Problem-Solver, Series 14
A family-owned and operated Asphalt Plant in West-Central Missouri had a kiln which was causing many-a-sleepless nights during the busy summer months.
It was tough working through the night repairing the kiln and then having to mix hot asphalt for another 10-12 hours!
The kiln was powered by two 75 hp electric motors driving four Falk
Quadrive shaft mounted drives. Each shaft mount drives a steel trunnion wheel.
Each pair of trunnion wheels transmits torque, through friction, to two steel "tires" which encircle the tubular kiln.
Uneven wear of these trunnion wheels causes the drives to fight one another until finally, gear tooth failure occurs.
The steel trunnion wheels could be remachined to identical outside diameters but this operation is very expensive and the kiln would be down two weeks or more.
There had to be another way to adjust the output speed of each trunnion wheel.
A Rexnord distributor was called and after a careful investigation, the salesman concluded that the kiln's drive system could be reworked while production continued, though at a reduced capacity.
Current Problems
Because of its design, there was no practical way to balance each trunnion wheel's surface speed.
The result was the destruction of perfectly good drives and more sleepless nights!
When the kiln was started, the instantaneous application of the motors locked rotor torque caused the trunnion wheels to slip and accelerate their wear.
Across-the-line starting of the two original motors was causing KVA problems in the form of peak-billing by the local utility company.
Lost production is very costly as any business lost could not be made up during the relatively short season.
The True Torque Solution
By replacing each 75 hp motor with two 40 hp motors equipped with
True Torque fluid couplings, trunnion wheel wear could be compensated for by
adjusting the amount of fluid in each coupling to vary their slip.
The kiln will start smoother as the fluid couplings will limit starting torque to 170% of each motor's rating.
No more trunnion wheel slippage will occur.
As the fluid couplings can slip at 100% for short periods, the motors can now be stagger-started to reduce in-rush current dwell time.
Fluid couplings transmit torque through a fluid, dampening out the vibrations and shock loads which can cause breakdowns of all components in the drive system.
Implementation
The kiln drive was reworked, replacing both 75 hp motors with four 40 hp motors equipped with
True Torque fluid couplings. The kiln now starts smoother, produces less vibration and has been 100% available when needed.
Production has increased and everyone involved is satisfied.
Let us show you how much a good night's sleep can affect your operation!
CONTACT YOUR REXNORD FLUID COUPLING DISTRIBUTOR FOR THE SOLUTIONS TO YOUR POWER TRANSMISSION PROBLEMS.
Form 880227
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