Minimize Downtime with Condition-Based Monitoring

Are you looking for ways to minimize downtime in the facilities you manage or design? Would you like enhanced awareness of what is happening in your system? Condition-based monitoring (CBM) may be the solution you need.

CBM is a type of predictive maintenance strategy that uses sensors to continuously measure the status of equipment over time. CBM is not a new technology for predictive maintenance; however, it is new to implementation within variable frequency drives (VFD). When included as a software feature add-on in VFDs, CBM increases customers’ knowledge of what is happening in their systems so they can be notified of maintenance concerns prior to issues becoming critical, thereby reducing system downtime.

What is CBM Capable of Monitoring?

CBM can monitor three points: motor stator winding, load envelope and vibration. With motor stator winding monitoring, the VFD uses its current monitoring capabilities to detect short-circuits in the motor before the motor burns out. Load envelope monitoring compares actual system performance with baseline data to determine if components are wearing out or not while running as they normally should. Vibration monitoring can detect mechanical misalignment, wear-out and looseness across all VFD speeds.

Condition-based maintenance increases real-time knowledge of what is happening in the system.

How Does it Work?

When the VFD is initially commissioned, the embedded CBM software can be programmed to run a baseline of normal operation over a specified time range, from a few days up to six months. Once the baseline is established, thresholds are set and the VFD will constantly be comparing what is happening in the system with the standard baseline. If the current operation goes beyond the threshold, the VFD will trigger a warning to notify the user that something is wrong.

There are two levels of warnings that can be programmed accordingly. If the system goes considerably beyond the two warning thresholds, the VFD will trigger an alarm and discontinue power to the motor until the fault has been cleared by a technician. These notifications can be shown on the VFD display and pushed to the building automation system and/or remote monitoring cloud services.

The Role of Maintenance Teams

CBM is not meant to eliminate maintenance teams but, rather, increase their real-time knowledge of what is happening in the system. If the user is stocking motors or running into long lead time issues when their motor fails, CBM can help bridge the gap. Short-circuits in the motor winding occur over time, so by detecting them early, the end-user can be prepared to replace the motor prior to the problem reaching a critical stage.

Motor stator winding monitoring will send a warning prior to motor failure and allow for the additional time that is needed to obtain a replacement. Load envelope monitoring can send warnings to maintenance staff about leaks in the water system, clogged air filters, broken pump impellers or pumps that have become fouled/sanded. These warnings provide useful information to help keep the system running efficiently and smoothly.

Vibration monitoring will keep track of any changes in vibrations that would start to wear out mechanical equipment more quickly. The VFD will monitor acceleration/deceleration and all speeds in-between that the VFD is running. Customers can choose to monitor any or all of these points in their systems.

Condition-based maintenance is not a new technology for predictive maintenance; however, it is new to implementation within variable frequency drives (VFDs).

Why Use CBM in Your VFD?

In the current climate of increased lead times and expectations of decreased downtime for systems and buildings, CBM will give you an edge. Most maintenance teams will monitor only some of the points that CBM is capable of. Those teams may also only go out with a meter at a specific point in time when the VFD may be operating at a speed where the issue is not occurring. Undetected problems lead to the continued degradation of components in the system, which may not be noticed until the system fails and operation is halted. CBM will keep you notified at all frequency levels 24/7/365.

This article was submitted by Jackson Tiedmann, regional sales manager, Danfoss Drives. For questions on Condition-Based Monitoring or selecting the right VFD for your application, reach out to Danfoss Drives at 888-DANFOSS.