What is Preventative Maintenance
Start at the Beginning
To put it all into one sentence, your job is to carry out preventative maintenance to all plant and equipment in a cost effective and efficient manner so as to ensure downtime is kept to a minimum. We have now had a look at the tools you can create to streamline your planning side of the work, so we will now take a look at some of the tasks to be performed. Take a look at the example we used for the Waste Water Pump 1. Start at the supply board where the circuit originates from Here we have a 63A 3 pole Circuit Breaker.
- Perform correct Lock Out Tag Out procedure
- Move to the Control Board and perform test to ensure all power to this board is OFF
- Check all circuits, make sure you do not have multiple supplies to this board. Only once you have ensured all power to this Control Board has been isolated can you proceed
Now you can start with the Preventative Maintenance
1 Remove the cover from the motor terminal box
2 Test Motor connections again before touching
3 Check that all connections are clean and secure
4 Perform complete motor test and record all readings
5 Check cable gland to ensure it is secure
6 If you are satisfied with test results, replace cover and make sure you maintain the seal
7 Check the cable from the motor to the local disconnecting switch. Make sure there is no damage to the cable, it is securely fastened and protected from any possible mechanical damage. Record findings and any remedial work done
8 Remove the cover on the local disconnecting switch and test all conductors for power
9 Inspect the enclosure and cover for any visible damage like cracks, damaged seal etc. Record findings and any remedial work done
10 Inspect the switch for any visible damage, clean and tighten connections. Record findings and remedial work done
11 Check the continuity of the earth conductor. Record reading
12 Once complete, close the switch and again, make sure you maintain the seal
13 Check the cable between the switch and the control board for any damage, ensure it is securely fastened and that all cable glands are secure
14 Open the control board and test all active conductors. Be on the lookout for multiple supplies in the board. Make sure to also test the control circuit. Never trust the fact that you have turned the supply off, locked it and placed your tag on the lock! Always test before you touch!
15 Once you have established that there is no power on the equipment, start by performing a visual inspection. Be mindful of discoloration of leads at the terminations as this is a giveaway for a loose connection and/or faulty switch. Record your findings and any remedial work done
16 Now start on the power circuit and clean and tighten all connections
17 Check the circuit breaker ratings against the cable size to ensure all conductors are protected against overcurrent. Pay particular attention to control circuit cabling tapped into the load side of the main switch as I have come across this on a number of occasions. Should you find this, carry out the necessary remedial work. Record all findings and work done
18 Check the setting of the overload protection device and record the setting. Make sure it matches the maximum rated current of the motor
19 Move to the control circuit when done and go through each device connected in the circuit. Check for any damage, wear, connections and carry out necessary remedial work. Record all findings and work done
20 If your company performs regular injection testing, record the date on which it was last done. If not, consider the implementation of such a schedule or at least perform a thermal imaging test on the equipment when under load
21 Once you have completed all the tests, inspection and remedial work, perform a complete installation test and record all readings. Where it is a Legislative requirement, complete the Electrical Certificate of Safety as stipulated.
22 Notify the relevant manager that you have completed your work and will be restoring power.
23 Once the unit is running at full load, record the current drawn by the unit, check this against the overload setting and the motor rating
24 With the motor running, it is also the perfect opportunity to listen for noisy bearings should you have missed it when performing the motor test. You will quite often hear the Electrician saying that the bearings are not his responsibility as it is mechanical. I would rather make that part of my work rather than having to replace the motor because of bearing failure!
Up to this point we have not done anything out of the ordinary and could easily sign off on this job as complete. As we are aiming to go the extra step, here is what we do next
- Calculate the number of starts/day of the motor
- Check the switching duty of the contactor. This should be available from your supplier
- Make sure the contactor duty cycle is correct for this application and if not, replace it with the correct unit
- Should the duty cycle be correct, find the life cycle for this contactor (number of switching actions)
- If you have the date on which it was installed, calculate the time left before recommended replacement and schedule the task. Without the date it is a bit harder as you may have to estimate a time. This is where Thermal Imaging will be of great benefit. By doing this you unfortunately do run the risk of it failing before the scheduled date. What is important is to make sure you record everything you do.
Although we have looked at contactors in the above, the important thing here is the method and record keeping. You can apply the same method to establishing the expected life cycle of switching relays. Try to avoid the run to destruct method as this is the most costly form of repairs
Make Use of Pictures
When you set up your Journal, don’t discard the use of pictures/photos. This is a very valuable item to add to your Journal. It is always useful to have a visual of the equipment when you refer to it, goes a long way with any audits your company may have etc.
Control Board D5
Enter a description of the board, number of devices etc. for use as a quick reference.
We have now worked through a very simple procedure on a very basic installation. The most important thing here is to set up your Journal for each individual piece of the installation and machines. The procedure remains the same
Once you have done this Journal, make sure you use it and update it every time you perform any work. The one thing we have not discussed here is the analysis of each failure. Never accept anything as normal. Always try to establish the cause and then find ways to improve it
I hope that you find this information of use and that you will put it to practice
In the future releases we will focus on safety circuits, fault finding of Electrical circuits and more so be on the lookout for them
The author of this information accepts no responsibility for any damage resulting from using all or part of this. This information is also aimed at suitably qualified persons to perform electrical work.
It is also crucial that any person performing electrical work will at all times follow the correct safety procedures