Success Story: Motor-Gearbox Monitoring

A special thanks to our friends at PFE Limited for this success story

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Introduction

Our friends at PFE Limited were commissioned to conduct a series of cross-phase checks on a large motor-gearbox unit in a plant in the United Kingdom. Through their analysis, PFE Limited identified a crucial relationship between seemingly "random" extreme increases in vibrations on this gearbox setup.

The customer is now aware of the root cause of these occurrences and has a clear strategy to prevent the issue moving forward.

Hardware

PFE Limited utilized the following vibration analysis hardware:

shown above, left to right:

AC292-1D Compact sensor, 100 mV/g, ±5%

MH103-1B Flat surface mounting magnet, 40 lbs. pull strength

CB103-C314-015-K2C Cable assembly with CB103 cable C314 connector on the left side and K2C connector on the right side

shown above, left to right:

TCEB331 Miniature circular triaxial sensor, 100 mV/g, ±5%

MH114-3T Multipurpose mounting magnet with triaxial locating notch, 50 lbs. pull strength

CB117-C597-010-J4C-SFT Cable assembly with CB117 coiled cable with SFT breakaway safety feature, C597 connector on the left side, and J4C connector on the right side

shown above:

ACOEM Falcon Data Collector

In the photo above, you may notice the lower accelerometer (TCEB331) is positioned in a non-conventional location on the frame - this was intentional! When conducting phase analysis, it is beneficial to consider the entire machine train rather than focusing solely on bearing locations. This broader approach allows for a more comprehensive understanding of how the entire assembly moves in relation to itself.

Here are a few expert tips on phase from Jake at PFE Limited:

Phase analysis has numerous applications, but in simple terms, it measures the timing between two signals. This can be between a tachometer (or keyphasor) and an accelerometer - referred to as an absolute phase - or between two accelerometers at a specific frequency, commonly known as relative phase. Phase is a valuable parameter when diagnosing low-frequency faults.

For example, consider the 1x running speed of a machine. When two synchronously acquired signals reach their peak, the time difference between these peaks can be measured using one as a reference and the other as a comparison. This time difference, or phase "lag," is typically expressed in angular degrees. If half a cycle passes before the second signal reaches its peak, the phase difference is 180 degrees.

Understanding phase relationships between signals allows analysts to determine whether the motion is opposing or not. The insight helps diagnose specific faults and visualize machine movement more effectively than relying on single-point measurements.

While phase analysis is not typically performed during routine monitoring, it is invaluable for fault diagnosis. That's why all of our portable analyzers feature cross-phase functionality, and our engineers always carry two sensors to quickly conduct a cross-phase analysis when needed.