight line and it's easy to work on." Drives at the Phoenix Cement plant range from Mercury units rated at 2 hp on a screw conveyor application through 60 hp Neptune reducers on belts that take the raw feed from the crusher to the stacker.
Planetgear reducers are available in single, double, triple and quadruple reductions, with a broad range of ratios and torque ratings. The planetary gear train is self-aligning, with carrier modules that float radially and axially to distribute all loads. Gearing is carried entirely on roller bearings, and shock loading is distributed over at least six teeth in contact per reduction, instead of at a single point as in conventional reducers. Operating efficiency is in excess of 97.5% per reduction.
Mercury Series Planetgear reducer transmits power from a 10 hp motor connected by an
Omega coupling to this screw conveyor.
Service life has been excellent, D'Avignon reports. The taconite-duty seals are very effective in operating conditions that include considerable dust, dirt and grit, as well as temperatures that range from about 115˚F down to about 15˚F during the plant's all-year, around-the-clock operation, other than for scheduled maintenance shutdowns.
Belt conveyor from secondary crusher to finish pile storage is powered by 25 hp motor driving this
Earth Series Planetgear reducer through an Omega coupling, visible through guard.
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