In environments with such harsh conditions, most predictive technologies fail. Perhaps the most obvious example of this are the vibrating screens found in mining operations around the globe. This machine class is designed to vibrate at high levels to allow for sifting and sorting to achieve the desired separation of material sizes. As one could imagine, this type of machine function has traditionally made vibration analysis nearly impossible. Despite these realities, KCF Technologies is uniquely positioned to monitor and identify developing failure modes on vibrating screens thanks to a few key components.
1. Center of Mass
Sensor stability is critical to wireless vibration monitoring. KCF’s patented design incorporates a low center of mass which creates an incredibly stable sensor. This becomes increasingly more important when attempting to monitor vibrating screens. Because of the incredibly aggressive nature of screens, using a sensor that is top-heavy (high center of mass) creates a high likelihood that this type of sensor will not be able to maintain a solid mount. In addition to the low center of gravity, KCF’s wireless vibration sensor is equipped with a stud mounting option which can be directly threaded into the machine, or a mounting puck which can be welded into place and the sensor threaded on for a rock-solid mount.
2. Banding Vibration
Once the sensor is securely mounted and continuous data trending, the next challenge to overcome is making sense of what the data is telling us. Most vibrating screens are equipped with an eccentric shaft mechanism which, when the drive motor is operating, will cause the “shaking motion” that allows the screen to sift material. This motion creates extremely high levels of vibration, but only at a specific frequency. This is known as the operating or shaking frequency. Once this frequency is identified, KCF utilizes vibrating bands to begin to trend different aspects of the screen’s health, rather than trending overall vibration levels. By doing this, we can address the most common conditions that cause catastrophic failure on screens.
The trendline to the left shows overall vibration levels on a screen bearing at a mine. The levels before a vibration band is applied are heavily influenced by the intentional vibration of the eccentric mechanism. As a result, the trend remains consistently high with little room for observing behavioral change. This is significant because most of the development of bearing defects will not produce enough energy to influence this trend.
Conversely, the left trend represents a vibration band between 100-4200Hz. This effectively “ignores” the intended vibration of the screen and allows SMARTdiagnostics to trend any high frequency developments that may occur due to bearing health issues. Identifying the earliest stages of increase have been particularly helpful for maintenance teams because it allows them to more regularly change the oil and limp the equipment to a planned outage, where they can prepare for the corrective maintenance and perform it during a planned outage. By applying these types of bands to screen monitoring and coupling them with automated notifications, KCF’s customers have been able to make screen bearing failures a thing of the past!
