This post will cover the standard procedure of motor maintenance, clearance from production and thereafter isolate the power supply and lock-out tag-out the equipment that I have experienced working different plants. To carry out the Preventive Maintenance activity as per given procedure and standard Preventive Maintenance sheet.
I can say that companies have their own standard procedure based on their best practice and company they are working with. Even the some condition must be considered too when motor is in running condition and cannot be stopped, or should be swapped to other just for PM.
But keep in mind that our goal for Preventive Maintenance is to test the motor for trending, to prolong it’s lifespan by preventing fault to happen and rectify abnormalities.
Definition of terms
Before we proceed to procedure, let’s first define such terms.
- A motor is a device that transfers electrical energy into mechanical energy and used to rotate the machinery.
- Maintenance of Motors include complete checkup of its functioning, electrical wiring and lubrication the required parts.
Also, we need to consider the potential hazards before we start the procedure. See below examples:
1. Exposure to lubricants
2. Inhalation of dust during cleaning
3. Falling from heights
4. Exposure to energized electrical line
5. Exposure to rotating part of machines
Thus, we have to protect ourselves using the following PPEs‘:
1. Safety belt
2. Safety helmet
3. Safety goggles
4. Insulated hand gloves
5. Safety shoes
6. Dust mask
Following procedure refers to general procedure for motor maintenance including the testing.
1. Get clearance from supervisor and accomplish work permit.
2. Isolate the equipment and Lock-out Tag-out at the same time. Make sure that keys and locks are properly installed and handed over. Before starting the job. Make sure LO-TO already applied to ensure power will not be enables by other personnel.
3. Ensure proper and adequate PPEs’ while cleaning, lubricating and shifting of motor. WD40 normally used to clean outside part of the motor as well as the grounding terminals and mounting bolts.
4. Electrical tests should be done to monitor the motor winding status such as Winding and Insulation Resistance. Winding resistance for each phase must be balance and not shorted to ground. Insulation resistance must be in recorded for trending of value from previous Preventive Maintenance. When getting the insulation resistance, the Polarization Index must be check to by calculating the 10 minutes over 1 minute test of Insulation Resistance test.
5. Check motor terminal tightness and physical conditions. Some terminals might be brittle and melted and must be checked and replaced.
6. Check for oil leaks if motor is coupled with gear box.
7. Check condition of motor fan and grounding terminals.
8. Observed hints of corrosions and accumulation of dusts.
9. If possible, manually rotate the shaft to check motor rotor free wheel action for the bearing.
10. Observe motor cables and lugs for signs of heating and discoloration.
If motor needs to replace, see general procedure for reference
1. Remove all electrical wiring.
2. If required, use a chain pulley block to shift motor safely on pallet or trolley.
3. Place new motor at the location with the help of pallet, trolley, or man lift etc.
4. Use chain pulley block if required and do necessary coupling with mechanical personels
5. Fix and align motor at the location and do the electrical connections.
6. Conduct no-load test and note down the parameters especially current.
7. If all everything are completed, ask for permission to run with load and get the load current to put on record.
Note: Any improvement or preventive actions must be done while on PM. Sometimes, PM date have to adjust or they call it as opportunity shutdown to correct possible problems before it happen.
Nomally, motor Maintenance comes with the MCC maintenance to check devices and rectify some issues found from predictive analysis. If you found out some hotspots using thermal imager, Preventive Maintenance can be one of the opportunities to rectify issues if its not critical. Otherwise, you have to do an action immediately.
MCC Preventive Maintenance includes the cleaning of the enclosure by blower and vacuum to make sure no any chance if dust accumulation. Checking of magnetic contactor, Overload relay and circuit breakers terminals tightness and physical appearance. There should be no signs of discoloration in cable, lugs and terminals result of overheating.
If you have high rated contactors, it should be opened to check internal parts. Contacts must be cleaned and apply contact cleaner.
Simulation of controls can be done during preventive maintenance. This will ensure the functionality of the power and control devices. This will allow you to check contact continuity for contactors and relays, proper delay of control timers and signalling of alarm such as overload.