Power has no season. Consumers use electricity whether summer heat demands air conditioning or dusky winter evenings call for extra lights and electric blankets. In a coal-fired power plant, equipment must operate 24/7. Coal-fired power plants utilize multiple coal pulverizers to generate this electricity. Pulverizing coal results in less emissions and a more efficient use of fuel. Constellation Energy's H.A. Wagner power plant in Baltimore, MD, was experiencing costly downtime, maintenance, and material expenses associated with v-belts on a coal pulverizer drive system.
The pulverizer was using a 10 groove 5v cross-section banded belt drive. Normal, daily operations allowed belts to stretch over time and sheaves to wear quickly.
"Due to warm ambient temperatures, stretching occurs quickly and weekly tensioning of the v-belts is common," says John Ernst, Lovejoy national sales manager. "Improper tension results in belt slippage, which also wears out the large sheaves. Both are expensive and time-consuming to replace."
To eliminate this problem, a Lovejoy® Rosta® Heavy Duty (HD) Tensioner was installed to manage the tension on the v-belts. This tensioner was designed to address situations involving larger horsepower motors -- in this case, the coal pulverizer's 300 hp belt-drive. The Lovejoy Rosta HD Tensioner automatically self-adjusts to compensate for normal stretching and absorb shock loads. Its rubber-torsion spring principle is based on a unique engineered design that uses four tough elastomeric inserts to isolate the tension arm while providing constant tensioning of the v-belts. (Shown here, side view of tensioner.)
The sliding base system previously used by this coal pulverizer required the maintenance team to slide an enormous 1 ton motor along the mounting rails, losing precious production time. The Lovejoy Rosta HD Tensioner does not replace the existing motorbase, but instead utilizes fabricated arms and an idler pulley between the arms to apply the correct tension to the belts.
"We were able to leave the existing sliding base intact, setting the alignment and allowing just enough room to slide the new belts over the sheaves," says Ernst. "Then, we applied the Lovejoy Rosta HD Tensioner against the belts to give them proper tension."
The beauty of the Lovejoy Rosta HD Tensioner is that it's easy to install and maintain. The motor is set so that when releasing tension, the belts can be taken off and new belts reinstalled without moving the motor.
"The Lovejoy Rosta HD Tensioner eliminates the need for monthly maintenance except for biannual lubrication of the idler ball bearings," says Ernst, "and proper tension has reduced downtime and stopped belt slippage."
Additionally, the Lovejoy Rosta HD Tensioner keeps chains and belts taut, eliminating slip and vibration and preventing uneven drive surges and power loss. As an added benefit to the design, the Lovejoy Rosta HD Tensioner increases motor life by protecting the radial loads on the output shaft bearings. The elastomeric elements absorb shock loads and in addition, decrease vibration and noise levels -- an important OSHA® consideration. The predicted lifespan for the Lovejoy Rosta HD Tensioner is 10 to 15 years.
