The Big Interview
Jon Barrett of EMS chats to Mike Herring of Whitelegg Machines, on the aspects of conventional insulation testing of electric motors and how the trusted Meg-ohm test has some major limitations in what it can find.JB: Mike, what are the traditional methods for testing the insulation systems of electric motors?
MH: The majority of companies use a low resistance ohm-meter and a DC meg-ohm test.
The ohm-meter is used to check for balance between the three phase windings, and can locate loose connections open circuits and dead shorts. The meg-ohm test is used for checking the insulation resistance to earth by applying typically 500 volts DC to the winding (for a 415volt AC motor) and noting the leakage current and the meg-ohm or gig-ohm reading after one minute. Low meg-ohm readings indicate a winding problem or shows that the windings could be damp for example.
A FEELING FOR WHAT’S LIKELY TO FAIL..jpg)
As assets become smarter and CMMS/EAM packages become more integrated across various asset classes within a manufacturing company, responsibility for facility management (including facility maintenance) has become spread over multiple departments. Historically, facility and plant maintenance were the sole responsibility of the Maintenance Department which ultimately reported to the Plant Manager or Works Manager. However, plant equipment is the focus of most Maintenance departments in a manufacturing environment, except in the largest and most complex multi-site facilities. 
It is common knowledge that a range of Condition Monitoring (CM) techniques are available such as Vibration Analysis, Oil & Wear Debris Analysis, Thermography and Acoustic Emission. Each of these techniques has its own particular areas of strength and in this regard the Acoustic Emission (AE) technique has the noted advantage of giving real time information with early sensitivity to faults and applicability to a wide range of rotational speeds including slowly rotating (source : ISO 22096).
A very important part of a cost-effective preventive maintenance program is what I call the route-based activity. These are activities that are easiest to do, and to administer, if they are presented in a list. This list can be presented in electronic format or in a paper format and includes such activities as lubrication and inspections by maintenance craftspeople and equipment operators. There are two major things that surprise me regarding these basic preventive maintenance activities:
