Monday, October 23, 2017

 

         
 

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Cooling fins are there for a purpose ... Protect them with The MotorCoverô

"Just 2/10ths of an inch of pulp on the cooling fins
can increase rewind frequency by more than50%"


A Southeastern USA Paper Mill rewinds a 200 hp, 447T frame TEFC motor 3 to 4 times per year.  Why?   The motor is constantly covered with stock from the pulper.  It costs this mill $3,300.00 per rewind for an annual rewind cots of $13,200.00!  Can this mill eliminate this cost?  Yes!

A 1987 article pupublished in the TAPPI Journal focused on the devastating effects of pulp on electric motors and was based on an exhaustive study conducted by General Electric and the Savannah Mill of Union Camp.   These companies paired up to determine the effects of pulp contamination on ac induction, TEFC, premium high efficiency motors.  The results were surprising.

As the table below demonstrates, just a small amount of pulp on the cooling fins alone can double the number a rewinds a motor will require during its lifetime.  Add pulp contamination to the air intake and the motor and you can expect an 85% increase in motor rewinds!

Critical areas of Pulp & Paper Mills are motors located directly underneath the paper machine where wet stock and water spill through to coat the motor.   In the pulp mill expect the motors in the digester area, pulp tanks, bleach plant, lime kiln and black-liquor areas to see severe conditions.  Lastly woodyard motors will become coated with wood chips and a fine sawdust.  In all these areas, expect the annual rewind and maintenance costs to be higher.  Even a simple task of vibration analysis takes longer when an operator has to first scrape, wipe, chisel or otherwise clean the motor befor testing.

The MotorCoverô  was designed with this study and these areas in mind.   By preventing accumulation on the cooling fins and protecting the air intake with a canopy the motor cooling system (ie: fan and fins) are able to operate according to the manufacturers design specifications.

The results of the study are as follows:

Test Test Condition Increase in number of rewinds
Cooling Fins Air Intake
A CLEAN CLEAN 0% (FULL LIFE)
B CLEAN 50% BLOCKED 40%
C LIGHT PULP CLEAN 50%
D LIGHT PULP 50% BLOCKED 75-85%
E HEAVY PULP CLEAN 75-87%
F HEAVY PULP 50% BLOCKED 87-93%
* Under condition "C" a light coating of pulp (2/10ths inch) would cause the motor to burn out after achieving just half its design life.

** Study published in the May 1987 TAPPI Journal.

 
         

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