Problem-Solver, Series 9
A Southeastern Ohio power plant is supplied steam coal directly from a mine by a series of 18 belt conveyors,
spanning a distance of 5 miles at the rate of 1,200 tons/hr. One 2,000' conveyor had been troublesome
almost since it had been installed. The demand horsepower is less when the conveyor is loaded (30bhp) than when empty (60bhp) because of its declining profile.
All prime movers had been standardized on 125hp, 1775rpm, frame 505-S motors. As these motors are
pre-NEMA, their starting torque capabilities are awesome.
When the conveyor was started loaded, the belt would lift off the concave section so violently that the belt covers would be knocked off and coal would be catapulted
over 40' into the air! The instantaneous jolt on start-up also caused both take-ups to dance so uncontrollably that severe structural damage occurred as the counter-weights
exceeded their travel limits and slammed into the stops.
Many expensive proposals to correct these problems had been offered, with little promise of success . . . Until the user contacted a
Rexnord distributor presented the following facts:
Current Problems
Being oversized, the prime mover was damaging the belt cover and causing structural
damage to belt tensioning take-ups.
Coal spillage was so great at the concave section, the local DNR office was threatening court action if the problem wasn't corrected.
Most proposals for correcting the problems were expensive and would require months of down-time; the User could not take a chance, as promises of success were slim.
The True Torque Solution
A True Torque fluid coupling will limit transmitted starting torque to a
safe level, regardless of motor output.
A True Torque fluid coupling will help correct the belt lift-off and reduce the take-up movement by assuring a smooth controlled acceleration of the conveyor.
The True Torque fluid coupling installation would require only a one day shutdown and the distributor and local Falk representative would be on hand to assist in the installation and start-up.
Implementation
The Rexnord distributor selected and supplied a 420HFD-20 which was set-up for the BHP of the loaded conveyor based upon motor ampere readings.
After the installation was completed, personnel were positioned at both take-ups and at the concave section of the conveyor.
The prime mover was energized and the conveyor now accelerated smoothly up to running speed in 10 seconds.
The belt tensioning take-ups moved barely a foot each and the belt never left contact with the idlers along the concave section.
The coal remained on the conveyor belt.
After the initial astonishment wore off and handshakes were given, the Plant Superintendent ushered our Distributor and
Rexnord Representatives into his office for discussions on other applications within the complex.
Let us show you how to relieve tension and that banging sensation!
CONTACT YOUR REXNORD FLUID COUPLING DISTRIBUTOR FOR THE SOLUTIONS TO YOUR POWER TRANSMISSION HEADACHES.
Form 861001
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