We currently are using a Metrix velocity sensor and vibration monitor module track vibration on an industrial mixer gearbox. We use the monitoring module to provide a high vibration shut-off alarm as well as a real-time analog trend of displacement. We have continually been experiencing periods of large spikes in the vibration levels (there are two identical units side by side and typically both readings will spike). Often this occurs when the units are not even running. It is difficult to associate these spikes with any particular event. They are more frequent, however, when people are accessing the area in proximity to the sensors. I have spoken to the vendor and they have not been much help. Any ideas what could be causing the spikes? I believe they are false readings as there is no other source that could be inducing this magnitude of vibration. Any advice would be greatly appreciated. Thank you.

A few questions come to mind. Is the tank heated with steam? Anything else dumped to tank?Do the spikes happen to both machines at the same time and at what frequency are they happening? Low frequencies can appear as a "ski slope" at the low end of the spectrum. If the transducer is really sensitive my guess is its picking up any random event that happens such as a door slamming, etc. The mixing shaft speed (1x) may increase if tank contents are disturbed by steam injection or added flows, which are also affected by tank level. These changes may cause the 1x of the mixing shaft to increase. I guess for starters it's real important to find out the frequency of the spike. I hope this helps, Dave.