CASE STUDY 9501
Repetitive Downtime Eliminated
Summary: Quality assurance test identifies insulation defect
Motor Information:
Type: Wound Rotor
Volt: 4160
HP: 1250
RPM: 1191
FLA: 166
Problem
A wound rotor motor was sent for a routine overhaul. Before
reinstallation, quality assurance
testing with MCE was performed. The rotor failed the polarization
index test and the inductive imbalance was 99%.
Looking for the Root Cause
Additional quality assurance testing with vibration recorded .4
in/sec at two time the RPM. Investigation revealed a dime sized
hole in the insulation under two slip rings. Post-repair MCE
testing produced a good polarization index test and an inductive
imbalance of less than 3%. Vibration dropped to .04 in/sec.
Savings
By conducting a three-minute MCE test, substantial time and money
were saved and a potentially hazardous incident avoided. Testing
a new or refurbished motor serves two purposes: quality assurance
and establishment of a baseline for tracking and trending.
Estimated Failure Costs
-Downtime $288,000
-Removal/Installation $42,000
-Motor Repair $133,000
Total Losses Prevented $463,000
Industry: Refinery
Application: Quality Assurance