If a structural looseness is suspected, which type of vibration signature would likely be observed?

When structural looseness is suspected, the vibration signature typically exhibits a 1x peak in both directions. This reflects a condition known as a "looseness pattern," where the looseness can produce vibrations that manifest at the fundamental frequency of the rotating machinery (the 1x frequency). The presence of significant energy at the 1x frequency indicates that the source of vibration is related to the fundamental operational characteristics of the machine.

Further, the dual-direction observation highlights that loose components may move independently, resulting in vibrations that produce peaks in both directions (e.g., axial and radial). This can often be seen in the time waveforms or spectrum by examining the phase relationships; a clear 1x peak with substantial amplitude in both directions suggests that the looseness is affecting the structure symmetrically around the rotational axis.

In contrast, other options suggesting different peak characteristics, such as strong harmonics or high-frequency noise, are typically more indicative of other forms of mechanical issues or operating conditions, such as imbalance, misalignment, or bearing defects, rather than structural looseness itself.